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RENEWABLE ENERGIESInnovation for the future
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Publisher: Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU)Public Relations Division • D - 11055 BerlinE-mail: [email protected] • Internet: www.bmu.de
Editors: Dr. Wolfhart Dürrschmidt, Gisela ZimmermannBMU, Division Z III 1 “General and Fundamental Aspects of Renewable Energies”
Alexandra LiebingBMU, Referat Z II 3 “Public Relations”
Content: Dr. Joachim Nitsch, Dr. Wolfram Krewitt, Michael Nast, Dr. Franz Trieb, Stephan Schmid, Uwe Klann, Dr. Peter ViebahnDLR – Deutsches Zentrum für Luft- und Raumfahrt
Dr. Manfred Fischedick, Dietmar SchüwerWuppertal Institut für Klima Umwelt Energie GmbH
Dr. Martin Pehnt, Dr. Guido ReinhardtIfeu – Institut für Energie- und Umweltforschung Heidelberg GmbH
Design: Block Design, Berlin
Photos: © AG Solar NRW / Universität Essen: 34 (1)© Aral: 79 (3)© Arsenal Research / Christian Halter: 34 (2)© Bundesverband Wärmepumpe: 74 (1); 76; 77© H. Burkhardt GmbH & Co. KG: 69 (2)© C.A.R.M.E.N.: 55 (1)© DLR: 49© EnBW: 30 (2)© Enercon: 23 (2), 25, 26© EVS: 23 (1)© ExpoStadt: 45 (1); 51 (1, 2)© Flagsol / Solarmillenium: 41 (1)© Fraunhofer ISE: 37 (2)© Geothermische Vereinigung e.V. / Oliver Joswig: 69 (3)© Gesellschaft für Handel und Finanz mbH: 30 (3)© Haase: 55 (2), 57 (2)© Kramer Junction Company: 39 (3)© Krüger: 59© Michael Nast (DLR): 45 (2); 50 (1, 2); 57 (1)© Thomas Kläber: 29 / Montage: © Block Design© NEG Micon: 23 (3)© Nordzucker: 63 (3)© Norsk Hydro Electrolyseurs: 79 (1)© Picture Alliance / ZB: 84 (3)© Sandia: 41 (2)© Schlaich Bergermann und Partner: 39 (1); 42; 43 (1); 84 (2)© Solarmundo: 43 (2)© Solarverein Ditzingen / Norbert Breuer: 34 (3)© Stadtwerke Bad Urach: 69 (1)© Stadtwerke Bielefeld: 79 (2)© Uwe Strobel: 51 (3)© ThermoLux: 45 (3)© ufop: 68 (2); 65© Vorarlberger Illwerke Kopsee: 30 (1)© Rainer Weisflog (front page)© Wodtke: 55 (3)© Wolfgang Steche / Agentur + 49: 27© Wuppertal Institut: 84 (1)
Date: May 2004 First edition: 20,000 copies
1
for our energy supply to become sustainable, it needs to satisfy a large number ofrequirements: climate compatibility, sparing use of resources, low risks, social equityand public acceptance. At the same time it should also give a fresh boost to innova-tion and help to create jobs with a future. Numerous worldwide and regional studiesindicate that renewable energy sources are capable of meeting these requirements.Relevant global and national scenarios for the future indicate substantial growth inthe share of energy supplies that will be accounted for by renewable energy sourcesin the decades ahead. It is becoming increasingly clear that faster expansion of rene-wable energy systems is a necessary requirement for a sustainable energy future.
At the end of 2003, more than 3 % of Germany’s primary energy – 7.9 % of its elec-tricity, 4.1 % of its heat and 0.9 % of its fuels – was obtained from renewable energysources, thereby avoiding 53 million tonnes of CO2. It is gratifying to note that therapid expansion of recent years has been maintained. This means we have progres-sed further along the road to the expansion objectives that the Federal Governmenthas set itself. But there is still a long way to go, because the objectives are:
––– To double the contribution made by renewable energy sources by 2010 (compared with 2000), i.e. a share of at least 12.5 % of electricity supply and at least 4.2 % of primary energy supply.
––– In the medium term the Federal Government is aiming for at least a 20 % share of electricity supply by 2020; the Federal Environment Ministry takes the view that renewable energy sources should account for at least 10 % of primary energy supply by 2020.
––– In the long term the Federal Government’s goal is that renewable energy sources should account for at least 50 % of total energy supply by the year 2050.
The revised Renewable Energy Sources Act creates the ideal framework for furtherexpansion of electricity generation from renewables. In the automotive fuel sectorthe tax exemptions for bio fuels are also ensuring market growth. In the next fewyears it will be important to expand this dynamic growth to the heat supply sectoras well. Together with a further exploitation of energy saving potential and ongoingimprovements in energy efficiency, the restructuring of energy supply in the direc-tion of sustainability will become unstoppable.
DEAR READER,
2
Today it is already beyond dispute that increased utilization of renewable energysources is indispensable for environmental protection and sustainable development.This means the prospects are improving for a large number of qualified jobs and forgrowing export markets. Highly promising growth markets are opening up formachinery and plant manufacturers. Sections of the building industry and the crafttrades are profiting increasingly from growing markets. And finally, the importanceof development, planning, information, advice and training is growing all the time.Already some 120,000 jobs in Germany are connected with renewable energysystems.
This overview of the progress of renewable energy technologies, their possible uses,potential and development prospects, provides detailed and up-to-date informationfor members of the public who want to make their own contribution to environmen-tal protection and sustainable development in the energy sector, or who want toform their own opinion on renewable energy systems.
This publication documents the fact that the technologies for utilizing renewableenergy systems are ready for use and available for a rapid market roll-out. The lookahead to the energy supply sector in the year 2050 – based on the conclusions ofseveral extensive studies commissioned by the Federal Environment Ministry – makesit clear that given ecological and economic optimization, renewable energy systemscombined with even more efficient use of energy in all sectors offer excellent pro-spects for the sustainable development of our national economy.
Jürgen TrittinFederal Minister for the Environment, Nature Conservation and Nuclear Safety
Requirements for a sustainable energy supply 6
Sustainability in the energy context 6Fossil fuels – the motor of today’s global economy 6The global climate is becoming unbalanced 10Nuclear power – the risks exceed the benefits 12Energy-squanderers and energy have-nots – an explosive situation 13The ways towards a sustainable energy economy 14Renewable energy – guarantor of a sustainable energy supply 18
Wind power 23
Wind power – a strong upwards trend 24Wind turbine technology 24Exploiting new offshore potential 26Continuously lower costs 27Wind power and environmental protection 27Wind power in Germany 29
Hydropower 30
Water power – established but still modern 31Storage power plants 31Run-of-river power plants 32Small-scale hydropower plants 32Ecologically compatible expansion 33
Photovoltaic systems 34
Photovoltaic systems – solar power everywhere 35From milliwatts to megawatts: a dynamic market 35Grid-connected systems 36Small-scale stand-alone systems 37Worthwhile from an ecological point of view 37
Solar thermal power plants 39
Solar thermal power plants – an insiders’ tip for climate protection 40Parabolic trough power plants 40Solar tower power plants 41Parabolic dish power plants 41Solar chimney power plants 42Fresnel concentrators 42The costs of solar-thermal power plants 42
Solar collectors 45
Solar collectors – bringing the sun into the house 46Technical trends 48Costs 49Market developments 49Prospects 49
3
CONTENT
Passive use of solar energy 51
Passive use of solar energy – possible through building design 52Windows: Sources of heat or of heat losses? 52The additional costs of heat protection 52Conservatories and transparent thermal insulation 53The German Energy-Saving Ordinance 54
Biomass combustion 55
Biomass – a long-term alternative for heat and electricity 56The oldest form of use: Burning 56Electricity from biomass 57Biogas – bacteria at work 58Costs 59Prospects 60Uses today 61Environmental use of biogenous fuel 62
Biofuels 63
Biofuels – a contribution to mobility from plants and waste 64A wealth of possibilities 64Environmentally friendly on the road – with bio-alcohol 64Raw material rape speed: Rape seed oil and Biodiesel 64Life cycle assessment of biofuel 66Costs 67A look at the future of biofuels 67
Geothermal Energy 69
Geothermal energy – energy from the earth’s interior 70Hot-Dry-Rock method 70High-temperature hydrothermal systems 71Low-temperature hydrothermal systems 71Deep geothermal energy probes 72Near-surface geothermal energy 72Research needed 72
Heat pumps 74
Heat pump – a hybrid 75Energy is not just energy 75The principle of the heat pump 75There is still much unused energy in the air, earth, and water 75Monovalent – bivalent – mono-energetic? 76Costs and prospects 77Heat pumps – Part of a sustainable energy supply? 77
Hydrogen and renewable energy 79
Hydrogen – energy carrier with a positive image 80It’s the process that counts 81The optimal strategy 81
4
Stand-alone systems 84
Stand-alone systems – far away from the public grid 85Technologies and applications 85Wind power 85Solar energy 86Biomass 86Hydropower 86Hybrid systems and their components 86Power inverters and current rectifiers 87Storage media 87Control and communication devices 88Market developments and prospects 89
Technical potential and environmental performance 90
Global availability of energy 90The potential for using renewable energy sources in Germany and associated costs 92Sources of renewable energy for the developing countries 96“North” and “South” – beneficiaries of a common energy strategy 97The ecological attributes of renewable energy 98
Prospects for renewable energy within the scope 102
of sustainable development
Today’s use of energy in Germany 102More rational energy conversion and usage – prerequisites for a sustained energy future 102The doubling goal for 2010 – the stepping-stone to substantial use of renewables 104The long-term prospects – a scenario of optimal renewable energy use 106Support for renewable energy 109Renewable energy in the European Union 113Present-day use of renewable energy in the European Union 113Technical potential for renewable energy 114The prospects for renewable energy in Europe 115
Contacts in Germany 118
References 120
Glossary 124
5
6
Sustainability in the energy context
For about two decades now, the term “sustainable development” has characterised the discussions about taking better care of our natural environment, a fairer distribution of prosperity throughout the world, and more humaneliving conditions for all people. Sustainability encompasses not only ecological but also economical and socialaspects, which must always be considered collectively and in their interactions. A comprehensive definition forsustainability was worked out for the first time by the Brundtland Commission, adopted by the Rio Conference1992, and has since been refined, and interpreted [Brundtland 1987; Rio-Agenda 21, 1992]. The Brundtland reportdefines sustainable development as a development that “meets the needs of the present without compromising theability of future generations to meet their own needs”. Energy plays a crucial role in sustainable development. Theway it is available influences practically all fields of social, economical, and political activities; the state of the envi-ronment and the climate are influenced by it, and often it determines whether nations will live in peace or conflictwith each other. Accordingly, “the use of energy is only sustainable when the sufficient and permanent availabilityof suitable energy resources is assured, while at the same time, the detrimental effects of supplying, transporting,and using energy is limited.” [BMU/UBA 2002]
More specific guidelines can be defined to help orient the actors dealing in the energy sector and guide the deve-lopment of political strategies regarding energy [HGF 2001]. In accordance with this understanding of sustainabi-lity, these guidelines are to be seen as minimum requirements for a sustainable development. Other major activi-ties for the further development of societies and states, like assuring economic growth, increasing prosperity, andimproving mobility, should therefore only progress to an extent that the minimum requirements for sustainabilityare not endangered (textbox).
These fundamentals call for a deeper understanding of progress and development, particularly in the highly indu-strialised countries, if the course towards sustainability shall be successful at a global level. Despite the certainlyprogressive status in environmental policies in certain areas like e.g. in the protection of waters or pollution reduc-tion in electricity generation, Germany is today still far away from a sustainable development path. If today’s ener-gy supply is measured on the basis of these guidelines, then major deficits are identified:
––– Excessive consumption of finite energy resources––– The looming changes in the global climate––– Extremely large differences in energy consumption between the industrialised countries and
developing countries––– Risks associated with using nuclear power
Fossil fuels — the motor of today’s global economy
Since the beginning of industrialisation, energy consumption has increased considerably more rapidly than thenumber of people on the planet. Whereas the world population has quadrupled since 1870, to 6 billion at present,the world-wide energy consumption, and therefore the consumption of fossil resources in the form of coal, oil, andnatural gas, has increased by a factor of sixty to the present level of 423 EJ/a (2000; EJ = Exajoule, refer to the glos-sary). The average person today consumes fifteen times more energy than a person 130 years ago, significantlymore for those living in the industrialised countries. Temporary drops in the past, caused e.g. by the two worldwars, the oil-price crises, or the serious decline of industrial production in the states of the former Soviet Union,interrupted this upwards trend in growth only for short periods of time. The current rapid increase in energy con-sumption started about 1950; the energy consumption world-wide doubled between 1970 and 2000. Moreover, no fundamental change of this growth trend is expected in the foreseeable future.
At the present time, the traditional use of biomass in many of the less-developed countries, in the form of the non-commercial use of firewood, constitutes 9 % of the world-wide consumption of primary energy. The other types of
REQUIREMENTS FOR A SUSTAINABLE ENERGY SUPPLY
1 In energy statistics, the ratio for converting electricity from water, wind, and solar irradiation into primary energy is 1:1, whereas electricity from nuclear
power is converted by the ratio of 3:1 into (thermal) primary energy; the fossil sources of primary energy and biomass are characterised by their calorific value
(refer to the glossary)
7
Guidelines for a sustainable energy supply
Equality of access:
Equal opportunities in accessing energy resources and energy services shall be assured for all.
Protection of resources:
The different energy resources shall be maintained for the generations to follow, or there shall be comparableoptions created to provide sufficient energy services for future generations.
Compatibility with environment, climate and health:
The adaptability and the ability for regeneration of natural systems (the “environment”) may not be exceededby energy-related emissions and waste. Risks for human health – by e.g. an accumulation of problematical pol-lutants and harmful substances – shall be avoided.
Social compatibility:
It shall be assured when realising the energy supply systems that all people affected by the system are able toparticipate in the decision-making processes. The ability of economic players and communities to act and shapemay not be restricted by the systems being set up, but rather shall be expanded wherever possible.
Low risk and error tolerance:
Unavoidable risks and hazards arising from the generation and use of energy shall be minimised and limited intheir propagation in space and time. Human errors, improper handling, wilful damage, and incorrect use shallalso be taken into consideration in the assessment.
Comprehensive economic efficiency:
Energy services shall – in relation to other costs in the economy and of consumption – be made available atacceptable costs. The criterion of “acceptability” refers, on the one hand, to specific costs arising in conjunctionwith the generation and use of the energy and, on the other hand, to the overall economic costs while takingthe external ecological and social costs into consideration as well.
Availability and security of supply:
The energy required to satisfy the human needs must be available according to the demand and in sufficientquantities, in terms of both time and location. The energy supply must be adequately diversified so as to beable to react to crises and to have sufficient margins for the future and room to expand as required. Efficientand flexible supply systems harmonising efficiently with existing population structures shall be created andmaintained.
International co-operation:
Developing the energy systems shall reduce or eliminate potential conflicts between states due to a shortage ofresources and also promote the peaceful co-existence of states by a joint use of capabilities and potentials.
renewable energy, first and foremost hydropower, add up together to a share of 4.5 % 1. Nuclear power meets 6.7 %of the demand. Thus some 80 % of the world’s energy supply is based on finite fossil energy carriers, in commer-cial applications this figure is as high as 88 %. These results demonstrate that the energy supply both world-wideand in Germany is based primarily on the finite fossil energy carriers of coal, mineral oil, and natural gas. Thus itis clear that, even in the event of very rapid changes in the energy supply, fossil-based energy will still be needed
for decades to come, and possibly to an even greater extent than today. Therefore, the question of which resourcesare then still available and for how long is an issue of central importance.
The term “reserves” concerns those quantities of energy which are proven to exist and the exploitation of whichare economically feasible applying today’s engineering techniques; the term “resources”, on the other hand, des-cribes either those quantities which have been proven to exist geologically, but cannot yet be exploited economical-ly, or those that are not proven, yet are presumed to exist in the area in question for geological reasons. The reser-ves of fossil sources of energy still remaining amount to some 34,000 EJ (status 2001), an amount equivalent toapproximately eighty times the present consumption of energy in the world today, but only 2.4 times the totalquantity of fossil energy already consumed. Coal constitutes more than 60 % of these reserves. Conventional mine-ral oil constitutes 20 % of the remaining reserves, and is therefore the most-exploited energy carrier of all the fossilenergy sources.
Comparing this fact with the major significance assigned to mineral oil, with a 35 % share of the global energysupply, it becomes clear that, in the foreseeable future, we will also have to resort to exploiting non-conventionaloil reserves (heavy oil, oil shale, oil sands) and costly resources, if we are to continue meeting the (still increasing)demand in the future. Including natural gas here as well (without taking into account the very uncertain dataabout aquifers and gas hydrates – Glossary), then just the resources of hydrocarbons with some 28,200 EJ are of the same order of magnitude as the reserves of all fossil energy carriers. Resources as large as 116,000 EJ are beingpresumed for coal.
The trends indicating scarcity in the reserves of oil and natural gas are also reflected in the static lifetime of theseresources, representing the time remaining until these reserves are completely exhausted should the present-daylifetime of consumption continue. At 43 years (2001), the shortest static lifetime is for conventional mineral oil. If unconventional mineral oil – i.e. heavy oils, oil sands, and oil shale – is included as well, then the static lifetimeincreases to 62 years. Assuming a constant rate of consumption, natural gas will last for approximately another 64 years, whereas the reserves of coal will be available for about another 200 years. Uranium, another finite sourceof energy, will only last for about another 40 years when using light-water reactors and without processing thenuclear fuels.
From the individual’s point of view, these time periods might not seem to be cause for concern, since the reserveswill not likely be exhausted within our lifetime and, additionally, considerable amounts of resources are still avail-able which principally can be used. Such considerations do not, however, include the following two aspects:
––– On the one hand, the world-wide maximum in mineral oil production – the so-called “mid-depletion point” –is expected to be reached in the next 10 to 20 years. The price of crude oil is very likely to increase considerably bythe latest at this point in time. Natural gas alone cannot make up for the deficits, and the reserves of unconventio-
8
500
400
300
200
100
0
Pr imary energy consumpt ion , EJ/a
Non-commercial biomass
Renewables
Nuclear energy
Natural gas
Mineral oil
Coal
Development of the world-wide consumption of primary energy between the years 1870 and 2001, and the distribution of energy sourcesincluding the non-commercial use of biomass (firewood).
1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Development of primary energy consumptionSource : IEA stat ist ics and others
nal oil are always more expensive. On the other hand, the reserves of mineral oil and natural gas are distributedvery unequally over the globe. More than 70 % of the mineral-oil reserves, and more than 65 % of natural-gasreserves, are to be found within the “strategic ellipse” of countries extending from Saudi Arabia in the south, overIraq and Iran, up to Russia. Considering these two facts together, it becomes very apparent how explosive the sup-ply situation for the “energy-hungry West” may become in the foreseeable future. Assured access to cheap energyresources is already of such major significance for the industrial countries today that it is contributing to the deve-lopment and propagation of political and even military conflicts.
––– The intra-generative equity, i.e. the just distribution of resources between present-day and future generations,a major principle of sustainability, is also being ignored. Even if today’s generation were to conclude that appro-priate room for action shall be left for future generations despite the exploitation of the reserves of fossil andnuclear energy carriers, then the minimum requirement must be to already introduce today new energy technolo-gies which do not depend on fossil or nuclear fuels, due to the long time needed to develop and introduce thesenew technologies, and to not prescribe any structures which would make changes either impossible or impedechange in any significant way. A power plant has a useful service life of between 30 and 40 years, new brown coalpits last for about 60 years, and even the development and any appreciable market launch of a new generation ofenergy converters, like e.g. fuel cells, can take between 20 and 30 years.
The limitations and the geographical distribution of energy reserves thus emphasise how important it is to begin asearly as possible with setting up a sustainable energy supply system. This statement still applies even when fossilenergy resources are taken into account, considering those deposits still not worth developing under present-dayconditions. Assuming that the global energy consumption continuously increases at the rate of about 2 % per year,then including these resources will extend the availability of mineral oil and natural gas by only a few decades lon-ger than for reserves alone. The exploitation of these resources is however associated with a disproportionately higher effort than is the case today in accessing the reserves.
Furthermore, the environmental effects associated with their exploitation are not known with any certainty. Forexample, the risks from emitting large quantities of the climate-relevant trace gas methane during the productionof gas hydrates is still unknown. If, on the other hand, we now start to reduce the consumption of finite energycarriers, then we are protecting ourselves from the risks of future and possibly similarly drastic price increases likethose experienced for mineral oil in the seventies. At the same time, we comply with the guidelines given for envi-ronmental and climate protection.
Comparing the time it took for the fossil energy carriers to develop with the time taken to use up these reserves,then the overexploitation of these natural resources by man becomes even more apparent. Several hundred millionyears of photosynthesis were necessary to form these energy-rich hydrocarbon compounds, and these valuable rawmaterials have been consumed within the space of only a few hundred years and, at the same time, their residueshave put a strain on the environment.
9
Crude oil Natural gas Brown coal Hard coal
5,200
6,360
2,825
2,200
5,110
500
1,960
6,100
17,670
Source : BGR 2003
Reserves of fossil energy sources in comparison with the quantities already consumed, for 2001.
Reserves of fossil energy
0
Energy, EJ
16,000
12,000
8,000
4,000
– 4,000
Consumed per end of 2001: 14,000 EJ Reserves, conventional: 31,100 EJ Reserves, non-conventional: 2,825 EJ
The global climate is becoming unbalanced
Presumably, we will not primarily be forced to change our energy usage habits because of the depletion of fossilenergy resources. It is more likely the limited capacity of the environment to absorb the waste products of ourenergy consumption which will demand resolute actions towards a more sustainable energy economy. This condi-tion applies primarily for the products released into the atmosphere. During the combustion of fossil energy car-riers, pollutants like sulphur dioxide and nitrogen oxide are formed which contribute to the formation of acid rain.An incomplete combustion process causes emissions of carbon monoxide, unburned hydrocarbons and soot parti-cles; the combustion of solid fuels also produces considerable amounts of dust. These emissions, along with a num-ber of others, not only have a detrimental effect on the environment, they are also directly injurious to humanhealth. Improved combustion and the use of catalysts and filters can however considerably reduce those emissions.Significant progress in this respect has been made over the last three decades in many industrialised countries, par-ticularly in Germany. The driving force behind these efforts has been an effective environmental policy supportedby substantial financial resources. As a result, the air has become cleaner, particularly in the more congested urbanareas. One serious problem however still remains – the nitrogen oxide emitted as a result of the growing individualmobility. It shall be reduced by tighter exhaust emission standards for new vehicles. In the less-developed countries,the burdens from these emissions are quickly growing and with all the negative impacts we already know from thepast in the industrialised countries.
Besides these emissions, often referred to as the “classic” air pollutants, carbon dioxide is always emitted during thecombustion of fossil fuels. Although this gas is not toxic for organisms, it has the detrimental effect of boosting thegreenhouse effect and thereby increasing the mean global temperature in the lower atmosphere. Since the begin-ning of industrialisation, the concentration of carbon dioxide in the atmosphere has risen by one quarter and hasthereby caused the mean temperature near the ground to increase by 0.6 ± 0.2 °C. If no countermeasures areundertaken to reduce the emissions of this and other greenhouse gases, a further increase of the mean temperatu-re is expected in the range of 1.4 °C to 5.8 °C by the year 2100, as calculated in the scenarios of the IPCC. Alongwith the temperature increase, changes in the distribution of precipitation, an increase in the frequency of extre-me weather conditions, a shift in climate and vegetation zones, and a degradation of soil quality are to be expec-ted with fatal results for the already strained global nutritional situation. Changes in the climate are natural phe-nomena and have often occurred in the geological history of the earth. However, the menacing aspect of the pre-sent changes is that they are too fast and too abrupt. Human civilisations and the environment will not have suffi-cient time to adapt to such rapidly changing conditions.
Energy-related CO2 emissions contribute to about half of the man-made greenhouse effect. The efforts of climateprotection activities are therefore focussing on reducing these emissions. The current increase of some 23.5 billiontonnes of CO2/yr, resulting from the steadily growing global energy consumption, has led to the emission of a totalof 1,000 billion tonnes of additional CO2 into the atmosphere since the beginning of industrialisation, 80 % of thisamount was emitted in the last 50 years. Since the growth has taken place mainly in the industrialised countries, it is these nations who are responsible for about 90 % of the CO2 emissions generated from energy consumption.
Source : BGR 2003
60.8 %
13.5 %
8.1 %
9.5 %
8.1 % 9.6 %
35.9 %
10.9 %
10.3 %
33.3 %
Oil reserves 2001: 6,360 EJ Natural gas reserves 2001: 5,110 EJ
OPEC-Gulf
OPEC-others
OECD
CIS
Others
Distribution of the reserves (2001) of conventional mineral oil and natural gas by country groups.
Distribution of the reserves
10
At the present, these countries account for two thirds of the global CO2 emissions. Germany emitted some 860 mil-lion tonnes of CO2 in 2000, corresponding to nearly 4 % of the world-wide emissions. Each inhabitant of Germanyis thus responsible for emitting more than 10 tonnes CO2 of carbon dioxide every year. An American produces 22 tonnes, more than twice as much. In contrast, the amount attributable to a Chinese is only 2.7 tonnes and a person in India produces just 0.7 tonnes. The huge responsibility of the industrialised countries for the green-house effect is clearly demonstrated by these facts.
Global climate change due to the combustion of fossil energy carriers, to the overexploitation of forests, and to anindustrialised agriculture (emission of the greenhouse gas N2O) is considered today as proven. To keep the tempera-ture rise within reasonably low limits, the current concentration of CO2 in the atmosphere around 360 ppm mustnot be allowed to rise above 450 ppm before the end of this century. To comply with this target, it is essential thatthe world-wide energy-related CO2 emissions are reduced by more than half of the present amount by the year2100. Bearing in mind the way the world population is growing, each of the prospective 10 billion humans mayonly emit slightly more than one ton of CO2 per year. To meet this long-term goal, Germany would have to reduceits national CO2 emissions by 75 % by the year 2050 compared to the 2000 emission level. If instead we assume acontinued unlimited coverage of our growing energy consumption by predominantly fossil-based energy, then theCO2 emissions will rise considerably and the resulting temperature changes will reach uncontrollable values, accor-ding to the scenario A1FI from the IPCC presupposing extensive consumption of all fossil resources. Therefore, wit-hin the space of only a few decades, an effective combination of technologies are needed for a more efficient ener-gy usage in all sectors, as well as CO2-free or low-CO2 energy conversion technologies, to keep the climate changesalready taking place within tolerable limits.
In contrast to the classic air pollutants, the negative impacts of the CO2 emissions are of a solely global nature –they do not act instantaneously, but rather in a gradual way and with regionally very different results. A reductionof these emissions does not lead directly to any immediate advantages for the local energy consumer. Only world-wide measures can reduce the CO2 emissions to the necessary extent. Individual states or groups of states can playan important guiding role here. The global dimensions of the greenhouse effect therefore call for more compre-hensive political action than when dealing with exclusively national problems.
Another difficulty arises from the way carbon dioxide is formed during each combustion process. So far, no techni-cal measures exist to separate and to deposit it at reasonable costs. The classical “end-of-pipe” technologies, whichhave been very successful in reducing the other pollutants, do not apply in the case of CO2, or they would be moreexpensive than directly reducing the consumption of fossil energy carriers, or to replacing them by non-fossil ener-gy sources.
In view of the far-reaching risks associated with the greenhouse effect, climate protection is one of the prime rea-sons for introducing a sustainable energy economy. Of course, the on-going reduction of other pollutants is of
11
Source : DLR
24
22
20
18
16
14
12
10
8
6
4
2
0
Development of global energy-related CO2 emissions since 1870 and the main causes: the growth of the population and the combustion ofcoal, mineral oil, and natural gas (1 Gt. coe: 1 billion tonnes of coal equivalent corresponds to 29.3 EJ)
1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
CO2 emissions (Gt/a)
Primary energy (Gt. coe/a)
Population (billions)
Development of global CO2 emissions
major concern as well. Also, the far-reaching impacts of present energy use, e.g. the destruction of landscapes bymining lignite, coal, and uranium and by oil production, pollution of the seas by tanker accidents, increasing envi-ronmental pollution by the degradation of unconventional hydrocarbons, and last but not least, the severe conse-quences of large hydropower plants, especially when large areas of land are flooded, should not be forgotten.
Nuclear power — the risks exceed the benefits
As electricity generation from nuclear fission is almost completely CO2-free, nuclear power is often considered asbeing indispensable for achieving our CO2 reduction targets. This view does not however withstand any in-depthanalysis: As climate protection requires a large reduction of CO2 over a long time period, the contribution of nu-clear energy to the global energy supply would need to be increased by more than one order of magnitude andmaintained over several centuries. Besides the increased risk stemming from each new nuclear power plant (manyof them operated in countries with lower safety standards and with a lower level of political stability than inEurope), the limited availability of resources prevents nuclear energy from fulfilling these requirements. Even attoday’s level of nuclear energy use, the availability of cheap uranium for light-water reactors is expected to last foronly another 40 years. The long-term supply of a large amount of electricity requires the use of reprocessing andbreeding technologies which are not only more costly, but also involve greater risks than those associated withtoday’s reactors.
Nuclear energy already conflicts with the basic requirements of a sustainable energy supply:
––– Beyond-design accidents in nuclear reactors, leading to unacceptable human health risks, cannot be ruled out. The regions affected by such an accident would suffer from extreme consequential damages. (Refer to Guideline 3.)
––– All processes of the nuclear fuel chain, including fuel preparation, processing, and waste disposal generate radioactive material, some of which is emitted. The large remainder requires a safe and long-term separation from the ecosphere, the technical feasibility of which has not yet been demonstrated in spite of the consider-able expenditures in research and development. (Refer to Guidelines 3 and 4.)
12
Source : IPCC 2002
90
80
70
60
50
40
30
20
10
0
CO 2 emiss ions (Gt CO 2 /a)
Historical
Scenario “A1FI”
Scenario “550”
Scenario “450”
Development of energy-related CO2 emissions in different IPCC scenarios and their impacts on the atmospheric CO2 concentration andtemperature (A1FI = Meeting growing energy demand mainly by fossil energies; “450” and “550” = average values of scenarios whichresult in a stable concentration of CO2 in the atmosphere).
Scenario:
Cumulative CO2 (Gt C):
CO2 concentration in 2100 (ppm):
Mean temp. rise (°C):
Historical “A1FI” “550” “450”
300 2200 1000 700
(360) 950 550 450
0.4 — 0.8 4.5 — 5.0 2.5 — 3.0 1.5 — 2.0
Development of energy-related CO2 emissions
1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100
––– Complete protection against the misuse of the plutonium by-product from nuclear fission seems to be impossible, in particular if plutonium must be handled within an international breeding economy. Any misuse of weapon-grade plutonium by individual states or supra-national groups is a continuous threat for humanity. (Refer to Guidelines 5 and 8.)
––– Full protection of nuclear facilities against external forces and sabotage is impossible, or would lead to extremely high costs and a limitation of civil liberties. (Refer to Guidelines 4 and 6.)
––– A limitation of the use of nuclear power to only the “highly developed” countries in order to reduce the risks described above would hinder a peaceful world-wide co-operation and is thus not a viable proposition for political reasons. (Refer to Guideline 8.)
As a result of a comprehensive and thorough consideration of these issues, the benefits of a carbon-free electricitysupply from nuclear power would seem to be small compared to the risks inherent to the continued use or evenfurther expansion of nuclear power. Fortunately, there are more than adequate non-fossil energy sources available.The huge technical potential of renewable energy is sufficient to meet the global energy demand several timesover, as has been established recently by the German Advisory Council on Global Change (WBGU). The decision in2000 to phase out nuclear energy was reached by the German Government and the electricity utilities in Germany,indicating that this conclusion has been recognised and that action for re-routing will now being taken.
Energy-squanderers and energy have-nots — an explosive situation
A further severe sustainability problem is the huge disparity in energy consumption between industrialised anddeveloping countries, which has increased rather than decreased in recent years. Today, 24 % of the world popula-tion in the industrialised countries consumes 65 % of the conventional energy carriers and 75 % of the electricity.In contrast, 32 % of the world population living in the “less-developed countries” have access to only 1 % of econo-mic wealth and just 4 % of the energy. They are “responsible” for only 5 % of the global CO2 emissions.
While the mean values across groups of countries conceal some of the differences between country-specific in-dicators, the discrepancies are even more extreme when looking at individual countries. The per-capita energycosumption of a North-American citizen is 15 times higher than that of an African (a factor of 30 for commercialenergy carriers), and 5 times above the world average. The inhabitants of the poorest countries, like Yemen, Niger,and Bangladesh, have to survive with just one hundredth of the energy consumption of a North-American. The
13
Source : UN 2001 / IEA 2001
35 %
32 %
24 %
1%
8 %
11 %
1. Population: 5.9 billion
3. Primary energy: 410 EJ
2. GNP: 32 trillion US $ (95)
4. CO2 emissions: 23.1 Gt
11 %19 %
4 %
66 %
10 %20 %
5 %
Prosperity and world wide energy consumption
9 %
80 %
65 %
Characteristics of a divided world. The poorer you are the less there is – the industrialised countries have the greatest shares of pros-perity and energy (IC = industrialised countries, HDC, MDC, LDC = high, medium, and low developed countries)
IC HDC MDC LDC
per-capita energy consumption in Europe and Japan is about 50 % lower than in North America, indicating thatprosperity is not directly linked to a high level of energy consumption. However, the average energy consumptionof about 140 GJ per capita and year in Europe is still 2.5 times higher than the world average. Even just a tenden-tial compensation for the grave differences in the use of energy, which is absolutely necessary to address socialsustainability, unavoidably leads to a further growth in the world energy demand related to the increase in theworld population to 9 or 10 billion people by the year 2050. Since the type and extent of energy supply in theindustrialised countries is considered in the more poorer countries to be exemplary because of the considerableprosperity attained here, these countries are moving into the same resource-consuming direction which we set along time ago, thereby further increasing the deficits in sustainability. Therefore, it is only when we make funda-mental changes in the way we supply our energy that there will be any change at all in keeping the pre-program-med increase in the global energy consumption within limits and at the same time, reducing the use of fossil-basedfuel for climate protection reasons.
The ways towards a sustainable energy economy
Looking at it today, a completely objective consideration and weighting between overall recognition of endange-ring the global climate, the expected tendency for fossil fuels to become scarce and costly, the diverging attitudestowards the risks associated with nuclear power, and the economic and social damage given by the extreme in-equality in access to energy does not appear possible. The previous discussion does however allow certain basicconclusions to be drawn: a future energy supply should not be based on fossil and nuclear energy carriers. Instead,a system needs to be established which is in accordance with the guidelines for sustainable energy supply, orwhich at least allows us to move towards the sustainability targets we aim for. There are three basic strategic ele-ments supporting the restructuring of the energy supply system, which are referred to as “efficiency”, “consisten-cy”, and “sufficiency”: None of these elements alone can ensure success – they are complementary and onlythrough their close interaction can sustainability goals be met. A significant reduction of energy consumption is re-quired to allow renewable energy to provide a reasonable share of energy demand in a cost-effective way. Only an
14
World
North America
Oceania
Europe
CIS
South America
Asia
Africa
OECD
EU (15)
Arab Emirates
USA
Germany
Japan
South Korea
Italy
Portugal
Mexico
China
Indonesia
India
Haiti
Yemen
Bangladesh
68
345
190
140
131
45
30
25
195
155
417
348
172
170
161
122
100
64
37
26
20
11
6
5
0 50 100 150 200 250 300 350 400 450GJ per cap ita
Comparison of per-capita energy consumption
Comparison of per-capita energy consumption (1999) by countries (including non-commercial energy).
Source : IEA 2001
15
Basic strategic elements
Efficiency:
Energy is always needed in the form of certain services like a comfortable room climate, hot water, illumination,powering of machines, or mobility. During the conversion of primary energy to such energy services, energycarriers run through several steps, all of which are associated with efficiency losses. These losses can be reducedconsiderably by modern conversion technologies and energy management techniques. Besides even greater effi-ciency in the energy conversion and a more rational use of energy in all equipment, the substitution of high-grade energy by less valuable energy is also part of this strategy (e.g. substituting electricity used for heatingrooms with heat from co-generation or with improved thermal insulation). The efficient use of the energy inunavoidable, non-recyclable waste materials is also of great importance.
Consistency:
Currently, fossil and nuclear energy resources are taken from beneath the surface of the earth, yet their conver-sion products are disposed of in the environment. The present energy system is “open”. Only “closed” systemsare however sustainable in the long run. To a great extent, closed systems provide energy without the consump-tion of raw materials and always return the material to the energy cycle. Energy systems that use relativelysmall parts of the natural energy cycles driven by the sun, by gravitation, or by geothermal heat are very closeto this ideal. The materials employed within these processes (like e.g. solar collectors) can be recycled to a greatextent as these are not contaminated or otherwise modified in an irreversible way: thus they are not “con-sumed” in the sense of fossil or nuclear energies.
Sufficiency:
The energy needs depend on the lifestyle and consumer habits. Changes in the human activities and needs, e.g. in recreational behaviour, can have a strong impact on the resulting energy consumption. The scope of self-dependent responsibility is rather large, ranging from a deliberate renunciation of energy-intensive products orexaggerated mobility to an intelligent assortment of foods and transportation means. From an awareness thatold habits calling for “further, faster, and more” will not be sustainable in the long run, a change of values inthe industrial countries calling for “living better instead of having more” would have a considerable influenceon future energy demands.
energy-conscious way of life will pave the way for the success of energy-efficient technologies. On the other hand,each unit of energy saved makes saving any additional unit of energy more difficult. As we do not envisage a “zero-energy society”, the sustainable use of renewable energies is necessary. A more efficient use of energy sources andthe substitution of finite resources by renewables are two sides of the same coin. In a parallel development, thevalues in society must be reoriented away from the constantly growing consumption of goods to a more qualitativesatisfaction of consumer needs and a strengthened sensitivity towards the environment. Such a change does, howe-ver, need a long time. In particular, the ongoing globalisation of all kinds of activities, including consumer beha-viour and the strong focus on short-term economic successes, hinders such re-orientation. A large variety of “socialinnovations” is therefore required before being aware of how we treat natural resources becomes a matter of course.
