four7. 01 Twenty 2007twentyfour7.studio.crasman.fi/pub/web/pdf/magazine+pdfs/ID0107-W… · Test bench for common rail technology . . . . Wireless temperature monitoring . . .

WÄRTSILÄ TECHNICAL JOURNAL

The Electricity gameFlexibility is a common denominator of all Wärtsilä power plants

Azerbaijan re-energizedFive new power plants make Azerbaijan energy self-suffi cient

[ WWW.WARTSILA.COM ]

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Common rail enginesWärtsilä medium-speed CR engines have now exceeded 540,000 running hours

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Designs for lifeSCHIFFKO takes ship design into a new era

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Dear ReaderIT IS A GREAT PRIVILEGE and pleasure for me to introduce In Detail magazine, the latest addition to our family of customer publications.

It is, has always been, and will always remain our intention to meet the needs and wishes of our customers around the world. In Detail is one more example of this drive to be a ‘doer’ by serving those who have expressed the desire to get a deeper understanding of the technologies that support Wärtsilä’s leadership role. We are in every sense an ‘Engine of Industry’, and the contents of this magazine will hopefully help explain the enormous depth and scope of our commitment to technical excellence.

IN TERMS OF QUALITY, information, and as an illustration of the values of Wärtsilä Corporation – namely energy, excellence, and excitement, In Detail magazine is a natural complement to its sister publication, Twentyfour7. While Twentyfour7 is monitoring industry and corporate developments from a business perspective, In Detail will focus on the technical and theoretical aspects that impact the industries we serve. Material from both publications can be found and downloaded from our internet pages at www.wartsila.com.

THIS FIRST ISSUE contains a wealth of information. In the energy section, amongst the things we look at are the new concept of boxing the production of energy in a cube, and an overview of the electricity game. We also survey some examples where viable solutions have been created from Wärtsilä innovations. The marine section looks at how environmental, as well as technical considerations are contributing to our commercial solutions.

OUR ABILITY TO SERVE everyone everywhere has always been an essential element of our lifecycle offering. So it remains today. In Detail magazine is one more step along the path to serving our customers.

Thank you for choosing Wärtsilä.

Mikael Simelius

Editor-in-Chief.

Contents

issue no. 01.2007 p

The Electricity game . . . . . . . . . . . . . . . . . . . . . .

Power from renewables . . . . . . . . . . . . . . . . . . .

Wärtsilä BioPower for Belgium . . . . . . . . . . . .

Fundamentals of power plants . . . . . . . . . . . .

Azerbaijan re-energized . . . . . . . . . . . . . . . . . . .

Power in a cube . . . . . . . . . . . . . . . . . . . . . . . . . . .

Designs for life . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cruising on gas . . . . . . . . . . . . . . . . . . . . . . . . . . .

Combating particulate emissions . . . . . . . . .

Controlling emissions . . . . . . . . . . . . . . . . . . . .

The Airguard seal system . . . . . . . . . . . . . . . . .

Automation capturing the market . . . . . . . . .

Viking Gas Avant . . . . . . . . . . . . . . . . . . . . . . . . .

The common rail engine today . . . . . . . . . . . .

Test bench for common rail technology . . . .

Wireless temperature monitoring . . . . . . . . .

In-place crankshaft repair . . . . . . . . . . . . . . . . .

ENERGY

MARINE

Publisher: Wärtsilä Corporation, John Stenbergin ranta 2, P.O. Box 196, FIN-00531 Helsinki, Finland | Editor-in-Chief: Mikael Simelius | Managing Editor and Editorial Offi ce: Maria Nystrand | English editing: Tom Crockford, Crockford Communications | Editorial team: Marit Holmlund-Sund, Arnauld Filancia, Virva Äimälä, Maria Nystrand | Layout and production: Kynämies Oy, Helsinki, Finland | Printed by: PunaMusta, Joensuu, Finland | ISSN 1797-0032 | Copyright © 2007 Wärtsilä Corporation | Paper: cover Lumiart Silk 250 g/m² inside pages Berga Classic 115 g/m² | Cover Photo: LNG cruise ship concept

Wärtsilä’s PowerCube provides users with a complete pre-engineered power plant.

