RES - Task2 - Erasmus 2012 2013.pdf

7/30/2019 RES - Task2 - Erasmus 2012 2013.pdf

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Task2:Techn

icalapproach

UniverzavLjubljani

FacultyofMechanicalEngineering

Erasmus

Stu

dents

2012-2

013

REN

EWABLEENERGY

SOURCES

COURSE LEADERS:

PROF.SAO MEDVEDASSIST. PROF.CIRIL ARKAR

AUTHORS:

J ORGE CUBELOS ORDSJ AVIER ESTEFANELL ALSJ ORGE SANZMUSTIELESJ AVIER GAVILN MORENO

MACARENA RAMREZ PRADOSFRANCISCO CORREIA DA FONSECAJ ORGE RODRGUEZ LARRADADRIN FERNNDEZ GARCA


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ableEnergySourcesTask2:Technicalapproach

Renewable Energy Sources

Task 2: Technical approach

IndexSOLAR ENERGY 1

SOLAR THERMAL ENERGY CONCENTRATED SOLAR POWER (CSP) 1INTRODUCTION 1STORAGE MAKES ALL DIFFERENCE 1STAND-ALONE CONCENTRATED SOLAR POWER 1HYBRIDS 2

PARABOLIC TROUGH PLANT 2FRESNEL COLLECTORS 4CENTRAL RECEIVER PLANT 6PARABOLIC DISH ENGINES 8FUTURE TRENDS AND COSTS OF CONCENTRATED SOLAR POWER (CSP) 9CONCLUSION OF THE THREE CSP TECHNOLOGIES 11SOLAR CONCENTRATION RATIO:PRINCIPLES AND LIMITATIOS OF CSP SYSTEMS 12

PHOTOVOLTAIC 14INTRODUCTION 14PHOTOVOLTAICS SYSTEMS ELEMENTS 15SOLAR CELL 15POWER PRODUCED BY A COLLECTOR 17COSTS OF THE ENERGY 17SOLAR COLLECTOR EFFICIENCY 19

INDEX OF FIGURES SOLAR ENERGY 22REFERENCES 22

GEOTHERMAL ENERGY 23HOW GEOTHERMAL ENERGY IS CAPTURED 23GEOTHERMAL POWER PLANTS 23

HOW A GEOTHERMAL POWER PLANT WORKS? 24GEOTHERMAL HEAT PUMPS 24

HOW A GEOTHERMAL HEAT PUMP WORKS? 25GEOTHERMAL ENERGY COSTS 25

ELECTRICITY AT STABLE PRICES 26HISTORICAL GROWTH 26

THE FUTURE OF GEOTHERMAL ENERGY 27ENHANCED GEOTHERMAL SYSTEMS (EGS) 28CO-PRODUCTION OF GEOTHERMAL ELECTRICITY IN OIL AND GAS WELLS 28

INDEX OF FIGURES GEOTHERMAL ENERGY 30WINDENERGY 31

THE WIND RESOURCE 31

ADDRESSING THE VARIABILITY OF WIND POWER 32THE MECHANICS OF WIND TURBINES 33


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THE VISIBLE BITS 34THE INSIDE PARTS 35

GLOBAL MARKET FOR WIND ENERGY AND WIND TURBINE 35MAIN GEOGRAPHIC MARKETS 38AVERAGE PRICE PER KW/H CURRENTLY 38

HOW MUCH DO WIND TURBINE COST? 39WIND TURBINE POWER CALCULATIONS 39

SCENARIO 39PROBLEM STATEMENT 39MATHEMATICAL MODEL 39CALCULATION WITH GIVEN DATA 41CONCLUSION 42

INDEX OF FIGURES WINDENERGY 43REFERENCES 43

OCEAN ENERGY 44

INTRODUCTION 44PHYSICAL PRINCIPLE OF EXPLOITATION 44

WAVE POWER 44TIDAL ENERGY 49THERMAL GRADIENT ENERGY 51SALINITY GRADIENT ENERGY 52

EFFICIENCIES 54ECONOMICS DATA 55INDEX OF FIGURES OCEAN ENERGY 58REFERENCES 59

BIOMASS ENERGY 60INTRODUCTION 60EXPANSION OF THE MARKET 60BIOMASS CONVERSION ENERGIES 60

COMBUSTION 61CO-FIRING PROCESS 64GASIFICATION 65PYROLYSIS 66OTHER PROCESSES 67

BIOMASS POWER PLANTS 68

BIOMASS IN SPAIN 71INDEX OF FIGURES BIOMASS ENERGY 74REFERENCES 74

BIOFUEL ENERGY 75COMBUSTION ENGINE 75COMBUSTION OF THE FUEL 76

EMISSIONS 76COMBUSTION ETHANOL VS GASOLINE 77BIODIESEL VS DIESEL 79

INDEX OF FIGURES BIOFUEL ENERGY 81REFERENCES 81


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HYDROPOWER ENERGY 82FUNDAMENTALS OF HYDROPOWER AND PHYSICAL PRINCIPLES 82PARTS OF HYDROPOWER PLANTS TYPE (EXPLANATION IN A PUMPING CENTRAL) 85

HYDRO PUMP 86DAM 87

THE SPILLWAY 88HYDRANTS 88BYPASS CHANNEL 88SURGE SHAFT 88PENSTOCKS 88ROUNDHOUSE 88

TURBINES 92OPERATIONS AND CALCULATES AND COSTS 95

CALCULATING AVAILABLE POWER 96COSTS 96

INDEX OF FIGURES HYDROPOWER ENERGY 97REFERENCES 97

CONCLUSION TO TASK2 98INDEX OF FIGURES CONCLUSION TOTASK2 100


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Solar energy

Solar thermal energy Concentrated Solar Power (CSP)

IntroductionUnlike photovoltaic generation, which produces electricity directly from any ambient light, the more

stable and fully dispatch able CSP approach requires direct solar radiation. Solar Thermal plants

require at least 1900 kWh/m2/y as found on the sun-belt. CSP is the ideal approach to harvesting the

suns free energy for large scale grid connected power generation but it is also suitable for remote

industrial applications.

Storage makes all the difference

Figure 1: Sun distribution

Because Solar Thermal plants warm a thermalfluid, unlike photovoltaic solar, they inherently have

the ability to smooth out the effect of passing clouds. But how do you get power long after sundown

when people need it?

By integrating thermal storage into the solar plant, the power production can be extended for many

hours after dark. During the day, a fraction of the heat captured from the sun will be stored in a

thermal storage medium (molten salt). In the absence of the sun, the process is reverted and the

stored heat is used to produce steam for continued power generation a major advantage over

photovoltaic solar.

Stand-alone Concentrated Solar Power (CSP)

Stand-alone CSP plants are the ideal choice for sun-belt locations where clean fuel-free power is

required. At present, supporting incentives are necessary but technological advances mean solar

thermal fields will soon rival fossil fuel plant energy prices.


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If needed by the customer, based on its consumption structure, the addition of a storage system to a

CSP plant significantly adds to the project value with only a marginal increase in the overall

investment.

Hybrids

Hybrids are an important cornerstone in the transition to widespread solar energy production. Theyallow reduced fossil fuel consumption and more efficient solar energy to electicity conversion in base

load or despachable plants. Hybrids make optimal use of currently available assets and are thus the

least cost solar solutions.

- Repowering:

-

A Solar Thermal plant can complement or fully replace an existing fossil boiler,

while still leveraging the existing powerblock: Solar efficiency >20% to 100%.

Parallel GT:

-

a small gas turbine/Heat Recovery Steam Generator (HRSG) arranged parallel to

the solar system allows alternating or parallel operations to handle peak duties. Solar

efficiency 35 to 80%.

Integrated Solar CC:

-

Combined cycle power plants with fully integrated solar steam

generation. Solar efficiency 10-30%.

Solar Boost:

Existing steam or gas plants can also benefit from the addition of a solar add -on to generate

additional carbon-neutral steam with no extra fuel costs. Because all the infrastructure and grid

connections already exist, the overall investment is relatively low.

CSP can be used for partial or full pre-heating of condensate, feed water. Solar

efficiency: 5-10%.

Parabolic Trough Plant

A Parabolic Trough is a type of solar thermal energy collector, constructed as a long parabolic mirror

with a receiver tube running its length at the focal point.