The figure below outlines an ideal global energy supply scenario (SEE) where the four main sustainability problemsdiscussed above are approached. The starting point of such a development is the stabilisation of the present percapita energy consumption of 70 GJ/yr, whereby a significant growth of energy services and goods with a perma-nently growing energy productivity is still allowed. The modern industrialised countries (OECD) will halve theirenergy input to reduce the extremes in the discrepancies to be seen in world-wide energy consumption. This cut-back allows the per capita consumption in the developing countries to double, leading to a 75 % share of the pri-mary energy consumption (635 EJ) in 2050 – in line with their growing population. The mitigation of the othersustainability deficits requires that fossil fuel consumption be reduced by 50 % by the year 2050, the phasing out ofnuclear energy, and a transformation in the traditional use of biomass to an environmentally more friendly and
16
“modern” use of biomass. The contribution of new renewable energy technologies should therefore grow by a fac-tor 24 by the year 2050 at which time it will cover 75 % (470 EJ/a) of the world’s energy demand. While the techni-cal potential of renewable energy, even under stringent restrictions, is large enough to cover today’s world energydemand at least six times over, such a development is a tremendous challenge from a structural point of view asmobilising the new energy technologies in time requires that their current contribution be doubled about everyten years (equal to an average global growth rate of 6.4 % per year over 50 years). At the same time, energy sup-ply structures and energy-consuming appliances around the world must become much more efficient.
Scenarios of global energy supply take the strategies for sustainable energy supply into account in different ways.The main driving force for the growth of energy consumption is the continuous increase in the world’s grossdomestic product (GDP) which, according to most studies, amounts to between three and four times the currentGDP. Future energy consumption – which differs considerably amongst the scenarios – depends mainly on the developments in energy productivity.
Scenarios with a high increase in energy consumption are characterised by a long-term average growth rate forenergy productivity of about 1 % per year, whereas scenarios with significantly lower energy consumption assumean annual growth rate for the energy productivity of between 1.5 % and 2.2 % (factor 4). The German AdvisoryCouncil on Global Change also addressed this issue in its recent report on “World in Transition – Towards Sustain-able Energy Systems”. The council assumes a scenario with a dynamically growing world economy, resulting in anincrease of world GDP by a factor of six until 2050. Most of the increasing energy demand can however be compen-sated due to the growth of energy productivity of 1.5 % per year, so that this scenario is comparable with otherswith respect to the level of energy consumption. In nearly all the scenarios, renewable energy provides the majorshare of the energy supplied in 2050, its contribution ranging from 22 % in the WEC B scenario to 73 % in the SEEscenario. In absolute terms, renewables supply between 185 EJ/a (WEC B) and 614 EJ/a (WBGU), indicating that thecontribution of 470 EJ/a from renewables in the above mentioned “ideal” scenario is not necessarily an upper limit.
A high share of renewables alone does not ensure that all sustainability criteria will be fulfilled, but rather requiresin parallel a significant increase in energy productivity (see four ‘high-efficiency scenarios’ on the right hand sideof figure “Current scenarios for global primary energy consumption”). Doubling the energy consumption by theyear 2050 would result in enormous pressure on non-renewable energy resources in spite of the then high propor-tion of renewable energy. Climate-change targets cannot be met neither unless carbon sequestration and storageare included in the scenario strategy.
Idealised scenario of a sustainable global energy supply structure for the year 2050 with a considerable reduction of the major sustain-ability deficits (growth of population from 6 billion in 2000 to 9 billion in 2050)
Pr imary energy consumpt ion , EJ/a
Reg ions 2000 Regions 2050 Energy sources 2000 Energy sources 2050
196
122
32
70*
92
92
65
70
Source : N i tsch / DLR 2003 Idealised scenario of a sustainable global energy supply structure
Developing countries CIS, East Europe, Middle East
OECD* Mean per capita consumption, GJ/a
Modern renewables
Nuclear energy
Traditional biomass
Fossil energies
600
500
400
300
200
100
0
The WBGU scenario, for example, presupposes the sequestration and storage of about 200 billion tonnes of carbon(710 billion tonnes of CO2) between 2010 and 2100 in order to achieve the goal of “acceptable” CO2 concentrations.The sequestration rate reaches a maximum in 2050 (4.5 billion tonnes/year CO2) and then falls off steadily to zeroby the year 2100. The Shell scenarios also require CO2 sequestration and disposal. The beginnings of uniform actionby politics or society with regard to the further development of the energy economy towards greater sustainabilityat a global level are nevertheless already to be seen at the present time. The follow-up process of the Rio conferen-ce, the Kyoto protocol, and the path-paving efforts of the IPCC suggest that at least some harmonised policy actionsaiming at a sustainable energy economy can take place at a global level.
However, national economic and political interests still hinder the final implementation phase, as was demonstra-ted by the USA when they abandoned the global climate protection process during the 6th Conference of the Parties in The Hague in 2000. During the 2001 follow-up conference in Bonn, other countries like Japan, Russia,Australia, and Canada insisted on extensive concessions with respect to the treatment of CO2 sinks which wereaccepted to save the Kyoto protocol. The well-known potential for conflicts was also apparent everywhere duringthe Johannesburg world summit held in 2002. An agreement on mandatory targets for expanding renewable ener-gy was blocked by the USA and the G-77 group (currently including 140 developing countries), which was stronglyinfluenced by the OPEC-countries.
More positive signals are coming from Europe. The European Parliament as well as the European Commission arestimulating the discussion process and support is being given by certain important and pioneering decisions. Asearly as 1997 it was decided to double the share of renewables by the year 2010. The European Union’s Directiveon Renewables, which came into force in September 2001, specifies indicative targets for the contribution of renew-able energy to the electricity supply in each EU-member state so as to achieve an increase in the share of renew-ables in Europe from 14 % in 1997 to 22 % by the year 2010.
Based on the political responsibility towards future generations, the German Federal Government is, together withthe other EU member states, actively supporting the international processes aiming for global sustainable develop-
17
Pr imary energy, EJ/a
2000 WBGU Shell SCA WEC A3 WEC B Shell DAS RIGES SEE WEC C1 Factor 4
825 854
636 635597
431
1,0491,1211,169
423
compi led by DLR
Renewables Traditional biomass Nuclear energy
CoalNatural gas Oil
Current scenarios for the global primary energy consumption for the year 2050 for a growth in population to 9 or 10 billion people by theyear 2050 2. (Sources: WBGU 2003; WEC 1998; Shell 2001; Johannson 1993; Lovins/Hennicke 1999; Nitsch 2003.)
Current scenarios for global primary energy consumption
2 WBGU = Exemplary development path (2003); Shell: SCA = Spirit of the Coming Age, DAS = Dynamics as Usual (2001); WEC: A3 = Growth, B = Business as
Usual; C1 = Ecological priority scenario (1998); RIGES = Renewable intensive scenario (1993); Factor 4 = Revolution in efficient energy use (1999); SEE = Solar
Energy Economy.
1,200
1,000
800
600
400
200
0
ment. Complementing the Kyoto target (21 % reduction in the emissions of greenhouse gases by the year 2010), theGerman Government has set the target in its climate protection programme to reduce greenhouse gas emissions by40 % by 2020 (based on 1990 levels). Another long-term target of the German Government is to increase the shareof renewable energy to at least 50 % by 2050. Germany led the initiative to create the Johannesburg declaration“The Way forward on Renewable Energy”, in which some 100 countries agreed to establish ambitious targets forthe expansion of renewable energy. To this end, specific bilateral and multilateral co-operations shall be arrangedduring the World Summit on Renewable Energy to take place in Bonn in June 2004.
Renewable energy — guarantor of a sustainable energy supply
Although there are different opinions about the potential of efficiency enhancements in the energy sector andabout the feasibility of CO2 sequestration, all scenarios conclude that only a significant expansion of renewableenergies offers the chance to join a path of sustainable energy. Renewable energy is thus the only dependable guarantor for a future energy supply.
A distinguishing characteristic of using renewable energy is that minor components of the natural energy fluxesare temporarily withdrawn from the atmosphere and returned in form of lower-temperature heat after supplyingcertain energy services. The inexhaustible vigour of the sun is the ultimate source of this energy. The sun is agigantic fusion reactor which has been supplying abundant and safe energy to the earth for billions of years andwill continue to do so in future. All life on earth obtains its energy from the sun. Plants grow and synthesise bio-mass by using solar energy. The sun drives the weather, wind, and precipitation, thus creating the preconditionsfor wind power and hydropower. Solar thermal collectors, photovoltaic systems, and concentrating solar powersystems directly use solar irradiation without needing other media. Heat pumps make use of ambient energy fromthe air, water, and soil. Geothermal energy, a renewable source based on the radioactive decomposition takingplace at great depths in the earth, can be used as well.
For thousands of years, man relied exclusively on renewable sources of energy, however only at a very low level andwith low efficiency. Compared with our ancestors, we now have considerable advantages. Technologies are avail-able today which make renewable energy services possible at the same high level as fossil and nuclear sources. Theassociated costs are affordable as well if such techniques are applied on a large scale and if the possibilities existingfor reducing costs are exploited. Moreover, costs must always be judged in relation to the environmental and socialquality of the services provided, while also considering the external costs and damages that would result from apossible adherence to fossil and nuclear energy systems. After assessing all these considerations, we find that re-newable energies fulfil all essential requirements of a future sustainable energy supply system.
18
Economic efficiency
Security of supply Environmental concerns
Reachab le for RESAcceptable pricesEfficient Markets
Suppor ted by RESMarketstability and robustness
Geopolitical stability
Guaranteed by RESNature conservationClimate protection
No nuclear accidents
The energy triangle – all essential requirements of a sustainable energy supply system can be fulfilled by renewables, alreadytoday or in the future.
Renewable energy is characterised by a diversity of resources and technologies for the enormous power range from a few watts to hundreds of megawatts. Renewable energy can be adapted to any kind of energy service andbe closely inter-linked with conventional modern energy technologies to ensure security of supply at all times andat any location. Renewable energy technologies are compatible with modern supply systems which increasinglyrely e.g. on distributed generation and network integration, like in “virtual” power plants and district-heat supplysystems.
19
External costs — how to correctly determine the costs of energy
The environmental damage caused by energy conversion and energy use can, under certain circumstances,lead to considerable costs to the economy. Since these costs are not borne by the cause itself and are also notreflected in the market prices for electricity or heat, they are termed external costs. Such external effects lead to – in the language used by economists – a non-optimal allocation of scarce resources, that is to say that the envi-ronment is being overexploited.
The solution to the problem is simple in theory: the external effects have to be “internalised”. That is to saythat the costs attributable to the burdens on the environment have to be allocated to the cause such thatthe market prices include all the relevant costs associated with the product or services. This internalisationcan be realised by means of environmental tax, levied charges, trading with emission rights, and similar instru-ments. Unfortunately, putting theory into practice is not that simple. It presupposes the exact determination of thedamage to the environment and making an economic valuation of the damage. The complexity of the ecologicaland economical inter-relationships already suggests the difficulties encountered in this task. In order to establish acausal relationship between the burden on the environment, and additionally to assess the damage in any quanti-fiable terms, an attempt is made to describe the entire chain of effects attributable to a substance from its emis-sion, including transportation and conversion processes, right through to the effects on human beings or ecologicalsystems. In a large research project set up by the European Commission (ExternE – External Costs of Energy), appro-priate methods and models were developed to describe how pollutants behave in the environment and to modeltheir impacts. Despite the sometimes considerable uncertainties, models have been developed which allow quanti-tative estimates of the effects air pollutants have on materials (e.g. higher corrosion), on human health (from slightrespiratory symptoms through to higher mortality risks), or through the acidification and eutrophication of ecolo-gical systems.
Various studies in recent years have also attempted to estimate the damage caused by global climate chan-ge and the resulting costs. The uncertainties in estimating the costs of the damage from the greenhouseeffect are however very high, since the consequences are still partially unknown, so that it is not possible todefine a reliable monetary assessment of the damage. A ‘second-best’ method is therefore applied: Those costsare taken which must be expended to attain an emission reduction target – the so-called marginal avoidance costs.It must however be emphasised that these costs depend strongly on the conditions given by the particular energypolicy in place.
Environmental damage caused by generating electricity from fossil fuels is mainly caused by air pollutants and thegreenhouse gases, especially CO2, emitted by the power plant. The external costs are essentially determined by thehealth hazards, in particular due to increased concentrations of fine dust, some of which is directly emitted by thepower plant, but is also a result of the chemical conversion of sulphur dioxide (SO2) and of nitrogen oxides (NOx) toform sulphate and nitrate aerosols. Also, the higher concentrations of acidic and oxidising air pollutants can accele-rate corrosion of the surface of materials, shortening maintenance intervals. The resulting external costs are howe-ver relatively low compared to those from health effects. Due to the already low SO2 background pollution in Eu-rope, additional emissions of sulphur dioxide sometimes even has a fertilising effect and thus increase the yields ofagricultural products. Nevertheless, the additional depositions of sulphur and nitrogen lead to an increase in thearea where the critical loads for ecological systems are exceeded. An assessment based on avoidance costs showsthat besides the health damage and the greenhouse effect, acidification and eutrophication are among the mostdamaging effects of electricity generation.
The values currently available are “best estimates” from today’s point of view and should not be interpretedwithout considering the above-mentioned uncertainties and limitations of the methods used. For new lignite-fired power plants, the external costs are 3.8 Cent per kWh electricity; while external costs from hard coalfired power plants are 2.5 Cent/kWh, which is the same order of magnitude of current electricity generation costs.
On the other hand, intercontinental grids can effectively combine the different regional resources to give thenecessary redundancy for supply systems. Large centres of supply will evolve at sites with very abundant and thuscost-effective renewable energy resources for providing electricity and renewable hydrogen to the regions of highdemand, i.e. large urban areas in industrialised and developing countries, by means of high voltage direct current(HVDC) transmission as well as by pipelines. At the same time, such centres will become a regional nucleus of eco-nomic development and wealth, and will help to stabilise socio-economic structures. Most of those centres will beestablished in developing countries e.g. in North Africa, contributing considerably to the positive progress of ourdeveloping world. The basis of the above-mentioned idealised scenario “Solar Energy Economy” (SEE) is thus outli-ned. The resulting manifold primary energy structure is illustrated in figure “The idealised scenario SEE”. All ener-gy sources are represented in the 73 % covered by renewable energy (465 EJ/a) in the year 2050. The proportions ofthe individual technologies range from 6 % (hydropower) to up to 15 % (biomass, geothermal energy, solar-thermalpower stations) 3. Each according to its potential, the technologies employing solar energy (photovoltaic systems,solar-thermal power plants and collectors) provide the largest contributions of about 30 % together. Fossil-based pri-mary energy will continue to increase to about 370 EJ/a (coal 115 EJ/a, oil 160 EJ/a, natural gas 95 EJ/a) in the year2020, to fall again after the year 2030 to similar levels as today, and in the year 2050 they still constitute with
20
3 To better compare the renewables with the primary-energy contribution by fossil and nuclear types of energy and with one another (biomass, geothermal energy), they
are all shown here based on their thermal equivalent (substitution principle).
External costs of 1.1 Cent/kWh for gas-fired power plants – although considerably lower – cannot be neglected either. Comparing these costs with estimates for removing CO2 from the exhaust gases of fossil fired power plantsgives a cost increase in the same order of magnitude. CO2-free electricity from conventional power plants will thusbe more expensive than today’s electricity – reflecting the internalisation of the external damage costs.
The quantification of external costs from nuclear power plants is difficult, in particular due to the controversy onthe valuation of large accidents and the extremely long time horizon which needs to be addressed with respect toradioactive waste. External costs for nuclear energy thus very much depend on the assumptions taken.
Electricity generation from photovoltaic systems, wind, and hydropower is free of emissions. Environmentaldamage is practically only caused by the emissions from upstream process steps like e.g. producing the material ormanufacturing system components. The generation of electricity from wind and hydropower therefore leads to verylow external costs of 0.16 Cent/kWh (wind power plant with an output of 1 MW) or of 0.11 Cent/kWh (hydropowerstation of 3 MW). In the case of a photovoltaic system (5-kW roof installation), the currently still expensive manu-facturing processes, requiring large amounts of fossil energy carriers, causes the relatively high costs of 0.8 Cent/kWh.The type and magnitude of the emissions, determining the damages allocated to constructing the installations,result primarily from the fossil energy carriers used in the preceding processing stages. In contrast to fossil firedpower plants, the emissions of CO2 for renewable energy installations will decrease proportional to the increasingdegree of low carbon or carbon-free energy carriers used in the future energy supply system. In addition, the technical possibilities for improving the manufacturing processes of this very young technology are still large.
These comparisons make clear that in determining the most “cost-effective” energy supply today we areassuming inadequate prerequisites. Fossil and nuclear energy is more expensive than indicated by the economi-cal calculations. And they will become even more expensive in the future. In contrast, the costs of renewable energy are already telling the ecological truth today. These costs can become significantly less in the future becau-se of growing markets and the even greater technical advances being made. It is therefore only a question of timebefore energy from renewable energy sources will be more cost-favourable than energy from conventional sources.Therefore, those wanting to use cost-effective energy in future should invest in renewable energy today. And themore effectively the external costs are internalised, the sooner the fundamental changes necessary in the presentenergy supply system will become more attractive from the economical point of view. Energy policy is required toprovide an appropriate policy framework, and “guiding barriers” to ensure that besides the short-sighted way oflooking at the market, the longer-term perspectives of a sustainable economy are established as well. One examplefor a good approach into this direction is the ecological tax, which aims at an internalisation of environmentalexternalities. Also the German Renewable Energy Sources Act can be seen as giving an idea of the corrections already overdue in the price of energy. The feed-in tariffs guaranteed by the Renewable Energy Sources Act mightbe considered as a compensation for the external costs avoided due to the use of renewable energy sources.
170 EJ/a a share of 27 % of the total primary energy consumption. The scenario presented here characterised by asignificant expansion of renewable energy sources does of course only constitute one example for an energy supplysystem for the future. Other strategies for ways to meet the sustainability criteria (compare with the scenarios infigure “Current scenarios for the global primary energy consumption”), call for other efforts weighted differently,yet are generally even more sophisticated (e.g. capturing the CO2 from fossil energy with less efforts in efficiencyimprovements).
21
2000 2010 2020 2030 2040 2050
Spec i f ic energy costs Renewable energ ies :
— Young technologies, large potential for technological progress and cost
reduction
— Infinite, global availability
— No risk from misuse
— External costs are low
Foss i l und nuc lear energy :
— Limited resources, unbalanced regional availability
— Long term costs are expected to increase
— Expensive and high risk nuclear technologies (breeder technology) are required
to substitute fossil resources
— Potential for misuse and risks from nuclear technologies are high
— External costs: prohibitive in the long term for fossil fuels (climate change),
probably prohibitive for nuclear
external costs
fossil and nuclear energies
renewable energies
Development of costs for renewable and conventional energy sources
Renewable energy sources in the long run provide the cheapest energy.
Source : DLR
Globa l pr imary energy, EJ / yr
1980
325
Source : DLR
1990
379
2000
427
2010
475
2020
517
2030
560
2040
600
2050
635
The idealised scenario “Solar Energy Economy” (SEE)
Global primary energy consumption in the idealised scenario "SEE” with a balanced mobilisation of all renewables and a reduction offossil primary energy to half of the present amount by the year 2050.
600
700
500
400
300
200
100
0
Other renewables Geothermal (electricity, heat) Traditional biomass
Hydro
Natural gas
OilSolar thermal (electricity, heat) Wind
Nuclear energy CoalPhotovoltaics Modern biomass
22
The necessary changes in the global energy supply within the next half century can therefore only be successfullyinitiated when, at the very least, the majority of the global community of nations gets together and agrees onquick and effective action. As a next decisive step, the implementation of the Johannesburg Declaration during theWorld Summit on Renewable Energy which will take place in Bonn in June 2004, and an effective continuation ofthe Kyoto process beyond the goals of 2010, are therefore of the highest priority.
23
WIND POWER
––– Resource: Kinetic energy from the wind
––– Sites: World–wide, preferably coastal regions, and hilltops, as well as offshore instal-lations
––– Field of application: Electricity generation
––– Capacity: 0.05 kW to 5 MW per wind turbine, wind farms of 100 MW and more
––– Electricity costs today: 5,5 bis 13 Cent/kWh
––– Figures: Wind power station, Onshore wind park,Offshore wind park
L o w w i n d v e l o c i t y
H i g h w i n d v e l o c i t y
Wind power has been used by man from time imme-morial. Before the steam engine was invented, tradeacross the oceans was only possible by means of sailingvessels. Windmills ground grain and drove waterpumps for irrigation and drainage purposes. Therewere reportedly some 30,000 windmills still operatingat the turn of the last century in northern Germanyalone, and only when electricity became available andaffordable everywhere in Germany did the windmilldisappear from everyday life.
The first endeavours to revive this environmentally-friendly technology were undertaken in the fifties bysuch German pioneers as Hütter. However, it wasn’tuntil the oil crisis of the seventies, together with anincreasing awareness of the environment, which hel-ped to revive wind power in recent times.
Modern wind turbines utilise the lift principle ratherthan the resistance principle. Similar to the wing of anaircraft, the wind flow passing over the rotor blades ofthe wind turbine generates a lifting force, which makesthe rotor turn around. While only a maximum of 15 %of the wind energy can be transformed by applying theresistance principle, a yield of up to 60 % can be achie-ved by applying the lift principle. At their optimum,modern wind power stations already achieve an effi-ciency of 50 %; the average efficiency is 45 %. Modernwind turbines therefore already produce electricitywith an energy yield very close to the theoretical maxi-mum.
Depending on the wind velocity, it is possible to diffe-rentiate between four phases of operation. At verylow wind speed, the wind energy is not sufficient toovercome the system’s moments of friction and inertia,and the rotors remain stationary. Starting at a certainwind velocity – about 3 m/s depending on the design –the wind turbine will turn. In this phase, the poweroutput increases as a function of the wind speed to thepower of three, i.e. twice the wind velocity produceseight times the electrical power. If the wind velocityincreases further, then the maximum capacity of thegenerator will be approached, and the energy genera-tion has also reached its maximum. The surplus energyfrom a further increase in wind velocity must be bypas-sed. The maximum power of the system is thus deter-mined by the flow over the rotor area, and does notdepend on the number of rotor blades.
There are three different concepts for controllingpower output: In the case of stall-controlled systems,the rigidly fixed blades and the constant rotor speedstall above a certain wind velocity. In this case, therotor performance remains almost constant even if thewind velocity increases further. The straightforwarddesign of stall-controlled turbines resulted in its wide-
spread installation in the early years of wind energyuse. In the megawatt range, the blade-controlleddesign of turbines (also referred to as pitch control)dominates. In these systems the rotor blades can rotateabout their longitudinal axis and adjust to the relativewind conditions. As a result, the power output of therotor can remain constant after the rated power is rea-ched. Although pitch-controlled turbines are more com-plicated to construct, they achieve a better yield andthe thrust of the rotor on the tower and foundations islower than for stall-regulated turbines. The active-stall regulation is a compromise between pitch andstall. At low wind speeds, the blades are pitched like ina pitch-controlled wind turbine in order to achieve ahigher efficiency. When the wind turbine reaches therated capacity, the active stall-regulated turbine willpitch its blades in the opposite direction and stall.
During a gale (wind speed of about 24 – 26 m/s, this isequivalent to wind force 10), The mechanical load onthe rotors is too high. Pitch-controlled turbines andactive-stall systems are then taken off the grid and theentire rotor is turned out of the wind to protect theoverall turbine structure. The rotor spins with no load.Stall-regulated systems are halted aerodynamically withblade-tip brakes.
The specific characteristics of different wind turbinesare given by the manufacturer’s particular design.Some systems start running as of a very low wind velo-city and soon reach their nominal capacity. These sys-tems are well suited for regions with only moderateaverage wind speed, e.g. onshore sites favourably expo-sed to wind. In contrast, areas where strong winds pre-vail are more suitable for wind turbines which reachtheir nominal capacity at higher wind speed, and arethus capable of converting even strong wind into elec-tricity.
Wind turbine technology
While wind power in mechanical form is also used fordriving pumps in other regions of the world, wind tur-bines in Germany are used only for grid-connectedelectricity generation. The dynamic developments ofthe last 10 years resulted in some completely new con-cepts in design, control techniques, and in generatorengineering. As a consequence, the efficiency of windturbines was increased, and various qualitative impro-vements were introduced like e.g. improved grid inte-gration or reduced noise emissions.
Nearly all the wind turbines installed today have threerotor blades, since the mechanical loads are easier tocontrol with this design and because three-blade rotorsare considered by most people as optically more har-
24
WIND POWER — A STRONG UPWARDS TREND
monious than single or two-blade rotors. The bladesthemselves are usually made of glass-reinforced plasticsand are more than 50 metres long for large turbines.The rotor blades of the largest turbines currently availa-ble cover some 10,200 m2, an area almost as large astwo football pitches.
Depending on their rated capacity, modern large-sizerotors turn at 10 to 30 revolutions per minute. Sincecontrol and constancy of the power output are of majorimportance, particularly for large turbines, the numberof turbines with a variable rotor speed has increasedsignificantly in recent years. The operating point forthe greatest efficiency can be maintained over a largewind-velocity range by matching the speed to the rotoraerodynamics.
Gears are needed if the common four-pole type ofgenerator is used to transform the low rotor speed tothe required generator speed of 1,500 revolutions per
minute. The losses attributed to the gears are about 2 % per stage and, additionally, the gears are themsel-ves a source of noise emissions. Gearless systems donot have these problems, however they require special-ly manufactured multi-pole generators.
Generators can be realised with synchronous or asyn-chronous designs. The advantages of the asynchro-nous generator are in the relatively simple controlsystem construction and the possibility for direct con-nection to the grid. However, it is relatively inflexiblein adapting to the grid and does not allow continuousregulation of the rotor speed. A variant of the simpleasynchronous principle is the double-feed generatorwhere the current from the rotor in the asynchronousgenerator is regulated by an inverter. This principlemakes it possible to regulate the speed over a widerange. A comparable rotation-speed variability is givenby the synchronous generator in combination withan inverter. In stand-alone operation, the synchronous
25
Rotor with horizontal axis: noise emissions from a three blade rotor are lower
generator is able to establish and stabilise its own elec-trical grid.
The towers of the largest wind turbines today are morethan 120 metres high, so that together with the rotorblades the wind turbines reach a height of up to 170 m.As a rule: the higher the tower, the less interferencefrom air turbulence caused by ground roughness, andthe mean wind velocities are higher. The towers aregenerally realised as steel-jacketed constructions whichleast influence the surrounding countryside due totheir slim design. Positive experiences have been madewith painting the base of the tower in the predomi-nant colour of the surroundings, and the rest, higherup, with a non-reflecting colour (light grey).
Over the last 20 years, the technical development ofwind turbines concentrated mainly on realising everlarger constructions in order to optimally exploit thosesites where the wind conditions are most favourable,thereby triggering a phase of rapid technical progress.While the average capacity of wind turbines installedin 1987 was less than 50 kW, it has since increased bya factor greater than thirty to 1.5 MW in 2003. It is dif-ficult to predict today which capacity will represent thetechnical and economical optimum. The first wind tur-bine with a capacity of 4.5 MW was installed in 2002.The yield from such a system covers the electricitydemand of about 5,000 households.
There is still significant potential for further impro-ving wind turbines. This potential lies both in theindividual components and in optimising the system.Increased practical experience allows a further reduc-tion of building material. More slender rotor bladespromise to enhance the aerodynamics and thereby toincrease the efficiency. New control systems areexpected to reduce the mechanical loads on systemcomponents. Early warning detection of faults and
malfunctions can reduce maintenance and equipmentdowntimes. Intensive work is also dedicated to furtherminimise noise emissions.
Exploiting new offshore potential
Since suitable areas to further expand wind power onland are becoming scarce, work has already started todevelop the very large potential at sea (offshore).Wind parks operating offshore have a minimal impacton landscape and the environment. Additionally, thewind speed is considerably higher than on land, so thatthe electricity yield can be increased by up to 40 %over that from a good site near the coast on the main-land.
The potential for offshore wind power is considerable:in the long term it seems possible to install wind parkswith a total capacity of up to 25,000 MW along theGerman coast and in the Exclusive Economic Zone. Theannual yield is estimated at 85 to 100 TWh, which isequivalent to about 15 % of the present-day electri-city consumption in Germany. Prerequisites for explo-iting the large offshore wind potential are, however,sufficient underwater cable capacity and a suitableconnection to the national grid to be able to trans-port the electricity produced offshore.
In contrast to countries like Denmark and Sweden,appropriate offshore sites in Germany are characterisedby a considerable water depths and long distancesaway from the coast. When selecting a specific site,not only economic aspects but also environmentaland nature conservation and the interests of naviga-tion, of certain industries (like e.g. fishing, mineralresources) and military use have to be considered. Sinceoffshore installations represent a long-term intrusioninto the marine environment over a large area, andbecause the effects of offshore wind parks on the mari-ne environment are still uncertain, the expansion ofoffshore wind power should only proceed step by stepfollowing the precautionary principle.
Taking into account the various nature conservationconcerns, suitable areas for exploiting offshore windenergy have been identified in collaboration with seve-ral ministries of the German federal government. Anyfuture expansion pre-supposes a positive evaluationof the first installations with regard to their envi-ronmental and nature conservation compatibility.Within the Federal Nature Conservation Act, adopted1.2.2002, the German federal government has identi-fied areas in the so-called Exclusive Economic Zonewhich are to be protected as well as those deemed particularly suitable for wind power installations.
26
In Klettwitz (Brandenburg) one of the largest European windparks (38 turbines) was built on the top of mining wasteheaps.
Continuously lower costs
The average investment costs for wind turbines instal-led today are about 800 to 900 Euro/kW. Experienceshows, however, that this specific value normalised tothe wind turbine’s capacity – often used in energy eco-nomics – is not that meaningful in the context of windturbines, since the electricity yield of a wind turbinedoes not depend primarily on the size of the generator,but rather on the rotor area, the hub height, the con-trol system, and on various aerodynamic factors. Analternative characteristic value is to normalise theinvestment costs to the annual electricity yield.Between 1998 and 2001, the yield-based costs werereduced by almost 10 %.
In addition to the costs for the wind turbine itself,there are costs for the foundation, grid connection,access to the site, the land, and for planning andengineering services. The auxiliary investment costsamount to approximately 30 % of the costs for thewind turbine. The total project costs for a 1.5 MW windturbine thus amount to about 1.8 million Euro. Sincethe early eighties, the specific costs for wind turbineshave dropped to less than a third of the levels theyused to be (Figure: Development of costs for windpower turbines).
Considering the operation and maintenance costs, electricity generation costs are between 5.5 and 13 Cent/kWh, assuming typical average wind speeds of 5 to 6 m/s on the coast and 4 to 5 m/s (50 m abovethe ground) at good onshore sites (the RenewableEnergy Sources Act assumes a reference site with anaverage annual wind speed of 5.5 m/s at a height of 30 m above the ground).
Depending on the distance from the coast and thedepth of the water at the site, the additional invest-ments required for grid connection and foundation ofan offshore wind park amount to up to 200 % of thecosts for the wind turbines. Since the additional costsdepend in the first instance on the depth of the waterand the distance from the coast, and only to a lesserextent on the capacity of the wind turbine, offshorewind parks are planned to be as large as possible foreconomic reasons. Due to the high costs for grid con-nection, an offshore wind park will be much largerthan its counterpart on the mainland. A large potentialfor cost reduction, as experienced with onshore windinstallations, is expected with the large-scale introduc-tion of offshore wind power, so that the costs for elec-tricity generation from offshore wind parks will bereduced significantly in the long term.
Wind power and environmental protection
Related to the rapid growth of wind energy in Germany,there is also growing concern about the environmental
impacts of wind energy. This discussion, however, re-quires careful balancing of the advantages and dis-advantages of wind energy as compared to the alter-natives. In particular, the environmental damage avoi-ded elsewhere due to the use of wind energy must betaken into account. Environmental impacts from windturbines include noise emissions, the potential distur-bance of animals (in particular birds), and detraction of the landscape.
Noise emissions from modern wind turbines could bereduced significantly compared to early installations asa result of aerodynamic improvements, a more effectiveinsulation of the nacelle, and by avoiding certain com-ponents. Today, a sound power level of about 100 deci-bel is measured close to a typical modern wind turbine.At a distance of 50 m, the level is only 55 decibel –which is equivalent to a radio at a household noiselevel. At a distance of 500 m, which is the generallyrequired minimum distance from a residential area,the noise from the wind turbine is virtually inaudible.Often the natural rush of the wind is louder than thenoise emitted by a wind turbine. All wind turbinesmust comply with the stringent German technicalrequirements concerning noise (TA Lärm).
Many years of observation have shown that birds inflight will bypass a wind turbine during the day, and itis rare that a bird impact actually takes place. However,migratory birds, flying in the dark and in fog, someti-me collide with all sorts of obstacles – like a powerpole or a transmission mast – and can therefore fly intoa wind turbine as well. Moving rotor blades are detec-ted by birds through the changes in the air flow, sothat a wind turbine can usually be avoided even inpoor visibility. Nevertheless, wind turbines shouldobviously not be installed in the main routes of migra-tory birds, and neither should they be erected in natu-re conservation areas. Since a building license is neces-sary to build a wind turbine, compliance with suchrequirements is always reviewed as a part of the appro-
27
View from the nacelle
val process. Since 2001, a formal environmental impactassessment is required for wind parks with three ormore units.
The influence of wind turbines on the appearance ofthe countryside is assessed differently. Some peoplesee a detrimental change being made to the countrysi-de, whereas others consider a wind turbine a positiveasset to compliment our cultural landscape alreadymarked by man in other ways e.g. by the 200,000
power poles in Germany. Although the conflict bet-ween different subjective perceptions cannot be resol-ved, it might be easier to accept wind turbines by ta-king into account the related ecological benefits. Justone wind turbine with a capacity of 1.5 MW during itstechnical lifetime of 20 years prevents some 64,000 tonsof CO2 being emitted into the atmosphere. The contri-bution to conserving our resources is considerable aswell: a single 1.5-MW wind turbine can prevent morethan 80,000 tons of brown coal being consumed in
28
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
Spec i f ic insta l lat ion costs in Euro 2000 /kW ( inc lud ing costs for foundat ion , gr id connect ion etc . )
Source : DLR Development of costs for wind turbines: specific project costs in Euro
Specific costs of wind turbines decreased continuously
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 Year
3
6
9
12
15
18
21
24
TWh/a
0
Source : ISET / DLR Installed wind capacity
Wind energy in Germany – a vehement development
Annual installed capacity in MW Annual yield in TWh
3,500
3,000
2,500
2,000
1,500
1,000
500
0
MW
3,200
2,800
2,400
2,000
1,600
1,200
800
400
0
conventional power plants. Piled up, this quantity ofbrown coal would form a hill as high as the wind tur-bine itself (Figure: Equivalent power output). It is the-refore the task of the land use regulation authorities,and hence of the German federal states, to assess thevarious aspects of nature conservation and environ-mental protection, and thus to identify areas that aresuitable for building wind turbines, as well as areaswhich are not to be used for wind energy.
Even if future offshore wind parks produce electricityout of sight from the beach tourist, the operation ofthese installations is still associated with certain effectson nature which cannot be completely avoidedthrough technical measures. The ecological monito-ring being carried out at the first offshore pilot plantswill help to better understand the influences on mi-gratory birds or the effects of low-frequency noiseemissions on marine fauna. In accordance with theGerman Marine Facilities Ordinance §2a, specific areasthat are suitable for offshore wind parks shall beidentified. Following the idea of a step-by-step exploi-tation of the offshore wind energy potential, the Ger-man federal government has, in the meantime, identi-fied the first low-conflict areas on the basis of the datacurrently available. These areas are classified as beingparticularly suitable for the start-up and the first ex-pansion phases under current conditions. Areas inside“Important Bird Areas” are principally not suitable forsetting up wind parks. Wind turbines are also not allo-wed in areas meeting the status requirements of a de facto bird protection area.
Wind power in Germany
The installed wind capacity in Germany has been gro-wing considerably for years now. New wind turbineswith a capacity of 2,645 MW were installed in 2003,thereby increasing the number of wind power stationsto some 15,400 installations with a total installed capa-city of 14,600 MW by the end of 2003. With a totalelectricity yield of 18.5 TWh, wind power now provi-des some 3 % of the electricity generated in Germany,which is equivalent to a reduction of CO2 emissions ofabout 15 million tons.
There is no country in the world with more windturbines than Germany (Figure: Installed wind capaci-ty). More than half of the installed capacity is in thewind-rich coastal states. The state of Schleswig-Holsteincan thus cover almost one fourth of its electricitydemand from wind turbines. Nevertheless, thanks tothe technical developments made in recent years, theuse of wind power has also increased in inland regions.The expansion to more and more inland sites doeshowever lead to higher electricity generation costs aswell. This situation was taken into account in theRenewable Energy Sources Act by introducing a diffe-rentiated reimbursement scheme.
Potentially, onshore wind turbines in Germany couldgenerate ca 50 TWh of electricity per year, about 10 %of Germany’s electricity demand. The potential forGermany’s offshore wind parks is estimated to be ashigh as 110 TWh per year. Thus, in total, about 30 % ofthe current gross electricity generation could be delive-red by wind power.
29
Cumulated electricity production during a wind tubine’s life-time avoids burning coal in a conventional power plant. Piledup, this quantity of brown coal would form a hill as high as thewind turbine itself.
30
HYDROPOWER
––– Resources: Kinetic energy and water pressure
––– Sites: High- and medium-altitude mountains, rivers, streams
––– Field of application: Electricity generation, energy storage
––– Capacity: Storage and run-of-river power stations up to 5,000 MW, Small-scale hydropower stations up to 1 MW
––– Electricity costs today: Storage and run-of-river power stations: between 3 and 10 Cent/kWh, Small-scale hydropower stations: between 10 and 25 Cent/kWh
––– Figures: Storage power plant, run-of-river-plant, small-scale hydropower plant
C u r r e n t T u r b i n e
Hydropower was already used in preindustrial times fordriving mills, sawmills, and hammer works. Both thekinetic energy and the potential energy from flowingwater can be converted into mechanical power by aturbine wheel, which in turn can drive machines orgenerators. Today, hydropower is used almost exclusive-ly for generating electricity in Germany.
Hydropower is a mature technology which, world-wide,generates the second largest share of energy from rene-wable sources, after the traditional use of biomass. 17 % of the electricity consumed in the world todayis generated by hydroelectric power stations! Of allthe sources of renewable energy, hydropower still provi-des the largest contribution to the generation of electri-city in Germany today. The proportion of the total elec-tricity production attributed to water power is about3.5 %.
Almost 90 % of the electricity from hydropower is gene-rated in Bavaria and Baden-Württemberg, because thebase of the Alps provides favourable slopes in these sta-tes. There are currently some 5,500 small-scale hydro-power stations, each with a capacity of less than 1 MW,in operation in Germany today, the majority of whichare being operated by small companies and individuals.The contribution from these stations is, however, rela-tively small. More than 90 % of the electricity fromhydropower comes from the ca 400 hydroelectricpower stations with a capacity of more than 1 MW,which are mainly operated by the utility companies.