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E-mail and feedback: [email protected]

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MORE ON PAGE 13 MORE ON PAGE 43 MORE ON PAGE 44

CRUISING ON GASThe Wärtsilä/Aker Yards LNG -cruise ship

concept offers cleaner cruising. PAGE 26

Second biopower plant for Belgium

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Belgian power company Renogen has ordered a second biomass-fuelled combined heat & power plant. Scheduled for delivery mid-2008, the new plant will be based on Wärtsilä’s modular concept.

LLC propulsion for Eidesvik Offshore

Eidesvik Offshore’s LNG vessel, the Viking Gas Avant, will be the fi rst of its kind to utilize Wärtsilä’s low-loss propulsion concept, offering greater effi ciency and less pollution.

Smokeless with common rail engines

The cruise ship Coral Princess can meet smoke-free operation requirements thanks to Wärtsilä common rail engines that have now already accumulated more than 30,000 running hours each.

WÄRTSILÄ TECHNICAL JOURNAL | WWW.WARTSILA.COM

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Regardless of where in the world the electrical grid is located, some things are as common as the laws of nature. As the system stability and reliability demands of modern society are to be met, each electrical system must manage the following issues and challenges.

n Since no one has developed a way to effi ciently store large amounts of electrical energy, the actual production of electricity must match the consumption in real time, second-by-second. Otherwise, the grid will not be able to maintain stability (Figure 2).

n To be able to match the varying demand with the correct supply at

all times, the system operator needs, amongst other things, to collect historical data, plan ahead, arrange plant dispatch orders, and arrange for adequate capacity reserves in case of unforeseen occurrences (Figure 3).

n Since power demand is not controlled by the supply system, the demand not only varies according to the time of day, seasonal changes, or social and economic variables, but there is also a fast, minute-by-minute fl icker on the load curve, caused by numerous electricity loads (elevators, fans, pumps, refrigerators etc.) turning on and off. The generation units must, therefore, be capable of following these very rapid load changes in the grid (Figure 4).

n The electricity systems in different countries have quite similar reliability requirements, which stipulate that a certain reserve capacity must be running at all times. This is to cover the sudden shut down of even the largest single plausible loss (largest contingency) in the grid, and also to maintain a certain level of reserves in

standby mode to start rapidly. These contingency reserves are divided according to the timeframe of response.

n The system must have adequate capacity, plus reserves, to cover the highest annual peak load. In the cold zones of the world, these typically occur during the winter, and in the warmer zones with air conditioning, during the summer. Capacity reserve rules do not exist in all countries and systems, but are needed, nevertheless, in some form or another. There must be someone with the responsibility to maintain adequate reserve capacity, otherwise system reliability will be hampered.

Since electricity production costs need to be optimized, the production units are normally started and shut down in a certain sequence. Those with the lowest production cost (fuel and other variable production costs) balanced with the necessary fl exibility, go on line fi rst and stay there the longest as the load decreases. There are great differences in the time needed to start up a power plant. Nuclear and steam power plants take a long time, and each start and shut down costs a substantial amount of money. These are typically referred to as baseload generation units. Irrespective of any specifi c power system distinctions, the following fl exible features are valuable in any reliable and optimized electricity production system:

n The size of the plant should match the need as accurately as possible. Operating a larger plant at part load reduces effi ciency. Being able to enlarge the plant at a later date by additional units is always a good fl exible option.

n Fuel fl exibility. The ability to change fuels according to fuel prices, availability or emissions.

n Dispatch fl exibility. Fast starting, loading, and stopping for standby capacity (non-spinning reserves). The capability to rapidly change the load up or down (load following, regulation or spinning reserves).

n Effi ciency. Being able to generate at full, part or low loads while maintaining high effi ciency.

n Low emissions and minimal environmental impact (noise, outlook, possibility to place the

[ ENERGY / IN DETAIL ]

Over the years, Wärtsilä has delivered more than 36 GW of dependable power plants to customers around the world. These power plants serve many different purposes and loads. With each power plant supplied by Wärtsilä, however, there is one special feature that brings value to all our customers – fl exibility.