Sunlight is reflected by the mirror and concentrated on the receiver tube. The trough is usually

aligned on a north-south axis and rotates to track the sun as it moves across the sky. Heat transfer

fluid runs through the tube to absorb the concentrated sunlight, which increases the fluid

temperature to some 400 C (752 F). The heat transfer fluid is then used to heat steam in a standard

turbine generator. In the Parabolic Trough plants currently under construction and which use this

technology, thermal storage systems with an output of 6 to 8 hours are being implemented. Central

Receiver storage systems are being developed to reach even 15 hours.

Technology developments

Parabolic trough systems represent the most mature solar thermal power technology, with 354 MWe

connected to the Southern California grid since the 1980s and over 2 million square metres of

parabolic trough collectors operating with a long term availability of over 99%. Supplying an annual

924 million kWh at a generation cost of about 12 to 15 US cents/kWh, these plants have

demonstrated a maximum summer peak efficiency of 21% in terms of conversion of direct solar

radiation into grid electricity (see box The California SEGS Power Plants).


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Advanced structural design will improve optical accuracy and, at the same time, reduce weight and

costs, thus resulting in higher thermal output. By increasing the length of the collector units,

investment savings can be achieved in drive systems and connection piping. Next-generation receiver

tubes will also further reduce thermal losses while, at the same time, improving reliability.

Improvements to the heat transfer medium will increase operating temperature and performance.

Figures 2 and 3

New structural collector designs have recently been developed in Europe and the USA and are

currently in their test phase, whilst work on improved receiver tubes is under way in both Israel and

Germany.

What promises to be the next generation of parabolic collector technology has been under

development at the European solar thermal research centre, the Plataforma Solar in Spain, since

1998 by a European R&D consortium Known as EuroTrough, it aims to achieve better performance

and lower costs by using the same well-tried key components ( parabolic mirrors and absorber tubes)

as in the commercially mature Californian plants, but significantly enhancing the optical accuracy bya completely new design for the trough structure. With funding from the European Union, both a

100m and a 150m prototype of the EuroTrough were successfully commissioned in 2000 and 2002

respectively at the Plataforma Solar.

In the USA, an advanced-generation trough concentrator design that uses an all-aluminium space

frame is currently being implemented in a 1 MW pilot plant in Arizona. The design is patterned on

the size and operational characteristics of the LS-2 collector, but is superior in terms of structural

properties, weight, manufacturing simplicity, corrosion resistance, manufactured cost, and

installation ease.

The commercial plants in California use synthetic oil as the heat transfer fluid, because of its low

operating pressure and storability. However, R&D efforts are under way at the Plataforma Solar to

achieve direct steam generation within absorber tubes and to eliminate the need for an intermediate

heat transfer. This increases efficiency and will further reduce costs.

For the Spanish 50 MW AndaSol 1, 2 and 3 projects, the German project developer Solar Millennium,

in full collaboration with an American engineering company, designed a six to 12 full load hours

thermal storage system operating with molten salt, which was successfully tested in the 10 MW USA

Solar Two solar tower pilot plant. Although this will reduce efficiency, the developers expect a

considerable potential for cost reduction since the closer arrangement of the mirrors requires lessland and provides a partially shaded, useful space underneath.


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To date all existing commercial parabolic trough plants use a steam cycle, with a back-up natural gas-

fired capability to supplement the solar output during periods of low radiation, up to an annual

maximum of 25% of primary thermal heat input. Parabolic trough plants can be built in unit sizes up

to 200 M

Fresnel collectors

Figure 4: Schematic diagram of CSP parabolic trough plant

A Linear Fresnel Reflector (LFR) array is a line focus system similar to parabolic troughs in which solar

radiation is concentrated on an elevated inverted linear absorber using an array of nearly flat

reflectors. With the advantages of low structural support and reflector costs, fixed fluid joints, a

receiver separated from the reflector system, and long focal lengths allowing the use of conventional

glass, LFR collectors have attracted increasing attention. The technology is seen as a lower-cost

alternative to trough technology for the production of solar process heat and steam.

An LFR can be designed to have similar thermal performance to that of a parabolic trough per

aperture area, although recent designs tend to use less expensive reflector materials and absorber

components which reduce optical performance and thus, thermal output. However, this lower

performance seems to be outweighed by lower investment and operation and maintenance costs.

In 1999, the Belgian Company Solarmundo erected the largest prototype of a Fresnel collector, with a

collector width of 24 m and a reflector area of 2,500 m2.


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The next step should be a pilot plant to

demonstrate the technology in a larger-scale

system under commercial operational

conditions. Most convenient and cost-effective

would be a plug-in solution for a Fresnel

collector connected to an existing power plant.In 2003, the Australian company Solar Heat and

Power constructed a test field for its new Fresnel

collector concept, equivalent to 1 MW electric

capacity, and tested it. In 2005 we saw the start

of the enlargement of the Fresnel solar field,

comprising 20,000 m which was going to be

connected to the large coal-fired Liddell power

station using solar steam as feed-water addition.

The final stage was a roll out to 135,000 m.

Figure 4: Fresnel collector operation

Cost trends

Between 1984 and 1991, the installed capital costs of the Californian SEGS Rankine-cycle trough

systems with on-peak power operation fell from US$ 4,000/kWe to under US$ 3,000/kWe mainly due

to the increase in size from 30 to 80 MWe units and series experience. The investment cost of

parabolic trough fields has currently dropped to 210/m2 for enhanced collectors like the SKAL ET

EuroTrough design with large solar fields, and will fall to about 110-130/ m2

According to a World Bank assessment of the USA/European solar thermal power plant market, the

installed capital costs of near-term trough plants are expected to be in the range of 3,500-

2,440/kWe for 30-200 MWe Rankine-cycle (SEGS type) plants and about 1,080/kWe for 130 MWe

hybrid ISCC plants with 30 MWe equivalent solar capacity.

for high-production

runs in the long term.

The projected total plant power generation costs range from 10 to 7 cents/kWh for SEGS type

plants and less than 7 cents/kWh for ISCC plants.

The expected further drop in capital costs of grid-connected ISCC trough plants should result in

electricity costs of 6 cents/kWh in the medium term and 5 cents/kWh in the long term. The

promising long-term potential is that Rankine-cycle trough plants can compete with conventional

peaking to mid-load Rankine-cycle plants (coal- or oil-fired) at good solar sites. The cost reductionpotential of direct steam generation trough technology is even greater in the longer term. In

Australia, the CLFR total plant electricity costs have been estimated to be about AU$ 0.045/kWh

when used in conjunction with coalfired plants, and AU$ 0.07/kWh to AU$ 0.09/kWh as a standalone

solar thermal plant.

Table 2.3 shows how substantially these cost reductions could be achieved over the next five to ten

years, especially for plants with very large solar fields. Similarly, the analysis shows that projects

could be built cheaper outside the developed world. In a pre-feasibility study for a CSP plant in Brazil,

for example, it was estimated that the construction cost of a 100 MW Rankinecycle plant would be

just US$ 2,660/kW today, 19% lower than in the USA, with savings in labour, materials and, to someextent, equipment. A number of companies interested in building GEF projects have indicated that


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using local labour and manufacturing capabilities in India, Egypt, Morocco and Mexico will be the key

to their competitive bidding at a low cost.An American initiative called the Parabolic Trough

Technology Roadmap, developed jointly by industry and the US Department of Energys SunLab,

identified a number of potential improvements. The initiative suggests that further cost reductions

and performance increases of up to 50% are feasible for parabolic trough technology.

Central receiver plant

This method of collecting energy is based on concentrating the sun's energy onto a common focal

point to produce heat to run a steam turbine generator. It has hundreds of large mirror assemblies,

called heliostats, which track the sun to reflect the solar energy onto a tower where a black receiver

absorbs the heat.

High-temperature heat transfer fluid is used to transport the heat to a boiler where the steam is used

to spin a series of turbines, much like in a traditional power plant. This solar thermal storage system

improves handling of the central tower plants and considerably increases its capacity factor to 70%

or more.


Figure 5: Schematic diagram of a CSP central receiver plant

The average sunlight concentration of tower systems varies with the process temperature from

about 500 times for 540C steam cycles to several thousand times concentration for applications at

1,000C and beyond for gas turbine or combined cycles electricity, and thermo chemical cycles for

production of industrial materials or synthetic fuels like hydrogen.

For gas turbine operation, the air to be heated must first pass through a pressurized solar receiver

with a sealing window. Integrated Solar Combined Cycle power plants using this method will require

30% less collector area than equivalent steam cycles. At present, a first prototype to demonstrate

this concept is being built as part of the European SOLGATE project, with three receiver units coupled

to a 250 kW gas turbine.