There are different types of turbines with differentareas of application, depending on the flow rate andthe head (pressure) of the water.
The Kaplan water turbine functions like a marinescrew propeller on a vertically suspended axle. Bothrunner blades and distributor are adjustable and canbe optimally adapted to the flow conditions. The waterflows along the axis through the runner. A variation ofthe Kaplan water turbine is the tubular turbine inwhich the axis of rotation is horizontal. Kaplan andtubular turbines are used for low heads and high flowrates.
The conventional Francis water turbine is one of theoldest types of turbines and is still mainly being usedin small-scale hydropower plants. Typical for the Fran-cis turbine is the spiral-shaped housing. It is used forsmall heads and medium flow rates. Only the distribu-tor is adjustable with this type of turbine. The waterflows radially into the runner and exits along the axisof rotation. Special forms of the Francis turbine canalso be used for large heads and high flow rates.
The Pelton turbine is suitable for large heads and lowflow rates. After passing through a penstock, the wateris injected at a high rate through the nozzles onto thepaddles of the turbine.
Direct flow turbines are used in the case of low headand low flow rates, with a low rate of power produc-tion. The water passes through the running wheel at atangent.
Storage power plants
Storage power stations utilise the large heights of falland the storage capacity of dams and mountain lakesfor electricity generation. In the case of a dam-type sto-rage power station, Kaplan or Francis turbines are com-monly used and these are usually located at the base ofthe masonry dam. In the case of a mountain-lake stora-ge power station, a lake at a higher altitude is connec-ted by pressure pipes to a power station located in thevalley. Pelton-type turbines are normally used in thiscase due to the very high water pressure. Storage-typepower stations can be used both for meeting the elec-trical base load as well as for peak-load operation.
31
WATER POWER — ESTABLISHED BUT STILL MODERN
Total hydropower potential: 25.5 TWh/aSource : G iesecke 2002
Hydropower potential
Potential for using hydropower in Germany
Pump storage power stations are not fed by naturallyaccumulating water, but rather are filled by pumpingwater up from the valley. In this way the electricalpower generated in low-load times can be stored inter-mediately through the potential energy of the water, tobe used from a turbine during peak-load times.
Run-of-river power plants
Run-of-river power stations use the flow of a river or acanal to generate electricity. Characteristic here is thelow head for a relatively large volume of water, whichoften fluctuates seasonally. For economic reasons, thesekinds of power stations are often built in combinationwith sluices. Run-of-river power stations mainly use aKaplan turbine, tubular turbine, or direct flow turbine.
Small-scale hydropower plants
Besides modernising large run-of-river power stations,there is also a certain development potential in small-scale power stations. This case is particularly true formodernising and reactivating existing plants whichhave regained economic viability due to the supportgranted by the Renewable Energy Sources Act and sub-sidies for investments. However, environmental protec-tion and the ecological requirements of the watersystem must also be considered. Small scale hydroelec-tric plants can be either run as a stand-alone applica-tion or connected to the grid. From the technical pointof view, such plants are also storage or run-of-riverplants with a small capacity because of the lower headsor flow rates, and which therefore use only Pelton-,Francis-, or direct-flow turbines.
32
Example and principle of a run-of-river power plant
Principle of a run-of-river power plantSource : ExpoStadt
Headwater
Generator
Kaplan-turbine
Underf low
Example and principle of a dam storage power plant
Source : Werksfoto Tauernkraf t / Verbund
Reservoir
Pressure pipe
Power houseDam
Principle of a storage power plant
Investment costs for new and reactivated small–scale hydropower stations as a function of the installed capacity.
The costs of a hydroelectric power station are determi-ned mainly by the installed capacity and local condi-tions like, for example, the height of fall. New small-scale hydropower plants with a capacity of 70 to 1,000kW cost between 8,500 and 10,000 Euro/kW. The costof generating electricity in such a plant are between 10and 20 Cent/kWh for the typical 4,000 to 5,000 full-load hours per year. As costs decrease with increasingcapacity, the specific investment costs for a large hydro-power station (10 to 100 MW) are between 2,000 and4,000 Euro/kW, resulting in electricity generation costsof 4.5 to 10 Cent/kWh. When reactivating or moderni-sing existing plants, electricity costs of as low as 2.5 to6.6 Cent/kWh can be realised.
Ecologically compatible expansion
In 2003 a total of 20.4 TWh were generated fromhydropower plants in Germany with an installed capa-city of about 4,600 MW (excluding pump storage
power plants). Even though the existing potential forhydropower in Germany is not yet completely exploi-ted, further expansion is only possible to a limitedextent. Operating a hydropower station is always associ-ated with a serious intrusion into ecological systems.
Aspects of nature protection have to be taken into con-sideration before furthering the use of hydropower.Modernising or expanding existing hydropower sta-tions, while meeting ecological requirements, canhowever help to activate a significant part of the rene-wable energy potential. By realising appropriate ecolo-gical compensation measures like e.g. setting up sepa-rate migration routes for fish, the ecological conditionof the water body can even be improved. Even newpower plants can contribute to improving the ecologi-cal quality in sections of rivers which have already beendisrupted. Through the expansion and modernisationof existing hydroelectric power stations alone, an addi-tional potential of more than 2 TWh/year can be ex-ploited in an ecologically compatible way.
33
0 100 200 300 400 500 600 700 800 900 1,000 Insta l led capac i ty in kW
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Investment costs in Euro/kW
Source : IÖW / ISET Investment cost for small–scale hydropower stations
New construction
Revitalisation
Modernisation
34
PHOTOVOLTAIC SYSTEMS
––– Resources: Direct sunlight and diffused solar radiation
––– Sites: Everywhere, especially on roofs and facades
––– Field of application: Electricity generation
––– Capacity: A few watts to several MW
––– Electricity costs today: 50 to 80 Cent/kWh (Central Europe),30 to 50 Cent/kWh (North Africa)
––– Figures: Photovoltaik façade, Solar power plant, Grid-connected system
+–
n - t y p e s e m i c o n d u c t o r p - t y p e s e m i c o n d u c t o r
C o n t a c t
S o l a r i r r a d i a t i o n
Solar cells directly convert sunlight into electricalpower without any mechanical, thermal, or chemicalintermediate steps. At the core of all solar cells is asemiconducting material, usually silicon. Solar cells uti-lise the photovoltaic effect: for certain arrangements ofsuperimposed semiconductor layers, free positive andnegative charges are generated under the influence oflight (photons). These charges can then be separated byan electrical field and flow as electrons through anelectrical conductor. The direct current thus generatedcan be used for powering electrical devices or stored inbatteries. It can also be transformed into alternatingcurrent and fed into the national grid.
From milliwatts to megawatts: a dynamic market
There are solar cells in all conceivable sizes. Miniaturecells can be found in pocket calculators and wristwat-ches. In the kilowatt range, whole households can besupplied with power from solar cells. Put together insolar fields, solar cells have recently entered the mega-watt range. Although there is less sunshine in Germanythan in more southern countries, photovoltaic systemsare also useful at our latitudes since solar cells can alsoconvert diffuse solar radiation into electrical power.The annual average of solar radiation is higher in thesouth than in the north of Germany (Figure: Distribu-tion of global radiation), amounting to between 900and 1,200 kWh of incident energy per square metereach year. A modern solar cell can convert, on the ave-rage, one tenth of this solar energy into electricity.
There is no lack of space either: In Germany there is a total of 2,300 km2 on roofs and facades of buildingsand at other locations in developed areas which is available for solar-technical utilisation. Assuming thatthis area is equally divided between photovoltaic sys-tems and solar collectors, then 105 TWh of electricitycould be produced each year from solar cells – nearlyone fourth of the current electricity consumption inGermany.
Solar cells with a capacity of 400 MW were installedworld-wide in 2001 – 40 % more than in the previousyear. The volume of the German photovoltaic marketrose from 0.6 MWp/a to 80 MWp/a in the period from1990 to 2001. With a total capacity of approximately400 MWp (end of 2003), Germany is the second largestmarket after Japan for photovoltaic systems.
During recent years we could not only observe a dra-stic increase in demand for photovoltaic systems,but also a significant reduction of costs. The costs fora PV system now are about half of what they were in
the early nineties. The investment in a roof-installedsystem on a house today costs about 6,500 Euro perkilowatt of installed capacity, while larger systems aresomewhat cheaper at about 5,000 Euro per kilowatt.Whereas electricity from photovoltaic systems costabout 1.5 Euro/kWh in 1985, the electricity gene-ration costs in Central Europe today are between 0.50 Euro/kWh for large grid-connected generators and0.75 Euro/kWh for decentralised small-scale systems,depending on the particular application and techno-logy.
Considerable cost reduction is expected in the future aswell. It is assumed that present-day costs will be halvedby the year 2010, especially as a result of significantlyincreased series-production volumes. Improved materi-als yield – today a large proportion of the semiconduc-tor material is lost by sawing the wafers and duringother processing steps – and higher efficiencies willhelp to lower the costs associated with this innovativesource of electricity.
35
PHOTOVOLTAIC SYSTEMS — SOLAR POWER EVERYWHERE
Source : Deutscher Wetterd ienst
Schleswig
Hamburg
Bremen
Osnabrück
Essen
Köln
Bonn
Frankfurt/M.
KasselHalle
Leipzig
Weimar
Dresden
Chemnitz
Berlin
Neubrandenburg
Wittenberg
Schwerin
Rostock
Nürnberg
Stuttgart
MünchenFreiburg
Saarbrücken
Hannover Magdeburg
Ulm
Aachen
Annual average solar irradiation in kWh/m2
Distribution of global radiation
900 – 950
951 – 1,000
1,001 – 1,050
1,051 – 1,100
1,101 – 1,150
1,151 – 1,200
In the meantime, many different kinds of semiconduc-tor materials are available for making solar cells.However, silicon is still the most important element.Silicon is produced in three variations:
––– Very pure mono-crystalline silicon is expensivedue to its complicated manufacturing process, but itenables the highest conversion efficiencies;
––– Poly-crystalline silicon is more simple and chea-per to produce. However, the lower purity of the mate-rial leads to a somewhat lower efficiency, which in turnrequires larger areas and frames for the same electrici-ty production;
––– The thin-film cells from amorphous silicon areeven cheaper to produce. Both the efficiency and thelifetime are however much lower than for crystallinecells, a fact which largely compensates the cost advan-tages.
Besides silicon there is a variety of other materials andcombinations of material being developed and under-going testing. Considerable cost reductions are expec-ted especially in the field of thin-film technology,where considerably less material is needed than for cry-stalline cells. Besides amorphous silicon, the most im-portant materials for solar cells are e.g. gallium arse-nide (GaAs), germanium (Ge), cadmium telluride (CdTe)and copper indium diselenide (CIS). A very promisingconcept for the future is that of the so-called tandemcell, in which several semiconductor materials are com-bined in such a way that a larger range of the irradia-ted sunlight spectrum can be converted. Laboratory-scale cells with a combination of gallium arsenide andgallium antimonide, measured under concentratedlight, have achieved efficiencies that are significantlyhigher than those of the basic solar cell.
Grid-connected systems
A typical system consists of a solar generator integratedinto the roof or the façade of a building. The generatorprovides direct current power when irradiated, which istransformed into alternating current by means of a cur-rent inverter, and can then be used directly by dome-stic appliances or fed into the grid. While the capacityof a typical domestic solar installation is between 2 and5 kWp, large-scale systems like that on the roof of thenew exhibition buildings in Munich have a capacity ofmore than 2 MWp. Large solar parks in open meadowsare, however, a controversial issue because they occupyadditional ground space. Current legislation is targetedtowards supporting large-scale solar systems only indeveloped areas, where the ground is already covered,or restricting them to re-naturalised farmland no lon-ger being used for agriculture.
In 1999, the German federal government introducedthe 100,000-roof programme to encourage the marketintroduction of photovoltaic systems by providing low-interest loans. Together with the financial support fromthe Renewable Energy Sources Act, which regulates thefeeding-in of electricity from renewable sources intothe grid, this programme led to a considerable boost inthe demand for photovoltaic systems: it was thus possi-ble to increase the installed photovoltaic capacity bet-ween the years 2000 and 2002 by almost 400 %. Withan installed capacity of more than 300 MW, the targetof the 100,000-roof programme has now been reached.To continue stimulating the cost reduction for photo-voltaic systems, the financial support for new systemsby the Renewable Energy Sources Act is decreased gra-dually by 5 % each year.
36
1985 1990 1995 2000 2005 2010
800
700
600
500
400
300
200
100
0
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
Insta l led power (MW p ) E lectr ic i ty costs (Euro/kWh)
Source : DLR Market developments
Electricity costs
Installed power
Expected development
Market development in Germany, costs of electricity generation from PV
Small-scale stand-alone systems
A further major application of photovoltaic systems aresmall-scale systems not connected to the grid, used e.g.for supplying power to remote radio and measurementstations, emergency call boxes, garden sheds, and ca-bins. An inverter may be needed, depending on whet-her the devices require direct current or alternatingcurrent. A battery and a charge controller are usuallyalso necessary in order to bridge fluctuations in theirradiation as well as to provide electric power fromsolar energy at night.
In developing countries, where the utility grids are notyet satisfactory, photovoltaic systems are already suc-cessfully powering individual houses (solar home sys-tems), supplying villages with power, or used for pum-
ping systems. In many cases, the fuel-independent andlow-maintenance PV-systems represent the most appro-priate and often also the most economical solution fordecentralised small-scale applications that are far fromthe grid.
Worthwhile from an ecological point of view
Solar cells have no chimney: there are no emissions, nofuel consumption, and no noise associated with electri-city generation. The production of conventional solarcells is, however, still an energy-intensive process. Thecells must operate for between two and five years toproduce the amount of electricity which was consumedin manufacturing the cell. Each kilowatt-hour after-wards, however, is “free” from the ecological viewpoint
37
Principle of a grid-connected PV-house supply system
Principle of grid-connected photovoltaic systemsSources : P i lk ington So lar Internat iona l GmbH; ExpoStadt
PV-generator
Principle of a stand-alone system
Small-scale, grid-independent systemSources : Fraunhofer ISE , Fre iburg
Controller
Battery
PV-so lar generator
Own consumpt ion
Inverter
Own consumption
Publ ic gr id
Electric meter
(refer also to the Chapter “Ecological qualities of rene-wable energies”).
Producing the photovoltaic cells indirectly affects theenvironment if the required energy is provided by theconventional power plant mix. There are, however, twoaspects to be considered: On the one hand, these emis-sions are a problem of the present energy system andnot a problem of a future energy system. If the energy
for producing the solar cells had also been generatedby solar cells, then there would not be any of theseemissions. On the other hand, the reduction potentialis immense. The “ecological backpacks” of solar cellscan be reduced even further – not only through advan-ced technologies and series manufacturing – but alsothrough the expected future transition to less material-intensive processes.
38
39
SOLAR THERMAL POWER PLANTS
––– Resources: Direct solar irradiation, possibly with storage system; hybrid operation with fossil and bio-fuels also possible
––– Sites: Arid regions in southern Europe, North Africa, the Arabian Peninsula, and North America (“Sun Belt” of the Earth), Chile, South Africa, Mongolia
––– Field of application: Electricity generation, combined heat, and power generation
––– Capacity: Paraboloid approximately 10 kW per module; tower, trough, 5 to 200 MW
––– Electricity costs today: Solar only: 9 to 16 Cent/kWh, hybrid: 3 to 8 Cent/kWh
––– Figures: Parabolic dish, solar tower and parabolic trough power plants
Solar co l lector
Thermal storageFue l
Power mach ine (e lectr ic i ty / heat)
40
Solar-thermal power plants use the high-temperatureheat from concentrating solar collectors to drive con-ventional types of engines. The plants generate electri-city or coupled heat and power, which is when bothelectric power and process heat are generated at thesame time. In this way, a solar-thermal power plant cansimultaneously produce electricity, provide cooling bymeans of an absorption chiller, generate industrial pro-cessing steam, and produce drinking water with a sea-water desalination plant, thereby converting as muchas 85 % of the absorbed solar heat into useful energy.
Efficient thermal storage of the generated solar heatand the additional firing of fuel is indispensable inorder for the power plant to continuously meet theload. The power plants can be used in two ways:during the day as a solar power plant and during thenight as part of the conventional power system. Notonly is the overall fuel consumption reduced in thisway, the construction of conventional back-up powerplants also becomes unnecessary. Thus the benefits tothe environment are two-fold and the costs of genera-ting electricity can be halved compared to purely solaroperation. Thermal storage reservoirs are already tech-nically feasible today and will be first included in asolar power plant in Spain in 2006. With the thermalreservoir, the solar power plant can be operatedaround the clock 100 % in the solar mode – directlyfrom the collector field during the day, and at nightfrom the heat reservoirs which were replenished withsolar heat during the day. Suitable sites for these plantsare mainly located in the hot and dry regions of theworld south of the 40th latitude, because only the direct
share of the radiated sunshine can be concentrated bymirrors. The high proportion of diffuse irradiation andthe overall lower radiation levels hinders their econo-mic feasibility at northern latitudes.
Five types of solar thermal power plants have been realised so far:
Parabolic trough power plants
This concept involves using parabolic mirrors – up to 6 meters across and 100 meters long – to concentratesunlight onto an absorber pipe, which is thereby hea-ted up to about 400 °C. The absorber pipe is insulatedto prevent heat losses with selective coatings and anevacuated glass tube. The absorbed heat is transferredby thermal oil flowing through the tube and is used toproduce steam after passing a heat exchanger. Thissteam then drives a conventional steam turbine genera-tor system. Integration in the steam section of a mo-dern combined cycle power plant is also possible, butthe solar contribution is then limited. Major compo-nents such as the mirror units and the absorber pipesare of German manufacture.
Steam generating stations with solar trough collectorshave been operating in California since the mid-eigh-ties. A total capacity of 354 MW has been installed,with individual systems rated up to 80 MW. A peak effi-ciency of more than 21 % for the conversion of solarradiation into alternating current has already beendemonstrated during operation. Since their commissio-
SOLAR THERMAL POWER PLANTS — AN INSIDERS’ TIP FOR CLIMATE PROTECTION
Source : DLR
Concentrated irradiation Air, 1,000 °C, 15 bar
Air, 400 °C, 15 bar
AbsorberWindow
Pressure vessel
Pressurised volumetric receiver (REFOS): air at high pressure is heated up to 1,000 °C to drive a gasturbine ora combined cycle power plant.
Principle of a compressed–air absorber
41
ning, these plants have been supplying some 150,000households with electrical power every year and havealready realised revenues exceeding one billion US$.
Current research work being conducted in this field ison lowering the costs by improving the structure ofthese collectors, optimising the operational strategy,and dispensing with the intermediate thermal oil circu-it by generating the steam directly in the absorberpipes. A new parabolic trough collector (SKALET) deve-loped in Germany started operation at one of theCalifornian power plants in April 2003.
Solar tower power plants
In a solar tower power plant, the solar radiation is con-centrated by a field of individually tracking mirrors(heliostats) onto the top of the tower. Temperatures of1000 °C and more can be achieved with this concept.An absorber at the top of the tower converts the raysinto heat, which is then delivered to a conventionalpower plant process by a heat-transfer medium.
The 10-MW experimental plant Solar Two in Barstow,California, uses a pipe-bank heat exchanger as theabsorber and molten salt as the heat-transfer medium.One advantage here is the good energy storage capaci-ty of molten salt which, by using two storage tanks, canbe used for both day and night operation. One draw-back, however, is the danger of local overheating in theabsorber pipes. Furthermore, the salt can solidify atsome points in the system.
The German concept ‘PHOEBUS’ uses a metallic spongeinstead of the pipe-bank absorber. The sponge is alsoreferred to as a volumetric absorber, since the incidentradiation can be absorbed both at the surface and inthe interior of the wire mesh to be converted into heat.
Outside air is sucked through the sponge into the inte-rior and is thereby heated to temperatures as high as800 °C. It is subsequently used to generate steam in aconventional power plant. The advantage over pipe-bank absorbers is that the heat does not have to passthrough a wall, allowing higher energy-flow densities,operating temperatures, and efficiencies. In the earlynineties, a prototype was successfully tested at thePlataforma Solar in Almeria, Spain. A new developmentis the sealed or pressure-charged volumetric receiver(REFOS concept). The compressed air from the compres-sor stage of a gas turbine is heated in this absorber bysolar energy and then drives the turbine. The principlewas successfully applied to generate electricity for thefirst time at the end of 2002 at the Plataforma Solar inSpain. A pilot plant for the combined generation ofelectricity and cooling by absorption is currently beingmanufactured for a semi-commercial application inItaly. With this technology, it is also possible to channelsolar energy directly into a modern, high-efficiency gasand steam turbine power plant where it is convertedinto electricity with a high degree of efficiency excee-ding 50 %.
Parabolic dish power plants
With a typical output of several tens of kW’s, parabolicdish power plants are particularly suitable for decentra-lised use. This concept involves a parabolic mirrorwhich tracks the sun using two axes and concentratesthe solar energy directly onto an absorber suspended atthe focal point of the mirror. In this way, a working gas(helium or air) is heated by this mirror to temperaturesof up to 900 °C, and can then drive a Stirling engine ora gas turbine located directly next to the absorber.
Paraboloid power plants have successfully demonstra-ted their technical maturity during many years of test
Structurally improved European concentrating solar trough col-lector SKALET under-going testing at one of the solar powerplants in Kramer Junction, USA
Solar tower power plant in Barstow, California
operation and, with values of up to 30 %, have realisedthe overall best proven solar-electrical efficiencies. Thenext step is to realise series production of these plantsand thereby to lower their costs.
This type of power plant is especially suitable for provi-ding villages in the developing countries with power.Several parabolic dish stations can be linked togetherto give a small power plant farm. In combination withbiomass combustion or a storage system, operationaround the clock is also possible.
Solar chimney power plants
In the solar chimney power plant, the sun heats the airunder a large collector roof made of glass or plasticfoil. The warm air flows to a chimney located in themiddle of the collector roof where it then ascends. Theascent of hot air drives the wind turbines installed atthe base of the chimney, generating electricity. Threewell-known physical effects are thus combined:
1. The greenhouse effect, causing the air under theglass roof to heat up.
2. The chimney effect, causing the air heated under theglass roof to ascend through the chimney.
3. The turbine, which removes energy from the air flo-wing in the chimney and converts it into electricalenergy through a generator.
Upwind power plants function solely with air and donot need any cooling water. This fact is a major advan-tage in many sun-rich countries which already haveserious problems with water supply. Since, unlike theplants described above, the solar irradiation is not con-centrated, diffuse radiant energy can also heat the air
underneath the glass roof. The power plant can there-fore operate even when the skies are partly or comple-tely overcast. Additionally, the ground underneath thecollector can serve as a natural heat storage mediumand hence ensure uniform electricity generation. Theheat stored during the day is released at night so thatelectricity can still be generated after sunset.
The technical feasibility of this concept has alreadybeen demonstrated in a Spanish experimental powerplant over many years of operation. There are currentlyseveral projects being developed for large-scale chim-ney power plants. The greatest progress has been madeby a project in Australia where a 200-MW plant with a1,000-meter-high chimney and a collector diameter ofbetween 6 and 7 km is planned.
Fresnel concentrators
In the beginning of 2001, a collector design was pres-ented in which the concentrator consists of individualpanes of flat mirrored glass. Since the light concentra-tion of this system is weaker than for a solar troughsystem, a second concentrator is installed above theabsorber pipe to concentrate the light a second time.Water is directly evaporated in the absorber pipe. Thesystem is characterised by a simple and cost-effectiveconstruction and can be expanded to several 100 MW’s.A prototype for steam generation has been operatingfor several years and successfully tested. The next stepis to realise a fully functional, semi-commercial pilotplant for electricity generation.
The costs of solar-thermal power plants
The costs for the solar collectors are primarily due tothe initial investments. It is like purchasing and storingall the fuel required for the entire operational phase ofa power plant at the beginning of the project. Theinvestments also incur taxes, interest, and insurancepremiums, whereas fossil fuel must only be purchasedas required, and is in many countries not only tax-freebut subsidised as well. The economic starting positionfor solar electricity is thus extremely unfavourable. Inparticular, solar electricity is generally more expensivethan electricity from conventional power plants due tothe currently low price of fossil fuels. The FederalMinistry for the Environment, Nature Conservation,and Nuclear Safety (BMU) has therefore, together withthe German Kreditanstalt für Wiederaufbau, the UnitedNations Environment Programme (UNEP), and theGlobal Environmental Facility (GEF), launched a marke-ting initiative for solar thermal power plants in orderto introduce and promote the necessary financial andtechnical steps on an international level.
Well-located solar thermal power plants can operate forabout 2,000 to 3,000 hours per year in the purely solar
42
Tower of the planned 200-MW solar chimney power plant (height1,000 m, with special spoked wheels for support), Below: thecollector roof (diameter 6 km)
43
mode without an energy storage medium, resulting inpresent-day electricity generation costs between 9 and16 Cent/kWh. These costs can be halved within thecoming decade if the existing cost-reduction potentialof the pending global market introduction is realised.
Dual operation, i.e. with additional fuel combustion,leads to a better utilisation of the thermal engine, sinceit can operate for more hours in this way, and consider-ably improves its ability to compete with conventionallyoperated power plants. Depending on the proportionof additional firing required and on the fuel prices, thecosts for generating electricity can be as much as 50 %
lower than for purely solar operation as illustrated inthe figure below. In this way, costs for electricity gene-ration can already be reached today which – withoutfinancial support – are only a few Cents higher thanthose from conventional power plants.
Energy storage increases the solar proportion of thepower plant, and also enhances the operational beha-viour, enable a higher utilisation of the power plantblock, and improve the revenue situation. In the frame-work of feed-in legislation in Spain, a first solar-thermalpower plant is planned to start operation in Andalusiaas of 2006, providing electricity for about 16 Cent/kWh.
Parabolic-dish with Stirling engine, operated at the Plataformade Almeria, Spain. Parabolic power plants have realised theoverall best proven solar-electrical efficiencies with values ofup to 30 %.
Collector system of a Fresnel system. Below: the mirror sectionsof the Fresnel reflector, Above: the absorber pipe at the centreof the secondary-stage concentrator. One collector branch is 24 m wide and can be as long as 1 km in the power plant version.
1980 1990 2000 2010 2020 2030 2040
0,50
0,40
0,30
0,20
0,10
0
Euro/kWh
Source : DLR
Expected development of electricity generation costs from solar thermal power plants (8 % discount rate, technical lifetime of 25 years,solar irradiation of 2,300 kWh/m2a.
Cost development for electricity from solar-thermal power plants
Parabolic trough
Solar tower
Dish-Stirling
44
Resulting from the interaction of the above-mentionedfactors, the solar electricity produced from solar-ther-mal power plants with integrated storage techniques ischeaper than from a plant operating without any stora-ge capacity. To this end commercial solar-thermal stora-ge concepts shall be developed and the first plants bebuilt by about 2005.
Solar-thermal power plants constitute an important linkbetween the fossil-based supply of energy today and
the “solar” energy sources of the future, because theyunite major elements of both. They use conventionalpower plant processes combined with solar technologyto transform the radiant energy. As hybrids, they canrealise the step-by-step transition from the fossil erainto the solar age, both technically and economically.Furthermore, through combined heat and power gene-ration (in particular for the purpose of processing sea-water to drinking water) they allow extremely efficientutilisation of the collected solar primary energy.
45
SOLAR COLLECTORS
––– Resources: Direct and diffuse solar irradiation
––– Sites: World-wide
––– Field of application: Heating, hot water
––– Capacity: 1.5 to 200 MWh/a; no real upper limit
––– Heating costs today: between 10 and 25 Cent/kWh
––– Figures: Evacuated tubular collector, flat plate collector, plastic mat absorber
Absorber
Water used as heat transfer medium
Irrad iat ion
46
By using solar collectors, the radiated sunshine is trans-formed into heat, e.g. for hot water for daily use, or forheating the building. The principle can be simply un-derstood by imagining a garden hose filled with waterwhich is left out in the sun: the water is hot after ashort period of time. In the simplest technical version,a heat-transfer medium flows through black plasticmats, so-called absorbers, which are exposed to thesun. High temperatures cannot be reached with thistype of system. However, the initial costs are low andthey are already used for heating the water in outdoorswimming pools. Since this method is usually cheaperthan running a fossil-fired boiler, it already contributesto lowering the costs for the swimming pool operator.
Flat plate collectors are technically more refined. Toprevent heat losses from the collector by convectionand conduction, the absorber in this type of collector ismade of metal and is well insulated. The side wherethe sun is shining onto the absorber is covered with apane of glass and a thick layer of insulating materialincluded on the opposite side. Losses due to reradiationof the heat already absorbed can be prevented byapplying black solar lacquer or more-effective selectivelayers.
Exposed to the same solar radiation, this type of flatplate collector can reach temperatures that are higher
than those achieved using the black plastic mats men-tioned above. Since they can still supply heat evenwhen it is already colder outside, flat collectors are thepreferred choice today for solar water heating in house-holds (Figure: Efficiency curves). The collectors current-ly available on the market normally have a useful surfa-ce area of between 2 and 6 m2. Several modules are puttogether to obtain the required heat output. A typicalhot water system for a single-family home will usuallyrequire 6 m2 roof area, meeting 60 % of the annualdomestic hot water requirement. The collector com-pletely meets the needs in the summer, and during therest of the year, the conventional boiler must furtherheat the water already warmed by the collector(Figure: Collector system).
Heat losses by conductance and convection are almostcompletely prevented in evacuated tubular collectors.Here the absorbers are enclosed in evacuated glasstubes, insulating like a thermos bottle. This design hasthe highest efficiency amongst the collector technolo-gies. They can still supply heat even at low outside tem-peratures in winter, when flat plate collectors lose theheat gained from the sun. Evacuated tubular collectorsare thus particularly suited for heating buildings andproviding process heat. In order for any collector towork efficiently, regardless of the type, the requiredoutput temperature level should be as low as possible.
SOLAR COLLECTORS — BRINGING THE SUN INTO THE HOUSE
0 10 20 30 40 50 60 70 80 90 100 T col lektor — T ambient (K)
100
80
60
40
20
0
Eff ic iency (%)
Source : DLR
The better the insulation of the collector, the higher the temperature of the heat produced. Characteristics of different collectors at aninsulation of 500 W/m2 and the resulting areas of application.
Efficiency curves
Characteristic absorber
Characteristic flat plate collector
Characteristic evacuated tubular collector
Swimming pools Hot water Heating Process heat
47
If rooms are also to be solar heated, then underfloor orwall-heating systems are recommended. Furthermore,the building to be heated must also be very well insula-ted in order to keep the heat requirement as low aspossible. A system with 11 m2 (evacuated tubular collec-tor) or 14 m2 (flat plate collector) can provide some 20to 30 % of the total heat required for a well-insulatedhouse by solar energy. Solar collectors are particularlyeffective during the transitional spring and autumnseasons.
The alignment of the collector towards the south andthe angle of its inclination play a far less significantrole than is generally assumed (Figure: Thermal yieldand alignment to south). Simulations indicate that devi-ations of +/– 60° from true south lead to losses of onlyabout 10 % in the solar yield. If the slope of the roofdiffers by 20° from the optimum slope of 50° at ourlatitude, then the energy yield is reduced by approxi-mately 5 %.
A heat store is indispensable for a solar collector sys-tem. It stores the heat provided by the collector duringperiods of no demand, and releases it again when heatis required. Solar collector systems for heating domesticwater typically need to store 350 litres in a single-fami-ly house. If the solar collector is to be used for heating
purposes as well, then a larger storage capacity ofapproximately 70 litres per square meter of collectorsurface area will be needed. These heat stores can onlycompensate for the difference between the availableenergy and the required energy over a few days. Theyare not large enough to store the solar heat until winter.
Considerably larger heat stores and also larger collectorsurface areas are needed for storing summer heat intothe winter. There are various demonstration projects inEurope with this goal. The currently largest Germanproject in Neckarsulm will, when completed, supply1,200 dwellings with solar heat – even in winter – from15,000 m2 collectors and a 150,000 m3 reservoir. Someof the collectors are installed on school roofs, thesports hall, and several residential buildings, others aremounted over car parks (Figure: Settlement suppliedwith solar energy) or along noise-protection walls. Cost-effective solutions are necessary for the seasonal storesused with such projects because, in contrast to the nor-mal stores in the boiler rooms, they are only chargedand discharged once a year. Besides the approach cho-sen in Neckarsulm, which uses the natural ground clayas a cheap storage medium, there are also other verypromising developments such as to feed the heat intounderground layers carrying water (aquifer storage),
1030507090West 10 30 50 70 90 East
Source : DLR
Solar ass isted heat ing
30 - 30
- 50
- 70
50
70
70 %
80 %
90 %100 %
10 - 10
0
0
s lope of the roof (degree)
South
Az imuth (degree)Az imuth (degree)
Thermal yield and alignment to south
The thermal yield (max. 100 %) is decreasing only modestly, if the collector is not alligned exactly to south.
48
using pits filled with coarse-grained gravel and water,or constructing concrete tanks filled with water andpartially embedded in the ground. Each of these stora-ge concepts has both advantages as well as disadvanta-ges. The successful development of cost-efficient long-term storage will lead to further application areas forsolar energy, which will extend far beyond the predo-minant application of today of providing hot water fordomestic purposes in summer.
Technical trends
Experiments attest that solar collector plants have, inthe meantime, reached a high degree of maturity such
that dependable service over 20 years is now possi-ble. Nevertheless, further technical improvements havebeen made recently. Heat reradiation can be reducedby using new selective coatings on the absorber surfa-ce, improving the efficiency. Furthermore, these selecti-ve coatings are more environmentally compatible thanthe electroplated layers used so far and are also lesssensitive to mechanical disturbances and high tempera-tures. Losses due to reflection off the cover glass on flatplate collectors could be reduced by applying a specialsurface treatment. Lower flow rates through the collec-tor allow the use of smaller-diameter pipes, which inturn allows the use of thinner pipe insulation, reducesthe materials expenditure, and less electricity is requi-red to run the pump. The trend is towards ever larger
Year ly insta l led co l lector surface area ( 1 ,000 m 2)
1990
Source : DLR / BSi
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Yearly installed collector surface area
Sales of collectors have increased twenty-fold since 1990.
Evacuated tubular collectors Flat plate collectors
1982 1986 1990 1994 1998 2002 2006
Source : Drück / ITW
The costs for solar-thermal systems are falling continiously. The graphic shows the development of the average costs for complete solarsystems for heating domestic water and for supporting the heating system.
Costs of solar–thermal systems
Solar hot water system
Solar heating system
Trend
20,000
16,000
12,000
8,000
4,000
0
Investment cost in Euro
1,000
800
600
400
200
0
49
individual modules for further cost reduction. Additio-nally, the roof mounting systems are being simplified,even to the point that the collectors can even replacethe conventional roof, i.e. the roofing tiles and gutter,so that the costs for these parts of the roof structurecan be saved. Control units and pumps are delivered inpre-mounted and integrated subassemblies. No-brazepipe connections are available, considerably simplifyingthe on-site installation for the talented amateur.
Costs
Total system prices have sunk considerable over thepast 18 years as a result of technical progress and mar-ket expansion. At the present time, the specific invest-ment costs for a complete system including storage,piping, and installation are about 830 Euro per squaremeter collector area (Figure: Costs of solar-thermalsystems). Even though solar collectors cannot quitecompete with the current prices of fossil energy car-riers, they can provide dependable protection againstthe risk of future increases in the price of energy.Another point: the energy payback time is only 1 or 2 years, by then it has harvested the energy originallyexpended for its production.
Market developments
About 550,000 m2 of glass-covered collectors were soldin Germany in 2002. There are a total of 5 million m2
of collectors installed on German roofs. More than 2.5 billion kWh of fossil fuels have been substituted inthis way, equivalent to 250 million litres of heating oil(Figure: Yearly installed collector surface area).
In 2002, the market dropped by 40 % compared to theprevious year following cuts in the financial supportavailable for solar plants. Once the subsidy conditionswere improved, the federal market stimulation pro-gramme once again received record numbers of aidapplications in 2003, so that new installations are esti-mated to amount to 840,000 m2 of glass-covered collec-tors.
This progress does not yet make Germany the leader insolar energy usage – there are five times as many solarcollectors installed per capita in neighbouring Austria,where the collectors have become a very lucrativeexport item. Other EU countries like France, Italy, andEngland are even further behind in these develop-ments.
Further market expansion can be hoped for throughthe increased demand for even larger plants andsystems. Solar collector systems are still predominantlyinstalled on the roofs of single-family houses. There arehardly any such systems to be seen on the roofs of
apartment buildings or other large buildings so far, alt-hough the solar heating costs, especially for larger-scalesystems, can be considerably lower. Nevertheless, themarketing for these systems is more difficult: It is notthe owners who benefit from the solar heat, but ratherthe tenants. In this case, the owner’s delight while sho-wering using “home-grown” heat generated from aninexhaustible source is lost. Instead, the economic crite-ria are increasingly dominating. Some housing con-struction companies have decided in favour of solarsystems for their rental properties. In this way, thedwellings are easier to lease and the numbers of un-occupied flats can be reduced.
Prospects
In the long term, solar heat can contribute to a sustai-ned energy supply in Germany to a considerable ex-tent. There is enough space on the roofs of buildingsfor 800 km2 of collectors. Additional space for installa-tions are on south-facing facades, above parking spaces,and on road embankments (Figure: Noise-protectionwall with solar collector). In total, as much as 1,300 km2
collectors could be installed, already taking into ac-count that some of the roof area must be kept reservedfor solar cells generating electricity (photovoltaic sys-tems). With this potential collector surface area, itwould be theoretically possible to meet approximatelyhalf of the present-day heat demand for heating andhot water. Today, solar heat contributes only 0.2 % tothe total heat needed in Germany.
In order for solar heat to be a major contributor to theenergy supply, it will not suffice to cover every roofwith collectors and install a storage system in every cel-lar. It is rather necessary to link up a large number ofbuildings within a district heat network and then toconnect the network to one large and common storagesystem. Only in this way can the heat from the summersun be stored for use in the winter months at reasona-
Collector system
50
ble costs. The collectors supply heat to the storage sys-tem from where it is then transferred as required tothe buildings within the system.
Setting up district heating networks is a crucial pre-requisite for the extensive use of solar heat. Districtheat can also contribute to the cost-effective use ofwood chips, straw, miscanthus, and geothermal energyto a considerable degree. A good example here isDenmark where today already 60 % of all homes areheated by means of block or district heating. Morethan one third of the heat being fed into networks originates from renewable energy sources, and the re-mainder is mostly produced with the equally environ-mentally compatible combined heat and power genera-tion.
District heat is flexible and open for the future. For thebenefit of a sustainable heat supply, a decisive expan-sion of such systems in the next decades is to be strivedfor in Germany as well. This task will not however bean easy one.
Above: Kill two flies at one go: Collectors for district heat andnoise–protected residential areas.
Below: In Neckarsulm even the parking spaces are used for generating heat.
51
PASSIVE USE OF SOLAR ENERGY
––– Resources: Direct and diffuse solar radiation
––– Sites: Everywhere
––– Field of application: Heating buildings
––– Costs: As a rule, the saving in fuel costs compensate for the additional invest-ment
––– Figures: Transparent insulation, architectural measures, translucent facades
direct heat ing
ind i rect heat ing
Wal ls are used for heat storage and insu lat ion
Irrad iat ion
52
Passive use of solar energy is characterised by the factthat the solar energy is used without any technicalsupport like e.g. pumps. The prime example is ofshade-free windows facing directly south throughwhich, especially in winter, the rays of the low-lyingsun can reach the interior of the house and warm it:the building itself acts like a solar collector.
Included in the area of passive use are also other trans-parent parts of the outer building shell, like conservato-ries or transparent thermal insulation. The architect’stask is thus to design the building to maximise thegains from passive solar energy, without overheatingthe building in the summer, and to keep any additionallosses due to enlarged window areas within acceptablelimits. The passive use of solar energy, more than anyother technology, requires the holistic consideration ofthe building structure and energy supply (Figure:Characteristic energy values of buildings).
Windows: Sources of heat or of heat losses?
During the day, solar radiation can make a considera-ble contribution to heating a house. The better thehouse is already thermally insulated, the more pro-nounced are the effects. During the night, on the otherhand, there is more heat lost through even the best ofwindows than through a well-insulated wall. Whetheran overall positive or negative energy balance results
from an enlarged window area depends considerablyon the quality of the glazing (Figure: South-facing win-dow area). An enlargement of the south-facing windowarea does not necessarily improve the building’s heatrequirement. In particular, passive-energy houses canonly be realised by using first-class glazing construc-tions.
The additional costs of heat protection
A new construction with a lower heating requirementwill also have a lower heating bill. On the other hand,its construction also incurred higher costs (Figure:Additional costs). Low-energy houses can already berealised for low additional costs. For passive houses,additional investment costs of 200 Euro per squaremeter of useful area have to be assumed. In return,these houses provide reliable protection against futureincreases in the price of energy and – at a lower roomtemperature – can manage without any extra heating,even in winter. Further thermal insulation, togetherwith a solar collector and a very large heat store insidethe house, would meet all of the building’s require-ments, so that no external fuel or heating electricityare needed. This construction is, however, still very costly.
Improvements in older buildings are even more impor-tant for a sustained development than in new construc-
PASSIVE USE OF SOLAR ENERGY —POSSIBLE THROUGH BUILDING DESIGN
Stock
WSchVO = German Thermal Insulation Ordinance; EnEV = German Energy-saving Ordinance; LEH: Low-energy house Energy demand in kWh/(m 2 a)
Source : Luther 2001
WSchVO 1995 EnEV 2002 LEH 2002 3 ltr house Zero heating energySolar passive house
Characteristic energy values of buildings
Characteristic energy values for various thermal insulation standards, taking the single-family house as an example.
Heating Hot water Electricity, infrastructure Electricity, household
50
100
150
200
250
300
0
53
tions. When modernisation is necessary anyway, addi-tional heat protection can be included for only slightlyhigher costs which are quickly amortised.
Particular attention should therefore be given to thethermal insulation when renovating a building, sincethe next favourable opportunity will only be during thefollowing renovation in about another 30 years time.
Conservatories and transparent thermal insulation
Conservatories are generally very popular. In the transi-tion months, a conservatory provides additional unhea-ted living space which is illuminated with natural day-light, it is close to nature and yet protected. In winter,energy for heating purposes can be saved as well. Thiseffect is however low and can easily be reversed – e.g.
The window as a means of heating: For good glazing (triple-pane glazing), the heating requirements fall as the proportion of south-facingwindows increases.
0 10 20 30 40 50 60 70 Propor t ion of g laz ing in %
0
10
20
30
40
50
60
70
80
Heat ing demand in kWh/(m 2 a)
Source : IWU 1997
Low-energy house
Pass ive house
South-facing window area and heating demand
traditional double-pane
Glazings:
coated double-pane
coated triple-pane
Source : FhG- ISE
Trad it iona l insu lat ion
Heat loss
Heat gain
Irradiation
Reflection
Heat gain
Irradiation
Backscatter
Reflection
Transparent insu lat ion
Heat loss
Transparent thermal insulation
Operating mode of the transparent insulation
54
by occasionally leaving the door to the heated livingquarters open in winter.
Transparent thermal insulation can be added to thefacades and panels of old and new buildings alike.Transparent thermal insulation consists of a layer trans-parent to light yet is of good thermal insulation, made,for example, of fine glass or plastic tubes. The incidentlight passes through the transparent insulating layerand is absorbed on the structural wall, thereby heatingthe wall. Since this heat is already behind the insula-ting layer, it can no longer escape to the enviromentand thus – with a time delay – heats the living quartersbehind the wall (Figure: Transparent thermal insula-tion). In the summer, a system of shades may be neces-sary to protect from overheating.
The usefulness of transparent thermal insulation de-pends on the wall’s cardinal orientation, on the qualityand the construction of the other transparent compo-nents (windows), as well as on the structure of the wallbehind the transparent thermal insulation. Accordingly,appropriate planning is absolutely necessary.
The German Energy-Saving Ordinance
The new German Energy-Saving Ordinance (Energie-einsparverordnung = EnEV) has been in effect since Fe-bruary 2002. This new legislation replaces all previousheat-protection and heating-system laws. Instead ofregulating the heating requirement, i.e. the quantity ofheat provided by the heaters, it now limits the primaryenergy requirement. Primary energy is the quantity ofenergy contained in the amount of coal, oil, gas, oruranium which is necessary to heat the planned newbuilding and to supply it with hot water. A transitionalexception was made for electrical heaters. The energy-saving regulation gives the property developers thechoice of whether to meet the more demanding goalsof the new regulation by better thermal insulation, byenergy-saving heating systems, or by using sources ofrenewable energy. The property developer can nowoptimise the entire system – the decisive advantage ofthe new regulation. For example, a projected single-family house can reduce the demands on the thermalinsulation or the heating requirements by 15 % byinstalling a well-designed solar water-heating system.
Additional costs for heat protection per square meter of useful space
0 20 40 60 80 100 Heat ing demand (kWh/m 2a)
600
500
400
300
200
100
0
Addit iona l costs in Euro/m 2
Source : Ger t is 2001 Additional costs for heat protection
Passive house
Low-energy house
55
BIOMASS COMBUSTION
––– Resources: Wood, grain, vegetation containing sugar and starch, plants containing oil, organic leftovers, and bio-waste
––– Sites: World-wide, depending on the availability of the biomass
––– Field of application: Electricity generation, heating purposes, combined heat, and power generation
––– Capacity: 1 kW to 50 MW (thermal)
––– Costs: Heat: between 1 and 10 Cent/kWhElectricity: between 5 and 30 Cent/kWhStrongly dependent on fuel costs, and onthe revenues from heat, electricity, and disposal services
––– Figures: Combined heat and power plant using wood residuals, biogas plant, pellet stove
Biomass
Heat E lectr ic i ty
Cond it ion ing
Thermic or b iochemica l convers ion
56
The use of biomass for generating electricity and heatis a particularly attractive form of energy conversionfrom the climate point of view. When growing, the bio-mass first removes the greenhouse gas CO2 from theatmosphere and binds the carbon in the biomass. Thiscarbon is later released into the atmosphere again –e.g. as a result of combustion or when the biomass isrotting. Therefore, when biomass is used for energypurposes, then only that CO2 is released which was pre-viously removed from the atmosphere when the plantwas growing.
The biomass regulation, which determines which sub-stances are considered as biomass for the renewableenergy regulation, defines them as “energy carriersfrom phyto-mass and zoo-mass”, i.e. materials origina-ting from vegetation and animals, including the “con-sequential and secondary products, remains and waste,the energy content of which originated from phyto-mass or zoo-mass”. Furthermore, the biomass regula-tion specifies which processes are allowed and the envi-ronmental requirements.
Included amongst the most important biogenous fuelsare of course wood and leftover timber accumulatingfrom forestry, in sawmills or as old timber. Fast-growingtrees, e.g. poplars and willows, can be planted in so-cal-led short-turnaround plantations and be harvested wit-hin a few years. Reed (miscanthus) is potentially a veryhigh-yield regenerative raw material, however it requi-res high-quality fertile land and a good water supply.Residuary straw, as well as special grain plants like e.g.
the wheat-rye hybrid triticale, are also suitable for pro-ducing energy. Plants which contain sugar and starch,like corn and sugar beets, can be used for making bio-alcohol. Also included as biomass are those oil-contai-ning plants which, by pressing and subsequent proces-sing, can be converted into liquid energy carriers (formore information see the chapter on biofuels).
Organic residuals are also suitable energy sources.Liquid manure, bio-waste, sewage sludge, and munici-pal sewage and food leftovers can be converted intohigh-energy biogas. Biogas is also released from land-fills. However, biogas from landfills and sewage-treat-ment plants is not recognised as a biogas in the con-text of the biomass regulation, because it falls under a special clause of the Renweable Energy Sources Act.
The oldest form of use: Burning
The oldest and simplest way of using energy is to burnthe biomass. To assure complete combustion and lowemissions, while taking into consideration the ash con-tent, the fuel composition, and the shape and size ofthe fuel particles, different types of burning, whichessentially differ in the type of fuel processing and thefuel feed method, were developed for the various plantsizes.
Present-day use of biogenous solid fuels in Germany ismostly in very small plants (less than 15 kW) or insmall-scale plants. Automated fuel feed, together with
Source : F la ig 1998
Fill level control
Secondary air
Boiler
Pilot burner
Mechanical feed
Air supply
Bed ash Ash container
The stoker fired burner is an example for an all-round applicable biomass burning system. By adjusting the move-ment of the grate and the air flow the furnace can be controlled precisely.
Biomass burning system
BIOMASS — A LONG-TERM ALTERNATIVE FOR HEATAND ELECTRICITY
57
Stock of wood chips in Sweden: One kilogram of dry wood con-tains the same amount of energy as half a litre of heating oil.
a suitable combustion control system, have increasedthe ease of operation. Small-scale plants are therebysubject to the emission limits of the emission controllegislation in Germany.
Besides firewood and straw, wood pellets and woodchips can also be used. Wood pellets are small com-pressed beads of untreated wood, usually from sawdustand planing shavings. They can be delivered like hea-ting oil by tank trucks, or sold in sacks. Pellets can befired in ovens with a chimney just like in large-scale,fully-automated and low-emission central heatingsystems. The space needed for storing this type of fuelis almost as small as for an oil-fired central heatingsystem.
Generating heat is not limited to small-scale systemsonly. Firing wood can also be used for district heatingnetworks (see also the chapter on solar collectors). InAustria, a country which has been systematically sup-porting the use of biomass for many years now, thereare already more than 500 district heating plants run-ning on biomass. It is worthwhile to invest in greatertechnical optimisation of these larger incineration faci-lities. Very low emission values can be reached for theflue gas. Thus district heating plants become especiallyattractive for health resorts and tourism.
Both the efficiencies and the emissions of modern bur-ning systems have been improved. For example, theefficiency can be increased considerably by condensingthe flue gases, since the transformation energy whenthe water vapour condenses into liquid can be used,and by pre-drying the biomass. The exhaust-gas valuescan be improved by a continuous combustion processand efficient dust recovery. In recent years, it has beenpossible to considerably reduce the emissions of carbonmonoxide and unburned hydrocarbons, especially forsmall plants.
Electricity from biomass
The interest in producing electricity from biomass hasincreased considerably since adoption of the biomassregulation in mid-2001. The electricity generation fromwood alone (approximately 1.2 billion kWh in 2002)will, according to the current plans, more than doublein the next three years. The preferred fuel in the newlyconstructed power stations is cost-effective old timber.Economic operation of the plants is not possible withthe more expensive untreated wood. The days of beingable to charge a disposal fee for accepting contamina-ted wood are long gone because of the considerablyincreased demand for this wood. After 2005, the oldtimber will be largely exhausted, and other techniqueswill be necessary to continue the growth in electricitygeneration from biomass.
The most efficient form of using the energy from bio-mass is through combined heat and power genera-tion. Unlike pure electricity generation, the waste heatis not simply dissipated, unused, into the surroundingenvironment – like with the old-timber power stations– but rather is used for heating buildings or for dryingprocesses. The efficiency levels which can be reachedtoday are still, however, unsatisfactory, particularly forsmall plants. New technologies are therefore beingdeveloped like the Stirling engine, which, unlike thesteam turbine, still exhibits high electricity and heatyields in the output range of less than 1 MW. Its com-mercialisation is, however, still in its infancy (Figure:Generating electricity from biomass).
A very promising alternative to burning is the gasifica-tion of biomass. Using gaseous biogenic fuels, it is pos-sible to apply proven and efficient techniques like gasturbines and cogeneration units . The future use of bio-mass in fuel cells, which provide high yields of electrici-ty even from small-power units, is possible with gasifiedwood. The principle of wood gasification is not new.
This cogeneration unit uses biogas to produce heat and elec-tricity.
58
They were used e.g. after the war for powering lorriesdue to the lack of more motor-gentle fuels. The fuel isnot completely oxidised in the wood gasifier. Whenappropriately performed, the wood can be completelyconverted into a hydrogen-rich gas and some ash resi-due. The largest technological challenge associatedwith improving the wood gasifier is to produce a tar-free gas which can be used in combustion engineswithout depositing any harmful residues. Newly develo-ped wood-gasifier pilot plants coupled with cogenera-tion units are currently undergoing long-term opera-tion tests.
Biogas — bacteria at work
Biogas can also be used to generate electricity, prefer-ably in cogeneration units. Biogas is liberated whenorganic material is decomposed by special methanebacteria. This process is called fermentation. Two majorprerequisites must be met to obtain an energy-rich gas:anaerobic (oxygen-free) conditions must prevail, andthe temperatures in the biogas reactor must be suitablefor the desired bacteria. Most biogas systems operate attemperatures between 30 and 37 degrees Celsius.
The bacteria decompose the organic matter in severalstages. The final products of this decomposition chainare the gases methane (CH4) and carbon dioxide (CO2).One hundred cubic meters of biogas develop from bet-ween a half and one ton of bio-waste, corresponding tothe daily excrement from 90 cows or 12,000 chickens.
The first German biogas plant was already built in theOdenwald in 1948. Since then, the process engineeringhas improved continuously. However, the core compo-nents have been retained (Figure: Large co-fermenta-
tion plant): In the conditioning phase, the organicmass is comminuted and interfering materials are re-moved. The heart of the plant is the methane reactorwhere the actual bacterial decomposition takes place.Depending on the size of the plant, this reactor can bemade of concrete, plastic, or steel. For agriculturalsmall-scale plants in the developing countries, the bio-gas reactors are often brick constructions buried in theground. The organic substrate stays in the reactor bet-ween 10 and 35 days before the fermentation leftoversare ejected and processed, for example, as fertiliser orcompost. The resulting biogas is subsequently cleanedwith a gas purifier and, if necessary, also desulphurised.
With a calorific value of about 6 kWh, one cubic meterof biogas is equivalent to 0.6 litres of heating oil or 0.6 m3 of natural gas. Biogas is suitable as a fuel forcombustion engines. In Germany, the biogas formed inthe reactor is used almost exclusively in cogenerationunits. The cogeneration unit initially covers the plant’sown energy requirements for electricity and heat: anaverage plant needs between 5 % (agriculture) and 40 % (bio-waste) of the total electricity production forits mixers and other electrical equipment, and between5 and 50 % of the heat produced for heating the reac-tor (depending on the time of the year).
The benefits of biogas plants for the farmers are seve-ral-fold: The largest economic benefit is given by theelectricity generated in the cogeneration unit. Some ofthis power is used locally, whereas the remainder is fedinto the national grid at the price regulated by the Re-newable Energy Sources Act. The heat is used for hea-ting the buildings and sheds. Larger plants can alsodistribute this heat in a district heating network. Also,the liquid manure is processed into a higher-value,reduced-odour fertiliser.
Solid Biomass
Combustion
Gasification
Liquefaction
Coal or gas power plant
Steam-turbine or engine
Stirling engine
Gas turbine / Gas and steam plant
Cogeneration unit (piston engine)
Fuell cell
30 – 40 %
15 – 20 %
10 – 15 % *
20 (GT) – 30 %
approx. 25 %
30 – 45 % **
Generating electricity from biomass
Various technologies are available to produce electricity from biomass ( * less power output than stream turbine; ** depending on thekind of fuel cell).
59
By co-fermentation, i.e. simultaneous fermentation ofmanure and organic waste from households or indu-stry, the yield of biogas can be increased, resulting inadditional revenue from the additional electrical powerthus generated. Additionally, there are revenues interms of fees for the environmentally compatible dispo-sal of bio-waste materials. The regulations concerninghygiene are, however, much more stringent for co-fer-mentation plants, and the legal conditions are muchmore complicated as well. Considerably higher invest-ment and operating costs result, which reduce the eco-nomic benefits of co-fermentation.
Costs
The diversity of the biogenic starting substances is alsoreflected in the costs of generating electricity fromthese sources. Decisive for the economic efficiency ofthe plant are, as a rule, the costs of providing the fuel,ranging from “negative” costs – from credits for landfilland disposal costs not incurred – through to 3 Cent/kWhfor grain-type whole plants. The costs of regenerativeraw materials are currently around one-and-a-half totwo times higher than those of most leftovers. Theheat-production costs can be derived from the invest-ment and fuel-production costs, whereby the electricityfrom combined heat and power generation is remune-rated according to the Renewable Energy Sources Act(Figure: Economic efficiency of biogenic heat genera-tion). Low heat-production costs are mostly achieved by large steam-based heating and electricity power stations running on cost-effective wood and timber leftovers.
Under favourable conditions, for example with a highlevel of personal contribution and cost-effective fuelsources, even small-scale systems can exhibit lowerheat-production costs than comparable plants runningon fossil fuels. This case is often true for firewood boi-lers. On the other hand, it is much more convenient touse wood pellets for heating purposes. Pellet-run sys-tems must however still be subsidised to be competitivewith oil-fired heating systems.
The costs of biogas systems depend largely on the sizeof the system, the co-fermentation percentage and thepotential disposal revenues, the gas yield, the quantityof electricity the plant itself needs, the external heatingrequirements, and any other uses (like e.g. fertiliser
Source : Haase
L iqu id manure Bio-waste
Store
San it izat ion stage at 70 °C
Mix ing vesse l
Methane reactor
Gas storage
Cogenerat ion un i t
Fer t i l i ser Process steam Electr ic i ty D istr ict heat
Fer t i l i ser tank
In this methane reactor the biomass is fermenting best at 37 °C.
From manure to electricity – schematical diagram of the process
Large co-fermentation plant
60
enhancements). No blanket statement can therefore bemade. With many agricultural systems, economic effi-ciency is only then realised when there are disposalrevenues and investment subsidies available. Additio-nally, farmers can save considerably on the construc-tion by personally erecting them. It is important for theplant to run at its maximum capacity. Thus in Denmarkcommunal systems for several farming operations arebuilt to enable a better utilisation and due to the eco-nomies of scale.
Landfill gas accumulates continuously and in a predic-table manner. The gas must be collected by a pipelinesystem buried in the deposits of the landfill anyway. Anappropriate dimensioning of the system can assurecost-effective operation. Sewage-gas systems are econo-mical if a fermentation tower (biogas reactor for thesewage sludge) is included in the design.
Prospects
Wood today provides by far the largest contribution ofbiomass for energy purposes. This situation will remainin the future as well. Part of the wood that has beengrown in the forests cannot be sold to the timber-pro-cessing industry. This leftover material includes youngslender tree trunks from thinning out plantations, and
thick branches and other waste from felling matureforestry stock. Other sources of untreated timber arethe waste and residuals in the sawmills (the so-called“by-products”) and in the remaining wood and timber-processing industry. A large proportion of this woodcan be processed in the papermaking and particle-board industry, so that only the surplus can be used forenergy purposes.
Furthermore, wooden products at the end of their use-ful life are usually available as contaminated old tim-ber, some of which can still be materially recycled. Theborderline between using wood as a material or for itsenergy is variable, depending on the selling price ineach case. Fully exhausting the possibilities for usingthe energy in wood would provide a potential 173 bil-lion kWh/a. Additional potential can be developed byusing straw, biogas, and energy crops.
Straw is needed for animal husbandry and must oftenbe returned to the fields in order to maintain the quali-ty of the soil. Only approximately 20 % of the totalamount of available straw could be used as a source ofenergy. Straw is a problematical fuel and is therefore –unlike in Denmark – hardly used in Germany today. Itsfuture use is possible through the cost-effective and effi-cient co-firing in coal-fired power plants.
Wood residuals, for free
Industrial residuals
Forest leftover
Plantation
Industrial residuals
Forest leftover
Plantation
Forest leftover
Plantation
5 MWth; Sawmill residuals
5 MWth; Forest leftover
300 kWth; Forest leftover
Straw
Liquid manure, 250 LU
Co-fermentation, 3 MWgas
Liquid manure, 120 LU
0 2 4 6 8 10Cent / kWh
Economic efficiency of biogenic heat generation
Systems fuelled with cheap residuals and big heating plants are the most economic choice for producing heat from biomass, today. Real interest rate 4 % and depreciation within 15 to 20 years (Key: LU = Livestock unit).
Source : DLR
Steam cogeneration plant ; 3 MWel Central heating; 40 kWth Straw heating plant
Biogas plant with cogeneration unitWood heating plant; 3,2 MWth Wood gasification with cogeneration unit
61
The largest potential for producing biogas is to befound in agriculture. More than 200,000 plants couldbe realised in Germany with agricultural waste alone –considerably more than the ca 1,500 plants currently inoperation (Figure: Biogas plants in Germany).
Besides using residual and waste materials, there is alsothe possibility to specifically grow biomass. Assumingthat some 2 million hectares (corresponding to a sixthof the arable land currently used in Germany) could bemade available for growing energy crops in Germany– using for example land not farmed in order to reducethe food surpluses in the EU – then about 94 billionkWh of energy per year could be produced from thissource. It is however by no means obvious that suchareas should be used for growing energy crops. Anagriculture using less synthetic fertiliser would alsorequire a large proportion of this area.
Assuming that the 2 million hectares of farming landand all the residual and waste materials were available,then a proportion of about 9 % of the current primaryenergy consumption could be met with biomass (Figure:The potential of biogenic fuels).
Uses today
It is only in the cases of landfill and sewage gas, and inthe near future with old timber as well, that more thanhalf of the potential is already being used. Today, onlyabout 1 % of all dwellings are being heated with wood.In 2003, there was a total of some 80 billion kWh ofprimary energy provided by biomass, the largest pro-portion of which was heat from solid fuels. Thus bio-mass contributes approximately 2.1 % to the primary-energy needs in Germany. This proportion is subject to
considerable fluctuations, since approximately one infive dwellings in Germany has either an open fireplaceor a similar type of wood-burning oven in addition to
Source : DLR
Overa l l 360 b i l l ion kWh per year
The potential of biogenic fuels
Source : Fachverband Biogas 2001
Biogas plants in Germany
The small agricultural biogas plants are mainly located inSouthern Germany, whereas the larger plants are to be foundin North Germany.
Biomass can be used in many different forms for producing energy. The potential value represents an upper limit. The range in which biomass fluctuates is rather large, between 140 and about 400 billion kWh per year.
Energy crops 26 % (2 mio. ha)
Forest leftover 23 %
Manure, organic waste 14 %
Residuary straw 10 %
Sewage and landfill gas 3 %
Industrial residuals 5%
Old timber 9 %
Unused accrescence in forests 10 %
62
central heating. How intensively these firing systemsare actually used depends also on the price of heatingoil.
Environmental use of biogenous fuel
Common to all forms of using biogenous fuels is theconsiderable contribution to climate protection andresources conservation. To make biomass available,only fractions (of the order of one tenth) of the energycontained must be expended in the form of fossil ener-gy. This value applies both for the residual and wastematerials which are collected, transported, and proces-sed, as well as for the energy crops where the cultiva-tion and production of operating materials (fertilisers,pesticides etc., depending on the type of agriculture)must also be included in the balance. Not only doesthis positive energy balance protect the reserves of fini-te energy carriers, it also reduces the climate-active CO2
emissions because fossil energy carriers are being sub-stituted by sources with a closed CO2 cycle – the netgreenhouse-active CO2 emissions are null (see above).Even when considering the greenhouse gases methaneand nitrous oxide – the latter is produced when cultiva-ting energy crops through the production of fertilisersand the material processes taking place in the soil –the overall balance still remains clearly positive.
There is a further benefit for the climate when usingbiogas for energy purposes. In a poorly ventilated bio-waste compost site, and in waste landfills or putrifica-tion tanks, the gas methane develops as a fermentationproduct which is then liberated in an uncontrolledmanner. The effects of methane on the climate arehowever 21 times higher than those of CO2. The com-bustion of this methane to CO2 in the biogas plantsthus “defuses” the greenhouse gas.
The environmental balance is not decisively positive forall environmental problems (Table: Ecological balancefor using biomass). In the case of regenerative rawmaterials, e.g. the method of growing these, the lo-cations, and the fertzilizers used, all have a largeinfluence on the emission of harmful substances.
The conflict of goals between conserving the stocks offossil raw materials and protecting the climate on theone hand, and certain other ecological problems areason the other hand, cannot be resolved from the scienti-fic viewpoint alone. The decision-making process mustalso include weighting factors. At the political level, ahigh value is currently assigned to climate protection.Additionally, ecologically optimised extensive farmingof biological energy carriers, where the use of fertilisersand pesticides is kept low, and by using leftovers asmuch as possible, can harmonise these conflicting goals.
Biofuels substituting coal
WheatMiscanthusPoplar (energy crops)Wheat strawWood leftover (fir)
Biofuels substituting natural gas
WheatMiscanthusPoplar (energy crops)Wheat strawWood leftover (fir)
Source : Ka l tschmitt / Re inhardt 1997
+ + — + / — —+ + — + ++ + — + ++ + + / — + ++ + + / — + +
+ + — — —+ + — — —+ + — — —+ + — — —+ + — — —
Consumption ofresources
Global warmingeffect
Stratosphericozone depletion
Addification Toxicity(example NOx)
Ecological balance of using biomass
Environmental effects of the energetic use of biomass in comparison to fossil fuels. Key: + advantage of biofuel; + / — balanced resp. depending on the method of valuation; — disadvantage of biofuel
63
BIOFUELS
––– Resources: Various biomass sources
––– Sites: World-wide
––– Areas of use: Combustion engines, in the future: fuel cells
––– Costs: More expensive than fossil fuels
––– Figures: Wood gasifier, Harvested rape, Sugar beet processing
Biomass
Fue l
Cond it ion ing
Thermo- or b iochemica l convers ion
64
Transportation requires a lot of energy. In Germany in2002, more than 60 million tons of petroleum-basedfuel were purchased, burnt, and finally emitted intothe atmosphere as carbon dioxide. Some 85 % wasconsumed by road transportation and 10 % fuelled air-crafts. All in all, transportation is the single largestconsumer of energy in Germany with nearly 30 %,closely followed by households (28 %) and industry (26 %).
Three problems are giving incentive to change this situ-ation: The dependency on imports of petroleum pro-ducts, the finite nature of fossil resources, and theproblem of global warming. The transportation sec-tor is dependent on crude oil imports like no other sec-tor, and any oil price increases are unpleasantly felt bythe consumers. The foreseeable end of the growth inpetroleum production could already have a major ef-fect on the price in the next 25 years, and now is agood time to start thinking about “what would happenif ...”, as mobility is important to all of us. Finally, weare concerned about climate change and its conse-quences, which can already be observed today. CO2
emissions from the combustion of fossil fuels affect theclimate considerably. Biofuels offer a good opportunityto partially substitute petroleum as an energy carrier inthe transport sector, since its use addresses all threeproblems at once. The feedstock can be produced inthe country of consumption – the reliance on importsis thus reduced, and they grow again – so they arerenewable. And, finally, a further enormous advantageof biofuels is that they are in principle CO2-neutral,because the CO2 emitted by their combustion wasabsorbed from the atmosphere during cultivation.
A wealth of possibilities
There is not just the one biofuel, but rather a wholerange of liquid and gaseous bio-energy carriers whichcan be used in the transportation sector. Best knownamong the liquid biofuels are the vegetable oils fromrape seed and sunflower seeds, and the processed formof rape oil called biodiesel (methylester from rape-seedoil). Ethanol from sugar beets, grain, potatoes, etc., andmethanol from lignocellulosis material such as woodare major types of liquid biofuels as well. There are alsoseveral kinds of biogases, like e.g. biogenic gas, sewagegas, and landfill gas, as well as bio-hydrogen and woodgas, which are more or less suitable for use in transpor-tation. The feedstock is equally diverse, as they origina-te from agriculture, forestry, and fishery, from residualand waste materials, or as products from thermo-chemical processes.
Environmentally friendly on the road — with bio-alcohol
The alcohols ethanol and methanol are very suitablefor use as fuels in transportation, proven by years ofexperience. Even Nikolaus August Otto, the inventor ofthe spark-ignition engine, used ethanol as the fuelwhen developing his engine, and Henry Ford designedhis famous Model T to run on ethanol as well.
Pure ethanol can only run special motors, like thosefound in Brazil’s vehicle fleet in the eighties, or thoseused in the so-called “Flexible Fuel Vehicles”. A smallfleet of these is operating in Sweden and in the UnitedStates. A more simple method is to add bio-ethanol topetrol, by which means bio-ethanol could be introdu-ced into the market with little effort. Up to 5 % by volu-me are allowed by the DIN norm without causing anyproblems to today’s vehicles. Pure bio-ethanol can beused or – with an additional positive environmentaleffect – its derivative ETBE (ethyl tertiary butyl ether).ETBE could replace the octane enhancer MTBE (methyltertiary butyl ether), which is added to petrol, and thereby reduce the emission of air pollutants. However,it has not yet been clarified whether ETBE, comparedto MTBE, is less hazardous to the ground water. In anycase, MTBE has already been banned in both Californiaand Denmark for this reason.
The almost legendary Brazilian bio-ethanol vehicle fleetis however declining strongly. Changed market condi-tions and an excessive demand for vehicles for whichno bio-ethanol could be provided have since causedthese vehicles to disappear from the market. Never-theless, Brazil is the world’s largest producer of bio-ethanol today, which, however, is now mostly mixedwith petrol. In the US, the second-largest producer ofbio-ethanol, 15 % of the petrol on the market alsoincludes ethanol. Spain is the largest producer of bio-ethanol in Europe since 2002. Here the bio-ethanol isconverted to ETBE and admixed directly with petrol.This development had its origins in the year 1995 whenethanol was exempted from tax. A subsequent conti-nuous increase in the production of bio-ethanol fol-lowed. In France bio-ethanol is also admixed as ETBEwith the petrol.
Raw material rape seed: Rape seed oil and Biodiesel
Even the inventor of the diesel engine foresaw the useof biofuel for his engine. “The use of vegetable oil as afuel might be insignificant today. Yet, over time, thesefuels could become as important as paraffin and the
BIOFUELS — A CONTRIBUTION TO MOBILITY FROMPLANTS AND WASTE
coal-tar products of today”, noted Rudolf Diesel 1912 in his patent. Rape-seed biodiesel (RME), also known asFAME (fatty acid methyl ester), is the most widespreadbiofuel in Germany – with a strongly increasing trend.The sales of biodiesel increased by a factor of five from130 thousand tons in the year 1999 to 650 thousandtons in the year 2003, and the production capacity in2003 grew to approximately 1.2 million tons.
There are more than 1,600 petrol stations throughoutGermany where biodiesel is available, currently amoun-ting to 1.7 % of the total sales of diesel fuel. One reasonfor this success: biodiesel, compared to fossil diesel, ischeaper by about 6 – 10 Cents per litre! The exemptionof biodiesel from the mineral oil tax makes this possi-ble, and a further increase in the market share to bet-ween 3 and 4 % can therefore be expected over thenext few years. Since a litre of biodiesel contains lessenergy than conventional diesel fuel, however, the fuelconsumption is higher, partly diminishing the priceadvantage.
Biodiesel is a high-grade diesel fuel – and can thereforebe used for a small vehicle as well as for the 40-tonlorry. Yet not all biodiesel vehicles are equipped for bio-diesel. One should therefore consult the manufacturerabout whether the particular model has in fact beenapproved for running on biodiesel, or check the own-er’s manual. Otherwise damage may occur e.g. to thefuel injection system, since biodiesel attacks certain pla-stics which are replaced by biodiesel-resistant plastics inthe vehicles which have been approved to run on bio-diesel.
Pure rape-seed oil cannot however be used in conven-tional diesel vehicles, with the exception of older trac-tors. Special engines are technically possible, e.g. en-gines using the duo-therm principle (Elsbett engines),yet the use of rape-seed oil will hardly gain acceptancefor the standard passenger car. Unresolved problemsare the cold-start properties of the cold-sensitive oil,compliance with the more stringent EURO-4 emissioncontrol requirements as of 2005, and a negative ecolo-gical balance as compared to biodiesel, will limit its useto a few niche applications.
65
Fuel from the field: rape seed as a raw material
Seed Fer t i l i ser Bioc ide Fue l
Cu lt ivat ion
Transpor t / storage
Oi l mi l l Rape seed cake
Extract ion+Hexan
Rape seed meal
Rape o i l
Re-ester i f icat ion
Biod iese l (RME)Ac id
NaOH
Methanol
G lycer in
Source : I feu
Process-flow chart of biodiesel production
Life cycle of biodiesel
66
Life cycle assessment of biofuel
Environmental and resource protection are two majorcomponents of sustainable development. Therefore, the ecological benefits of each new fuel must also beassessed. Life-cycle assessment is one method to deter-mine possible environmental effects in the course of aproduct life cycle. All major processes which are associ-ated with the production, use, and disposal should beconsidered. Crop cultivation, fuel extraction and condi-tioning, distribution, and combustion emissions are im-portant processes for the life-cycle assessment of bio-fuels.
First and foremost in the use of energy crops is theircultivation. One hectare of land can produce between 3 and 4 tons (dry weight) of rape seed, from whichapproximately 1,300 to 1,700 litres of biodiesel can beproduced. A space the size of a football field will thus suffice to provide enough fuel to run the average carfor a year. The rape seed is pressed and refined – there-by removing undesirable secondary products – and, inthe case of biodiesel, then chemically modified. In thisre-esterification process, the large rape-seed molecule isbroken down into three fragments by adding metha-nol. This method not only forms molecules resemblingthose of diesel fuel, but also glycerine – a raw materialin the chemical industry.
Ethanol can be produced in Germany from sugar beets,wheat, or rye, whereby the highest yield is given bysugar beets. The sugar beets are chopped up so that a sugar solution can be extracted from the vegetable.When using starch-containing plants, the starch mustfirst be dissolved out of the plants and then sacchari-fied. The sugar-containing solution is then first fermen-ted using yeast. Finally, the energy-containing alcohol
is separated. An average of 62 tons of beets per hectarewere harvested in Germany in 2000, an amount suffi-cient to produce approximately 6,600 litres of bio-etha-nol. Considering the energy content of the harvestedethanol, the yield is almost double that of RME.
The process of producing fuel does however need bothenergy and materials – and this is where the life-cycleassessment plays an important role. A large part of theenergy demand for growing energy crops is due to fertiliser production. And working the fields also re-quires energy. In the production of biodiesel, the re-esterification process consumes the most energy –approximately 40 % – mostly because of the largequantities of methanol needed. Approximately 30 % ofthe energy is required for the production of rape seed,and the rest is for harvesting and producing the oil.
And yet: the overall energy and climate balance for bio-diesel is significantly positive. The result does howeverdepend on whether the secondary products, in particu-lar rape-seed meal and glycerine, are used. Rape-seedmeal can be used as animal fodder instead of soy-beans. Glycerine is primarily used as a raw material inthe chemical industry, e.g. in cosmetics production.When glycerine produced from fossil sources is repla-ced by the regenerative glycerine, a CO2 credit is givenfor the biodiesel, which offsets the additional effortsneeded for re-esterification. Since glycerine is not a by-product of rape-seed oil production, biodiesel gains aconsiderable advantage on this point. An excellentenergy balance is also found for bio-ethanol from sugarbeets, wheat, and rye.
Whereas all bio-energy carriers make a considerablecontribution to conserving fossil resources and to redu-cing greenhouse gases, there are also some ecological
50 %
100 %
150 %
200 %
Compact-c lass D iese l equ iva lent to 100 %
Source : I feu 2003
RME Bio-ethanol from sugar beets
0 %
Life-cycle assessment for different biofuels
Ecological pros and cons of biofuels shown relative to a diesel passenger car of the compact class (ethanol as the petrol substitute; RMEas the diesel substitute). Reading example: If a diesel passenger car of the compact class were to be fuelled with bio-diesel instead offossil diesel, then, although the ecological balance is worse for acidification and summer smog, less than half the amount of greenhouse-gases are emitted.
Greenhouses gases Acidification Ozone potential
67
disadvantages associated with using rape-seed fuels. Forexample, the use of biofuels leads to higher acidifica-tion of the soil and waters, as well as to increased emis-sions of nitrogen compounds. Similar to the case of bio-mass as a heating fuel, the ecological significance ofthe individual benefits and drawbacks must be weigh-ted as a part of the decision-making process, wherebyclimate protection is currently very high up on the listof environmental policies.
Costs
Bio-energy carriers must not only be ecologically com-petitive, their costs must also be comparable to those offossil fuels. It is not surprising that biofuels are current-ly more expensive than conventional fuels. Crude oil ispractically free, only the costs for exploration, conditio-ning, and distribution must be paid. In the case of rapeseed, wheat, or sugar beets, however, the entire agricul-tural production must be financed – and of course allof the other processing steps as well. These costs cannot be compensated by the revenues from selling theby-products, e.g. the rape-seed extraction meal sold asfodder, and the glycerine from the bio-diesel produc-tion.
Today the production costs can be twice as high asthe cost of producing conventional diesel fuel. Onlyafter the exemption from the mineral oil and eco-tax, granted in Germany in summer 2002, can biodie-
sel compete with normal diesel on the fuel market.Since the beginning of 2004, all biofuels in Germanyare exempted from taxes, making bio-ethanol an attrac-tive economical alternative as well. Today, biofuels arebeing subsidised to a great extent – yet this does nothave to remain this way.