Various central receiver heat transfer media have been investigated, including water/steam, liquid

sodium, molten salt and ambient air. Those storage systems allows solar energy to be collected


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during daylight hours and dispatched as high value electric power at night or when required by the

utility.

Today, the most promising storage systems are

considered to be the European volumetric air

technology and the USA molten salt technology. Thelatter is now ready to be commercially demonstrated,

and a project led by Sener (Spain) is promoting the

first commercial central receiver plant with support of

EU and Spanish grants. This proposed 15 MWe Solar

Tres plant in Spain will utilise a 16-hour molten-salt

storage system to run on a 24-hour basis in

summertime. Molten-salt storage coupled with

central receiver/tower technology is unique among Figure 6: Central receiver plant operation

The European system involves irradiating fine wire mesh or ceramic foam structures, and transferring

the energy by convection at a temperature range of 700-1,200C. Tests conducted in the joint

German/Spanish Phoebus project; between 1993 and 1995, with a German 2.5 MWth pilot plant

demonstrated the feasibility of the volumetric air receiver system concept with a ceramic energy

storage system. As with parabolic troughs, efforts are under way to develop commercial central

receiver plants using solar/fossil fuel hybrid systems.

all renewable energy technologies in that the addition of storage reduces energy cost and increases

its value by enabling dispatch to peak demand periods.

Since heliostats represent the largest single capital investment in a central receiver plant, efforts

continue to improve their design with better optical properties, lighter structure and better control.Initiatives to develop low-cost manufacturing techniques for early commercial low-volume builds are

also under way, whilst prices for manufacture in a developing country could be roughly 15% below

USA/European levels

Central receiver plants have reached commercial status with PS10 plant, 11MW solar tower which is

the first of the new wave of CSP projects in Spain. Potential for improvement is already high, as solar

towers have good longer term prospects for high conversion efficiencies.

Cost trends

Central receiver plants will take credit, however, for their potential for the favorable application ofhigh-temperature energy storage systems. This will increase the plant capacity factor, reduce

electricity costs, and increase the value of power by enabling dispatch to peak demand periods.

Promoters of new near-term tower projects in Spain, such as the 10 MW PS10 plant with three hours

of storage, have indicated their installed plant capital costs to be roughly 2,700/kWe, with Rankine-

cycle turbines and a small energy storage system, and with predicted total plant electricity costs

ranging from 20 to 14 cents/kWh. The total capital cost for the 15 MW Solar Tres plant, with 16

hours of storage, is estimated to be 84 million, with annual operating costs of about 2 million. The

expected costs for installing the heliostat field range from 180 to 250/m2 for small production runs

in the USA, and from 140 to 220/m

2

in Europe. A 15% discount on the USA/ European price level


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can be projected for developing countries because of lower labor costs. Heliostat field costs are

expected to drop below 100/m2

In the future, central receiver plant projects will benefit from similar cost reductions to those

expected from parabolic trough plants. According to the World Bank, the expected evolution of total

electricity costs is that they will drop to 8 to 7 cents/kWh in the medium term (100 MWe Rankine-cycle plant or 100 MWe ISCC, both with storage) and to 5 cents/kWh in the long term (200 MWe

Rankine-cycle plant with storage) for high insolation sites with an annual DNI of more than

2,700kWh/m

at high production runs in the long term.

2

As the basic concept of these collectors is simpler in comparison to parabolic troughs, lower

investment costs for the reflectors can be expected. However, the comparable annual efficiency will

be somewhat lower.

.

Parabolic dish engines

For what are known as dish/Stirling systems, a parabolic reflector mirror (dish) concentrates the solarradiation onto the receiver of a connected Stirling engine. The engine then converts the thermal

energy directly into mechanical work or electricity.

These systems can achieve a degree of efficiency in

excess of 30 per cent. Prototype systems are

undergoing trials at the Plataforma Solar centre in

Almera, Spain. Although these systems are suitable

for stand-alone operation, they also offer the

possibility of interconnecting several individual

systems to create a solar farm, thus meeting an

electricity demand from 10 kW to several MW.


Figure 7: Functional principle of a dish/Stirling system

Parabolic dish concentrators are comparatively small units with a motor generator at the focal point

of the reflector.

Overall size typically ranges from 5 to 15 meters in diameter and 5 to 50 kW of power output. Like all

concentrating systems, they can be additionally powered by natural gas or biogas, providing reliablecapacity at any time.

As a result of their ideal point focusing parabolic optics and their dual axis tracking control, dish

collectors achieve the highest solar flux concentration, and therefore the highest performance of all

concentrator types. For economic reasons, systems are currently restricted to unit capacities of

about 25 kWe, but multiple dish arrays can be used in order to accumulate the power output

upwards to the MWe range. Because of its size, the future for dish technology lies primarily in

decentralized power supply and remote, stand-alone power systems.

Dish/Stirling engine systems in particular have an excellent potential for high conversion efficiencies

because of the high process temperatures in the engine. The record energy yield so far has been


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from a 25 kWe USA dish/Stirling system with a solar-to-electric efficiency of 30%. Dish/engine

prototypes which have successfully operated over the last 15 years include 7 to 25 kW units

developed in the United States by Advanco, the McDonnell Douglas Corporation, the Cummins

Engine Company and others. In Spain, six units with a 9 to 10 kW rating are currently operating

successfully. These were developed by the German company Schlaich, Bergermann und Partner

(sbp), working with Mero (suppliers of the collector system) and SOLO Kleinmotoren (Stirling engine).

Three of these dishes have been operated continually with great success since 1992, accumulating

more than 30,000 hours of operating experience.

The new EuroDish development, supported by the European Union, will advance this technology

further. At the same time, two industrial teams working in the United States Stirling Energy

Systems/Boeing Company and Science Applications International Corporation/STM Corp have

installed several second-generation 25 kW dish/Stirling prototypes for extended testing and

evaluation. Finally, WG Associates have demonstrated the first unattended, remote operation of an

advanced technology 10 kW dish/Stirling prototype.

Cost trends

The cost trend for dish collectors has already shown a sharp reduction from 1,250/m 2 in 1982 (40

m2 array, Shenandoah, USA) to 150/m2 in 1992 (44 m2

In terms of electricity costs, an attainable near-term goal is a figure of less than 15 cents/kWh. In

the medium to long term, with series production, dish/Stirling systems are expected to see a drastic

decrease in installed system costs.

array, German SBP stretched membrane

dish). Overall installed plant capital costs for a first stand-alone 9 to 10 kWe dish/Stirling unit

currently range from 10,000 to 14,000/kWe.

Advanced dish/Stirling systems are expected to compete in the medium to long term with similar-

sized diesel generator units at sunny remote sites such as islands.

Parabolic dish system commercialisation may well be helped by hybrid operation, although this

presents a greater challenge with Stirling engines. Gas-turbine based systems may present a more

efficient alternative.

In 2005, the USA dish developer SES announced, that the company might be able to offer electricity

from dish/Stirling engines in California for about the cost of a conventional generated peaking kWh,

if power purchase agreements of 500-1,000 MW were available.

Future trends and costs of Concentrated solar power (CSP)

Two broad pathways have opened up for the large-scale delivery of electricity using solar thermal

power. One is to combine the solar collection and heat transfer process with a conventional power

plant. The most favored current combination is the Integrated Solar/Combined Cycle system (ISCC).

Essentially, the ISCC system uses the CSP element as a solar boiler to supplement the waste heat

from a gas turbine in order to augment power generation in the steam Rankine bottoming cycle. In

this way, efficiency is improved and operating costs reduced, cutting the overall cost of solar thermal

power by as much as 22% compared with a conventional SEGS plant (25% fossil) of similar size.


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These systems could still have an equivalent solar capacity of 30 to 40 MWe, and promise to be quite

attractive as a way of introducing the technology to the market.

Environment Facility, an important source of funding, is supporting hybrid ISCC systems with a low

solar share.

Current drastically increasing fuel prices and power shortages for summer daytime peaking power in

South-west USA and Southern Spain suggest that CSP systems will today find their prime market

segment in this summer on peaks. Here, power generation cost differences, compared to typically

used gas turbine operation, are the smallest.

The market for 100% solar only operation will broaden still further with the use of thermal storage as

a way of storing the suns heat until required for power generation. A recent study, part of the USA

Trough Initiative, evaluated several thermal storage concepts, with the preferred design using

molten salts as the storage medium, as already chosen for the Solar Two pilot plant in California.

Such a storage system has also been implemented in most of the 50 MW parabolic trough plants in

Spain.