Three independent factors determine the economicefficiency to a large extent: the costs of the feedstock,the prices which can be realised for by-products, andthe price of petroleum on the international markets.On the one hand, the development of new breeds canlead in time to increased yields of energy crops, there-by reducing the costs of the raw materials. On theother hand, the price of crude oil will increase in thefuture because it is a limited resource. Both effects,together with the increasing experience in the produc-tion of biofuels, will contribute to reducing the costs ofproviding biofuels in the future.
A look at the future of biofuels
The European Commission has anchored the use of biofuels in European legislation by a directive issued in2003. Member states are committed to promote bio-fuels in the transportation sector. Initially 2 % of allpetrol and diesel fuels shall be replaced by the end of2005; and 5.75 % by the end of 2010. This directive alsoapplies for hydrogen and synthetic fuels from biomass,as well as for derivatives like ETBE. Therefore, biofuel-
Source : I feu
Consumption of resources
Greenhouse effect
Stratospheric degradation of ozone
Acidification
Photo-smog
Eutrophication
Human and eco-toxicity
• Savings in fossil energy
• Lower emissions of greenhouse gases
• Lower SO2 emissions• Lower marine contamination from the
exploration and transportation of crude oil
• Less contamination from oil spills after accidents
• Lower toxicity / better biodegradability
• Consumption of mineral resources
• Higher N2O emissions
• Greater acidification
• Higher potential for ozone to develop
• Higher NOx and NH3 emissions• Possible hazards to surface waters
• Possible strain on the surface waters from pesticides
• Possible strain on the ground water from nitrates
Advantages for bio-energy carriersCriterion Disadvantages for bio-energy carriers
Ecological pros and cons of biofuels
68
blends will also be available in Germany in the future –the petroleum industry has already signalled theiragreement.
The reasons for this support are manifold: A vital far-ming industry, a contribution towards assuring sup-plies, the creation of jobs, and last but not least ameans of fulfilling obligations to lower greenhouse-gasemissions. The potential alone given by utilising farm-land not being used otherwise would lead to 1.2 % to 5 % of the total consumption of petroleum products.Yet not all biofuels are necessarily linked to agriculturalfarmland. Organic waste in the form of oils and fats, aswell as wood-like raw materials, can also be used. Con-sidering the predicted growth in transportation of 2 %
over the next ten years, then the use of biofuels could,in any case, offset the effects from this growth in a climate-neutral manner.
The national governments have some freedom in thechoice of particular biofuels they support, since the climatic conditions are not all suitable for growingenergy crops. In Spain, bio-ethanol production fromwheat is preferred, with a year’s expected productionof 430,000 tons from three plants in 2004. In France,75 % of the ethanol is produced from sugar beets, andthe remainder from grain. In Germany, bio-ethanol isnot yet being used in the fuel sector. Germany is how-ever the leading producer of biodiesel in Europe. Inthis way each country chooses its optimal path.
69
GEOTHERMAL ENERGY
––– Resources: Geothermal: close to the surface (downto 400 m) 7 to 25 °C, hydrothermal: 25 to 120 °C,Hot-Dry-Rock systems: 175 °C and higher
––– Sites: Close to the surface: practically everywhere; hydrothermal: North-German lowlands, Upper Rhine Valley, region between the Danube and the footof the Alps, Swabian Alb, Upper Franken;Hot-Dry-Rock systems: Upper Rhine Basin, almost everywhere in the future
––– Field of application: Heating and cooling, seasonal storage of heat and cold, maintaining ice-free, process heat, electricity generation
––– Capacity: Close to the surface: Geothermalprobes 6 – 8 kW; hydrothermal: 3 to 30 MW thermal; Hot-Dry-Rock: 20 to 50 MW electrical
––– Production costs: Heat: < 2 to 6 Cent/kWhElectricity: 7 to 15 Cent/kWh
––– Figures: Hot Dry Rock, earth probe, hydrothermal heating central
Heat consumer
Product ion of hot water 80°C
2,000 m Aqui fer
Co ld water
In ject ion dr i l l -ho le
70
Geothermal energy, or heat from the earth, is heatwhich reaches the surface of the earth from the earth’smolten core. On the way to the surface, both the layersof earth and the rocks, as well as any undergroundwater reservoirs, are heated. In some locations, hotwater and steam reach the earth’s surface in the formof hot springs or geysers.
The deeper one penetrates the interior of the earth,the warmer it becomes. In Central Europe the tempera-ture increases by an average of 3 °C per 100 m depth.The temperature in the uppermost mantle is approxi-mately 1,300 °C; in the earth’s core it is probablyaround 5,000 °C.
The heat stored in the earth is inexhaustible by humanstandards. Several times as much energy as is used
world-wide ascends from the depths of our planet everyday and escapes unused into space. Most of this heatflow originates from the continuous decay of radio-active elements in the mantle and in the earth’s crust,a process which will continue for billions of years. Thissource of energy can be used practically everywhere.
A transportation medium is normally needed to tapthis underground heat. The basic principle is simple:
––– Either this transport medium is already availableunderground in the form of steam or hot water. In thiscase, it is brought to the surface where it cools downand is then normally returned underground again;
––– Or a medium, e.g. water, must first be pumped tothe required depths and returned heated to the surfaceagain.
The heat thereby acquired can then be used directly forheating purposes or for other heat consumers. Equallyattractive is to use geothermal energy for electricitygeneration, because it is available round the clock.Geothermal energy power stations could thus provide a major contribution to the basic supply of electricityfrom a renewable source.
Large quantities of heat are also produced during geo-thermal electricity generation. In the majority of cases,this heat can only be used by the buildings nearbywhen they are connected to a district heating network.A large increase in the numbers of district heat net-works is thus a major prerequisite for developing theconsiderable potential of geothermal energy.
There are principally four types of geothermal energyuse to be distinguished:
Hot-Dry-Rock method
The use of hot dry rock layers (HDR) at depths as fardown as 5 km is one possibility for geothermal gene-ration of electricity and heat. A heat-transfer mediummust be circulated through the usually crystalline rockto bring the heat to the surface. Without any additio-nal measures, the heat-exchange area and the permea-bility would be far too low to pass water through thelayers of rock. For this reason, a deep bore hole is firstmade from which the water is forced into the rockunder very high pressure and at a sufficiently high rateto provide a so-called “hydraulic stimulation”. Naturallyoccurring cracks and gaps are thereby expanded andsheared hydraulically to give new cracks, which increa-
GEOTHERMAL ENERGY — ENERGY FROM THE EARTH’S INTERIOR
Kiel
Rostock
Hamburg
Berlin
Bremen
Hannover
MünsterländerBecken
ThüringerBecken
Köln
Leipzig
Dresden
Süddeutsche Senke
Nordalpines Molassebecken
München
Norddeutsches Becken
Resources of geothermal energy
Hydrogeothermal resources in Germany
Source : GeoForschungsZentrum
Proven hydrothermal ressources
Potential of hydrothermal ressources
Probably without hydrothermal ressources
No aquifers available
ses the permeability of the rock. A “natural heat ex-changer” is obtained in this way.
A HDR plant is operated by pumping cold water to thedepths of an injection drill-hole and returning it to thesurface again through a second (production) bore. Thewater heated by the hot rocks at these depths can befed into district heating networks or provide steam forindustrial purposes. It is particularly attractive to gene-rate electricity from this steam, which can achieve tem-peratures up to 180 °C. So-called ORC turbines (ORC =Organic Rankine Cycle), which work essentially like asteam turbine, are used for this purpose. However, dueto the comparably low temperature of the heat transfermedium, between 100 °C and a maximum of about 180 °C, it is necessary to use an organic liquid with alow boiling point (e.g. ammonia) instead of water inthe steam turbine circuit. The electrical efficiency ofthis cycle is between 8 and 12 %.
Crystalline rock layers can be found undergroundalmost everywhere in Germany. The HDR techniquecan therefore exploit 95 % of the geothermal potential,an amount which is sufficient to cover the entire baseload of Germany’s electricity needs.
The exploitation of this potential is still inhibited by a lack of economic efficiency. Costs of 4 million Euromust be assumed just for one bore hole down to adepth of 5,000 metres. Thus locations are preferredwhere crystalline rock and high temperatures are to befound at comparatively shallow depths. This case is truein the Upper Rhine Basin. The total investment costs areestimated at about between 2,500 and 5,000 Euro/kW.The costs for generating electricity are then – for 8,000full-load hours per year – about 7 to 15 Cent/ kWh. In a research project in Soultz sous Forêts (Upper RhineBasin), an underground heat exchanger area of appro-ximately 3 km2 was opened up using the HDR techni-que at a depth of 3,900 m. Circulation trials conductedin 1997 determined a continuously available power out-put of between 10 and 11 MWth. In the meantime, twodeep bore holes were sunk down to depths of 5,000 m.Temperatures exceeding 200 °C were encounteredthere. A further delivery bore hole should be comple-ted in the spring of 2004. The goal is to reach a ther-mal output of 50 MW for an outlet temperature of 185 °C.
In Germany, the Federal Ministry for the Environmentis currently supporting the HDR technique in the cry-stalline rock at Bad Urach in Southern Germany, aswell as in the volcanic rock of the North-German low-lands (Groß Schönebeck, Brandenburg).
High-temperature hydrothermal systems
Under certain geological conditions, hot water can alsobe retrieved from water-carrying layers – the aquifers –
and then used for electricity and heat generation. How-ever, the temperature should exceed 100 °C for electri-city production. Furthermore, a sufficient quantity ofthermal water must be available. In a number of Euro-pean countries, e.g. Iceland and Italy, suitable thermalwater deposits can already be found at moderatedepths. In contrast, it is necessary to bore to depths ofat least 4,000 meters to reach adequately high tempera-tures and water quantities in Germany, and that only atspecial locations like the Upper Rhine Basin (UpperRhine Basin) and at the base of the Alps in Bavaria.
The thermal water is delivered to the surface of theearth through drill holes, and the heat is transferred toa steam turbine or other heat consumer. Again theORC cycle is implemented here. The water is thenreturned to the depths through a second bore hole inorder to maintain the underground water balance.These highly mineralised thermal waters cannot nor-mally be disposed of above ground for environmentalreasons.
Low-temperature hydrothermal systems
In other regions of Germany, especially in the South-German molasse (malmkarstic) basin, in the UpperRhine Basin, the Swabian Alb, and in parts of theNorth-German lowlands, the temperature of the under-ground water can reach between 40 °C and 100 °C, toolow for electricity generation. This geothermal energyis used instead for heating buildings and for hotwater, in thermal baths, and for commercial purposes(e.g. for heating greenhouses). In Southern Germany,especially in the region between the Danube river andthe Alps, the thermal water can also be used as drin-king water once it has cooled down because enoughwater is flowing underground and the mineral contentis low.
The investment costs for a geothermal heating plant liein the range of 400 to 1,000 Euro/kW for an installedheat capacity between 3 and 30 MW. A heat distribu-tion system incurs additional costs. Depending on thetemperature level and the abundance of the source,the costs for heat production can be between 2 and 4 Cent/kWh, assuming a utilisation of between 2,500and 3,000 full-load hours per year. For industrial custo-mers with a higher utilisation (more than 5,000 h/year),the costs of producing the heat can fall to under 2 Cent/kWh.
In Germany, the hydro-geothermal energy has longbeen tapped as an energy source. At the beginning of2003, there were 34 plants in operation, with a ther-mal output totalling 88 MW. Approximately one half ofthis power is for fossil-heated peak-time boilers, whichare only needed on cold winter days. The amount ofheat delivered from the depths of the earth are estima-ted at 0.11 billion kWh.
71
72
Deep geothermal energy probes
Existing deep bore holes sunk during explorations fornatural gas, geothermal energy, or to find possiblefinal-storage facilities for nuclear waste, can also beused in harnessing geothermal energy. Presumablythere are between 5,000 and 7,000 such bore holes inGermany.
So-called double-tube probes are fed into these deepbores down to depths as far as 4 km. Water circulatesthrough these probes in a closed circuit. Deep under-ground, the water is heated; at the surface the heat isdelivered to a heat-pump circuit (refer to the Chapter“Heat pumps”).
Technically, the potential of such probes in Germany isabout 800 billion kWh/a. The high costs are currentlythe main problem associated with this technology.Depending on whether an existing drill hole can beused, or whether a new bore has to be sunk, the heatproduction costs lie between 8 and 10 Cent/kWh forheating rooms and buildings (2,000 h/a), or between 3 and 5 Cent/kWh for industrial process heat utilisation(5,000 h/a).
The technical feasibility of connecting two deep boreholes underground is currently being studied in a pro-ject by the Technical University of Berlin “Study of aclosed geothermal heat exchanger”, financed throughan “investment programme for the future” by theFederal Ministry of the Environment.
Near-surface geothermal energy
The so-called near-surface geothermal energy, heatfrom the uppermost layers of the earth or groundwater, is also useful in heat pumps, as is described inthe following chapter entitled “Heat pumps”.
Research needed
Intensive research and development is necessary tomake progress in the production of energy, especiallyelectricity generation, from geothermal sources.Moreover, the creation of large-scale heat-exchangerareas deep under ground (HDR technique) and impro-ving the ORC process are to be optimised in future pro-jects. Drilling technology has to be adjusted to theneeds of geothermal energy. Also, the methods ofdetermining and registering the occurrences of hydro-thermal reservoirs must be improved.
The Federal Ministry for the Environment is suppor-ting seven projects within the scope of the “Zukunfts-investitionsprogramm” (Investment Programme forthe Future) to further develop pilot applications forgeothermal electricity and combined heat and powergeneration. Different technology concepts are applica-ble depending on the site conditions, including theHot-Dry-Rock technique, the use of existing deep boreholes, and the use of hot water from aquifers.
Supported by the Federal Ministry for the Environment,the first German geothermal power plant began opera-
Production and utilization of hydrothermal water
Hydrothermal system
Heat ing c i rcu i t
Geothermal c i rcu i t
Return temperature: 30 °CFlow temperature: 55 °C
Injection probe
Aquifer (gravel)
Production probe
Heat exchanger
Temperature: 32 °C
Possible production temperature: 80 °C
tion in Neustadt-Glewe in November 2003. The powerplant is equipped with an Organic Rankine Cycle turbi-ne and has a capacity of 210 kW. Thermal water at 97 °C, from a depth of 2,200 metres, is used for electri-city generation. The geothermal heating plant in Neu-stadt-Glewe has been operated successfully since 1995,providing 16,000 MWh heat per year. Since there is nodemand for space heating during the summer, a large
proportion of the heat energy remained unused. Thenew power station can produce additional electricityfrom this energy. It is expected that the annual electri-city generation of 1,400 to 1,600 MWh will meet thedemand of about 500 homes. Besides electricity genera-tion, the Neustadt-Glewe power plant is particularlyimportant for gaining practical experience to furthertechnical development.
73
74
HEAT PUMPS
––– Resources: Ambient heat in the ground, water and air
––– Sites: World-wide
––– Field of application: Hot water, heating
––– Capacity: 1 kW to 1 MW
––– Costs today: 5 to 10 Cent/kWh
––– Figures: Ground, water, and air as a heat source
Radiator
Heat source
Thrott le va lve
High pressure
Low pressure
Compressor Condenser
Vapor iser
Low temperature
High temperature
75
The utilisation of ambient heat with the help of heatpumps differs in one major aspect from using othersources of renewable energy. Namely, a heat pump isdriven by a considerable amount of external energy,amounting to anywhere between a quarter and onehalf of the energy which is used as heat, depending onthe exterior conditions. This technology is thereforealso considered as a rational use of energy, i.e. thesame category as low-energy heating boilers. Yet thereis also a major difference from these techniques: Heatpumps do not only use the energy supplied for runningthe pump, but also energy from the surroundings. Decisive is whether or not the renewable energy pro-portion predominates. Thus the heat pump is a hybridbetween an economical conventional use of energy anda source of renewable energy!
Energy is not just energy
The first rule of thermodynamics states that energycannot be lost. However, energy is degraded each timeit is converted from one form to another. When hea-ting a house, the chemically bound energy of the fuelis, through combustion, first converted into a hotflame, which heats the water in the radiators, which inturn increases the room temperature. Finally, this heatescapes to the environment. Energy is not being lost, itis merely that the temperature level of the energy hascontinually fallen. Heat pumps reverse this process,they “pump” the ambient energy present at a low tem-perature level back up to a higher temperature levelsufficient for heating purposes. Electrical energy or fuelis consumed during this process.
The principle of the heat pump
A fluid – e.g. a conventional coolant or propane – is circulated as a working medium in a closed system at different pressures. At low pressure, the working medium in the vaporiser absorbs the heat from the surroundings. A pump then compresses it to a higherpressure and temperature level. In the condenser, theworking medium releases the heat to the heating cir-cuit and thereby cools down again. A throttle valvelowers the pressure, the temperature decreases further,and the working medium can be returned to the vapo-riser. It is the same principle which is used in a refrige-rator, except that there is a cooling compartment in-stead of a heat source, and a heat exchanger is usedinstead of a radiator, which, in the case of the refrige-rator, is at the back of the unit.
There are different technical variants of heat pumps.The most widespread are the so-called compression
heat pumps. The compressors are often realised aspiston engines, though besides these, rotating-pistonand screw-type compressors are also used and these arevery suitable for regulating the speed. Small-scale heatpumps for space and water heating in single-familyhouses are normally driven by electric motors, largersystems can also be driven by gas-powered engines. Theadvantage of these gas-powered engines – which re-semble conventional combustion engines – is the high-efficiency transformation of primary energy, togetherwith the added advantage that the cooling water nee-ded for the engine can be used to increase the heatingtemperature even further. The specific investment costsare however generally higher, as are the operationaland maintenance costs. Work is continuing to furtherdevelop small-output heat pumps driven by gas-powe-red engines. Also, the heat pumps driven by electricmotors are subject to ongoing developments, especiallyso that they can better adjust to the immediate heatingneeds and the momentary temperature of the heatsource, and in this way attain a higher efficiency. Theunits currently available on the market are consideredtechnically mature.
Absorption heat pumps are different than compres-sion heat pumps. In an absorption heat pump, themechanical compressor is replaced by a thermal com-pressor, run on a two-component mixture. The absorp-tion heat pump can be operated by any type of ther-mal energy with a sufficiently high temperature level,e.g. with heating oil, natural gas, or with biofuels. Thispump is characterised by low-maintenance operationsince, apart from a small solvents pump, there are nomoving parts. Absorption heat pumps are frequentlyused in industry for utilising waste heat. The marketintroduction of a small-scale gas-driven heat pumpwhich, with a heating capacity of only 3.6 kW, is suita-ble for use in low-energy houses, is expected in 2004.Any higher capacity needed in winter or for hot wateris provided by a condensing boiler integrated in theunit.
There is still much unused energy in the air, earth,and water
Heat pumps can tap the ambient heat in differentways. Ambient air is most frequently used for the production of hot water. Its advantage is that air is available everywhere and at all times. A drawback isthat the ambient air is always coldest when the needfor heating is greatest, namely in winter, which lowersthe yield from the heat pump. The greater the diffe-rence in temperature between the heat source, i.e. herethe air, and the useful heat, the more energy is neededto drive the pump and obtain the same result.
HEAT PUMP — A HYBRID
It is energetically more favourable to use e.g. theground as the heat source. At a depth between 1 and 2 meters under ground, the temperature in winter doesnot generally drop under 5 °C. With pipes lain in theground carrying brine as a medium, the energy can beabsorbed and brought to the heat pump. In this way,the temperature range in the heat pump can be keptrelatively constant over the year and the amount ofenergy required is kept low. These ground collectors –referring to the pipes in the ground – are howevermore costly than those using ambient air. The areaneeded for horizontally laid ground collectors canamount to between one and one-and-a-half times thefloor space in the dwelling to be heated (Figure:Ground collector). The garden surrounding the housecan be used for this purpose and, once the collectorshave been laid, then still serve as the garden. If thisarea does not suffice for the heating purposes – andthis is often the case considering the land plots nowa-days for new constructions – then the collectors canalso be lain vertically as probes in the earth. For thispurpose, bore holes are sunk into the ground to adepth of as much as 150 m into which the brine-filledpipes are then inserted. One major disadvantage is thatthese earth probes are even more cost-intensive thanhorizontally lain ground collectors and, furthermore,permission concerning the water rights must be obtai-ned from the authorities. The energy collected by earthprobes is also primarily from the surroundings, i.e.
from the sun. In Werne-Fürstenhof (NRW), each of the120 buildings of a newly erected estate shall be fittedwith an earth probe and an appropriate heat pump. 70 of the systems have already been completed.
Ground water is another possible heat source. Thetemperature of ground water fluctuates only very littleover the year and usually lies in the range between 8 and 15 °C. It is however rarely possible to use groundwater as a heat source. Moreover, the cognisant autho-rities are very restrictive when granting the necessarylegal permission because protection of the groundwater is highly valued. Water from the sea, from lakes,and from rivers, when accessible, is also very suitableas a source of heat for heat pumps. Permission fromthe authorities must also be obtained in this case,though this is granted in the majority of cases sinceany cooling down of the thermally-stressed water sur-face is certainly desirable from the ecological stand-point.
Finally, the heat from man-made sources, like e.g.waste water and exhaust air, can be removed as well.Since the energy is usually at a rather high tempera-ture, the use of heat pumps is very effective. Due to thelow energy prices at the present time, and because ofthe short amortisation times demanded for the returnof their investments, the recycling of waste heat inindustry is usually neglected.
Monovalent — bivalent — mono-energetic?
In order to keep the investment costs low, heat pumpsrarely completely meet the heat requirement. They areusually designed for about 30 – 50 % of the maximumheating capacity needed. The heat pump must then beoperated in the “bivalent” mode, i.e. it is supplementedby a conventional heat generator. If this additional hea-ting is operated by means of the same energy carrier,e.g. supplementing an electrical heat pump by an addi-tional electric heater, then this mode of operation isreferred to as “mono-energetic”. If the heat pump is theonly heat source, then the system is termed “monova-lent”. These systems have the advantage that only onetechnology needs to be installed in the boiler roomand no chimney is required. Ground-coupled heatpumps are often designed these days to be monovalent.For new constructions with very good heat insulationstandards, this design can certainly constitute a attrac-tive economical alternative.
If the heat provided is to be used for heating purposes,then a low flow temperature in the heating system isadvantageous, because a small temperature differenceis important for highly efficient system operation. If theflow temperature is lowered by one degree, then theheat pump needs 1 % less energy. Underfloor heatingand wall heating systems are therefore very suitable.Hot-air heating systems also require only low flow tem-
76
Ground collector
peratures and they may become more common in thefuture, especially combined with controlled ventilation.
Costs and prospects
Electrically operated heat pumps with capacities rele-vant for single-family homes are available for specificinvestment costs between 500 and 1,000 Euro per kWof outputted heat. For other energy sources than air,the costs for the ground collector and earthwork mustalso be taken into consideration, and can amount tobetween 250 and 500 Euro per kW of outputted heat,depending on the particular circumstances. Typically,the total investment costs amount to between 7,500and 15,000 Euro for a heat-pump system in a single-family house. The actual heating costs depend stronglyon the extent to which the local electricity companyoffers special rates for electrical heat pumps. The speci-fic costs per kilowatt-hour of heat are somewhere bet-ween 6 and 10 Cent/kWh. Additional costs are incurredif construction measures to lower the flow temperatureare necessary. It is difficult to determine the technicalpotential of using ambient heat. Estimates assume that
14 to 16 % of the present-day needs for space heatingand hot water can be provided in Germany in this way.At the end of 2001, there were approximately 60,000systems installed in Germany which were poweredexclusively by electricity, of which 40 % were for water-heating purposes. Following a boom in the early eigh-ties when, because of high oil prices, heat pumps appe-ared to be a good economical choice, the demand forheat pumps declined considerably. Since the beginningof the nineties, however, the demand has increasedagain, not the least because of greater marketing eff-orts by the electricity companies. In 2001 there werenew instalments of 8,215 electrically driven heat pumpsfor heating purposes and another 4,827 for hot water.In total, about 1.4 billion kWh per year of ambientheat are used due to the heat pumps.
Heat pumps — Part of a sustainable energy supply ?
A considerable part of energy taken from the outsidemust be used for running the heat pump. For this rea-son, it is important to determine the ratio of inputtedenergy to the yield of useful energy for this technology,
77
Source : DLR
112 103
Gas boiler
100
Gas losses: – 9 Losses: – 3
7826 24
Heat pump
7676
Losses from power plant and grid: – 52
Ambient heat
Losses: – 2
Electro-heat pump
Gas engine heat pump
100
66 61 3419
19
Gas-poweredengine
Heat pump
4747
Gas losses: – 5Losses: – 8
100
Gas condensing boiler
Energy flow and degree of utilisation for the various heat-pump systems
Energy flow and performance of different heat pump systems in comparison to a condensing boiler. In the calculations a performancecoefficient of 4 is assumed for the electro heat pump.
78
thereby considering the entire chain from the energysource, its processing, and its use in the heat pump. If electricity is the external energy running the pump,then it is necessary to gain at least three times moreheat energy than the consumed electrical energy inorder for more heat energy to be provided to the buil-dings than is inputted from fossil or nuclear energysources. This ratio, designated as the performance co-efficient, is a result of losses incurred during electricitygeneration (at the present time about two thirds of theinputted primary energy). It determines in the overallbalance sheet whether renewable energy will be used
at all. For electricity, it has to average approximatelylarger than three over the year. Since the losses in-curred in the gas supply system are less than in thenational electricity grid, and there are no power-plantlosses, the required annual performance coefficientneeded for heat pumps driven by gas-powered enginesneed only be 1.1 in order for the system to be conside-red as using renewable energy (Figure: Energy flow anddegree of utilisation for the various heat-pumpsystems).
Regarding pollutant emissions – for example nitrogenoxides and carbon monoxide, but not carbon dioxide(CO2), the emission of which depends solely on theenergy carrier and on the degree of conversion effi-ciency – electrically driven heat pumps can offer ad-vantages over conventional heating boilers, in particu-lar oil-fired boilers, even for low performance coeffi-cients, because the specific emissions from powerplants in the Federal Republic of Germany are lowthanks to the efficient pollution control measures already in force.
The intensified use of electrical power for heating is,however, problematic for energy policy, since nuclearpower is being phased out and the electricity supply ispredominately based on fossil energy carriers. But withelectricity being generated increasingly from renewableenergy sources and from combined heat and powerplants, the electrical heat pump will become more andmore interesting from the ecological point of view.
Sinking the vertical drill holes for heat probes
79
HYDROGEN AND RENEWABLE ENERGY
––– Resources: Fossil primary energy carriers through gasification and reformation Electricity from renewable energy sources through electrolysis of water (in the long-term other, direct methods also possible)
––– Sites: Widespread using a distribution infra-structure; as a buffer in stand-alone systems
––– Field of application: Like other chemical energy carriers; also as a storage medium
––– Capacity: 1 kW to 50 MW (thermal)
––– Hydrogen costs: Coupled to the costs of primary energy: hydrogen from natural gas approximate-ly 4 Cent/kWh; from biomass approxima-tely 9 – 13 Cent/kWh; from low-cost hydropower (electrolysis) approximately 8 – 10 Cent/kWh.
––– Figures: Dissociation of water by electrolysis,MCFC high-temperature fuel cell, Hydrogen filling station
80
Hydrogen from solar energy and water: this temptingvision was already formulated by Jules Verne in 1874. “I believe that hydrogen and oxygen, used alone ortogether, will one day form an inexhaustible source ofheat and light”, predicted a clever engineer in Verne’sadventure novel “The Secret Island”. Numerous con-cepts have been drawn up for a “hydrogen economy”since then, the majority of which is based on renewa-ble energy sources. Many of these proposals, however,gave the impression that hydrogen could be the cen-tral problem solver, both for energy supply shortages(limited resources of fossil fuels) and for the difficultieswith disposal (CO2 emissions and the greenhouseeffect), and that many intermediate steps and develop-ment stages of a changing energy industry could sim-ply be skipped. Most of the more recent studies, howe-ver, presuppose a more differentiated developmentpath over several decades, and numerous conditionshave been formulated in the meantime which must befulfilled to make a more extensive use of hydrogenmeaningful.
Today, hydrogen, the lightest element, is experiencinganother renaissance, mainly attributable to three deve-lopments:
––– Renewable energy is, in the meantime, beingtaken seriously as a major option for energy in thefuture. The time- and space-dependent supply charac-teristics of heat and electricity generation from re-newable energy sources need to be better harmonised
with consumption patterns. As a consequence, the further expansion of renewables is necessarily associa-ted with the rapid introduction of hydrogen.
––– The transportation sector is almost completelydependent on the most scarce fossil resource, i.e. onfuel oil. The demand for petrol, diesel, and kerosene isincreasing from year to year. Primarily hydrogen, pro-duced from other energy resources, is being proposedas a possible new fuel to satisfy the world-wide increa-sing demand.
––– The third reason for the renaissance of hydrogenis the fuel cell: This innovative and very efficient ener-gy converter transforms hydrogen and oxygen intowater while generating electrical and thermal energyand without producing any of the pollutants associatedwith conventional fuels and engines. An ideal symbio-sis between electricity and hydrogen thus appears to bepossible.
Only the first reason is truly related to renewable ener-gy and can thus rightly claim the extremely positiveimage associated with the terms “hydrogen” and “hy-drogen economy”. Concealed behind the two other ca-ses is the idea that coal, an abundantly available fossilenergy source, can be mobilized as “clean coal” for thehard times when drastic reductions in the greenhousegas emissions are needed, or to indirectly promotenuclear energy as a source of an emission-free fuel.
HYDROGEN — ENERGY CARRIER WITH A POSITIVE IMAGE
Hydrogen production from renewable and non-renewable primary energy sources
The process of hydrogen production
Natural gas Coal Biomass Electricity from renewables
H2O
CO2
O2Reformation – Gasification
Synthesis gas (CO, H2, CO2, H20)
CO-conversion, cleaning (CO2-separation)
H2
Electricity, Heat, Fuel
H2
Fuel, compensation for fluctuations
Electrolysis H2O
81
It’s the process that counts
Use and significance of a hydrogen economy dependfirst and foremost on the source of the hydrogen. Theeconomic and environmentally friendly production ofhydrogen is the key problem, even though hydrogen isthe most abundant element in the universe and alsothe fuel of our sun. Yet because it is so reactive, it isonly present on the earth in bound form: for examplein water, in carbohydrates, in biomass, or natural gas.Hydrogen, therefore, must first be chemically separa-ted, a process requiring energy. Hydrogen is only asclean as the process which produces it.
Hydrogen has long served as a chemical raw materialin the manufacture of plastics, in the glass, fertiliser,and electronics industries, as well as in refineries fordesulphurising petrol. 80 % of this hydrogen originatestoday from mineral oil and natural gas, 15 % is pro-duced from the gasification of coal, and 5 % from elec-trolysis. Producing hydrogen from hydrocarbons requi-res the use of a reformer where hydrocarbons aremixed with water vapour and split into hydrogen andother components. Not only is energy required forreformation, but also the greenhouse gas carbon di-oxide is invariably emitted. As a consequence, the spe-cific greenhouse gas emissions from fossil-based hydro-gen are always higher than those from the originalfuel (Figure: Greenhouse gas emissions). Therefore,except when particularly efficient energy converters,like natural-gas-supplied fuel cells, offset this drawback,the use of fossil-based hydrogen does not contribute tothe reduction of greenhouse gas emissions. Since CO2
emissions accumulate at the location of hydrogen pro-
duction and not, like in the case of oil or gas, primarilyduring consumption, the carbon dioxide can theoreti-cally be “disposed of”, i.e. be taken away in liquid orgaseous form and stored in secure underground depotslike e.g. exhausted natural-gas fields or in aquifers(glossary) for long periods of time. This concept repre-sents a “clean coal” hydrogen path. However, severalproblems must still be resolved and the concept mustfirst be proven in demonstration projects. Furthermore,the storage possibilities are limited, so only a certainamount of carbon dioxide could be removed from thecarbon dioxide chain by this method. The fact is, howe-ver, that carbon-dioxide-free hydrogen produced in thismanner would, at a price of 12 – 13 Cent/kWh, be con-siderably more expensive than today’s relatively cheaphydrogen from natural gas, which costs about 4 Cent/kWh. Hydrogen generated by electrolysis using renewa-ble electricity is still relatively expensive as well, butshould cost less in the medium term than “clean coal”hydrogen, as a result of the economy of scale, and isunlimitedly available. (Figure: Hydrogen costs). There-fore, in the medium and long term, a hydrogen econo-my is only a sustainable option when based on renew-able energy sources.
The optimal strategy
A special feature of power supplied from renewableenergy sources is that the useful energy – with theexception of biomass – is at first available “only” aselectricity and, in the case of solar radiation and geo-thermal energy, as heat of different temperatures.Energy in chemical form, when needed, requires
Fossil energy carriers:
Petrol
Diesel / Heating oil
Natural gas
Fossil hydrogen:
GH2 / Natural gas
GH2 / Heavy oil
GH2 / Coal
Hydrogen from renewable sources:
GH2 / scrap wood
GH2 / renewable energy source
0 50 100 150 200 250 300 350 400 450 500 550 600 g CO 2 -equ iv. kWhGreenhouse gas emiss ions
Greenhouse gas emissionsSource : DLR
Use Production Energy type, process control
Greenhouse gas emissions from fossil energy carriers compared with those from hydrogen production using fossil energy carriers, bio-mass, and electricity from renewable energy sources, in g CO2-equivalent per kWh, including all expenditures for production, transpor-tation to Germany, and compression of the gaseous energy carriers.
82
a second conversion step. The present-day conversionchain from chemical energy (coal and hydrocarbons) toelectricity is thus reversed, leading to considerable con-sequences for the final-energy supply structure. Whenincreasing the contribution of renewable sources to theenergy supply, hydrogen has considerable advanta-ges over other forms of chemical energy carriers (likee.g. methanol):
––– An energy carrier is needed which is relativelystraightforward to produce from electrical energy, sincein the long term it is electricity which can be providedeconomically and in very large quantities from renewa-ble energy sources.
––– The traditional methods for load managementfail if the share of renewable energy in the electricitysupply increases to levels significantly higher than 50 %. Surplus electricity thus needs a storable energycarrier into which it can be transformed in central ordecentralised facilities with a broad range of capacitiesand the highest possible efficiency.
––– The energy carrier needs to be multi-functional,useful both for heating (medium and high-temperaturerange) and as a transportation fuel. Furthermore, itsuse in innovative combined heat and power generationtechnologies (fuel cells) should also be possible in anefficient way.
––– Transportation and distribution of the energycarrier should be based on existing infrastructures.Also, seasonal storage of the energy carrier is required.
Only hydrogen from renewable energy sources com-plies with all these requirements. Hydrogen can beused to overcome the limitations resulting from thesupply structure of renewable energy sources and thusto ensure a reliable energy supply at all times for allenergy users. A further advantage is that another gaseous energy carrier, namely natural gas, is currentlygaining in importance. The current increase in naturalgas supply – which is however limited in the medium-term because of limited resources – is compatible withthe simultaneous expansion of renewable energy sour-ces. Natural gas is therefore a suitable fossil “transitionenergy” during the transformation of the energy sys-tem towards renewable energy and hydrogen. Naturalgas also provides a suitable transition infrastructure,which is otherwise often a limiting factor in establis-hing a new energy carrier. The existing natural-gasinfrastructure can be used in an almost ideal mannerthrough the admixing of hydrogen, while at the sametime decentralised local hydrogen networks are beingconstructed and later linked together. Since, however,losses during hydrogen production are unavoidable andthus result in additional costs, it is obvious that themore cost-effective options for using renewable energysources should be exploited first. The introduction ofrenewable energy is thus a door-opener for hydrogen –not the other way round.
The following conclusions can be drawn from theresults of recent studies on hydrogen and its contribu-tion to an energy supply system under the constraintsof far-reaching CO2-reduction targets:
Hydrogen costs, Cent/kWh
Foss i l hydrogen Renewable hydrogen Renewable hydrogen
Natur
al ga
s
Source : DLR
H 2, N
atur
al ga
s
H 2, c
oal
Water
Biomas
s
Wind, O
ffsho
re
STPP,
Impo
rt
Biomas
s
Wind, O
ffsho
re
STPP,
Impo
rt
Hydrogen costs
Costs of hydrogen production from fossil and renewable energy sources for large-volume consumers. Costing some 2 Cent/kWh, naturalgas is unrivalled today as a low-cost energy carrier. In the future, however, renewable hydrogen will be available at costs between 7 and 10 Cent/kWh as the most economic carbon-dioxide-free fuel (STPP = Solar thermal power plant).
Estimate with CO2 storage
Production, near future
Range
Production, near future
Range
Production after 2020
20
15
10
5
0
83
––– The introduction of hydrogen into the energysupply system will be necessary if the emissions of CO2
are to be reduced by more than 40 % (compared to the1990 emission level). For lower reduction levels, there isa clear priority for rational energy conversion and use,and the direct use of renewable energy sources. Recentstudies which analysed in detail the possibilities of loadmanagement for electricity from renewable energysources indicate that hydrogen needs to be introducedonly when CO2 reduction targets between 70 and 75 %are set. All scenarios include hydrogen when CO2
emissions should be reduced by more than 80 %.
––– The time and intensity of introducing hydrogenis mainly determined by CO2 reduction strategies inthe transport sector. A forced introduction of hydro-gen in the transport sector results in its significant par-ticipation in the final energy supply already at a 60 %CO2 reduction level. If the direct options for heat andelectricity supply from renewable energy sources aremore strongly emphasised, then hydrogen will onlybecome relevant at a CO2 reduction level of 75 %.
––– Extrapolating to the almost complete avoidanceof energy-related CO2 emissions requires that hydrogenfrom renewable energy sources contributes 30 – 35 %of the final energy consumption; hydrogen then
covers about 85 % of the energy demand in the trans-portation sector and 30 % in the heat supply sector.
––– Linking the CO2 reduction targets in the diagramwith a time scale indicates that the introduction ofhydrogen from renewable energy sources is not neces-sary before 2025 and, because of the still relativelyhigh costs, is not appropriate from the economicpoint of view either; on the other hand, a relevantshare of hydrogen should be achieved by 2050 at thelatest if we aim for CO2 reductions of more than 80 %,and if in the long-term energy supply should be basedon renewable energy sources.
––– Taking into account the long-term investmentcycles in the energy sector, it is already necessarytoday to prepare for the transition from natural gas tohydrogen, including the imminent use of stationaryfuel cells for combined heat and power production.Fuel cells play a central role within an efficient andlow-emission energy supply system. The advantages offuel cells compared to conventional energy convertersincrease at the same rate as hydrogen enters the ener-gy market. Fuel cells might thus be considered as anappropriate “bridge technology” in the transition pro-cess towards an energy supply system based on renewa-ble energy sources.