Figure 8 Flow diagram of solar field, storage system and steam cycle at the AndaSol-1 project, southern

Spain.

Solar energy collected by the solar field during the day will be stored in the storage system and then

dispatched after sunset. To charge the storage system, the salt is heated up to approximately 384C;

to discharge the system, it is cooled down again to about 291C. At both temperatures the salt is in a

liquid state. Cold and hot salt are stored in separate tanks, giving the system its two-tank label. A

thermal storage system with separate cold and hot tanks has the advantage that charging and

discharging occur at constant temperatures with a two-tank molten-salt storage system. In this

configuration, hot thermal fluid from the solar field is diverted to a heat exchanger where its thermal

energy passes to the salt flow arriving from the cold tank. This heats up and accumulates in the hot

tank. During the night or at times of reduced radiation, the charging process is reversed, and salt

from the hot tank is pumped to the heat exchanger, where the salt returns its thermal energy to the


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cold thermal fluid. The thermal fluid heats up to keep producing steam for the turbine, while the

cooled salt accumulates again in the cold tank.

In terms of costs, experience so far has come more from parabolic trough systems, such as the

Californian SEGS plants. For current trough systems with 100% solar operation, costs are in the range

of 15-17 US cents/kWh in high solar radiation areas of the US South-west and about 20 eurocents/kWh in the medium solar radiation areas of the Mediterranean.

These costs can be cut down by 30-50% through the implementation of the first 5,000 MW within

the market introduction concept of the Global Market Initiative for CSP.

Conclusion of the three CSP technologies

The steam produced in a CSP plant is in the optimal range for highly efficient steam to electricity

conversion.

Furthermore, hotter steam means greater returns on storage system investments.

Figure 9: trends of the CSP tecnhnologies


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Finally, here we have the comparison of the main characteristics of the three CSP technologies seen

before:

Figure 10: Comparison of solar thermal power technologies

Solar Concentration Ratio: Principles and Limitations of CSP Systems

The most practical and simplest primary geometrical concentrator typically used in CSP systems is

the parabola. Although there are other concentrating devices like lenses or compound parabolic

concentrators, the reflective parabolic concentrators and their similars are the systems with the

greatest potential for scaling up at a reasonable cost.

Parabolas are imaging concentrators able to focus all incident

paraxial rays onto a focal point located on the optical axis. Theparaboloid is a surface generated by rotating a parabola around its

axis. The parabolic dish is a truncated portion of a paraboloid.

For optimum sizing of the parabolic dish and absorber geometries,

the geometrical ratio between the focal distance (f), the aperture

diameter of the concentrator (d), and the rim angle (), must be

taken into account. The ratio can be deducted from the equation

describing the geometry of a truncated paraboloid: x2+y2

=4fz,

where x and y are the coordinates on the aperture plane and z is

the distance from the plane to the vertex.


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For small rim angles, the paraboloid tends to be a sphere, and in many cases spherical facets are

used. Therefore, in most solar concentrators the following correlation is valid:

1/

4 tan( / 2)f d

=

For example, a paraboloid with a rim angle of 45 has an f/d of 0.6 (see figure 2). The ratio f/dincreases as the rim angle decreases. A parabolic concentrator with a very small rim angle has very

little curvature and the focal point far from the reflecting surface. Because of this positioning, CSP

systems making use of cavity receivers with small apertures should use small rim angles. Conversely,

those CSP systems using external or tubular receivers will make use of large rim angles and short

focal lengths.

The equation describing the minimum concentration ratio as a function of the rim angle for a given

beam quality (), is:

2 2

2

sin cos ( )min

sinconc

C

+=

From this equation, it can be concluded that 45 is the optimum rim angle for any beam quality, in

terms of solar concentration (Figure 3). Therefore, f/d=0.6 is the optimum focal length-to-diameter

ratio in a parabolic concentrator.

The thermodynamic limit or maximum concentration ratio for an ideal solar concentrator would be

set by the size of the sun and not by the beam quality. By applying the geometrical conservation of

energy in a solar concentrator, the following expressions are obtained for 3D and 2D systems (for a

refraction index n=1)

2

1

max, 3 46, 2sin sC D =

1max, 2 2,15

sins

C D

=

Figure 12: Visualization of dependence of f/d -rim angle for a parabolic concentrator


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Figure 13: Dependence of minimum concentration achieved for a parabola versus rim angle and beam

quality.

Then, the semi-angle subtended by the sun is s=4,653x10-3 rad (16), and the maximum

concentration values are 46,200 for 3D and 215 for 2D. For real concentrators, the maximum ratios

of concentration are much lower, because of microscopic and macroscopic, tracking and mechanical,

sun shape and other errors. Engineers designing a specific CSP plant should give special attention to

the expected real beam quality and rim angle of the reflecting system to obtain an appropriate sizing

of the solar receiver.

Photovoltaic system

Introduction

A photovoltaic system (or PV system) is a system which uses one or more solar panels to convert

sunlight onto electricity. It consists of multiple components, including the photovoltaic modules,

mechanical and electrical connections and mountings and means of regulating or modifying the

electrical output.

Photovoltaic systems use solar electric panels to directly convert the sun's energy into electricity.

This conversion of sunlight to electricity occurs without moving parts, is silent and pollution free in its

operation. The solar electricity fed through electronic equipment is converted to utility grade

electricity for use directly in the home. The solar electricity can be used to offset the need forpurchased utility electricity or, if the PV electricity exceeds the home's requirements, the excess

electricity can be sent back to the utility, typically for credit.

Different types of photovoltaic products are available today from numerous manufacturers. The

supply of PV collectors worldwide has increased from 20 to 30 percent annually to keep up with the

demand for this renewable energy technology. Photovoltaic modules are usually rigid, rectangular

devices ranging in size from 2 by 4 to as large as 4 by 8. Some PV module technologies are flexible

and as large as 2 by about 20 or even larger. Rigid PV modules typically have a glass cover while the

flexible modules have a very durable film cover. Both types of PV module can survive storm and hail

damage and are resistant to degradation from ultra-violet rays.


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Most residential PV systems are used in conjunction with utility-supplied power. Excess power

produced during daylight hours can be fed back into the utility's lines, while utility electricity is used

in the home when the house demand is greater than can be supplied by the PV roofing. Typical

residential PV systems commonly have a peak power production of between 1,200 and 5,000 watts,

AC - requiring from between 150 to over 1,000 square feet of installed area depending on the

efficiency of the PV technology used.

Most often, PV panels are installed on roofs, but they can also be installed as free-standing units, on

a pole on the ground, or even on complex tracking structures that change with the sun's angle during

the day.

Photovoltaic systems elements

A photovoltaic system is a device that, from solar radiation, produces electricity in a position to be

exploited by man.

The system consists of the following:

- Solar generator:

-

consists of a set of photovoltaic panels that catch the light radiation from

the sun and transform it onto electrical energy. This energy depends mainly on the number

and type of modules installed, the inclination and spatial orientation, and incident solar

radiation.

Battery:

-

That stores energy produced by the generator and allows power available outside

the light hours or cloudy days.

Charge controller:

-

which controls the inlet and outlet on the battery and its mission is to

prevent overloading or excessive discharge the battery, which will result in irreversibledamage and ensure that the system always operates at the point of maximum efficiency.

Inverter:

Solar cell

optional device which converts direct current 12 or 24V stored in the battery,

alternating current of 230V.

It is an electrical device that converts the energy oflightdirectly intoelectricityby the

Assemblies of photovoltaic cells are used to make

photovoltaic

effect. When exposed to light, can generate and support an electric current without being attached

to any external voltage source.

solar moduleswhich generate electrical powerfrom

The solar cell works in three steps:

sunlight. Multiple cells in an integrated group, all oriented in one plane, constitute a solar

photovoltaic module.

- Photonsinsunlight

- Electrons are knocked loose from their atoms, causing an electric potential difference.Current starts flowing through the material to cancel the potential and this electricity is

hit the solar panel and are absorbed by semiconducting materials, such

as silicon.


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captured. Due to the special composition of solar cells, the electrons are only allowed to

move in a single direction.

- An array of solar cells converts solar energy into a usable amount ofdirect current

Solar cell efficiency

(DC)

electricity.

Itis the ratio of the electrical output of a solar cell to the incident energy in the form of sunlight.Theenergy conversion efficiency() of asolar cellis the percentage of thesolar energyto which thecell is exposed that is converted intoelectrical energy. This is calculated by dividing a cell's poweroutput (inwatts) at its maximum power point (P m) by theinput light(E, in W/m

2) and thesurfaceareaof the solar cell (Acin m

2

).

By convention, solar cell efficiencies are measured under standard test conditions (STC) unless statedotherwise. STC specifies a temperature of 25 C and an irradiance of 1000 W/m2with an air mass 1.5(AM1.5) spectrums. These conditions correspond to a clear day with sunlight incident upon a sun-

facing 37-tilted surface with the sun at an angle of 41.81 above the horizon.This represents solar

noon near the spring and autumn equinoxes in the continental United States with surface of the cell

aimed directly at the sun. Under these test conditions a solar cell of 20% efficiency with a

100 cm2(0.01 m2

The efficiency of the solar cells used in a

) surface area would produce 2.0 watts of power.

photovoltaic system, in combination with latitude and

climate, determines the annual energy output of the system. For example, a solar panel with 20%

efficiency and an area of 1 m will produce 200 watts of power at STC, but it can produce more whenthe sun is high in the sky and will produce less in cloudy conditions and when the sun is low in the

sky.

Figure 11: Solar cells conversion efficiencies


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Crystalline silicon

By far, the most prevalentmaterial for solar cells iscrystalline

Analysts have predicted that prices of polycrystalline silicon will drop as companies build additional

polysilicon capacity quicker than the industry's projected demand.

silicon (c-Si), also known as "solar

grade silicon".

Power produced by a collector

Figure 12: Structure of a silicon solar cell and its working mechanism

In order to calculate the power produced by a collector or a photovoltaic cell, we will use the same

formula used before:

Pm (power) = x K x Sc

Where: = efficiency of the technology, K = direct solar flux (W/m

[W]

2) , Sc = surface of the collector or

cell (m2

Costs of the energy

).

Costs of production have been reduced in recent years for more widespread use through production

and technological advances. As of 2011, the cost of PV has fallen well below that of nuclear power

and is set to fall further. The average retail price of solar cells fell to 2.43/W. For large-scale

installations, prices below 1.00/W are now common.Crystal siliconsolar cells

Levelize cost

have largely been

replaced by less expensive multicrystalline silicon solar cells.

Levelized cost" is the average cost of this renewable energy.

Levelized Cost = Net Cost to install a renewable energy system divided by its expected life-time

energy output.


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The table shows the total cost in US cents per kWh of electricity generated by a photovoltaic system.The row headings on the left show the total cost, per peak kilowatt (kWp), of a photovoltaic

installation. These photovoltaic system costs have been declining and in Germany, for example, were

reported to have fallen to USD 2200/kWpby the second quarter of 2012. The column headingsacross the top refer to the annual energy output in kWh expected from each installed kW p. This

varies by geographic region because the averageinsolationdepends on the average cloudiness andthe thickness of atmosphere traversed by the sunlight. It also depends on the path of the sun relative

to the panel and the horizon. Panels are usually mounted at an angle based on latitude, and often

they are adjusted seasonally to meet the changing solardeclination.Solar trackingcan also beutilized to access even more perpendicular sunlight, thereby raising the total energy output. The

calculated values in the table reflect the total cost in cents per kWh produced. They assume a 10%

total capital cost (for instance 4% interest rate, 1% operating and maintenance cost,and depreciation of the capital outlay over 20 years). Normally, photovoltaic modules have a 25year warranty.

Cost per kilowatt hour (US cents/kWh)

20 years 2400kWh/kWpy

2200kWh/kWpy

2000kWh/kWpy

1800kWh/kWpy

1600kWh/kWpy

1400kWh/kWpy

1200kWh/kWpy

1000kWh/kWpy

800kWh/kWpy

200$/kWp 0.8 0.9 1.0 1.1 1.3 1.4 1.7 2.0 2.5600$/kWp 2.5 2.7 3.0 3.3 3.8 4.3 5.0 6.0 7.51000$/kWp 4.2 4.5 5.0 5.6 6.3 7.1 8.3 10.0 12.5

1400$/kWp 5.8 6.4 7.0 7.8 8.8 10.0 11.7 14.0 17.5

1800$/kWp 7.5 8.2 9.0 10.0 11.3 12.9 15.0 18.0 22.5

2200$/kWp 9.2 10.0 11.0 12.2 13.8 15.7 18.3 22.0 27.5

2600$/kWp 10.8 11.8 13.0 14.4 16.3 18.6 21.7 26.0 32.5

3000$/kWp 12.5 13.6 15.0 16.7 18.8 21.4 25.0 30.0 37.5


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Solar collector efficiency

The graph is an expression of data obtained from official third party solar testing facilities, the

Solartechnik Prufung Forschung (SPF Rapperswil, www.solarenergy.ch), in Germany and Bodycote

Materials Testing Canada Inc.

Figure 16

Graph details

Ta = Ambient Temperature, or air temperature of surrounding space. For our purposes, allowing a

more intuitive interpretation of the graph, we have set Ta as a constant (unchanging), in this case

Ta=0C.

Efficiency = A fraction of 1... i.e. 0.3 on the graph represents 30%, 0.5 on the graph is 50%, and so

forth.

Tm = Mean temperature, expressed as (Tin + Tout)*

Equations

Two types of collectors are represented in the graph; Flat Plate designated FP, and the high

efficiency Evacuated Tube Collector designated ETC. The efficiency equation used by the European

(SPF Rapperswil) testing facilities for Mazdon (ETC), Apricus (ETC), Sunmaxx (ETC) and Veisman (FP)

collectors is:

2

1 20

2 2

in out in out T T T T a aG G

+ + =


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The efficiency eqn. for Enerworks(FP) is:

( ) ( )2

0.717 4.033 0.0184i a i aT T T T

G G

+ +=

The efficiency eqn. for ThermoDynamix (FP) is:

( )0.738 5.247

i aT T

G

+=

How to Read the Efficiency Graph

The graph represents collector performance when the ambient temperature (the outside air

temperature) is 0C. To determine efficiency (the percentage of solar radiation hitting the collector

that is directly transferred to heat water) chose the desired water temperature.

The slopes of the lines in the graph represent their heat loss factors. The steeper the slope, the

higher the collector loses heat. A line with a small slope represents a collector that loses very little

heat to its surroundings, and is very efficient at heating.

For example, if you wanted to use the collector to heat water for your home you would look at the

60 Temp value along the horizontal axis and follow the line up to see the efficiency of the collectors.

This means that if it is a moderately clear day, and the outside temperature is zero degrees, the

Thermomax collector would be able to convert about 70% of the available solar thermal radiation toheat your water tank to 60 degrees.

Gross Area Mistake

The most widely quoted efficiency performance results

found in North America are the results from the SRCC

(Solar Rating and Certification Corporation). The SRCC

evaluates Evacuated Tube Collectors (ETC) as if they were

flat plate collectors, which they are not. The resulting

efficiency graphs released by SRCC undervalue actual

performance of evacuated tubes by over 30%.

Gross Area = the gross area refers to the external mass of the collector; the area actually necessary

for installation, that is simply the length times the width of the collector.

Figure 17

Instead of including the spaces between tubes, the manifold, the lateral glass wall thicknesses, in the

gross area calculation, it would be much more accurate to base performance of collectors on

Aperture Area = the area through which solar energy enters the collector.


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Corrected SRCC Graph

Fortunately there is a simple solution for converting efficiency parameters from expression in terms

of collector gross area (total footprint of collector) to expression in terms of aperture area (area of

collector that gathers sunlight):

.g

a g

a

A

A =

Ag = Gross Area

Aa= Aperture Area

This formula was obtained from the NRC and ASHRAE standards, and is commonly used by the

European Solar Testing group SPF. The SRCC uses it to convert from aperture or absorber area to

gross area. We simply un-did the conversion. The result is a much more accurate graph:

How to Read the Graph

Figure 18

The slopes of the lines in the graph represent their heat loss factors. The steeper the slope, the more

the collector loses heat as temperature increases. A line with a small slope represents a collector that

loses very little heat to its surroundings, and is very efficient at heating.

The highest efficiency of each collector is when Ti-Ta=0, when the fluid entering the collector is thesame temperature as the ambient environment (outside). This is also known as the optical efficiency.