0 10 20 30 40 50 60 70 80 90 100 CO 2 reduct ion compared to 1990, %
Source : UBA 2002
Share of hydrogen in the final energy comsumption as a function of CO2 reduction targets in the German energy supply system, based onstudies performed since 1989. “Sustainability” and “Maximum” are scenarios from [UBA 2002].
Share of hydrogen in the final energy consumption
Various studies 1989 – 1998
Maximum scenario
Sustainability scenario
0
5
10
15
20
25
30
35
Share of f ina l energy consumpt ion , %
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STAND-ALONE SYSTEMS
––– Resources: Solar radiation, wind power, biomass, hydropower; possibly with a storage system; possibly as a hybrid system with additional fossil fuels
––– Sites: Regions far from power lines, and appli-cations in developing and industrialised countries
––– Field of application: Electricity generation, direct applications(pumps, lighting, purification of water, signalling...)
––– Capacity: Several watt to several megawatt
––– Production costs: Between approximately 0.30 and 1 Euro/kWh depending on the technology and the location
––– Figures: Wind/ solar hybrid system, Dish-Stirling system, Overshot waterwheel
85
A system is designated as an insular system or “stand-alone system” when it supplies electrical power inde-pendently of an organised utility grid. Originally thisterm described the electrical supply on a real island –like for example on the Greek island of Kythnos. Thegrid-independent supply of e.g. a solar-powered par-king meter is also an example of an insular or stand-alone system.
Approximately 2 to 3 billion people all over the worldstill live without electricity. By far the largest of thesepopulations are in the developing and threshold coun-tries, where the rural areas are often a long way awayfrom any electrical networks. Yet there are as many as2 million people on small islands and in remote moun-tain regions in Europe who do not have access to apublic power grid [BINE 2002].
The main target countries are therefore developing andthreshold countries. A large market potential is how-ever also in regions far from networks and for indivi-dual applications in industrialised countries. The re-quirements on stand-alone systems in technical, econo-mical, and social respects are accordingly very diverse.
Technologies and applications
The possible applications for stand-alone systems rangefrom the direct supply to individual power consumers
through to setting up small-scale networks for the elec-trification of households, individual buildings, or wholevillages. The power range is correspondingly large andcan extend from a few watts for small appliancesthrough to several megawatts for e.g. a local supplysystem for a village (Figure: Classification of stand-alonesystems).
In the past, the consumers in regions far away frompower supply networks were often supplied with elec-tricity from diesel-powered generators, sometimes inclu-ding a storage battery as a buffer. For climate protec-tion reasons, it is desirable to use a renewable energysource to replace or at least supplement the diesel unit.The first efforts towards renewable energy use were,however, usually only undertaken for practical or forfinancial reasons, e.g. the fuel supply became difficult,uncertain, or simply too expensive. There are severalrenewable energy sources which can replace or supple-ment an energy converter running on fossil fuel. Theyare described in the following:
Wind power
In the simplest case, a windmill drives a water pumpconnected directly by a set of gears. Many such millswere in operation in the Netherlands and in the USA(Western Rotor); today they are still used in droughtregions for pumping water from deep sources. In the
STAND-ALONE SYSTEMS — FAR AWAY FROM THE PUBLIC GRID
10 W 100 W 1 kW 10 kW 100 kW 1 MW 10 MW
Breakdown and output ranges of stand-alone systems
Classification of stand-alone systems
Small appliances Direct actuation
Direct applications
Stand-alone systems
Small-scale networks
Direct heating Home Systems Water treatment Systems for buildings Village network
RadioWater pump,
wind-powered
wind-powered Solar HS Desalination Schools
Lamp Wind HS Purification Hospitals
Battery chargerWater pump, solar-
powered
Hybrid systems
Agricultur
...
meantime, modern wind-power systems are available,the electricity from which can be used in various wayswithout being fed into a larger network. The possibili-ties for using such systems range from simple electricalheating using unregulated generators and changingnetwork frequency, to driving electrical water pumps,battery charging (e.g. for holiday lodges, mountainhuts, and measurement stations), through to supplyinglarger stand-alone systems in the megawatt range.
Windpower converters can also be combined with solarcells to give hybrid systems in which the fluctuatingwind- and solar-energy supply can be partially compen-sated (example: traffic control systems on motorways).
Solar energy
Similar to wind power, solar energy can also be usedfor driving water pumps without generating electricity.The first water pump driven by solar-generated steamfrom solar-trough collectors was constructed in 1875 byMouchot. Later, flat-collector-driven pumps were develo-ped. However, only photovoltaic systems have achievedworld-wide distribution so far. Large opportunities inthe future are however expected for solar-thermalpower plants.
Photovoltaic systems are of modular design and can –when properly connected – provide electrical powerranging from a few watts to several megawatts. Theysupply small appliances for signalling and in informa-tion technology (emergency phone boxes, signallingsystems, parking meters), everyday-use appliances (clocks, radios, pocket calculators, pocket torches, char-gers, toys), domestic appliances (lawn-mowers, watertreatment systems), or find uses in building enginee-ring (driving roller blinds, lighting, ventilation, alarms,motion detectors). The so-called “Solar Home Systems”in the output-power range from approximately 50 to100 W were developed especially for those developingcountries with an abundance of sunshine. These, toget-her with a battery charging system, are able to self-suf-ficiently supply the major installations of a house (lighting, radio) with power. Special applications likesolar-generated cooling and propulsion for boats (solarboats) can also be realised with photovoltaic systems.
Solar-thermal systems produce electricity in an indi-rect manner in that they first concentrate the incidentsolar radiation before converting it into thermal energyand then, in a further step, into electrical energy. Significant technical variants for stand-alone systemsare, especially the Dish-Stirling systems, but also thesolar-trough and tower systems which, in small units,can also be used for this purpose (for example 500 kWhpilot plant with combined power-heat-cooling for sup-plying a hospital in Empoli/Italy). The advantages ofsolar-thermal applications as opposed to photovoltaicsystems are, on the one hand, the more favourablecosts for generating electricity and, on the other hand,
the possibility to bridge periods of inadequate solarirradiation with the help of thermal storage media.The supply reliability can thus be increased in this wayfor applications far away from networks.
Biomass
Due to the storage capability of fuel, biogas systemswith incorporated generators are particularly idealapplications for supplying isolated villages. Besidesexcrement from inhabitants and reared animals, thebiomass accumulating from farming the fields could beused as well. The currently available solutions are,however, less suited for the generation of electricity indeveloping countries since the technologies are relati-vely complex for low-maintenance stand-alone opera-tion. To the extent it is possible in the future to buildsystems which are robust and simple to operate, a largepotential will develop for using biomass in the lowerpower output range as well.
Biomass-powered Stirling engines are already in usetoday. In contrast, the use of biomass in gas turbinesand BIG /GT systems (Biomass Integrated Gasification /Gas Turbine) is still unsuitable at the present time forgrid-independent operation, because these systems areonly economical in larger power ranges. Once themicro-gas turbine technology has become sufficientlymature, it might be possible to expand its applicationconsiderably.
Hydropower
Of the renewable energy sources, hydropower is themost significant so far. Nearly one fifth of the world-wide electricity production originates from hydroelec-tric power stations. Unlike the large-size dam-reservoirpower-plant projects, which can cause major social andecological problems, the smallest (< 100 kW) and small-scale (100 kW to 10 MW) hydropower stations are, ingeneral, less problematic in this respect. In the area ofdecentralised systems, immense potential is still un-tapped in the developing countries in particular. Thetechnology ranges from upper- and lower-shaft water-wheels, to spiral-type generators, and up to water tur-bines. Whereas waterwheels and spiral-type generatorsare particularly robust, low-maintenance, and compa-tible with fish life, turbines – and in particular those inthe high-performance range – are characterised byhigh efficiency and economic operation.
Hybrid systems and their components
In the most simple case, a stand-alone system consistsof an energy converter, a battery, and a charging unit.To increase the availability of the electricity-generatingsystem, it is however often meaningful to combine twoor more energy converters to create a “hybrid system”.
86
87
Such combinations can be realised as “fuel savers” (e.g. diesel /wind or diesel /solar systems), or as purelyrenewable systems (e.g. wind /solar systems). A furtherpossibility to increase supply reliability is to supple-ment the system by including an energy storage me-dium. The components of the entire system are then anenergy converter, a current rectifier, a storage medium,and the control and communication system. The pos-sible energy converters were already described in detailabove; the other components are the subjects of the following sections.
Power inverters and current rectifiers
Larger photovoltaic systems consist of several smallersolar-generator systems connected in series. In themeantime, modular and standardised concepts with so-called String power inverters have started replacingthe centralised power inverters.
The bi-directional power converter has gained signifi-cance in hybrid systems. As the link between the bat-tery storage and the insular network, it helps to stabili-se both network voltage and frequency, controls the
charging process, regulates both the active and the idlepower, and, when necessary, manages the energythrough load shedding. A DC-power battery combinedwith a current rectifier is known as an “Alternating-current battery”.
Storage media
In stationary systems, cost-effective lead-type batteriesare, as a rule, used for storing the electrical energy.Also suitable for smaller applications are the higher-grade nickel-cadmium, metal-hydride, or lithium-ionaccumulators.
Besides electrochemical storage in batteries, there arealso other ways to store energy:
––– Mechanical storage (pump storage, compressed-air storage, flywheels)
––– Electrical storage (super-capacitors, supra-conductive magnetic storage SMES)
––– Thermal storage (sensitive and latent-heat storage)––– Chemical storage (biomass, methane reforming,
hydrogen)
Ecological aspects Climate protectionSpecific emission of greenhouse gases per kWhSpecific emission of air pollutants per kWh
Resources protection Consumption of non-renewable energy
Noise protection Noise emissions
Socio-economic aspects General interests
Economic development potentialCultural compatibilityDegree of supply fairnessDegree of participation
Individual interestsWorkplace effectsHealth / hygiene effects
Economical aspects Low costs and pricesSpecific investment costs per kWCost of generating electricity per kWh
Repair and maintenance Requirements of specialists and the procurement of spare parts
Potential for the future Degree of know-how development
Economic independenceDegree of import dependency and the regional self-supplySupply dependability / availability
Exemplary catalogue of criteria for the assessment of stand-alone systems
C r i t e r i o n I n d i c a t o r
Project examples
Starkenburger Hütte (Source: ISET 2002)
Far away from any grid, a small-scale cogeneration unit/PV hybrid system supplies the Starkenburger Hütte in theStubaier Alps with electricity. This system has been demonstrating the successful practical use of an AC-power-coupled system since 1995.
1 x gas-powered cogeneration plant: 15 kWel
6 x photovoltaic generators: 5.28 kWpeak3 x alternating-current battery: 2.2 kVA/approximately 40 kWh
Energy park Geesthacht (Source: HEW 2001)
Although the energy park Geesthacht near Hamburg is not a stand-alone system, it is still an interesting examplefor a hybrid system. It consists of a pump storage plant which is fed using additional wind- and photovoltaic-powered pumps since 1994. In principle, such a plant could be realised as a stand-alone system.
Pump turbine output: 140 MWel
Solar field output: 60 kWel
Wind-power plant output: 500 kWel
Water-storage capacity: 3.3 million m3 (= 600 MWhel energy)Total electricity production: 62 million kWh/a (2001)Storage efficiency: approximately 70 %
Domestic solar systems in South Africa (Source: KfW 2003)
The South African Government has started a programme with the objective of equipping some 1.5 million house-holds, schools, and health clinics in rural regions with Solar-Home-Systems (SHS) within ten years. Decentralisedelectrification is environmentally-friendly and, in this case, is more cost-effective than connection to the nationalgrid. In addition to the enhanced comfort, there is also greater security against burglary, and health and accidentrisks are reduced. Additional applications can be developed in the small-scale commercial area.
The German Kreditanstalt für Wiederaufbau (KfW) is supporting this project financially with some 16 million Euro.The financing concept is at the same time a contracting model: With the support from the KfW, a private-sectorlicensor invests in the plants and thereby assumes responsibility for their installation and operation. The users paya monthly rate reduced accordingly by the amount subsidised. The fee covers the costs for repairs and maintenan-ce, among others. Payment is made by purchasing a chip card which enables SHS operation (“Fee-for-servicemodel”). Low transaction costs and a guaranteed collection of the fees are assured in this way.
Agreement running period: > 15 yearsFinancial support by the KfW: approximately 27,000 SHS with approximately 16 million EuroPower from the SHS: up to 0.2 kWh/d for supplying power for approximately 3 – 4 lamps,
a radio, or a black-and-white TV-set.
88
Some of these storage techniques, like e.g. pump andcompressed-air storage, are already in use on a largescale (individual systems of up to several 100 MWel).The use of capacitors and flywheels has so far beenlimited to small performance ranges (several milliwattsto a few kilowatts) and to niche applications. The po-tential for further development here is however verylarge. Technically tested, but not yet proven economi-cal, is the production of hydrogen as a means of sto-ring energy. The relatively cheap method of thermal
storage has developed into a very interesting option. It is suitable for large capacities and will play a signifi-cant role in the foreseeable future in combination withsolar-thermal power plants.
Control and communication devices
The needs for control and communication increasewith the increasing complexity of a stand-alone system.
Communication between the individual system compo-nents is necessary to keep the system stable, to mini-mise the operating costs, and to assure supply reliabili-ty. Feedback from the consumer to the higher-level con-trol system (load management system) must be possibleto e.g. block or shed the load of individual consumers.However, none of the systems available on the marketat the present time has become the established stan-dard.
Market developments and prospects
Stand-alone systems, starting from the straightforwarddecentralised diesel systems, have since progressed upto complex hybrid systems on the basis of renewableenergy. In many miniature applications, e.g. solar-ope-rated clocks or pocket calculators, the practical benefitsor the image given to the user predominates.
When supplying larger systems in remote regions, how-ever, a renewable system must primarily be able tocompete with conventional techniques in terms of cost-effectiveness. Despite the relatively high costs in therange between about 0.30 and 1 Euro/kWh for produ-cing electricity in today’s stand-alone systems, they aresometimes worthwhile if the procurement of fuel is dif-ficult or is not dependable. Not to be underestimatedare, additionally, the positive effects of avoiding fireand health hazards associated with the combustion ofkerosene, diesel, and paraffin in developing countries.A holistic assessment of renewable stand-alone systemscompared with conventional techniques or grid con-nection must therefore include ecological and socio-economical criteria along with purely economic aspects(refer to the table with the catalogue of criteria).
As a principle, it is necessary to differentiate betweenthe target groups in the developing and industrialisedcountries when analysing their market outlooks. Gene-rally, further research and development towards stan-dardisation and modularisation of system componentsis required and will be a major step towards cost-effec-
tive series production, as well as the simple and cheapinstallation and maintenance of the systems.
For the long-term success in developing countries, aninfrastructure has to be set up for repairs, trainingcraftsmen, and spare-parts logistics. Many projects fromthe past have shown that, for successful realisation, it isabsolutely necessary to consider the individual socio-economic conditions at the location. Financing modelsalso play a large role, because the people are generallynot in a position to finance in advance projects like e.g.Solar-Home-Systems.
The next step in the industrialised countries is to testdecentralised energy management systems (DEMS) asstand-alone systems. Besides the control system forgenerating and storing power, they include smartmanagement of the demand. “Virtual power plants”arise if several decentralised energy supply systems areconnected to an associated network, which is then con-trolled from one centre. The use of virtual power plantsrequires the capability to handle very large volumes ofdata, the testing of which has only just begun.
89
Example for the components of a decentralised energymanagement system (DEMS)
Decentralised energy management system
Battery storage systemWind-power plants Fuel cells
Photovoltaic systemConsumers Biomass plant
DEMS
Source : Konwer l 2003
90
Global availability of energy
Our energy needs can be met many times over by theextraordinarily large and inexhaustible flows of energyon our planet earth, without having to use any of thefinite resources of energy. These flows of energy, how-ever, must be tapped using the technologies describedin the preceding chapters in order to be useful. By ap-plying these technologies, the majority of the guideli-nes for a sustainable energy supply can be fulfilled aswell. Available to this end are solar irradiation, kineticenergy from the wind, energy in the waves, tides, andcurrents in the seas, biomass which grows again everyyear, the potential energy of water, geothermal energy,and thermal energy from the seas. These flows of ener-gy are equivalent to about 3,000 times the amount ofenergy needed annually in the world today. The tech-nical potential for use can be derived from the physi-cal potential of the renewable energy (Figure: Naturalavailability of renewable energy – large cube in thebackground), providing energy in a usable form – i.e.as useful heat of various temperatures, electricity, andfuel for heating and propulsion purposes, like e.g.hydrogen – for the end consumer.
There are various criteria to be considered when deter-mining the potential:
––– Limits for the efficiency, plant size, and tech-nical development potential of the techniques eithercurrently available or in the near future.
––– Structural restrictions due to location dependen-cy (e.g. geothermal energy), limited radius of transpor-tation (e.g. biomass), availability of appropriate areas orcompetitive uses (e.g. collectors, solar cells, growingenergy crops), nonexistent infrastructure (e.g. lack ofheat distribution networks), limited availability and reli-ability of the energy supply (e.g. electricity from fluc-tuating sources, like wind or solar irradiation).
––– Ecological constraints regarding the spacerequirements (e.g. wind power), impairments to theflow of the water (e.g. hydroelectric power), and chan-ges in the landscape (e.g. wind power), as well asrestrictions in the uses possible for biomass (e.g. rem-nant materials from forestry and agriculture; growingenergy crops).
The technical potential of renewable energy is thus nota constant over time. It represents a cautious indicationwith regard to the technical feasibility within a longer-term period, and shows which importance each of theenergy sources and the respective technologies couldhave for different countries and regions.
Considering these restricting criteria, only a few partsper thousand (solar radiation, wind) to a few percent(biomass, geothermal energy) of the natural energyflows are suited for exploitation – i.e. useful in theform of secondary energy carriers (cube in the fore-ground). Only hydropower already demonstrates techni-cal exploitation in the order of 10 %. Even for verystringent restrictions, the total global potential of tech-nically usable renewable energy is approximately sixtimes the current world-wide consumption of finalenergy. About 65 % is provided by the radiant energyfrom the sun.
Renewable energy can thus, in principle, still meet anincreasing demand for energy, completely and perma-nently. Accordingly, contributions from renewable ener-gy sources in the range of 50 % and more to the worldenergy consumption are already considered feasible inthe various scenarios for the future up to the middle ofthe next century. Currently, renewable energy actuallymeets some 5 % of the world energy consumption,without considering the ecologically problematical useof firewood in the less-developed countries. This valueis approximately equivalent to the world-wide contribu-tion made by nuclear power. About 19 % of the globalconsumption of electricity is generated from renewableenergy sources. Without the current mainstay, hydro-electric power, the share is just 0.2 % of the total worldconsumption and 1.5 % of the electricity consumed.
The availability of renewable energy differs considerab-ly throughout the various regions of the world. Thecase of solar radiation – the most abundant source – isshown on the world map using the example of thepotential for solar-thermal power plants (Figures: Globalpotential, and: Potential in the Mediterranean region)which use the solar radiation in concentrated form. Itcan be seen that the regions with the largest potentialall lie in the so-called “sun belt” of the earth, i.e. be-tween the 20th and the 40th latitudes of the southernand northern hemispheres. In particular, the overcasttropical skies around the equator and the low-pressureregions in the west-wind zones are responsible for thesun belt. A similar pattern is apparent for photovoltaicsystems as well. The influence of an overcast sky ishowever less dramatic, since photovoltaic systems canalso utilise diffuse irradiation. The correspondingpotential for wind power (Figure: Onshore and offshorepotential) depends on other factors: Over the land mas-ses of the continents, due to the harsh topography ofthe countryside which slows down the winds, the ave-rage wind speed is considerably lower than out at sea,where the wind can blow unhindered. On the otherhand, exposed areas on land exist with excellent windconditions due to the particular topography.
TECHNICAL POTENTIAL AND ENVIRONMENTAL PERFORMANCE
91
The regional differences in potential are even morepronounced if the technical restrictions and reductionsfor non-suitable or otherwise used areas are taken intoaccount. They narrow the regional potential consider-ably in some cases, as can be seen in the example of a world map showing the electricity production fromsolar-thermal power plants. Potentially useful areas areexcluded from this map since they are either unsuita-ble or not available for setting up solar-thermal powerplants due to restrictions like e.g. settled areas, forests,agricultural areas, bodies of water and swamps, dunes,protected areas, or steep topography.
As shown in the world map, North Africa, the Arabianpeninsula, and Australia all have an enormously highpotential for the solar-thermal generation of electricity.More than half of the world-wide potential is to befound in these areas. In North Africa alone more thana hundred times the world’s electricity requirementcould be provided by means of solar power plants, primarily due to the large areas available in theseregions. The potential is also very high at the southerntips of Africa and South America, Mongolia, the South-west of the USA, and in Mexico. Although there is alsopotential in Canada and Siberia, the area-specific re-turns are however so low that exploitation of theseregions is not economically sensible. In contrast, with
200 – 300 GWh/km2/a, each square kilometre of land atsites in North Africa could supply as much energy as aconventional coal or natural-gas fired power plant withan output of 50 MW and 6,000 full-load hours per year.The effects of the described restrictions on land arevery apparent on the map around the MediterraneanSea. Despite the many competing possibilities for usewhich, especially for the countries lining the northernMediterranean Sea, lead to a substantial reduction inthe potential, there is still enough area available inthese countries that considerable proportions of thenational electricity generation could be covered bysolar-thermal power plants. The area and irradiationpotential principally available in Spain alone wouldeven theoretically suffice to generate adequate quanti-ties of electrical energy to meet present-day needs inEurope.
Thus the following can be concluded: The technicalpotential of the individual sources of renewable energyvaries considerably from region to region – not everyenergy source is available in every country, and it isapparent that certain regions have sources which areparticularly favourable to develop. The greater thevariety of energy sources and technologies used – solarenergy, wind, geothermal energy, biomass, hydroelec-tric power – the easier it is to compensate for any
Source : DLR Natural availability of renewable energy
The natural availability of renewable energy (cube at the back) is extraordinarily large. The potential energy yield in the form of electrici-ty, heat, and chemical energy carriers (front cube) exceeds the present-day energy needs (grey cube) by a factor of six.
World energy demand
Geothermal power
Solar irradiation on the continents
Heat from the seas, energy from waves
Wind
Water
Biomass
92
regional deficits in a particular source of energy by tap-ping other potential sources of energy. A diversificationof energy sources and technologies is thus very sensiblewhen considering regional potentials. In practice how-ever, there are attractive renewable energy potentialsin every country just waiting to be exploited. In theforeseeable future, this domestic potential will guidenational developments in renewable energies, as theycan only be developed over decades. In the long-term,certain regions with substantial potential for renewableenergy can furthermore become suppliers of cost-effec-tive secondary energy. Thus today’s world trading withfossil energy carriers could at some time in the futurebe replaced by trading with electricity and hydrogenproduced from renewable energy sources.
The potential for using renewable energy sources in Germany and associated costs
Germany is a good example of how a country with amoderate climate can develop a variety of renewableenergy sources and by doing so, can meet considerableproportions of its own energy needs. Relative to thetotal primary energy, the potential for the useful re-newable energy sources within Germany amounts to6,200 PJ/a, equivalent to some 40 % of the present-dayprimary energy consumption. If the energy demand inGermany is reduced – more details on this efficiency
strategy can be found in the chapter “The long-termprospects – a scenario of optimal renewable energyuse” – then the proportion of these domestic sources ofrenewable energy alone will accordingly increase tolevels considerably higher than 60 %. The individualvalues for this potential were intentionally chosenrestrictively for areas which could be used for collectorsand solar cells, for wind power sites, or land for gro-wing energy crops. According to statistics, electricityfrom hydroelectric sources, wind, and solar plants isdefined as primary energy in the ratio 1:1.
Nevertheless, renewable energy sources are the mostimportant domestic source of primary energy. And justlike the fossil energy of today, energy carriers producedfrom renewable energy sources can also be imported inpractically unlimited quantities at a later point in time.Beginning with a low proportion of this potential as“indicators” in the reference potential for Germany,the corresponding value for the potentially availableprimary energy from renewable energy sourcesamounts to at least 9,000 PJ/a for Germany, with ca.400 PJ/a, only 4.5 % of this potential is being exploitedat the present time. More important than just informa-tion concerning the potential are those segments ofthe potential which are usable at a given point in time,since not all of the above-mentioned reference potenti-al is immediately available. It is important to classifypotentials into cost categories and consider possible
Protected terrain, m/s—1
> 6.0
5.0 – 6.0
4.5 – 5.0
3.5 – 4.5
< 3.5
Open plain, m/s—1
> 7.5
6.5 – 7.5
5.5 – 6.4
4.5 – 5.4
< 4.5
Coast, m/s—1
> 8.5
7.0 – 8.5
6.0 – 6.9
5.0 – 5.9
< 5.0
Offshore, m/s—1
> 9.0
8.0 – 9.0
7.0 – 7.9
5.5 – 6.9
< 5.5
Mountains and crests, m/s—1
> 11.5
10.0 – 11.5
8.5 – 9.9
7.0 – 8.4
< 7.0
Wind speeds at 50 m above the ground considering 5 different topographical site conditions. Left: Onshore, Right: Offshore (Source: European Wind Atlas, Risø National Laboratory, Roskilde, Denmark, simplified representation).
93
future cost reductions, enabling the economic potentialto be derived for a given point in time. Except forhydroelectric power and biomass, the possibility formaking, sometimes considerable, cost reductions isinherent in every technology. These possible reductions
depend essentially on the further technical progressand market development. Based on the analysis of pastcost developments, comparison with other technologieswhich are produced in a similar way as the plant forusing renewable energies, and from assumptions regar-
Above: Global technical potential for electricity generation from solar-thermal power plants. The electrical energy yield in one yearrelative to one square kilometre of available land is indicated. The resolution of radiation data used for determining the potential isapproximately 125 x 125 km2 at the equator. Below: The Mediterranean region as an energy supplier - technical potential for genera-ting electricity from solar-thermal power plants per square kilometre of land.
0 – 20 GWh /km2/a
21 – 40 GWh /km2/a
41 – 60 GWh /km2/a
61 – 80 GWh /km2/a
81 – 100 GWh /km2/a
101 – 120 GWh /km2/a
121 – 140 GWh /km2/a
141 – 160 GWh /km2/a
161 – 180 GWh /km2/a
181 – 200 GWh /km2/a
201 – 220 GWh /km2/a
221 – 240 GWh /km2/a
241 – 260 GWh /km2/a
261 – 280 GWh /km2/a
281 – 310 GWh /km2/a
94
ding the market turnover, it is possible to determinethe cost reductions achievable in the future for theseenergy technologies. The cost reductions can be appro-ximately derived from learning curves, which indicatethe percentage by which the costs of a particular tech-nology decline when the corresponding turnover isdoubled. Typical values lie between 10 and 30 %. Itcould be shown by the example of wind power thatsuch cost reductions really occur.
This relationship between market growth and costreduction is also of considerable significance when de-signing the supporting measures aiming to effectivelymobilise renewable energy sources on the long term.In any case, these measures must be effective enoughto sufficiently mobilise a large volume of the marketwhile, at the same time, exerting continuous pressureon the production costs so that the technologies caneventually assert themselves on the energy market wit-hin a reasonable short time period.
With costs of up to 0.075 Euro/kWh, the most cost-effective segment in the field of electricity at the pre-
sent time is 25 TWh/a from hydroelectric power, frombiomass, and from wind at favourable locations. Some65 TWh/a lie between 0.075 and 0.125 Euro/kWh.There is a further 190 TWh/a costing more than 0.125 Euro/kWh, of which 150 TWh/a from photovol-taics alone. If the market developments for technolo-gies are sufficiently stimulated, then the most cost-effective segment of the potential with costs less than0.075 Euro/kWh, resulting from a decline of costs andthe market introduction of new technologies (offshorewind; geothermal energy), can grow to some 90 TWh/aby 2010. For the same reasons, the overall potential canincrease to around 450 TWh/a. In the longer-term, i.e.after 2020, the cost-effective potential segment cangrow to some 350 TWh/a by further mobilising allthese technologies. The total potential can thus exceed600 TWh/a, thereby surpassing the quantities of electri-city being generated today. This capacity is enabled bythe import of electricity from renewable energy sourceswhich will then be possible, the widespread utilisationof offshore wind potential, and by exploiting the poten-tial for electricity generation from geothermal sources. The quantities of electrical power which can be supp-
Potent ia l in TWh/a 2 0 0 0 2 0 1 0 2 0 2 0
Source : HGF 2001
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
25
64
190
90
212
155
341
131 130
Potential for electricity generation from renewable energy sources
Potential for using renewable energy sources increases, and costs decrease. Electricity generation potential for three base-years, by cost category.
Import
Photovoltaic
Geothermal
Wind
Biogas
Hydro
Biomass
0
50
100
150
200
250
300
350
95
lied are to about two thirds from the fluctuating sour-ces of wind and solar radiation. A considerably morefar-reaching development of this potential thereforecalls for redesigning the supply structure, to modifypresent-day distribution networks, and to make appro-priate modifications in load management, reserves, andcontrol systems for power plants. Since such a processrequires decades to complete, it can be carried outalong with pending new investments while continuous-ly integrating technical advances.
The potential for providing useful heat can be structu-red in a similar manner as for generating electricity(Figure: Potential for heat production). A total potentialof 3,500 PJ per year (of final energy) results, equivalentto approximately 65 % of the quantities of fuel current-ly being used for generating heat. Heat from sources ofrenewable energy can be made available by stand-alone systems (e.g. wood-fired boilers, hot-water collec-tors) as well as by means of smaller and larger heatdistribution networks. The latter play a very significantrole in the further-reaching developments on the heatmarket.
In many cases, any utilisation at all is only possible bythis means (geothermal energy, large-scale collectorsfor heating purposes, biomass systems for combinedheat and power generation). The heat is made moreexpensive by its distribution; typical heat distributioncosts for district heat networks are between 2 and 3 Cent/kWh. However, since the larger centralised hea-ting systems have lower specific costs than the small-scale systems for individual buildings, the overall costsfor heat in district heat systems are, for a careful designand full use of the network, often lower than those forstand-alone heating systems. It must be noted that heatdistribution networks need to be constructed in alreadyexisting residential areas in order to sufficiently deve-lop the potential available through renewable energy.
At the moment, approximately two thirds of the heatpotential from renewable energy sources are often notdirectly available for structural and technical reasons.This situation concerns solar district heating systemswith seasonal storage, using the heat from deep underground layers, and biomass from plantations ofenergy crops. The cost-favourable potential under
Potent ia l in PJ/a
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
< 0.0
75 Euro
/kWh
0.075 –
0.12
5 Euro
/kWh
> 0.12
5 Euro
/kWh
345
465
235
850
1,040
305
1,425
Ω 1,815
215
Source : HGF 2001 Potential for heat production from renewable energy sources
Potential for heat production from renewable energy sources for three base-years, by cost category.
2 0 0 0 2 0 1 0 2 0 2 0
Geothermal Solar collectors Biogas Biomass
250
500
750
1,000
1,250
1,500
1,750
0
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0.075 Euro/ kWhth amounts to almost 350 PJ/a at themoment. It consists exclusively of biomass residuals andis economical compared to a price for fuel oil of appro-ximately 0.5 Euro/litre. Cost reductions, in particularfor collector systems, will increase this potential toaround 850 PJ/a by the year 2010. If the technicalpotential can be fully developed by the year 2020, thenapproximately 40 % (1,400 PJ/a) can be classified in thiscost category.
The conclusion should not however be drawn from thelow utilisation to date of the renewable energy potenti-als that economic considerations alone hinder theotherwise rapid expansion of renewable energy usage.Equally significant for a continuous development is toconsider the investment cycles in the fields of buildingsand power plants. An accelerated expansion of usingrenewable energy, as expressed in the considerationsfor more-effective climate protection, therefore calls fortheir timely and high-priority inclusion in all planningand investment decisions pertaining to the supply ofenergy, and particularly in the area of homebuilding.
Sources of renewable energy for the developing countries
From the energy supply point of view, developing coun-tries are usually considered as having “decentralised”supply structures, i.e. there are either none or only afew inter-linked supply structures. Isolated consumerstherefore have no access to an electricity network and,due to their low income, have only limited quantities ofoil at their disposal. This case holds for approximatelytwo thirds (some 3 billion people) of the inhabitants ofthe developing countries or about half of the world’spopulation. Some 2 billion people have no power sup-ply from electricity grids. These areas in the world areoverwhelmingly in the least developed of the develo-ping countries. In these regions, the consumption ofnon-commercial energy, i.e. fire-wood primarily for coo-king purposes, is also the highest. In many of thesecountries, this amount is as high as the commercialenergy consumption. Many people in these countriesonly manage to survive thanks to the time-consuming,exhausting, yet unproductive and ecologically questio-nable gathering of firewood.
At the same time, the developing countries are howe-ver undergoing an unstoppable process of urbanisation.Already 15 years from now, half the population ofthese countries (6 billion by the year 2015) will beliving in towns and cities which, in many cases, will bebigger than some of the largest in the northern hemis-phere. Of the currently 15 cities with more than 10 mil-lion inhabitants, there are 11 of these totalling 140 mil-lion people in developing countries. Mexico City, SaoPaulo, and Bombay are the largest of these. In the year2010, there will be more than 20 cities of this size withthen 350 million people in the developing countries.
A further one billion people will be living in cities withpopulations exceeding 1 million inhabitants.
These developments are also of considerable importan-ce for shaping the future energy supply in these coun-tries. They are facing a much larger challenge than theindustrialised countries when it comes to approachinga sustainable energy supply. Sustainable solutions mustlikewise be found for both areas – fast-growing metro-politan areas and rural regions. Considering the poten-tial, sources of renewable energy are abundant in thesecountries, they can however only be developed to therequired extent with the technical, and above all finan-cial, assistance from the industrialised nations. Also,increasing the efficiency in generation (combined heatand power generation in the industrial and commercialarea, high-efficiency gas-power plants), and in particu-lar in the efficiency in using the energy, are of para-mount importance; just as are the renewal and impro-vement of existing infrastructures.
In the rural areas of the lesser developed countries, “onsite” sources of renewable energy are already the onlymeaningful supply possibility, due to the poor roadwayinfrastructures which make the already very scarce fos-sil energy carriers even more expensive. Therefore, thebasic energy needs for the country’s population shouldbe based as quickly as possible on renewable energy,using “suitable” decentralised technologies, like small-scale water power, photovoltaic systems, wind power,and the efficient use of biogas and biomass. In thisway, the trend towards urbanisation might possibly beslowed down as well.
The obstacles which are encountered in realisingdecentralised renewable energy technologies in thedeveloping countries are usually of a different naturethan those in the industrialised nations. Of particularsignificance are the discrepancies between the highinvestment costs for renewable energy and the lack offinancing possibilities. Different financing mechanismsare therefore being tested. Small-size solar systemscould, for example, be funded in advance by large com-panies. The system is then activated by entering a pass-word received in return for a monthly fee. Yet there arealso very pragmatic problems to be resolved: Lack ofspare parts, absence of a roadway infrastructure – tur-bine housings for hydroelectric power plants often haveto be transported on the backs of human bearers – thesuccessful social integration of technologies in the eve-ryday life of the population, and many more as well.Yet there is still more to do. One part of a developmentstrategy in the energy field has to be the equallyurgent larger-scale “centralised” systems based on rene-wable energy sources. Examples are the large grid-con-nected wind parks, hydroelectric power stations ofappropriate size, and solar-thermal power plants, whichwill supply the already existing and the fast-growingurban regions with sufficient energy from renewablesources. Integrated “system solutions”, designed to
97
exactly meet the particular needs and which shouldconsist of a variety of different technologies, are nee-ded here. Production knowledge and capacities in therelevant countries must also be considered.
“North” and “South” — beneficiaries of a commonenergy strategy
In the industrialised countries, a “new optimisation” ofenergy-supply structures is already in progress towardsgreater “decentralisation” and “integration in systemsolutions”. This transformation is motivated by the en-gineering developments in energy technologies (e.g.gas turbines, fuel cells, renewable energy) and in infor-mation and communication technologies (managementof many decentralised plants), as well as the advancingliberalisation of the energy markets calling for less tied-up capital, shorter planning and construction times, together with greater flexibility and improved capabili-ty to respond to changes in basic conditions. For thedeveloping countries, it would be backward to imitatethe already outdated, very centralised energy supplysystems of the industrialised countries. These countries,right from the beginning, should set up the closest tooptimal combination of decentralised and centralisedenergy supply technologies. From the viewpoint of sus-tainability, i.e. also under the premises mobilising ashigh a share as possible of renewable energy in thelong-term, the question is not “centralised” or “decen-tralised”, but rather to find the most efficient and com-plementary combination of plants of different size andcapacity.
The developing countries could thus shorten the way toa sustainable energy supply for the future, and in thisway quickly catch up on the development deficits inthe energy field. To this end however, the industrialisedcountries must first provide considerable support bothin the design and concepts and the technical enginee-ring for the energy systems, as well as and in particularin financial aspects. This support will prove fruitful inthe long-term for both groups of countries.
Due to the prevalence of radiant energy, the more-sou-thern countries have a very high potential for renewa-ble energy, which will surpass by far even their ownfuture conceivable consumption. Thus, for example inMorocco, it would be possible with the help of solar-thermal power plants to generate enough electricity toequal today’s world-wide consumption. Using renewa-ble sources just for national consumption is thereforenot the only perspective for today’s developing coun-tries. In the long-term, continuous exchange of energywill be possible by means of electricity or chemicalenergy carriers, or even a global supply on the basis ofrenewable energy will be technically possible as well –similar to the case already today with natural gas andto a certain extent also with electricity. Such countriescould, in a few decades time, become “exporting
regions” for the cost-effective and inexhaustible energycarriers produced from renewable energy sources. Thisarrangement provides considerable benefits for bothpartners since together, much larger potentials can bedeveloped for the benefit of both. This type of strategyis in full agreement with the guidelines given inChapter 1 for a sustainable energy economy.
Energy is not the only scarce asset. In many countries,it is already apparent that there will be a considerablylack of clean water, especially for agricultural purposes,in the coming decades. North Africa expects a deficitin drinking water about the size of the Nile by 2025. A major contribution to a sustainable development ofthe countries in the arid regions of the world wouldtherefore be combining the production of electricityand drinking water. Solar-thermal power plants forcombined heat and power generation can serve thispurpose. The decoupled heat is used for the thermaldesalination of seawater which, unlike the reverse-osmosis method, supplies water with a salt content suf-ficiently lowered to be suitable for agricultural irriga-tion purposes. The production of desalinated watercould even be the prime objective here: Electricityaccumulates so-to-speak as a side-product, and can beused either in the country or, by means of high-voltageDC transmission, could even be exported to CentralEurope. The transmission costs, e.g. from Morocco, arein the range of a few Cents per kilowatt-hour, meaningthat costs for imported solar electricity of less than 6 Cent/kWh in Central Europe could be achieved. Tothis end, high-performance lines are needed like thosewhich have been realised on a world-wide scale withsome 60 GW capacity and transmission distances up to 2,500 km.
Establishing these high-voltage DC transmission linesfor the renewable electricity link could become part offuture European investment plans and be classified asan infrastructure measure for a sustainable develop-ment. The Mediterranean countries are already beingaffected today by less precipitation resulting from cli-mate changes. An accelerated European changeover toCO2 -free electricity is therefore just as much in theinterests of these countries as is the emission-free pro-duction of larger amounts of drinking water. In thisway, solar-thermal power plants and other electricity-generating technologies for using renewable energycould become part of an international co-operationboth for global climate protection and for sustainabledevelopment for both regions. This type of strategywould also contribute to reducing the risks of nationaland international conflicts over the scarce and increa-singly more costly assets of water and energy.
Subsidised development aid would thus be replaced bythe revenues from the “green electricity trading” bet-ween North Africa and Europe. The potential for syner-gy in both regions, of which the one has large amountsof technical and financial means at its disposal and
98
a large demand for energy, whereas the other has alarge potential for solar energy and an abundance ofopen space, would be used for a common sustainabledevelopment and economic co-operation.
The ecological attributes of renewable energy
The chapter entitled “Requirements for a sustainable energy supply ” described how our present energysystem is still revealing numerous sustainability deficits,in particular with respect to its impacts on ecosystems.It is based on energy carriers with limited availability.It burdens our atmosphere, our soil, and water withpollutants and greenhouse gases. And more: Leaks inoil pipelines, oil-tanker accidents, area-devastating coal-mining, an unresolved question of how to dispose ofnuclear waste, and the possibilities of reactor accidents.The list of environmental problems in the field of ener-gy is long.
A more intensive use of renewable energy promises to be the remedy. The fuels for the corresponding energy conversion technologies are the natural flows of energy surrounding us in the form of radiated solarenergy and the wind, the energy from flowing watersand the energy from waves, the energy contained inbiomass and geothermal energy. By using these flowsof energy abundant in nature, the consumption of fos-sil and nuclear energy on our planet can be avoided.
Renewable energy is largely compatible with ourclimate and resources. With one restriction: Theinstallations needed to convert these flows of energymust first be constructed, operated, and finally be dis-mantled at the end of their useful service life.
Raw materials and energy are necessary for these pur-poses. What are the effects on the environment compa-red to using conventional energy? Two key parameterscan clarify this question: the energy payback time, i.e.the time needed by an energy system to generate thesame amount of energy required for its construction,operation, and disposal; and the cumulated green-house gas emissions.
For fossil fired or nuclear plants, the energy paybacktime for the construction of the plant is around 2 to 3 months. Yet in terms of their overall operation, theseplants never amortise because more energy always isconsumed in the form of fuel than is produced in theform of useful energy! Water, wind, and solar-thermalpower plants need between 3 and 13 months for amor-tisation of their construction energy, i.e. considerablyless than their useful service life. Once this amortisa-tion time has elapsed, each hour of operation then pro-vides valuable energy which is “ecologically gratis”!
The production of solar cells is energy intensive.Today’s systems based on crystalline silicon have energyamortisation times of several years at our latitude,
Europe North Africa
Technology resources
Solar energy resources
Financial resources
Land resources
Electricity needs
Water needs
Pot. Europe Synergy Potential Pot. North Africa
Synergy potential in Europe and North Africa for the joint sustainable development of an energy supply. Using a transcontinental powerlink, this potential can be used for a common use of the most abundant sources of renewable energy from this region.
Potential for synergySource : DLR
Solar-thermal generation of electricity and desalination Wind power Hydroelectric power
Geothermal energy High-voltage DC transmission line network Expanded inter-linked network
99
however, their useful service life is a multiple of thistime period. Further progress in the production andtechnology of solar cells should reduce this value tobetween one and two years within the next decade.
Similar conditions prevail in the generation of heat.Solar collector systems require 18 to 30 months,installations utilising hydrothermal geothermal energyneed only 7 to 10 months to amortise. Therefore, a multiple of the energy originally expended in con-structing these systems using renewable energy is pro-duced within their operational lifetime – quite theopposite to both fossil-fired plants and nuclear powerstations. This low consumption of resources is alsoreflected in the associated emissions of green-housegases (Figure: Greenhouse gas emissions). These emis-sions from constructing the plants, whereby the pre-sent-day energy supply structure was taken as the base-line, for most renewable energy technologies – exceptphotovoltaics – is between 10 and 25 g/kWh of usefulenergy. In the case of photovoltaic systems, reductionsare possible in the medium term to about 50 g/kWh.The values fluctuate between 20 and 65 g/kWh of use-ful energy for the use of biomass in heating boilers,depending on the cultivation and the harvesting of thewood. The greenhouse gas emissions of fossil-basedenergy plants are, in contrast, considerably higher. If the future energy supply were to include higher pro-portions of renewable energy, then the emissions of
greenhouse gases resulting from constructing theplants would fall even more, since more low-emissionenergy would then be used and technical progresswould optimise the efficient and ecological production.Thus, on the ecology balance sheet, renewable energycan be designated as being an environmentally verycompatible energy technique, even when consideringthe plant construction.
For an ecologically optimised expansion of renewableenergy, it is furthermore necessary to consider otherenvironmental aspects as well. Besides the environmen-tal effects associated with the construction, operation,and disposal of the installation, there are other pro-blem areas characteristic for each individual technolo-gy which can lead to conflicts with the goal of natureconservation.
By definition, wind power plants need wind and the-refore must be installed at windy and exposed sites.Planning the installation must therefore, as a matter offact, consider all the needs of nature protection as wellas compatibility with bird flight routes and similaraspects. Compliance is assured by legislative require-ments and the designation of high-priority and suitableareas. Furthermore, in the case of offshore wind parks,the compatibility with the marine fauna must be assu-red. Even the disputed spoiling of the appearance ofthe country-side, in particular in the highly structured
The energy amortisation time describes the time which is needed by the installations to produce the same amount of energy as wasrequired for its construction, operation, and subsequent disposal. * Power plants based on exhaustible energy carriers never amortise inenergy terms since they always consume more fuel than the useful energy they generate.
Energy amortisation time for construction, operation, and disposal
Generation of electricity compared to today’s electricity mix
Generation of heat in comparison with a natural gas boiler
Wind power 3 to 7 months
Hydroelectric power 9 to 13 months
Solar-thermal power plant in North Africa 5 months
Photovoltaic system in Central Europe• Polycrystalline silicon, modern manufacturing technology 3 to 5 years• Thin-film cells 2 to 3 years
Gas power plant never *
Coal-fired power plant never *
Nuclear power station never *
Solar collectors 1.5 to 2.5 years
Geothermal energy (hydrothermal) 7 to 10 months
Gas-fired boilers never *
Oil-fired boilers never *
100
central mountain regions, can be subjected in part toobjective observations if, for instance, areas of particu-larly high visual sensitivity are represented by appro-priate GIS-supported methods (glossary). A balance bet-ween climate protection and the appearance of a localwind power plant can therefore be found. Even the useof hydroelectric power can be associated with furtherecological problems. In the case of run-of-river powerstations, the migration of the fish can be impeded byan interruption in the natural flow of the water. Theconstruction of weirs, discharge channels, and dam-
med-up waters, together with reduced flow rates, tur-bulence, and dragging power of the waters, can causechanges in the water structure, transportation of sedi-ments, and the ecological balance of the waters andthe surroundings.
Furthermore, dam-type hydroelectric power stationscan lead to conflicts of use with farming and to floo-ding of large open spaces. At the same time, however,these are also protect against high water and providedrinking water.
CO 2-Equ iva lent in g/kWh th
Source : DLR
Solar collectors Solar district heating
Geothermal Wood chips,Min. /Max.
Condensing boiler,gas
Condensing boiler,oil
Electrical heatpump
CO 2-Equ iva lent in g/kWh el
Source : DLR
HydropowerMin. /Max.
WindMin. /Max.
PhotovoltaicMin. /Max.
Solar thermalpower plants
Min. /Max.
Coal Natural Gas CC Nuclear
Greenhouse-gas emissions from heat production
Greenhouse-gas emissions from different heat production technologies, in CO2-equivalent per kWh. Emissions from renewable energysources are very low compared to the use of fossil fuels.
Greenhouse-gas emissions from electricity generation
Greenhouse-gas emissions from different electricity generation technologies, in CO2-equivalent per kWh. Emissions from renewable energy sources and from nuclear are very low compared to fossil fired power plants.
100
200
300
400
0
1,000
800
600
400
200
0
101
The conflicts in goals between protecting the climateand protecting the waters can be reduced by construc-tion measures. For example, upstream migration routesfor fish, re-routing, and sluice flows can improve thepassage through the rivers. The German legislation atthe federal and the state level regulates the environ-mental compatibility of hydroelectric power stations.For example, minimum amounts of water being dis-charged from power stations can prevent the build-upof sludge and damage to the mother bed. Environ-mental impact assessment required for authorizationplace high requirements on the ecological quality ofthe plant.
In Germany, the expansion still possible for hydroelec-tric power is concentrated on the reactivation andrenovation of older plants and constructing new plantsat already exploited sites. For appropriate sensitivity inplanning and execution, new plants can be designed tobe of considerably greater environmental compatibilitythan was the case earlier with the now older plants, sothat added advantages in water protection and natureconservation are possible along with generating moreelectricity. New constructions (e.g. at the Upper Rhine)can also be located at sections of rivers which were pre-viously changed by earlier human intervention, therebyopening up opportunities to correct earlier mistakes. At completely untouched stretches – only to be foundalong very small rivers these days – it is a matter ofconsequence to deny the construction of hydroelectricpower stations.
The use of biomass must be carefully analysed withparticular regard to the required surface areas. Todayand in the near future primarily residuals and wastematerial are used as bio-energy carriers. A significantincrease of biomass for energy use does however callfor the cultivation of energy crops in the medium term,especially with the purpose of producing motor fuels.Initially, such plants can be grown on farming land nolonger being used for agriculture due to the past food
production surplus. In the long-term, the cultivation ofbiomass for energy purposes will however competewith the ecologically desirable reduced intensificationof agriculture. This situation must be taken into ac-count in good time. In some points it can be in theinterest of nature protection to supply as much biomassas possible to an energy application and in this way,reduce the costs for caring for and attending to cultu-red landscapes. This case holds for woodland culturelandscapes (e.g. heather countryside) or in areas wherethere are excessive amounts of reeds, rushes, and waterplants.
All detrimental effects to the environment resultingfrom the use of renewable energy must be analysedwith great care so that new problems do not arisewhile attempting to establish a long-term sustainableenergy system. Exactness in planning, embedding inthe local conditions, compatibility of the utilised tech-nologies, consideration for ecology-based criteria, and asound mix of different kinds of renewable energy car-riers, must assure a maximum of environmental com-patibility when providing energy. The German FederalMinistry for the Environment is thus funding severalsocio-economic studies which analyse in detail the eco-logical benefits as well as potential weaknesses of rene-wable energy technologies. Based on the results ofthese studies, strategies for an ecologically optimisedexpansion of renewable energies in Germany are deri-ved.
The measures of environmental compatibility specifiedfor renewable energy must of course also be appliedfor the types of energy still being used today. Other-wise the danger exists of a one-sided and therefore bia-sed assessment, which can lead to a situation in whichsmall local impacts from using renewable energy areclassified as alarming, while considerably more seriouseffects on our entire habitat from using fossil andnuclear energy are overlooked.
102
Today’s use of energy in Germany
About 14,330 PJ of primary energy were consumed inGermany in 2003, equivalent to about 340 million tonsof oil or 4,000 billion kWh. The annual per capita ener-gy consumption is therefore 174 GJ, an amount equiva-lent to 6 tons of coal or 48,500 kWh. The energy sup-ply is still based mainly on mineral oil, contributingabout 36 % in 2003. However, the significance of hardand brown coal has decreased in recent years. Bothtogether contribute one quarter to the requirementand serve primarily for electricity generation. Naturalgas is becoming more and more important with cur-rently 23 %; besides domestic sources, natural gas issupplied by the Netherlands, Norway, and Russia.Nuclear power has a share of just 13 % of the primaryenergy consumption in Germany, occupying only thefourth place.
Renewable energy – mostly from biomass and hydro-electric power, with an increasing amount from windpower in recent years – met with 450 PJ/a about 3.1 %of Germany’s primary energy demand in 2003. Thecontribution of renewable energy to electricity genera-tion is much more significant. In 2003 renewables pro-vided about 8 % of the total electricity production andthis tendency is increasing. The largest proportion isstill being supplied by the hydroelectric power stations;yet in the meantime, wind power stations are contribu-ting more than 3 % of the electricity generation. Re-newable energy is now providing at least 4 % of theheat supply. Here wood is the major resource; the con-
tributions from solar collectors and geothermal energyare still relatively low. The share of renewable energyin the form of bio-diesel in fuel consumption is now 0.9 %.
Private households currently consume around 29 % ofthe total final energy. The consumption in the trans-portation sector has increased continuously in the lastfew decades, in particular because road traffic has in-creased considerably. Since 1999 it has remained atabout the same level as the private households, where-as the proportion of the final energy consumption dueto road traffic was still 25 % in 1990. On the otherhand, the energy consumed by industry is decreasingcontinuously as a result of more efficient technologiesbeing used and due to structural changes in the econo-my, providing more services and manufacturing lessenergy-intensive products. Today, we still need 25 % ofthe final energy for industrial production purposes; thesectors of trade, commerce, and services account forthe remaining 17 %. Due to these opposing trends, the final energy consumption has remained almost unchanged during the last 10 years, amounting to9,200 PJ/a in 2003.
More rational energy conversion and usage — prerequisites for a sustainable energy future
Despite the considerably higher economic performan-ce, the consumption of primary energy has remainedrelatively constant for years now – it could be decou-
PROSPECTS FOR RENEWABLE ENERGY WITHIN THESCOPE OF SUSTAINABLE DEVELOPMENT
Source : AG Energ ieb i lanzen / BMU 2003
25.4 %
21.2 %
12.6 %
37.7 %
3.1 %
2.1 %1.9 %PV = 0.3 %
17.1 %
15 %
63.6 %
Total primary energy Renewable energy
Structure of the primary energy consumption in 2003 in Germany and the individual contributions by renewable energy (PV = Photovoltaics).
Primary energy consumption and renewable energy sources
Renewable energy
PV / Solar collectors
Nuclear power
Geothermal energy
Natural gas
Wind power Hydro power Biomass
Mineral oil Coal
103
pled from economic growth. Each unit of economicperformance is being accomplished with less and lessenergy input; the energy intensity, the ratio of energyinput to the GDP (gross domestic product) is falling.The reasons are, on the one hand, the ongoing techni-cal progress in the conversion and use of energy, whe-reas on the other hand, structural changes in industrytaking place at the same time, moving from industrialproduction to providing services, also cause a reductionin this coefficient.
The average decrease in the primary energy consump-tion was 1.5 % per year in the last 20 years. In recentyears this process has slowed down. Today, less thanhalf the amount of energy is needed for the same eco-nomic performance as in 1950. The situation in theconsumption of electricity is however different. The spe-cific electricity consumption per unit of economic per-formance increased continuously until the mid-eighties,after which it slowed down. The drop in the electricityintensity is not however enough to completely stop theabsolute increase in the electricity consumption.
Since the use of energy is not free of charge, effortshave always existed and will continue to exist to lowerthe energy consumption, generally prioritised bymicroeconomic considerations. The technical potentialfor increasing the efficiency are however not at allexhausted. This situation is also true for the economicpotential not being developed today. The reason liesprimarily in the current price level for energy, so thatthese investments do not appear sufficiently attractive.An economy which is primarily oriented on a liberali-sed and globalised market calls for very short amortisa-tion times (the period of time in which an investmenthas paid for itself) of only a few years. It is often notconsidered that the technical lifetime, i.e. the time
period over which the energy savings are profitable,constitutes a multiple of the amortisation time.
The energy costs constitute only a very small part ofthe costs in both the private households and in themajority of companies. Absolute cost reductions arethus small in comparison to other areas of expenditure(e.g. labour costs). Due to the various external effects,the energy costs do not reflect the overall economiccosts associated with providing the energy (refer to thetextbox “External costs”, chapter “Renewable energy –guarantor of a sustainable energy supply”). Only whenthe energy prices change considerably in relation tothe other costs, can the greatest efforts for a morerational use of energy be expected, an insight whichinitiated the ecological tax reform. Yet even those ener-gy saving measures which, under today’s conditions,are already economical and have appropriately shortamortisation times, are often left undone.
A variety of barriers need to be overcome. Includedhere, besides insufficient information about the possibi-lities for technical improvements, are the existing struc-tures which encourage consumption and the oftencareless and thoughtless consumption of energy.Problematic is also the belief that economic optimisa-tion only concerns the processes of production, proces-sing, conversion, and transmission of energy. The eco-nomic assessment of the actual use, the service provi-ded by the energy, is usually neglected.
One example for clarification: The residents of a buil-ding are not really interested in whether natural gas orheating oil is used, but rather only in warmth andcomfort. These energy services do not have to be reali-sed only by heating. Warmth and comfort can beachieved just as well by better insulation and a more
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
160
140
120
100
80
60
40
Energy intens i ty ( 1970 = 100 %)
Source : DLR
The primary energy input is falling continuously relative to the gross domestic product. The input of electricity also follows this trendsince 1985 (prior to 1991 only former Federal Republic of Germany)
Energy intensity over time
Electricity
Primary energy
104
appropriate construction method. The initial invest-ments needed to this end must however take long-termenergy savings into account. Despite the profitabilityoften given over the lifetime of the measures, energy-relevant modernisation is often omitted. Some reasonsare e.g. the scarcity of capital available and the uncer-tainties associated with the way energy prices mightdevelop. A further barrier is often the landlord-tenantdilemma – it must be possible to allocate the additionalcosts from the investments to the rent, because it is thetenant who is saving heating costs all the time. Anenergy passport for each building documenting the“quality of the energy” and the quantitative energyconsumption would therefore be beneficial to increasethe willingness of the tenant to accept and participatein energy-saving measures.
The efficiency of energy conversion can still be consi-derably increased by the use of modern gas and steampower plants and further-developed coal-fired powerplants. Above all, increasing the use of heat from com-bined heat and power (CHP) generation plants throughdistrict and local heating networks, as well as in decen-tralised stand-alone systems, will considerably lower theconversion losses in the generation of electricity. Plantsfor combined heat and power generation are principal-ly more efficient than providing heat and supplyingelectricity separately. The extent to which the savingsin energy can be realistically attained, together withthe associated CO2 reduction, however, depends verystrongly on the scale and the method of constructingthe CHP plants, the design (e.g. the ratio of heat fromthe CHP plants to the heat from the peak-level boilers),the substituted systems, and the fuels which are used.Typical values for energy savings from CHP plants arebetween 15 and 30 %; the possible CO2 reduction com-pared to separate generation lies between 0 % (coal-fired CHP) and 50 % (gas-fired CHP), depending on thetype of fuel used. The higher the overall degree of utili-sation and the electricity coefficient for a CHP plant,the better are the benefits in terms of energy and theecology. Thus, in the long-term, appropriate technolo-gies like combined cycle power plants, fuel cell cogene-ration plants, and very efficient motor co-generationplants are favoured.
The above considerations for energy savings also applyto the economic performance of these power plants. Inthe liberalised electricity market, cheap electricity hasbeen available for some time now – and will still be fora few years to come – from old and already depreciatedpower plants (where the price of the electricity is onlydetermined by the fuel and operating costs). The invest-ments in combined heat and power plants will still bevery limited in the foreseeable future because thedepreciation times for their economic profitability arestill too long. To some extent, even already commissio-ned CHP plants have been put out of operation. Thelegislation which came into effect in April 2002 oncombined heat and power generation should stop thecutback and facilitate new investments. The successes
are however still far behind expectations, emphasisingthe need for further political action in order to achievethe desired development of combined heat and powergeneration.
The potential for saving energy is diverse and substanti-al. In-depth analyses assume that further savings bet-ween 35 and 45 % of the present energy consumptioncan be made without any sacrifices in the energy servi-ces provided. A large proportion of these savings couldbe realised by accelerated energy-saving modernisationof old buildings. A further and considerable part wouldalso be possible through the rapid introduction ofmore economical vehicles. Yet in other areas as well,e.g. domestic electrical appliances and in industry,there are still considerable savings to be realised. Anoverall reduction in the energy intensity of between 3 and 3.5 % per year is considered possible over a longtime period; this is twice that already achieved in re-cent years. In this way, the energy consumption coulddecline in absolute terms while the economy still growsat about the same rate as in the past. This condition isnecessary to sufficiently protect fossil energy resourceswhile allowing the impact of renewable energies todevelop fast enough. Modern high-efficiency technolo-gies are also an excellent export item, especially fornational economies with considerable need for impro-ving their energy services. The multitude of individualmeasures needed to lift the blockade on the economic,but not yet implemented, efficiency potential, however,calls for considerable efforts in politics and society tobe realised.
The doubling goal for 2010 — the stepping-stone tosubstantial use of renewables
In the numerous scenarios for the future (refer also toChapter 1), renewable energy accounts for as much as50 % or more in meeting the primary-energy demandby the year 2050. Today, we are still a long way awayfrom such high proportions in the supply; expandingrenewables to this extent takes decades to realise. Andyet these scenarios have, in the meantime, departedfrom the status of uncommitted visions to become con-crete targets in energy and climate policies. The goal ofthe European Community is to increase the proportionof renewable energy in the total energy supply to 12 %by the year 2010, and the proportion of electricity fromrenewable energy from 14 % (1997) to 22 % in the year2010. The goal for Germany foresees 12.5 % by the year2010, which is in line with the target set by the Ger-man government as a part of its Year 2010 doublinggoal. Additionally, the contribution to the total pri-mary-energy consumption shall increase to 4.2 % bythe year 2010 (2002: 2.9 %). According to the Germangovernment’s draft for the revision of the RenewableEnergy Sources Act, at least 20 % of the electricity inGermany shall originate from renewable energy sour-ces by the year 2020 (Figure: Growth dynamics).
105
The agreements and concrete plans concluded toimplement the 1997 Kyoto protocol – which foresees a5.2 % reduction in greenhouse gas emissions, compa-red to the level of 1990, by the industrialised countriesand 8 % in the EU (Germany 21 %) within the timeperiod from 2008 to 2012 – increase the pressure onexpanding renewable energy supplies. Work has thusbegun on setting up the national allocation plans(NAP), which establish both the branch-specific reduc-tion targets for carbon dioxide as well as the reductiontargets for the plants covered by the EU directive. TheNAP’s must be submitted to the EU Commission byMarch 31st, 2004, and the date to start emissions tra-ding was set to January 1st, 2005. A further directivefrom the EU parliament (2003/30/EG) and from thecouncil for “promoting bio-fuels and other renewablefuels in the transportation sector” from May 17th, 2003increases the opportunities for using renewable energyin transportation.
Yet there is still much more to be done. Similar supportlike that given by the Renewable Energy Sources Act isstill wanting for renewable energy in the heating sec-tor. Proposals for the way in which such an instrumentmight be designed are currently being evaluated. TheGerman government is pressing for even further mea-
sures, whereby greater harmonisation efforts in energyand emission-related taxes and in the area of environ-mental and efficiency standards are of primary impor-tance. Seen in the light of an enlarged EuropeanUnion, these efforts will soon be of major significance.Also, research and development, as well as practicaldemonstrations of renewable energy, should be increa-sed considerably in future.
The realisation of the doubling goal set by the Germangovernment – compared to the year 2000, further 90 TWh/a of electricity, heat, and fuels must be provi-ded from renewable energy sources – might possiblyaffect the individual energy sources as shown by theFigure “Growth dynamics”. Considering the develop-ments since 1997, it can be seen that there will alreadybe a considerable growth of renewables by the end of2003. In principle, the doubling goal can thus be rea-ched on time. A major share of the growth to date isdue to the continued dynamic expansion of windpower. The generation of electricity from wind powermight surpass the contribution from hydroelectricpower by the year 2004. The doubling scenario will nothowever succeed by itself. The rapid development ofwind power has already led e.g. to the occupation ofmany of the suitable locations and to increasing resi-
Electr ic i ty, usefu l heat , fue l in TWh/a
Source : Jahrbuch 2003 / BMU 2004
25.2
Hydro
43.2
Wind
1.4
Photovoltaic systems
9.4
Biomass E
0.6
77
Biomass H
5.9
Collectors
3.0
Geothermal energy H
12.0
Bio-fuels
Growth dynamics
Geothermal energy E
For the doubling goal 2010, wind power and biomass provide the largest growth rates, whereas the solar technologies, including photo-voltaic systems and collectors, and geothermal energy demonstrate the largest relative growth rates (E = electricity, H = heat [Jahrbuch2003, DLR 2004]).
0
10
20
30
40
50
60
70
80
1997: 65 TWh /a 2002: 105 TWh /a 2010: 178 TWh /a
106
stance from the viewpoint of landscape protection. Thecontinuous growth needed for the doubling scenariocan therefore only succeed if offshore wind power isincluded to an appreciable extent after the year 2005.Also, the use of biomass has increased substantially inthe generation of electricity, although the growth ratemust increase even further. Besides cost-effective oldtimber, the use of more costly forest-wood residualsmust be encouraged as well.
The need to catch up in the area of providing heat islarger than for electricity, yet at the same time, thegrowth rate is currently lower. In the case of biomass,although the increased use of forest-wood residualsensures growth in individual heating systems andopen-fire heating, the number of biogas systems hasincreased appreciably as well. A significant increase inheating centres with district-heat networks, which arealso necessary for doubling the heat contribution, ishowever still outstanding. Also, the foundation for astable market and for significant cost reductions for the still costly solar collector and geothermal energy
systems should be laid by the year 2010 with the helpof the doubling goal. Thus there is still much to bedone despite the major incentives through the consid-erable financial support provided by the market deve-lopment programme since 1999 (some 190 million Euroforeseen for 2003, where a major area of focus is heatprovision from renewable energy sources). In the mean-time, further support for reaching this doubling goal isgiven by the growing turnover of bio-diesel, which wasnoticeably stimulated by the tax exemption for bioge-nous fuels starting June 7th, 2002. Bio-diesel can there-fore also provide a considerable contribution to achie-ving the doubling goal.
The long-term prospects — a scenario of optimal renewable energy use
The aspired increase in renewable energy by the year2010 can already have considerable effects on Germany’s emissions balance. With regard to the tar-gets given in the Kyoto protocol for the major green-
Pr imary energy in PJ/a
Sources : BMU 2004
2000 2010 2020 2030
Development of the primary-energy consumption according to energy carriers (according to the efficiency method; CO2 emissions withoutindustrial processes (in 2000 = 25 million tons/year). The savings in primary energy attributable to improved efficiency are based on thereference scenario from the Energy Enquete Commission.
Primary energy in the long-term scenario for Germany
Nuclear power
835
2.4
717
5.3
588
12.7
451
22.2
309
32.5
195
43.6
Water, wind, photovoltaic systemsLignite
Biomass
Hard coal
Collectors, geothermal energyMineral oil Natural gas
Electricity imported from renewable energy sources Increased efficiency *)
2040 2050
CO2 emissions (millions of tons/yr)
Proportion of RES ( %)
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
house gas CO2, a reduction in the energy-related CO2
emissions compared to the levels of the year 1990 bysome 200 million tons to 780 million tons is requiredby the year 2010. At the moment, a major step towardsthis goal has already been reached with CO2 emissionsof 835 million tons a year, although these values havehardly dropped throughout the course of the nineties.Equivalent to some 50 million tons a year, renewableenergy is already contributing to the reductions inemissions achieved so far, and by the year 2010 willaccount for another approximately 30 million tons. Yetbecause the decision to abandon nuclear power stillhas to be compensated for, additional measures willneed to be taken in order to reach the long-term goalof protecting the global climate. By the middle of thiscentury, however, there should be reductions in theCO2 emissions by about 80 % compared to the 1990level, in accordance with the further-reaching mini-mum recommendations, based on the findings fromthe IPCC, drawn up by the Energy Enquete Commissionof the German Bundestag.
The research project financed by the German FederalMinistry for the Environment entitled “Ecologicallyoptimised expansion of renewable energy sources inGermany” [BMU 2004], indicates in a long-term scena-rio how this goal can be realised together with theother objectives of a sustainable development as descri-bed in Chapter 1 (Figure: Primary energy in the long-term scenario for Germany). In particular, the optimaluse of renewable energy in the interaction with otherenergy systems and the increased deployment of more-efficient energy technologies, together with very strin-gent nature-protection criteria, were investigated.According to the conclusions drawn from this scenario,the primary energy demand must be reduced consider-ably by the year 2010. This goal can be achieved if, inparticular, the contribution from combined heat andpower generation to the generation of electricity isincreased significantly (an increase of 50 % over 2000)and the available energy is used with a considerablyhigher degree of efficiency in all areas of application.Compared to the reference development – a scenariowhich highlights the trends if the political commit-ment is only very low and where the consumption ofprimary energy first increases and then starts to fallslowly only in 2010 – the primary energy consumptionis already 10 % less in the first ten years of the long-term scenario. The specific primary energy consump-tion normalised to the added value is lowered in thisway by about 2.5 % every year. Compared to the valuesof recent years, this corresponds to almost twice asmuch and can only be attained if this second pillar ofan effective climate-protection policy is granted moreattention in energy-policy efforts.
The attainability of the long-term reduction goals (40 %reduction of the emissions of CO2 by the year 2020) alldepends on whether the technical and structural possi-bilities for saving energy are in fact implemented. Theconsumption of primary energy in the year 2020 could
be 24 % less than the current level according to thelong-term scenario, representing savings of 20 % com-pared to the reference development. Particular signifi-cance is thereby assigned to the generation of electrici-ty. A sufficiently fast exploitation of the electricity-saving potential will thus be a major pillar for an envi-ronmentally-compatible compensation for abandoningnuclear power. According to the consensus concludedin the year 2000 between the operators of nuclear po-wer stations and the German government, this com-pensation must be accomplished by the year 2025 atthe latest. Further increases in efficiency result from expanding combined heat and power generation. Theircontribution increases from the present level of 14 % to30 % in the year 2020 and then reaches values ofabout 40 % of the total available electricity by the year2030. Above all, decentralised systems, and in particu-lar fuel cells, can play a major role here. They open upnew areas of applications for combined heat and powergeneration in the lower power range through an incre-ased supply for smaller individual objects. In the long-term scenario, the capacity of these decentralisedpower plants will increase to total about 23,500 MW.
The consequent efficiency strategy will realise a totalreduction of 40 % in the primary energy consumptionby the year 2050 compared to the reference develop-ment, also enabling the contributions by renewableenergy to increase up to 40 % of the remaining con-sumption within the same time frame, without exhau-sting any single renewable potential. Energy usagealways affects our natural environment – much moreso for fossil and nuclear energy sources than for rene-wable energy – so this strategy also assures as far-reaching protection as possible for our environment.Success in realising the structural changes shown in thelong-term scenario calls, among others, for suitablemeasures and financial support in order to assure long-term continued growth in renewable energy of thesame scale as in the last few years. The required envi-ronmentally compatible contributions to the energysupply by the middle of the century can only be assu-red in this manner. After 2010, mainly wind power andbiomass are still growing, then the large potential ingeothermal and solar energies start to unfold. Startingin 2020, cost-effective renewable electricity imports within a European power network begin to play anincreasing role.
Particularly noticeable will be the structural changeswhich will take place in the power sector. Due to thenecessary replacement of old conventional powerplants and the foreseen phasing out of nuclear power,there is a demand for several 10,000 MW of newlyinstalled power in the upcoming years. Along with theconstruction of new and therefore more-efficient con-ventional power blocks, there will be opportunityenough to expand decentralised combined heat andpower generation and renewable energies as well, the-reby fulfilling the demands of sustainable electricitysupply.
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108
In the year 2020, only 45 % of the power plants opera-ting in 2000, producing about 50 GW, will still be inservice, assuming a mean lifetime of 40 years andtaking into account the phasing out of nuclear powergeneration. To cover the electricity demand, which willthen have fallen by 12 % in the long-term scenario, 79 GW will come from new power stations: already 40 GW from renewable energy (without biomass), 12 GW from small to medium-sized (up to 10 MW unitcapacity) block heat and power plants based on engi-nes, gas-turbines, and fuel cells (including biomass),and 27 GW from large-scale power plants, of whichhowever 16 GW are operated as CHP plants, and 12 GW as condensing power plants. The contributionfrom renewable energy (without biomass) to the an-nual generation of electricity is then around 26 %, and that from all CHP plants will be about 29 %. By theyear 2050, practically the entire park of power stationswill have been renewed and provide a total capacity ofabout 144 GW at that time. The largest proportion ofthe installed power will then be provided by renewableenergy technologies with a total of 90 GW, 24 GW
coming from CHP plants and 31 GW from large-scalepower plants, 20 GW of which are thermal power sta-tions. The total installed capacity will be 27 GW largerthan today, because the dominating renewable energysources provide less full-load hours than today’s fossilor nuclear power plants and because hydrogen willalready be produced by electrolysis using some of thisrenewable energy. Due to the considerable decline inthe fossil-fuelled condensing power stations, which, bythe year 2050, will only still be in service as a backupfor fluctuating renewable energy supply, the lossesassociated with electricity generation will fall as well,and therefore also the emissions of CO2.
The combination of considerably greater efficiencyboth in the use and in the conversion of electricity,together with the expansion of renewable energy sour-ces, will reduce the emissions of CO2 in energy conver-sion alone by 40 % by the year 2020 and by 80 % bythe year 2050, compared to levels in 2000. This resultalso shows that nuclear power will not be needed inrealising the climate protection goal.
Insta l led power in GW el
Source : BMU 2004
2005 2010 2015
Increase in newly installed capacity in Germany as of 2001 in the long-term-scenario. Plants for combined heat and power generation andrenewable energy will dominate, condensing power plants cover the remainder of the demand (RES = renewable energy sources, withoutbiomass; CHP = combined heat and power generation, including biomass).
Increase in newly installed power in Germany
Condensing power plants (coal, gas)
13
21
2020
26
29
2025 2030
39
36
2035 2040
48
40
2045 2050
55
38
Wind, Offshore
Cogeneration plants (coal, gas)
Photovoltaic systems
Block heat and power plants + fuel cell (gas)
Hydro, geothermal energy Imported renewable energy
Block heat, power plants, fuel cell (biomass) Wind, Onshore
Prop. of renewable energy, %
Prop. of comb. heat & power plants, %
17
36
53
79
94
110
119
129
137
144
20
40
60
80
100
120
140
0
109
Similar combinations of increased efficiency and expan-ded use of renewable energy bring similar effects inthe heat supply and transportation sectors. They howe-ver also call for significant structural changes for newand more-efficient energy technologies to be able topenetrate each of the sectors as far as possible in thecoming decades. In the long-term scenario it will bepossible to lower the emissions of energy-related CO2,compared to the reference development, by the year2010 by some 110 million tons/year and thereby exceedthe Kyoto target by far. (Figure: CO2 reduction). In theyear 2020, the target of a 40 % reduction will be rea-ched with just 250 million tons/year of carbon dioxide,and an 80 % reduction by the year 2050 with some 500million tons/year, compared to the baseline value from1990. In the short and medium term, the effects fromthe efforts to improve the efficiency will dominate andthe significance of renewable energy contributions willgrow in the medium to long term.
If other countries follow this or a similar expansionstrategy – which in the light of merging markets is amajor prerequisite for a successful transformation ofthe energy supply in Germany – then, besides thedomestic sources for renewable energy, the cost-effec-tive resources from abroad can be used as well. In themedium term, electricity from wind power can beimported from the high-yield coastal regions in Europe,in the long term, “solar” energy can also be importedover a European power grid as electricity from solarthermal power plants located in the Mediterraneanregion. In the long-term scenario, the contribution ofimported electricity in the year 2050 is around 60 TWh/aand constitutes some 13 % of the total electricity gene-rated. Because of the considerably lower share of natu-
ral gas and mineral oil in the consumption of primaryenergy, the dependency on imported energy will stillbe much lower than is the case today.
An increasing part of the strongly growing energy sup-ply from renewable energy will be used towards theend of the considered period to produce hydrogen. Inview of the limited potential of biomass, the electrolysisof water using electricity from renewable energy provi-des one possibility to offer climate-friendly fuels in thetransportation sector as well. This possibility is only ofinterest after the year 2030 because, one the one hand,the infrastructure must still be established and, on theother hand, the CO2 emission minimisation effects aremuch larger with the direct use of renewable electricitythan with the use of hydrogen in the transportationsector.
Support for renewable energy
The various energy scenarios show that doubling thecontributions of renewable energy in Germany and inEurope only represent a beginning. Therefore, theGerman Federal Ministry for the Environment has al-ready formulated very early the long-term goal forGermany of raising the share of renewable energy to atleast 50 % by the year 2050 (2020: 10 %); the propor-tion of electricity generation shall be at least 20 % bythe year 2020. Considering the energy system as awhole, one thing is thus made clear: The lower theamount of energy consumed, the easier it becomes toattain a considerable renewable energy proportion ofthe total energy supply. Both renewable energy andthe efforts for more rational use of energy will have to
2010
Source : BMU 2004
CO2 reduction in the long-term scenario, compared to the reference development (REF): Considerable reductions in CO2 will be attainedby consequently improving efficiencies, and by expanding combined heat and power generation and renewable energies.
CO2 reduction compared to the reference development
Reduction in carbon dioxide, in millions of tons CO2/year
107
2020
243
2030
374
2040
462
2050
506
0
100
200
300
400
500
Renewable energy
Efficiency in heat
Combined heat and power
Efficiency in electricity
Efficiency in transportation
110
be supported in the future. These measures do nothave to start from zero, but can build on a number ofalready available instruments. Various measures andinstruments at the federal level are already supportingthe use of renewable energy.