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Index of Figures Solar Energy

FIGURE 1HTTP://WWW.ALSTOM.COM

FIGURE 2HTTP://WWW.SOLARPACES.ORG

FIGURE 3,5HTTP://WWW.SQM.COM/ES-ES/

FIGURE 4,7HTTP://WWW.RENEWABLES-MADE-IN-GERMANY.COM

FIGURE 6HTTP://WWW.ALSTOM.COM

FIGURE 8HTTP://WWW.SOLARPACES.ORGHTTP

FIGURE 9,10HTTP://WWW.SOLARPACES.ORGHTTP

FIGURE 11,12,13HANDBOOK OF ENERGY EFFICIENCY AND RENEWABLE ENERGY

FIGURE 14WWW.POWERFROMTHESUN.NET

FIGURE 15WWW.NREL.GOV

FIGURE 16,17,18HTTP://WWW.SOLARTHERMAL.COM

References

WWW.NREL.GOV/HTTP://WWW.SOLARPACES.ORGWWW.POWERFROMTHESUN.NETHTTP://WWW.SQM.COMHTTP://WWW.ALSTOM.COM/GLOBAL/POWER/RESOURCES/DOCUMENTS/BROCHURES/CONCENTRATED-SOLAR-POWER-SOLUTIONS.PDF

HTTP://WWW.RENEWABLESG.ORG/DOCS/WEB/APPENDIXE.PDFHTTP://WWW.MACSLAB.COM/OPTSOLAR.HTMLHTTP://ENERGYWORKSUS.COM/SOLAR_POWER_INCIDENT_ANGLE.HTMLHTTP://WWW.SOLAR-ESTIMATE.ORG/SHOWFAQ.PHP?ID=261HTTP://WWW.SOLARTHERMAL.COM


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Geothermal energy

Heat from the earth can be used as an energy source in many ways, from large and complex powerstations to small and relatively simple pumping systems. This heat energy, known as geothermal

energy, can be found almost anywhere, as far away as remote deep wells in Indonesia and as close as

the dirt in our backyards.

Many regions of the world are already tapping geothermal energy as an affordable and sustainable

solution to reducing dependence on fossil fuels, and the global warming and public health risks that

result from their use. For example, in thousands of homes and buildings across the United States,

geothermal heat pumps also use the steady temperatures just underground to heat and cool

buildings, cleanly and inexpensively.

How Geothermal Energy Is Captured

Geothermal energy can be captured through:

- Geothermal power plants, which use heat from deep inside the Earth to generate steam tomake electricity.

- Geothermal heat pumps, which tap into heat close to the Earth's surface to heat water orprovide heat for buildings.

Geothermal Power PlantsThe most common current way of capturing the energy from geothermal sources is to tap into

naturally occurring "hydrothermal convection" systems where cooler water seeps into Earth's crust,

is heated up, and then rises to the surface. When heated water is forced to the surface, it is a

relatively simple matter to capture that steam and use it to drive electric generators. Geothermal

power plants drill their own holes into the rock to more effectively capture the steam.

At a geothermal power plant, wells are drilled 1 or 2 miles deep into the Earth to pump steam or hot

water to the surface. You're most likely to find one of these power plants in an area that has a lot of

hot springs, geysers, or volcanic activity, because these are places where the Earth is particularly hot

just below the surface.


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FIGURE1

How a geothermal power plant works?

1. Hot water is pumped from deep underground through a well under high pressure.

2. When the water reaches the surface, the pressure is dropped, which causes the water to

turn into steam.

3. The steam spins a turbine, which is connected to a generator that produces electricity.

4. The steam cools off in a cooling tower and condenses back to water.

5. The cooled water is pumped back into the Earth to begin the process again.

Geothermal Heat Pumps

A much more conventional way to tap geothermal energy is by using geothermal heat pumps to

provide heat and cooling to buildings. Also called ground-source heat pumps, they take advantage of

the constant year-round temperature of about 50F that is just a few feet below the grounds

surface. Either air or antifreeze liquid is pumped through pipes that are buried underground, and re-

circulated into the building. In the summer, the liquid moves heat from the building into the ground.

In the winter, it does the opposite, providing pre-warmed air and water to the heating system of the

building.

In regions with temperature extremes, ground-source heat pumps are the most energy-efficient and

environmentally clean heating and cooling system available. Far more efficient than electric heating

and cooling, these systems can move as much as 3 to 5 times the energy they use in the process.


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FIGURE2

How a geothermal heat pump works?

1. Water or a refrigerant moves through a loop of pipes.

2. When the weather is cold, the water or refrigerant heats up as it travels through the part of

the loop that's buried underground.

3. Once it gets back above ground, the warmed water or refrigerant transfers heat into the

building.

4. The water or refrigerant cools down after its heat is transferred. It is pumped backunderground where it heats up once more, starting the process again.

5. On a hot day, the system can run in reverse. The water or refrigerant cools the building and

then is pumped underground where extra heat is transferred to the ground around the

pipes.

Geothermal energy costs

One of the most important uses of geothermal fluids is the production of electricity. The sizing and

design of a geothermal power plant is a very important aspect, because it depends on the cost of

kWh produced. The cost per kW installed decreases with increasing size of facility, but it should benoted that a larger central requires a higher number of wells therefore greater expenses, primarily

for the construction of steam lines, and maintenance of plant more difficult. The appropriate size of

the plant depends on well productivity and total estimated power resource. In plant construction is

usually used modules 40-50 MW when production per well is 4-5 MW.


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The production cost of geothermal energy is determined by

- Exploration costs:

- Drilling costs- Vapor transmission costs- Cost of the power plant- Cost per kwh

Real levelized costs for geothermal electricity generation are 4.5 to 7.5 cents of dollars per kilowatt-

hour, therefore geothermal energy is competitive with many fossil fuel facilities, but without the

pollution. Delivered costs depend on ownership arrangements, financing, transmission, the quality of

the resource, and the size of the project. Geothermal plants are built of modular parts, with most

projects including one or more 1050 MW turbines.

Geothermal plants are relatively capital-intensive, with low variable costs and no fuel costs. Usually

financing is structured so that the project pays back its capital costs in the first 15-20 years, delivering

power at 5 to 7 cents of dollar per kWh. Then costs fall by around 50 percent, to cover just

operations and maintenance for the remaining 1020 years that the facility operates.

Geothermal power, like all renewable resources, keeps economic benefits local. The most promising

geothermal project sites are in rural areas. Geothermal power provides local jobs, retains dollars

locally, pays local property taxes, and contributes royalties to the local county to support services.

Electricity at Stable Prices

Using geothermal resources for power can help protect against volatile electricity prices. For any

power plant, the price of the fuel used to generate power influences the price of the electricity

produced; if the price of fuel is unpredictable, the price of electricity is unpredictable. Unlike

traditional power plants that require fuel purchases, geothermal power plants secure their fuel

supply before the plants begin operating.

Since the price of geothermal resources will not change, it is possible to know what the price of

electricity generated at a geothermal power plant will be over time.

Fossil fuels have traditionally generated power for less, but the price of these fuels can suddenly

increase to a level that is more expensive than geothermal electricity. For example, in early 2004 the

price of natural gas was nearly three times what it was throughout the 1990s.

Power generated from geothermal sources increased from increased by an average of about 3.5%

per year between 1990 and 2000 (see figure below). In the decond half of the same decade, the

energy produce from direct use of geothermal sources increased by over 13% per year.

Historical Growth


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FIGURE3: WORLDWIDE GEOTHERMAL POWER GENERATION AND DIRECT USE

Geothermal energy has the potential to play a significant role toward a cleaner, more sustainable

energy system. It is one of the few renewable energy technologies that can supply continuous, base

load power (like fossil fuels). The costs for electricity from geothermal facilities are also declining.

Some geothermal facilities have realized at least 50 percent reductions in the price of electricity since1980.

The Future of Geothermal Energy

A considerable portion of potential geothermal resources will be able produce electricity for as little

as 8 cents per kilowatt-hour (including a production tax credit), a cost level competitive with new

conventional fossil fuel-fired power plants. There is also a bright future for the direct use of

geothermal resources as a heating source for homes and businesses in any location. However, in

order to tap into the full potential of geothermal energy, two emerging technologies require further

development: Enhanced Geothermal Systems (EGS) and co-production of geothermal electricity in oil

and gas wells.

One of the most important economic aspects of geothermal energy is that it is generated with

indigenous resources, reducing a nation's dependence on imported energy, thereby reducing trade

deficits. Reducing trade deficits keeps wealth at home and promotes healthier economies. Nearly

half of all developing countries have rich geothermal resources, which could prove to be an

important source of power and revenue. Geothermal projects can reduce the economic pressure of

fuel imports and can offer local infrastructure development and employment. Please note that the

figures shown ignore completely any contribution made by geothermal heat pumps.


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Figure 4

Enhanced Geothermal SystemsGeothermal heat occurs everywhere under the surface of the earth, but the conditions that make

water circulate to the surface are found only in less than 10 percent of Earth's land area. An

approach to capturing the heat in dry areas is known as enhanced geothermal systems or "hot dry

rock". The hot rock reservoirs, typically at greater depths below the earths surface than

conventional sources, are first broken up by pumping high-pressure water through them. The plants

then pump more water through the broken hot rocks, where it heats up, returns to the surface as

steam, and powers turbines to generate electricity. Finally, the water is returned to the reservoir

through injection wells to complete the circulation loop. Plants that use a closed-loop binary cycle

release no fluids or heat-trapping emissions other than water vapor, which may be used for cooling.

(EGS)


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One cause for careful consideration with EGS is the possibility of induced seismic activity that might

occur from hot dry rock drilling and development. This risk is similar to that associated with

hydraulic fracturing, an increasingly used method of oil and gas drilling, and with carbon dioxide

capture and storage in deep saline aquifers. Though a potentially serious concern, the risk of an

induced EGS-related seismic event that can be felt by the surrounding population or that might cause

significant damage currently appears very low when projects are located an appropriate distance

away from major fault lines and properly monitored. Appropriate site selection, assessment and

monitoring of rock fracturing and seismic activity during and after construction, and open and

transparent communication with local communities are also critical.

FIGURE5

Oil and gas fields already under production represent another large potential source of geothermal

energy. In many existing oil and gas reservoirs, a significant amount of high-temperature water or

suitable high-pressure conditions are present, which could allow for the production of electricity and

oil or gas at the same time. In some cases, exploiting these resources could even enhance the

extraction of the oil and gas itself.

Co-production of Geothermal Electricity in Oil and Gas Wells


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Index of Figures Geothermal Energy

FIGURE 1,2

HTTP://EPA.GOV/CLIMATESTUDENTS/SOLUTIONS/TECHNOLOGIES/GEOTHERMAL.HTML

FIGURE 3,4INTERNATIONAL GEOTHERMALASSOCIATION

FIGURE 5

WWW.EERE.ENERGY.GOV


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Wind Energy

The wind resourceThe wind resource, how fast it blows, how often, and when a significant role plays in its power

generation cost. The power output from a wind turbine rises as a cube of wind speed. In otherwords, if wind speed doubles, the power output increases eight times. Therefore, higher-speed

winds are more easily and inexpensively captured.

Winds speeds are divided into seven classes with class one being the lowest, and class seven being

the highest. A wind resource assessment evaluates the average wind speeds above a section of land

(e.g. 50 meters high), and assigns that area a wind class. Wind turbines operate over a limited range

of wind speeds. If the wind is too slow, they won't be able to turn, and if too fast, they shut down to

avoid being damaged. Wind speeds in classes three (6.7 7.4 meters per second (m/s)) and above

are typically needed to economically generate power. Ideally, a wind turbine should be matched to

the speed and frequency of the resource to maximize power production.

Classes of Wind Power Density at Heights of 10m and 50m

10 m (33 ft) 50 m (164 ft)

Wind ClassWind Power

Density (W/m^2)Speed m/s (mph)

Wind Power

Density (W/m^2)

Speed

m/s

(mph)

1

0 0 0 0

1004.4

(9.8) 200 5.6 (12.5)

2 1505.1

(11.5)300

6.4

(14.3)

3 2005.6

(12.5)400

7.0

(15.7)

4250 6.0

(13.4)500

7.5

(16.8)

5 3006.4

(14.3)600

8.0

(17.9)

6 4007.0

(15.7)800

8.8

(19.7)

7 1,0009.4

(21.0)2,000

11.9

(26.6)

Since the late 1990s, the DOE National Renewable Energy Laboratory (NREL) has been working withstate governments to produce and validate high-resolution wind resource potential assessments on a

Source: Energy Information Administration


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state-by-state basis. This data is being used to gradually replace a less precise national wind

resource assessment completed in 1991 by researchers at DOE's Pacific Northwest Laboratory. Wind

speeds of classes three and four are more common and more evenly distributed across the country.

Several factors can affect wind speed, and the ability of a turbine to generate more power. For

example, wind speed increases as the height from the ground increases. If wind speed at 10 meters

off the ground is six m/s, it will be about 7.5 m/s at a height of 50 meters. In order to take advantage

of this potential at higher elevations, the rotors of the newest wind turbines can now reach heights

up to 130 meters. In addition to height, the power in the wind varies with temperature and altitude,

both of which affect the air density.

The more the wind blows, the more power will be produced by wind turbines. But, of course, the

wind does not blow consistently all the time. The term used to describe this is "capacity factor,"

which is simply the amount of power a turbine actually produces over a period of time divided by theamount of power it could have produced if it had run at its full rated capacity over that time period.

A more precise measurement of output is the "specific yield." This measures the annual energy

output per square meter of area swept by the turbine blades as they rotate. Overall, wind turbines

capture between 20 and 40 percent of the energy in the wind. So at a site with average wind speeds

of seven m/s, a typical turbine will produce about 1,100 kilowatt-hours (kWh) per square meter of

area per year. If the turbine has blades that are 40 meters long, for a total swept area of 5,029

square meters, the power output will be about 5.5 million kWh for the year. An increase in blade

length, which in turn increases the swept area, can have a significant effect on the amount of power

output from a wind turbine.

Another factor in the cost of wind power is the distance of the turbines from transmission lines.

Some large windy areas, particularly in rural parts of the High Plains and Rocky Mountains, have

enormous potential for energy production, although they have been out of reach for development

because of their distance from load centers.

A final consideration for a wind resource is the seasonal and daily variation in wind speed. If the wind

blows during periods of peak power demand, power from a wind farm will be valued more highly

than if it blows in off-peak periods.

Dealing with the variability of wind on a large scale is by no means insurmountable for electric

utilities. Grid operators must already adjust to constant changes in electricity demand, turning power

plants on and off, and varying their output second-by-second as power use rises and falls. Operators

always need to keep power plants in reserve to meet unexpected surges or drops in demand, as well

as power plant and transmission line outages. As a result, operators do not need to respond to

changes in wind output at each wind facility. In addition, the wind is always blowing somewhere, so

distributing wind turbines across a broad geographic area helps smooth out the variability of the

resource.

Addressing the Variability of Wind Power


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Increasing our use of wind power can actually contribute to a more reliable electric system.

Todays modern wind turbines have sophisticated electronic controls that allow continual adjustment

of their output, and can help grid operators stabilize the grid in response to unexpected operating

conditions, like a power line or power plant outage. This gives grid operators greater flexibility to

respond to such events. Promising developments in storage technology could also improve reliability

in the future, though there is plenty of room to greatly expand wind use without storage for at least

the next couple of decades.

Modern electric wind turbines come in a few different styles and many different sizes, depending on

their use. The most common style, large or small, is the "horizontal axis design" (with the axis of the

blades horizontal to the ground). On this turbine, two or three blades spin upwind of the tower that

it sits on.

The Mechanics of Wind Turbines

Small wind turbines are generally used for providing power off the

grid, ranging from very small, 250-watt turbines designed for charging

up batteries on a sailboat, to 50-kilowatt turbines that power dairy

farms and remote villages. Like old farm windmills, these small wind

turbines often have tail fans that keep them oriented into the wind.

Most small wind turbines manufactured today are horizontal-axis,

upwind machines that have two or three blades. These blades are

usually made of a composite material, such as fiberglass.

Large wind turbines, most often used by utilities to

provide power to a grid, range from 250 kilowatts up to

the enormous 3.5 to 5 MW machines that are being

used offshore. In 2008, the average land-based wind

turbines had a capacity of 1.67 MW.x Utility-scale

turbines are usually placed in groups or rows to take

advantage of prime windy spots. Wind "farms" like

these can consist of a few or hundreds of turbines,

providing enough power for tens of thousands of

homes.

From the outside, horizontal axis wind turbines consist of three big parts: the tower, the blades, and

a box behind the blades, called the nacelle. Inside the nacelle is where most of the action takes place,

where motion is turned into electricity. Large turbines don't have tail fans; instead they have

hydraulic controls that orient the blades into the wind.