The national measures are supplemented by numerousactivities by the individual states, communities, andother stakeholders (e.g. energy supply companies). A good overview of the financial support available isgiven on the Internet homepages of the Federal Minis-try for the Environment (www.bmu.de), the industryassociations (e.g. www.solarfoerderung.de), the diffe-
rent energy agencies run by the Government and the various States, as well as the publication “Yearbook onRenewable Energies”. Even though many measureshave already been initiated, it is not expected that theywill suffice to reach the goal set for the year 2010 ofdoubling the level of renewable energy. One centralobstacle in the implementation of renewable energy isstill the lack of economical competitiveness comparedto conventional energy carriers under the present gene-ral conditions. Even the eco-tax, levied for the first timein April 1999, has not had much of an effect in thisrespect. In the field of electricity, the eco-tax resultedin the taxation of electricity also from renewable
Activities already being undertaken by the German government: Measures and instruments supporting renewable energy
The Renewable Energy Sources Act (EEG) superseded the very successful Electricity Feed-In Act in the year2000, and was subsequently adapted to meet the new basic conditions for the liberalised and hence more com-petitive markets. The Renewable Energy Sources Act foresees payment at a fixed reimbursement rate for an assu-red period of time for feeding electricity from renewable energy into the grid and increases the investmentsecurity for the operators, which are overwhelmingly in the private sector so far. Furthermore, it gives preceden-ce to renewable energy and also provides a contribution to internalising external costs. By reducing the reim-bursement rate for plants starting operation later in the future, it offers an incentive for cost-orientated innova-tions. Within the scope of the Renewable Energy Sources Act, specific issues concerning bio-energy are regula-ted by the Biomass Ordinance (Biomasse Verordnung). While retaining this proven basic structure, the currentgovernment’s draft from the end of 2003 to amend the Renewable Energy Sources Act adapts the reimburse-ment rates to current developments. At the same time, the amendments to the Renewable Energy Sources Actserve to implement the directive from the European Union from September 2001 on supporting renewable ener-gy and therefore now include the entire spectrum of renewable energies in the scope of the new RenewableEnergy Sources Act.
Within the 100,000-roof programme, low-interest loans were made available for the installation of photovol-taic systems. It was successfully concluded in 2003. With about 350 MW, significantly more new installationsthan foreseen could be financially supported by this programme. The further expansion of photovoltaic systemswill be supported by other, equally appropriate, measures.
In 2003, the volume of financial support from the German government for the market stimulation pro-gramme was around 190 million Euro and, according to the coalition agreement of the current government,will be increased to 230 million Euro by the year 2006. In this way, subsidies are being made available forinvestments. On the one hand, investment-cost subsidies are available which focus in particular on systems pro-viding heat (e.g. solar-thermal energy, geothermal energy), biogas systems, and systems which are operated bymultipliers (e.g. schools) (refer to www.bafa.de). At the same time, larger projects within the scope of this pro-gramme receive financial support in the form of low-interest loans, also allowing for partial remission of thedebt in some cases (see www.kfw.de). This programme attempts to compensate for the fact that electricity fromrenewable energy sources is not exempted from the electricity tax levied since April 1999 through the ecologicaltax reform.
Further low-interest loans are available for different parties from the Kreditanstalt für Wiederaufbau (= KfW),e.g. within the scope of the CO2 reduction programme or the CO2 building restoration programme (seewww.kfw.de). The programmes previously managed by the Deutsche Ausgleichsbank (= DtA) will be managed bythe KfW Mittelstandsbank following their merging with the KfW. A total of some 6.9 billion Euro were grantedby the KfW and DtA in the period 1999 – 2002 in the form of loans for renewable energy purposes.
Exemption for bio-fuels from the mineral oil tax.
Support provided in the form of advisory services, information, and public relations work.
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energy. An exemption, however, cannot be expected atthe present time because of the problems otherwisearising when importing electricity.
Whether the doubling goal is reached on time, willdepend on how the measures already existing todaywill progress towards this goal. Above all, effectiveinstruments still have to be created for the heat-genera-ting techniques, i.e. for solar-radiation collectors, bio-mass systems, and geothermal energy, to support theirmarket introduction, and these instruments need to beas successful as the Renewable Energy Sources Act hasbeen in the electricity sector. Promising instrumentsare currently being discussed by researchers, the powerindustry, and politicians.
Not the least because of the successes in Germany, elec-tricity from renewable energy sources are being sup-ported financially in other and future EU states on thebasis of the Renewable Energy Sources Act. To be men-tioned here are, for example, Spain, France, Estonia,the Czech Republic, Hungary, Slovenia, and Slovakia.This instrument did, however, only start to becomewidespread once a court ruling established its compati-bility with EU law, and a directive from the EU Com-mission on energy policy did not exclusively call for a quota agreement. Anticipating a decision against a minimum reimbursement like in the RenewableEnergy Sources Act, a number of EU states introducedquotas. At the present time, there are quotas in forcee.g. in Italy, Great Britain, Belgium, Denmark, andPoland. These measures obligate the electricity produ-cer to demonstrate that a given proportion (“quota”) ofhis production originated from renewable energy sour-
ces. The evidence to be provided does require the particular company to produce the energy. Rather, thisevidence can be in the form of certificates purchasedfrom the actual producers of electricity from renewableenergy sources. The little experience gathered to dateshows that a promising application calls for very care-ful planning and implementation down to the very lastdetail. This instrument was only successful up to nowfor the more mature technologies with less ambitiousgoals (like e.g. wind power in Texas). Since this instru-ment is comparatively complex, it will take some timeto identify the benefits and drawbacks under the vari-ous practical conditions. National invitations of tendersfor the desired renewable energy plants are, after thesobering experience gathered to date – above all inFrance and the United Kingdom – only still used in theEU by Ireland as a centralised support instrument.
The generation of heat from renewable energy is notbeing supported at the present time in any EU state bycomparable instruments, but rather by means of invest-ment subsidies, low-interest loans, or tax relief. In addi-tion to an instrument promising success similar to thatseen with the Renewable Energy Sources Act in thefield of electricity, communal measures are especiallyimportant in the area of heat. In particular, the expan-sion of solar-thermal heat generation is being accele-rated per ordinance in an increasing number of Spa-nish cities – amongst others in Barcelona, Seville, andMadrid – as well as in Germany in Vellmar near Kasselby means of an agreement for urban constructionaldevelopment. The ordinance prescribes e.g. in Barce-lona that 60 % of the hot-water needs for the majorityof new constructions as well as for larger restorations
Support provided for demonstration and pilot plants.
The programme for an eco-premium for homebuilders which, in addition to the normal owner-occupiedhome subsidies for the installation of solar energy systems, provided further financial support in the form of taxrelief, expired 31.12.2002. The volume of financial support amounted to roughly 60 million Euro in the period1995 – 2001.
Specific financial support programmes in the agricultural sector (amongst others, biogenous fuels and lubri-cants).
The Energy-Saving Ordinance which, in addition to thermal insulation, also permits active measures (e.g.installation of a solar system) in order to comply with specific energy requirements for the building.
The support of measures in the European environment, like e.g. participation in jointly establishing areas ofresearch to be focused on in Europe within the concept of the 6th Framework Programme of the EU, inclusion ofthe positive German experience made with the Feed-In Ordinance in the drafts for European directives, or thedirective for “Furthering the use of bio-fuels and other renewable fuels in the transportation sector”, in which a market share by bio-fuels of at least 5.75 % is foreseen by the year 2010.
An increased focus of energy research funds to renewable energies. In 2003, the German government relea-sed a total of about 162 million Euro for energy research projects. Of these, about 60 million Euro were used forresearch and development in the field of renewable energy.
112
have to be met by solar-thermal energy. In Vellmar it isforeseen by the urban development agreements thatthe town will pay for energy advisory services forhomebuilders who, in return, are committed to installa solar system covering e.g. at least 50 % of the energyneeded for hot water and 10 % of the energy needs forheating purposes. Such local initiatives work well incombination with the primarily financially orientatedbenefits from the instruments of the German govern-ment: The monetary instruments lower the measuresrequired by the communities; in return the communi-ties strengthen the effects of these monetary instru-ments and in the process, directly increase popularawareness of them.
On account of the market circumstances given today,we will have to accept that the expansion of renewableenergy according to the doubling goal will initiallylead to differences in costs compared to the largelyconventional methods for supplying electricity andheat. For the expansion status currently achieved forrenewable energy, there are already differences in costsincurred for electricity production amounting to 1.2 bil-lion Euro a year and these will increase to more than2.5 billion Euro throughout the course of realising thisdoubling goal. The largest share is initially for windpower but, towards the end of the period under consi-deration, the other technologies will have to be consi-dered to an increasing extent as well. Based on the pre-sent-day total consumption of electricity, the cost diffe-rences result in an additional financial burden on theelectricity customers of about 0.5 Cent/kWh (in compa-rison to the value today of just 0.25 Cent/kWh) in theyear 2010. Compared with the average household elec-tricity tariffs, the costs will increase by less than 3 %.For industrial customers, which pay considerably lowerprices for their electricity, such an increase is howevermore noticeable if these increases are fully passed onto this group of customers. In order to reduce thedisadvantages in competitiveness otherwise incurredhere, and hence any associated loss of jobs, there is alimit to the financial burdens included in the new issueof the Renewable Energy Sources Act foreseen for thosecompanies hit particularly hard. The differences incosts fall off again after 2010 since they diminish onceelectricity from renewable energy becomes more cost-economical. Depending on the technology applied,electricity from renewable energy can then becomecheaper than the electricity still being produced fromfossil-based energy carriers, which can expect continu-ously increasing costs for the fuels used and due toadditional requirements to be fulfilled in lowering theemissions of CO2 (e.g. by means of CO2 certificates).
In comparison with other applications in the field ofenergy, the differential costs to be covered for the mar-ket expansion of renewable energy are comparativelylow. These costs correspond to less than half of the pre-sent-day subsidies for coal and are an order of magnitu-de lower than those incurred primarily in the 60’s,
70’s, and 80’s for establishing nuclear power. Whendiscussing the support of renewable energy throughthe Renewable Energy Sources Act, it must also betaken into consideration that the additional costs arestill less than the external costs avoided by not genera-ting the electricity by conventional means. Such sup-port is therefore beneficial from the economics point ofview.
It is already clear today that these advance investmentswill be worthwhile. Not only does this apply for theprestige in foreign policy from the leading role beingtaken by Germany on issues of climate protection andlaunching renewable energy on the market, but rathermore importantly, in terms of strengthening Germany’sposition as a producing and exporting country. In 2002there were 45,000 people working for wind-energy uti-lisation alone. The figures for energy from biomass arecomparable. Including the indirect job effects as well,for example production by sub-suppliers, there aresome 120,000 people employed in the whole renewableenergy sector. In the course of their daily work, thesepeople are acquiring the experience needed for suc-cessfully developing the future export markets. Themarkets concerned here are international and hencesubstantial, which can be seen by the expansion ofrenewable energy scenario described in Chapter 1. In view of the volume of investments supported by thedoubling goal amounting to more than 50 billion Euroby the year 2010, there will also be incentive for jobson the domestic market.
The preparatory work needed today does however alsoconstitute an economical provision for the future. Assoon as the prices for electricity and heat generated byconventional means start to increase because of theforeseeable scarcity in the reserves of crude oil andnatural gas, the competitiveness of the German indu-strial system will benefit from the availability of alter-native energy sources ready by that time for the mar-ket. This effect will be supported by the contributionfrom renewable energy as a domestic energy carrier inassuring the supply of energy. An expansion of renew-able energy increases the degree of diversification inthe energy supply and reduces the dependency onenergy imports. It is with a particular view to the in-creasing geographical concentration of the crude-oiland natural-gas reserves that will make this investmentvaluable in the future.
A major conclusion can be drawn from the findingsand knowledge of the numerous scenarios analysed:Germany can play a significant role in the realisationof sustainability concepts for the future and in parti-cular for the expansion of renewable energy. As amajor industrialised country, Germany is without doubtone of those countries to be assigned particular respon-sibility in realising effective climate protection. Ger-many can however also particularly benefit from thisdevelopment by assuming a leading role in the deve-
113
lopment and market launch of new and environmental-ly-compatible energy technologies. The German energyand climate-protection policy should therefore recogni-se the opportunities given by this responsibility andturn these into substantial benefits for the populationby applying appropriately effective measures.
Renewable energy in the European Union
The increasing integration in Europe is also influencingthe future developments of renewable energy. Thedynamics of the expansion process are however essen-tially still determined by the national goals and regu-lations. Yet, besides the individual national goals forexpansion, both the EU Parliament and the EU com-mission formulated concrete goals for expanding re-newable energy by the year 2010.
For the longer-term periods until 2020 / 2030, there areholistic European energy scenarios in which the pro-portions of renewable energy are described in greaterdetail. Also, the EU Commission is exerting its influen-ce within the legally prescribed limits on the type ofsupport for these technologies in the individual coun-tries, and is thereby striving to harmonise the instru-ments of support in use today. Also, the markets for theindividual technologies will assert themselves and beco-me significant in the course of the increasing liberalisa-tion of the energy markets throughout Europe. There isincreasing evidence that the European Union will bethe leading region at the end of this decade for the use and marketing of renewable energy.
Present-day use of renewable energy in the European Union
The present-day use of renewable energy in Europe is dominated – as is the case in most of other conti-nents – by hydroelectric power and the traditional useof biomass for heating purposes. The primary energycontribution from renewable energy has been continu-ously increasing in Europe since 1989 (Figure: Primaryenergy contribution).
With 3,900 PJ/a, some 6.5 % of the total primary ener-gy consumed in the EU in the year 2002 was providedby renewable energy. Biomass with 64 % and hydro-electric power with 28 % dominate here, followed bygeothermal energy with just 4 % and wind power witha share of 3 %. Of the useful final energy, renewableenergy is providing some 3,500 PJ/a, constituting 8.5 %of the total final energy consumption. With 410 TWh/a,the contribution of renewable energy to the electricityconsumption corresponds to a share of 15 %. 75 % ofthe electricity is provided by hydroelectric power and15 % by biomass. The contribution by wind power hasrisen considerably in the meantime to 9 %, the share ofgeothermal energy is around 1 %, whereas with 0.1 %,solar electricity is still of no significance from the ener-gy economy point of view. Biomass is the dominatingrenewable energy source for providing heat. With ashare of 1 % each, the contributions from solar heatand geothermal energy are still very low.
The contribution from renewable energy in the indivi-dual European countries is very different (Figure:
0
1,000
2,000
3,000
4,000
Pr imary energy (EU-15) , PJ/a
Solar energy
Wind power
Geothermal energy
Biomass
Hydroelectric power
Primary energy contribution from renewable energy in the European Union – increasing continuously since 1989.
Primary energy contribution from renewables in the EUSource : Eurostat 2001 / IEA 2003
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
114
Countries in comparison), which is not surprisingbecause it is influenced by numerous conditions:
––– The country-specific potential for the individual renewable energy sources
––– The structural conditions like e.g. population density and population structure, associated with the expansion of long-distance and district-heat networks
––– The economical circumstances, like country-speci-fic energy prices and the charges levied on them
––– The level of prosperity and the related energy consumption
––– The political conditions like e.g. financial support for renewable energy and the goals set by energy policies
The significance of specific energy-policy goals andambitious measures promoting renewable energy isshown clearly by the example of Denmark with a shareof 9 % in the consumption of primary energy. A parti-cularly favourable effect on the development of the“new” technologies for using renewable energy (herewind) are thereby observed. Germany – even thoughthe share is still relatively low – is exhibiting the stron-gest growth rates (2.9 % in the year 2002), because ofthe effective financial support. On the contrary,
although they have similar conditions as in Denmarkregarding potential, renewable energy developmentshave hardly made any progress at all in Great Britainso far.
The contributions from hydroelectric power and geo-thermal energy mentioned at the beginning increasesignificantly when the three countries of Switzerland,Norway, and Iceland are included (right-hand side ofthe diagram). Norway and Iceland provide some 50 %of their primary energy (and practically 100 % of theirelectricity) by renewable energy, and in Switzerland itis nevertheless 18 %. In the whole of Western Europe,nearly 7 % of the primary energy was provided byrenewable energy in 1999; today it might already behalf a percent more. The five countries with the largestabsolute quantities of primary energy from renewableenergy sources are France, Italy, Sweden, Norway, andGermany with a total proportion of 62 %.
Technical potential for renewable energy
The numerous studies available on the potential forrenewable energy permit a sound statement to bemade today with regard to its assured technical poten-tial in Europe (Figure: Technical potential). The valuesare already limited considerably by structural popula-tion requirements and, in particular, by ecological cons-traints such that they constitute a lower limit for thepractical use of renewable energy. They can therefore
Swed
en
Austri
a
Finlan
d
Portu
gal
Denmar
kIta
ly
Franc
eSp
ain
Greec
e
German
y
The N
ethe
rland
s
Irelan
d
Luxe
mbour
g
Belgium
Great
Britain
EU to
tal
Switz
erlan
d
Norway
Icelan
d
Weste
rn Eu
rope
Propor t ion of renewable energy in the pr imary energy consumed in 1999 in %
Source : Eurostat 2001 Countries in comparison
Countries in comparison – Share of renewable energy in the primary energy consumption in the EU states, including Switzerland, Norway,and Iceland in the year 1999.
26.7
23.322.3
14.9
8.97.8 7.1
5.8 5.4
2.7 2.1 1.8 1.3 1.2 1.1
6.0
18.2
Ω 42.2 Ω 58.4
6.9
Biomass Hydroelectric power Wind power Solar energy Geothermal energy
35
30
25
20
15
10
5
0
115
certainly be considered as exploitable and acceptableby society. The potential shown here exceeds the pre-sent-day electricity production in Western Europe andcan cover some 75 % of present-day needs for heat,equivalent to primary energy totalling 38,500 PJ/a andtherefore some 62 % of the primary energy being cons-umed at the present time in Western Europe.
The technical potential is already being used in verydifferent ways. With 80 %, the potential for hydroelec-tric power has already been exploited to a large extentwhen excluding the installation of new power plants inclose to nature rivers. With some 50 %, biomass is alsoalready being used on a considerable scale.
All other potential values are only being used to verysmall fractions of their potential so far. In the overallbalance, the lower limit of this assured technical poten-tial indicates that 10 times the present amount of rene-wable energy can be provided in Western Europe.
Once all types of renewable energy have been establis-hed in the future energy supply system, other potentialsources can be developed in the long term. Someexamples are:
––– An extended use of offshore wind of the coast of Europe with some 2,000 TWh/a of additional electricity being generated;
––– Cultivation of energy crops on additional land no longer being used for agriculture – in particular following the expansion of the EU to the East – for an additional 3,500 PJ/a of primary energy from some 30 million hectares in total;
––– Utilisation of further resources of geothermal energy with a potential in Western Europe for generating as much as 1,700 TWh/a of electrici-ty;
––– Importing electricity from solar-thermal power plants located in North Africa within the scope of a Mediterranean electricity grid of about 10,000 TWh/a.
Additional potential for renewable energy is availablemainly in the form of electricity. The development ofany further potential for heat from geothermal energyor collectors is not meaningful, since low-temperatureheat below 150 °C must be adjusted to the needs forhot water and heating purposes. Surplus electricityfrom renewable energy can however be used to produ-ce hydrogen by electrolysis (refer to the section “Hydro-gen”) which can then be used as a fuel or provide high-temperature industrial process heat.
The examples given above indicate an additional technical potential for primary energy of more than 80,000 PJ/a. With the above-mentioned additionalpotential, energy supply exclusively through renew-ables is therefore possible, even if the demand for energy in Western Europe increases in the long-term.
The prospects for renewable energy in Europe
In the last few years, the European Union has set spe-cific goals for increasing the proportion of renewableenergy:
Source : DLR
Biomass
Photovoltaic systems
Wind power
Hydroelectric power
Solar-thermal power stations
Geothermal energy
Solar collectors
Assured technical potential: 38,500 PJ/a,
of which being used: 12 % (coloured segments)
Assured technical potential for renewable energy in Western Europe. Only hydroelectric power and biomass are being used to an apprecia-ble extent so far.
Technical potential
Pr imary energy, TWh/a
Source : Ecofys 2002 / DLR
1990
2000
Targ
et “W
hite P
aper
”
Prese
nt po
licy
Inten
sified
polic
y
Baseli
ne sc
enar
io
SEE s
cena
rio
2,770
3,700
7,620
5,110
6,656
4,314
5,770
Possible growth
Possible growth in renewable energies in Europe by the year 2010.
Hydroelectric power Biomass Wind power Geothermal energy Solar energy
––– In December 1997, the European Commission adopted the white paper: “Community Strategy andAction Plan Energy for the Future: Renewable Sourcesof Energy”. The goal is to increase the contributionfrom renewable energy to a proportion of 12 % of theprimary energy consumption by the year 2010. In 2001,this action plan was supplemented by a directive fromthe European Parliament expanding the input of elec-tricity from renewable energy. The goal is a share of 22 % in the year 2010. Specific target values are propo-sed for each of the member states.
––– The European Commission started a “Take-Off”campaign in 1999 for the goals laid out in the whitepaper, setting specific targets for the period 1999 –2003. In 2003, the European Commission legally esta-blished a guideline for the use of bio-fuels throughoutEurope. To begin with, the share of bio-fuels in the con-sumption of petrol and diesel shall be increased to 2 % by 2005, and to 6 % by 2010.
As a matter of fact, the growth of renewable energy inEurope has accelerated considerably since 1995. Where-as it amounted to an average 2.2 %/a in the period1990 – 1995, it increased in the following five-year
period to 3.6 %/a and at the moment is around 4 %/a.The goal set by the white paper does however call foran average growth rate of 7.3 %/a in the period up to2010, i.e. 2.5 times the growth rate of the past decade.
Numerous energy-policy instruments and measures areinvolved in the accelerated growth. One current study[Ecofys 2002], however, established that the expansiongoal will not be attained through the current set ofpolitical instruments, as indicated by the “Present poli-cy” bar in the “Possible growth” diagram for the year2010. Considering the set of instruments which cameinto force at the end of 2001, it can expected that onlytwo thirds of the target value will be reached by theyear 2010. Including those measures which are current-ly still being discussed, yet will presumably take effectwithin a foreseeable time (bar “Intensified policy”), itcan be expected that 80 – 85 % of the expansion target2010 (bar “White paper”) will be reached on time. Onlywind power with about 60 GW might exceed the ex-pansion target, whereas all other energy sources willfall short.
Particularly large differences will be expected fromtoday’s viewpoint in the expansion of photovoltaic
116
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
systems where only 20 % of the target will be achieved,and in the generation of electricity from biomass withonly 35 % of the target being reached.
Since structural changes in the energy supply takeplace over longer time periods, it is also importantwhen estimating the future significance of renewableenergy to consider the long-term changes in the EUenergy supply. In the European Commission’s GreenPaper “Towards a European strategy for the security ofenergy supply” [Grünbuch 2000] from November 2000,the prospects of the European energy supply by theyear 2030 are given under the assumptions of continu-ing present-day trends and current energy policy. Themajor data for calculating this development (bar“Baseline scenario” [Capros 2000]) are an 80 % highergross domestic product in 2030, a population sizeremaining approximately constant at about 380 millionpeople, and only a moderate increase in energy prices,e.g. with a barrel of oil costing 30 US$99/bbl in theyear 2030. For nuclear power it was assumed that thepublic opinion will not change appreciably and hencethere will be no new nuclear power plants built on alarge scale in the EU. Thus by the year 2030, the use ofnuclear power has fallen to approximately half thelevel of today’s values. Under these conditions, thedevelopments in the EU-15 member states lead to ener-gy consumption increasing by 11 %, a further increasein the import dependency from currently 49 % to 70 %and, because of the greater use of coal, to an increasein the emissions of CO2 by 22 % over the reference va-lue from 1990, or 3,068 Gt CO2. Also, a low growth inrenewable energy results from the mentioned inputdata.
Seen in this light, it is clear that the goal of the whitepaper cannot be reached in time based on the instru-
ments and policies currently in place, and that evenafter 2010 there would be no significant incentive forgrowth in renewable energy. The European energypolicy should therefore implement further measures inthe next few years in order to accelerate growth in therenewable energy sector. In the scenario “Solar EnergyEconomy” (bar “Scenario SEE”), the attempt was madeto derive a realistic estimation from today’s viewpointof the quantities of renewable energy which can bemobilised by the year 2010. The main assumption isthat the strategy designated as “Intensified policy”,with a purposeful further development of energy-policyinstruments effective until about 2005, will be effec-tively implemented such that it will remain effectiveuntil 2010. Except for the very large quantities of elec-tricity generated from biomass (230 TWh/a in 2010compared to 35 TWh/a in the year 2000) and a lowergrowth in the field of solar-thermal collectors as sup-posed in the white paper, the goals established here forthe period up to the year 2010 could be reached forthe other technologies.
A new technology – not yet included in any of the stu-dies so far – is the solar-thermal generation of electrici-ty in southern Europe with a contribution of 20 TWh/a,corresponding to a capacity of about 5,000 MW nowincluded in the scenario SEE by the year 2010. The mostrecent improved conditions from the feed-in ordinancein Spain, with a reimbursement of about 16 Cent/kWh,make the cost-even operation of solar-thermal powerplants possible. In the scenario SEE, the generation ofrenewable energy, with a total of 568 TWh/a, reaches a share of 20 % of the total quantity of electricity gene-rated in 2010. With 5.770 PJ/a, the contribution to thetotal quantity of primary energy being consumed atthat time increases to 9.5 %.
117
118
BINE, Fachinformationszentrum (FIZ) Karlsruhe (Hrsg.), www.bine.info
Bundesamt für Naturschutz, www.bfn.de
Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, www.bmu.de; www.erneuerbare-energien.de
Bundesministerium für Verbraucherschutz, Ernährung und Landwirtschaft, www.verbraucherministerium.de/
Bundesverband BioEnergie e.V. (BBE), Godesberger Allee 142 – 148, 53175 Bonn
Bundesverband Erneuerbare Energien e.V. (BEE), Teichweg 6, 33100 Paderborn
Bundesverband Solarindustrie e.V., Stralauer Platz 34, 10243 Berlin, www.bsi-solar.de
Bundesverband WindEnergie e.V., Herrenteichsstr. 1, 49074 Osnabrück, www.wind-energie.de
C.A.R.M.E.N, Centrales Agrar-Rohstoff-Marketing- und Entwicklungs-Netzwerk (C.A.R.M.E.N) e.V.,Technologiepark 13, 97222 Rimpar
Deutsche WindGuard GmbH, Windallee 15, 26316 Varel
Deutscher Wetterdienst, Frankfurter Straße 135, 63067 Offenbach/Rhein
Deutsches Windenergie-Institut GmbH, Ebertstr. 96, 26382 Wilhelmshaven, www.dewi.de
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Institut für Technische Thermodynamik, Pfaffenwaldring 38 – 40, 70569 Stuttgart, www.dlr.de/tt
Fachagentur Nachwachsende Rohstoffe (FNR), www.fnr.de/
Fachverband Biogas, Bauernschule Hohenlohe, Am Feuersee 8, 74592 Kirchberg/Jagst
Fichtner Ingenieurdienstleistungen und Consulting, Sarweystraße 3, 70191 Stuttgart
Fraunhofer-Institut für Solare Energiesysteme ISE, Heidenhofstr. 2, 79110 Freiburg
GeoForschungsZentrum, Telegrafenberg, 14473 Potsdam
Geothermische Vereinigung e.V., Gartenstraße 36, 49744 Geeste
Hamburger Klimaschutz Fonds, www.Klimaschutz.com
Institut für Energetik und Umwelt gGmbH, Torgauer Str. 16, 04347 Leipzig, www.ie-leipzig.de
Institut für Energie- und Umweltforschung Heidelberg, Wilckensstraße 3, 69120 Heidelberg
Institut für Solare Energieversorgungstechnik, Königstor 59, 34119 Kassel
Institut für Solarenergieforschung GmbH, Am Ohrberg 1, 31860 Emmerthal
Institut für Thermodynamik und Wärmetechnik, Universität Stuttgart, Pfaffenwaldring 6, 70550 Stuttgart
Institut für ZukunftsEnergieSysteme, Vollweidstr. 11, 66115 Saarbrücken
CONTACTS IN GERMANY
119
Kreditanstalt für Wiederaufbau (KfW), www.kfw.de
Öko-Institut Darmstadt /Freiburg /Berlin, www.oeko.de/
Passiv Haus Institut, www.passiv.de/
Projektträger Jülich, Projektträger des BMBF, BMWA und BMU, Forschungszentrum Jülich, www.fz-juelich.de/ptj/
Umweltbundesamt, Postfach 33 00 22, 14191 Berlin, www.umweltbundesamt.de
Zentrum für Sonnenenergie- und Wasserstoff-Forschung, Industriestr. 6, 70565 Stuttgart
120
AG Energiebilanzen Arbeitsgemeinschaft Energiebilanzen, Berlin, diverse Jahrgänge.
BGR 2003 Reserven, Ressourcen und Verfügbarkeit von Energierohstoffen. Rohstoffwirtschaftliche Länderstudien, Heft XXVIII, Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover 2003.
BGR 1998 Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Reserven, Ressourcen und Verfügbarkeit von Energierohstoffen 1998, Hrsg. BGR, Hannover/Berlin 1998, ISBN 3-510-95842-X.
BINE 2002 BINE-Projekt-Info 02/2002.
BINE 1993 BINE-Info Nr. 12/1993, Energieversorgung von Autonomen Messstationen, FIZ-Karlsruhe 1993.
BMU 2003 Erneuerbare Energien in Zahlen 2003; Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, Berlin 2004.
BMU 2004 J. Nitsch, W. Krewitt, M. Fischedick, G. Reinhard, u.a.: Ökologisch optimierter Ausbau der Nutzung erneuerbarer Energien in Deutschland. Untersuchung im Auftrag des Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit. DLR Stuttgart, WI Wuppertal, IFEU Heidelberg, März 2004.
BMU/UBA 2002 Nachhaltige Entwicklung in Deutschland – die Zukunft dauerhaft umweltgerecht gestalten. Erich Schmidt Verlag, Berlin 2002.
BMWI 2003 Zahlen und Fakten: Energie Daten 2002, Bundesministerium für Wirtschaft und Technologie.
Bundesregierung 2002 Perspektiven für Deutschland. Unsere Strategie für eine nachhaltige Entwicklung. www.dialog-nachhaltigkeit.de/downloads/Perspektiven_komplett.pdf.
Brundtland 1987 G. H. Brundtland, V. Hauff: Unsere gemeinsame Zukunft, Eggenkamp-Verlag, Greven 1987.
Capros 2000 Capros, P. et al.: Scenarios related to the Security of Supply of the European Union. National Technical University of Athens, Greece. Report for the EU, 2000.
EC-2003 /30 /EG 2003 Richtlinie 2003/30/EG des europäischen Parlaments und des Rates vom 8. Mai 2003 zur Förderung der Verwendung von Biokraftstoffen oder anderen erneuerbaren Kraftstoffen im Verkehrssektor. Amtsblatt der Europäischen Union (L123/42).
Ecofys 2002 M. Hamelink et al.: Implementation of Renewable Energy in the European Union until 2010. Project ecexuted within the framework of the ALTENER Programme of the European Commission, DG Transport and Energy. Ecofys, 3E, Fraunhofer ISI.
EUROSTAT 2001 Renewable Energy Sources Statistics in the European Union. Eurostat, Theme 8: environment and Energy, Brussels, Belgium. Edition 2001.
Fichtner 2003 Gutachten zur Berücksichtigung großer Laufwasserkraftwerke im EEG. Endbericht für das Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit. Fichtner, Stuttgart, Juli 2003.
Flaig 1998 H. Flaig et al.: Biomasse – nachwachsende Energie. Potenziale – Technik – Kosten. Expert-Verlag, Renningen 1998.
Gertis 2001 Öffentliche Anhörung der Enquetekommission am 20. Nov. 2001 in Berlin.
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Area unitsha = hectarem2 = square meterkm2 = square kilometre
1 ha = 10,000 m2
100 ha = 1 km2
AquiferPorous layer of rock filled with water which is coveredby impervious layers. The term aquifer storage is usedfor this layer when it is used for stocking liquids (e.g.oil) or gases as a reservoir of heat.
Biomass
Biomass refers to all forms of living matter producedeither directly or indirectly through the process ofphotosynthesis. Biomass for energy conversion can beclassified as biomass which is grown specifically as araw material for energy production, or as organic resi-dual matter or waste products.
Block heat and power plant
A block heat and power station consists of a stationaryengine which produces both electrical power as well asheat. The effectiveness of a block-type thermal powerstation is based on making use of the waste heatwhich, in other types of power stations, is dischargedvia the cooling water into rivers without being used.Significant energy savings are possible due to the highefficiency of block-type thermal power stations.
CO2 (Carbon Dioxide)
Carbon dioxide is one of the greenhouse gases which isimpermeable for long wave thermal radiation. An in-creased concentration of CO2 in the atmosphere dis-turbs the equilibrium between the incoming shortwave radiation from the sun and the thermal radiationfrom the earth’s surface, leading to the risk of a tempe-rature rise.
Coal equivalent (SKE)
Reference unit for the energy content of fossil energycarriers. 1 kg of fuel oil is equivalent to 1.44 kg SKE; 1 Nm3 of natural gas is equivalent to 1.44 kg SKE.Secondary energy carriers can also be converted intocoal equivalents: 1 kWh of electricity is equivalent to0.123 kg SKE.
Decibel (dB)
The decibel is a unit used to measure a sound level.
EfficiencyRatio of energy yield to energy input.
Energy carrier
An energy carrier provides useful energy either directlyor after a conversion process.
Energy productivity
The energy productivity is considered as being a mea-sure for the efficiency in handling energy resources. Itis expressed as GDP (gross domestic product) in relationto the primary energy consumption PEC (BIP/PEC). Themore total economic performance (GDP) can be “obtai-ned” from a unit of primary energy, the more efficientis the way the economy is handling the energy.
Energy units
J = JoulekWh = kilowatt hourSKE = coal equivalent (“Steinkohleeinheit”)
Kilo = 103
Mega = 106
Giga = 109
Tera = 1012
Peta = 1015
Exa = 1018
Conversion between energy units:
Unit kJ kWh kg SKE1 Kilojoule – 0.000278 0.0000341 kilowatt hour 3,600 – 0.1231 kg SKE 29,308 8.14 –
Fossil fuels
Energy feedstock that emerged from biomass withinmillions of years: oil, coal, natural gas. Problems rela-ted to the use of fossil fuels are their exhaustibility andthe environmental burdens resulting from the conver-sion of fossil fuels.
GLOSSARY
125
Gas hydrate
Gas hydrates are solid compounds, resembling ice, for-med between a gas (e.g. methane, carbon dioxide, hy-drogen sulphide) and water. Under natural conditionsthese develop in sediments on the sea bed and on thecontinents at permanent sub-zero conditions. Becauseof their molecular cage-type structures, there can be upto 164 cubic metres of gas contained in one cubic me-tre of gas hydrate. Rough estimates available up to nowindicate that world-wide, there is approximately twiceas much carbon present in gas hydrates as there is inall known deposits of fossil fuels (carbon, crude oil andnatural gas) together. The immense quantities of me-thane in natural gas hydrates therefore constitute apotential energy source of relevance which can possiblybe used in the future.
Geothermal energy
Heat within the interior of the earth.
GIS
Geographic Information System
Heating value
Heating value is defined as the amount of energy relea-sed when a fuel is burned completely in a steady-flowprocess and the products are returned to the state ofthe reactants. The heating value is dependent on thephase of water /steam in the combustion products. IfH2O is in liquid form, heating value is called HHV (hig-her Heating Value). When H2O is in vapour form, hea-ting value is called LHV (Lower Heating Value).
Heliostat
A mirror which tracks the sun in a biaxial way.
Hybrid System
Combination of two or more power-generating systemsto increase their availability.
Intergovernmental Panel on Climate Change (IPCC)
The Intergovernmental Panel on Climate Change wasset up in 1988 by the United Nations EnvironmentalProgramme (UNEP) and the World MeteorologicalOrganization (WMO). Its tasks are to compile the cur-rent status of knowledge on the various aspects of cli-mate, the assessment of the consequence of global cli-
mate change for the environment and for society, toformulate strategies for prevention or adaptation andto encourage participation in IPCC activities by thedeveloping and threshold countries. The IPCC itselfdoes not carry out any scientific work, but rather hasthe task to prepare periodical scientific status reportson subjects of research on global climate change andthe effects of these. These reports constitute the basisfor government level negotiations under the UnitedNations Framework Convention on Climate Change.
Inverter
Converts direct current into alternating current. It isrequired to convert the dc-current generated by e.g. a solar cell into ac-current fed into the public grid.
Joule –> energy units
Kilowatt hour –> energy units
Off-Grid System
Grid-independent or decentralised systems, whichmight be connected to small networks.
Peak capacity
Maximum power of solar energy converter at standardtest conditions: global irradiance of 1,000 W/m2, am-bient temperature of 25 °C and the spectral composi-tion of the solar irradiance at air mass 1.5. These valuesare normally used as a reference for photovoltaic sys-tems. Unit: 1 Wp (Watt-Peak)
Photovoltaic
Direct conversion of solar radiation into electricity witha semi-conductor, the so-called solar cell.
ppm
parts per million (ppm) is a measure for a very low con-centration of a substance.
1 ppm (parts per million) = 1 millionth = 0.000.1% = 1 milligram per kilogram (mg/kg) or 1 millilitre percubic metre (ml/m3)
Primary energy
Energy carriers that occur in nature and have not beensubjected to any conversion or transformation, e.g. fos-sil fuels like coal, crude oil, natural gas; nuclear fuel,renewable energy sources like hydropower, solar ener-gy, wind energy, geothermal energy.
Receiver
Absorber for solar radiation which is used in solartower power plants.
Renewable energy sources
Energy sources, which from the perspective of humanbeings are available infinitely. The three basic sourcesfor renewable energy are solar radiation, geothermalenergy, and tidal energy. They can be used directly, orin the form of biomass, wind energy, hydropower, waveenergy or ambient heat.
Solar collector
A solar collector transforms solar radiation into heat.The useful heat is transferred to a heat transfer me-dium (e.g. water). Heat losses are avoided due to e.g. a single or a multiple glass cover, insulation of thebackside, evacuation of the absorber pipe or by selec-tive coating.
Solar energy use
— active: systems actively used for the direct transfor-mation of solar energy into heat (solar collectors) orelectricity (solar cells, solar power plants)
— passive: systems which use direct as well as diffusesolar radiation to support the heating system of a building.
Solar irradiance
Solar irradiance is composed of two components:
— diffuse irradiance, which reaches the earth surfaceindirect from all directions due to scattering processesat clouds, atmospheric molecules and particles and
— direct irradiance, which reaches the earth surfacedirect from the sun. The direct irradiance can be con-centrated or redirected with mirrors or lenses. The sumof both components is the global irradiance.
Solar thermal power plant
Power plant in which solar radiation is transformedinto heat, transferred to a heat transfer medium (e.g.oil, air), and converted into electricity by using a powerengine (steam- or gas-turbine).
Useful energy
Energy that is available to consumers for use in appli-ances and systems after the final conversion process.
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Contact:Federal Ministry for the Environment, Nature Conservation and Nuclear SafetyPublic Relations DivisionD - 11055 BerlinFax: +49 (1888) 3 05 - 20 44Internet: www.bmu.deE-mail: [email protected]
This brochure is part of the public relations work of the German Federal Government. It is distributed free of charge and is not intended for sale. Printed on 100 % recycled paper.