In the most typical design, the blades are attached to an axle that runs into a gearbox. The gearbox,

or transmission, steps up the speed of the rotation, from about 50 rpm up to 1,800 rpm. The faster

spinning shaft spins inside the generator, producing AC electricity. Electricity must be produced at

just the right frequency and voltage to be compatible with a utility grid. Since the wind speed varies,
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the speed of the generator could vary, producing fluctuations in the electricity. One solution to

this problem is to have constant speed turbines, where the blades adjust, by turning slightly to the

side, to slow down when wind speeds gust. Another solution is to use variable-speed turbines, where

the blades and generator change speeds with the wind, and sophisticated power controls fix the

fluctuations of the electrical output. A third approach is to use low-speed generators.

An advantage that variable-speed turbines have over constant-speed turbines is that they can

operate in a wider range of wind speeds. All turbines have upper and lower limits to the wind speed

they can handle: if the wind is too slow, there's not enough power to turn the blades; if it's too fast,

there's the danger of damage to the equipment. The "cut in" and "cut out" speeds of turbines can

affect the amount of time the turbines operate and thus their power output.

The Visible Bits

The pole supporting the moving parts of the wind

turbine is called the tower (surprise, surprise).Directly on top of the tower is the nacelle, which is the

housing for all the parts of the wind turbine that arent

the giant blades.

Outside the nacelle is the most recognizable part of a

wind turbine, the three blades attached to the hub in

the middle. In slightly more technical terms, this

assembly is called a rotor. Pitch motors in the hub

allow the angle of the blades to be changed so that

they can meet the wind.

Also outside the nacelle are the anemometers (wind

vanes), which tell the turbine control system how fast

the wind is and in what direction its blowing (no use in

being able to adjust the blades if something isnt telling

them how to be adjusted).

Figure 3: Different parts in a Wind Turbine


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The Inside Parts

Inside the tower are ladders for (relatively) easy

access, and cables to export the electricity. Since

the height of a wind turbine can range anywherefrom 315 to 540, thats not a ladder Id want to

climb (although better the ladder than

attempting to scale the outside of the tower).

Figure 4: Mechanism in a wind turbine [Source:

NREL]

Inside the nacelle, the main shaft of the hub

connects to a gearbox and a brake. Since rotor

speeds are usually around 10-20rpm, which is

utterly useless for generating any kind of power,

the gearbox is responsible for converting that

speed to something like 1,500rpmmuch, much

better for generating electricity.

The final component inside the nacelle is the generator, which is connected to the gearbox and the

brake. It takes the 1,500rpm rotational energy and converts it into electrical power. The power is

then sent out of the turbine through the cables running down the length of the tower.

A wind turbine can start producing power at wind speeds of 7-11 mph, but it reaches its full output at

wind speeds of around 29mph. If its been appropriately placed, the turbine will generate over 40%

of its maximum capacity over the course of each year its operational.

Global Market for Wind Energy and Wind Turbine

The Global Market for Wind Energy & Wind Turbine is booming. Wind turbine expected to attainmarket size of USD 93.1 billion in 2016 while wind energy cumulative capacity will rise to 1,750,000

MW by 2030.

According to a new report published by Transparency Market Research, "Global Wind Energy &

Wind Turbine Market (2011-2016)" The global market for wind turbine registered growth rate of

25% CAGR over the last five years. The Global Wind Energy cumulative capacity accounted for

197,039 MW in 2010.Wind turbine expected to attain market size of USD 93.1 billion in 2016 while

wind energy cumulative capacity will rise to 1,750,000 MW by 2030.

The wind energy technology started paving its path approximately 20 years back and since then hascontinuously expanded its base all across the world. With the generation cost declining dramatically,

this technology is becoming more affordable and hence is increasing its entry even in previously

unexplored markets.

With the increase in understanding about a sustainable alternate source of energy worldwide, wind
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power is gaining stimulus importance across the globe. The global wind energy market is

estimated to have a growth rate of 25% CAGR over the last 5 years. Till 2010, Europe was considered

to be the largest market for wind energy followed by the Asia-Pacific and North American markets.

However, owing to the increase in investments, its long coastline and large land mass, China is

expected to attain the worldwide top rank in this market.

Due to steady evolution in the segment, the development of modern wind technology can now be

operated effectively at a wider range of sites suitable to high as well as low wind speeds. Further, the

development of light weight material has helped in phasing out bulky turbines and in introduction of

more sleek and effective turbine designs.

As per estimates, the wind turbine market has experienced an approximate growth rate of 28%

globally and is expected to grow at an increasing double-digit growth rate. Wind power, being the

fastest growing alternate source of energy is witnessing an increase in investment globally.

The Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT) together form the

two major segments for wind turbine market globally. However, the HAWT generate the major chunk

of revenue to the turbine market capturing approximately 90% share. The Wind turbine market is

characterized as highly competitive market and includes GE Energy, Gamesa, Vestas, Suzlon,

Siemens, Mitsubishi etc. as few major players.

In the present scenario, the onshore technology is leading with approximately 95% share and

offshore technology owing to its nascent stage is making its move with 5% market share. The cost

propositions with offshore technology rise because of their high O&M costs. Hence, the offshore

wind turbine market occupies only 5% share in the global wind turbine market. Particularly in

onshore wind energy market, U.S. was the largest onshore wind energy market in 2010 followed

by Germany and China. However, China is expected to rank ahead of U.S thereby becoming a market

leader by 2016.
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Main Geographic Markets

-U.S. and Canada

North America Wind Energy and Wind Turbine Market:

-France, Germany, Italy, Poland, Portugal, Romania, Spain, Sweden, Turkey and United

Kingdom

European Wind Energy and Wind Turbine Market:

-Egypt and Iran

Africa & Middle East:

-India, China, Japan and South Korea

Asia:

-Australia and New Zealand

Pacific:

-Brazil, Chile and Mexico

South America:

Average Price per KW/h currently

Method Cents/kW-h Limitations and Externalities

Wind

Currently supplies approximately

1.4% of the global electricity

demand. Wind is considered to

be about 30% reliable.

4.0 - 6.0

Cents/kW-h

Wind is currently the only cost-effective

alternative energy method, but has a number ofproblems. Wind farms are highly subject to

lightning strikes, have high mechanical fatigue

failure, are limited in size by hub stress, do not

function well, if at all, under conditions of heavy

rain, icing conditions or very cold climates, and

are noisy and cannot be insulated for sound

reduction due to their size and subsequent loss of

wind velocity and power.


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How much do wind turbines cost?

Total costs for installing a commercial-scale wind turbine will vary significantly depending on the

number of turbines ordered, cost of financing, when the turbine purchase agreement was executed,

construction contracts, the location of the project, and other factors. Cost components for wind

projects include things other than the turbines, such as wind resource assessment and site analysis

expenses; construction expenses; permitting and interconnection studies; utility system upgrades,

transformers, protection and metering equipment; insurance; operations, warranty, maintenance,

and repair; legal and consultation fees. Other factors that will impact your project economics include

taxes and incentives.

Wind turbines come in many shapes and sizes, but here is a general guideline on how much they

cost:

Most of the commercial-scale turbines installed today are 2 MW in size and cost roughly $3-$4

million installed. Wind turbines have significant economies of scale. Smaller farm or residential scale

turbines cost less overall, but are more expensive per kilowatt of energy producing capacity. Wind

turbines under 100 kilowatts cost roughly $3,000 to $8,000 per kilowatt of capacity. A 10 kilowatt

machine (the size needed to power a large home) might have an installed cost of $50,000-$80,000

(or more) depending on the tower type, height, and the cost of installation. Oftentimes there are tax

and other incentives that can dramatically reduce the cost of a wind project.

The costs for a utility scale wind turbine in 2012 range from about $1.3 million to $2.2 million per

MW of nameplate capacity installed. This cost has come down dramatically from what it was just a

few years ago.

Wind Turbine Power Calculations

Scenario

The energy available for conversion mainly depends on the wind speed and the swept area of the

turbine. When planning a wind farm it is important to know the expected power and energy output

of each wind turbine to be able to calculate its economic viability.

Problem statement

With the knowledge that it is of critical economic importance to know the power and therefore

energy produced by different types of wind turbine in different conditions, in this exemplar we will

calculate the rotational kinetic power produced in a wind turbine at its rated wind speed. This is the

minimum wind speed at which a wind turbine produces its rated power.

Mathematical Model

The following table shows the definition of various variables used in this model:

E = Kinetic Energy (J) ; = Density (kg/m3) ; m = Mass (kg)

A = Swept Area (m2) ; v = Wind Speed (m/s) ; Cp = Power Coefficient

P = Power (W) ; r = Radius (m) ;

= Mass low Rate (kg/s) ; x = distance (m)


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Documents

RES - Task2 - Erasmus 2012 2013.pdf