Fig. 1 – Wärtsilä has recently gained a fi rm position in the US ancillary services gas power plants market.

AUTHORS: Jussi Heikkinen , Vice President Business Development and Mikael Backman , Business Development Manager, Wärtsi lä in North America

The electricity game

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plants in urban areas, etc). n Technological benefi ts and

fl exibility (using different cooling systems, e.g. systems with no water usage in dry areas).

n Ambient fl exibility. Being able to generate effi ciently and reliably in warm and hot climates, or at high altitudes.

WÄRTSILÄ OFFERS FLEXIBLE CARDS TO PLAY THE ELECTRICITY GAME

Plant size and scope fl exibilityMost Wärtsilä power plants consist of several parallel units. The units can be installed simultaneously or more units can be added later. The units can be operated independently, and starting, loading, or stopping an engine does not affect the other units. There are also different standard sizes of units, so the plant can consist of different sized units.

Wärtsilä delivers power plants as equipment deliveries, or as turnkey (EPC) packages. EPC packages include the entire power plant, including buildings, installation work and project engineering. About 40% of all deliveries are turnkey projects, and Wärtsilä’s global strength, together with its local expertise, ensures its ability to act as a reliable contractor. Wärtsilä is also fl exible regarding the scope of the project. Alternatively, the customer may prefer just to purchase the generation equipment. Either way, we have the expertise and knowledge to support these efforts.

Fuel FlexibilityWärtsilä engines can operate with a wide variety of fuels, such as natural gas, diesel oil, heavy fuel oil, vegetable oils (renewable), or even more challenging fuels such as Orimulsion®. While maintaining a fuel-diverse product portfolio, we have developed these engines using the same proven technology and basic design. In addition to the upfront choice of fuel usage for generation, specifi c engines can also be converted at a later stage should the market circumstances change. Wärtsilä also offers dual-fuel engines that can switch on the fl y between fuels, for example, between natural gas and a liquid fuel. These types of engines have been especially popular in areas where there is a need for a back-up fuel in case of shortage, or where there is a need to

convert from HFO to gas at a later date. Unlike most gas turbines, Wärtsilä

gas engines do not require a high gas pressure to operate. A pressure of 4 Bar is adequate to operate the power plant at full output. This limits the use of gas compressors to extreme cases where a 4 Bar gas pressure is not available.

Dispatch Flexibility and Effi ciencyWärtsilä solutions using multiple generation units offer the fl exibility

of operating a plant effi ciently at any load, from the minimum load of a single unit, up to full load of all units. Wärtsilä power plants can be run in “effi ciency mode” (starting or stopping units as the load changes) or “reliability mode” (sharing the load between the units). This is a major benefi t when compared to other technologies that tend to be installed in confi gurations with fewer units, thereby suffering from reduced effi ciency at part load. p

Fig. 2 – A typical daily load curve during summer.

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Wärtsilä plants can also be quickly started-up to supply power to the grid within a few minutes, and can reach full load in less than 10 minutes. This benefi t is very valuable in power markets, whereby the plants can supply non-spinning reserve to the system operator through the ability to be on line quickly should the need arise. This can also be used to capture additional revenue in certain markets. If a power plant can generate profi ts for the owner, for example during the daytime with a changing hourly power tariff, it is benefi cial to get the plant on line as soon as the tariff price goes above the profi tability limit, and off again the moment the tariff price goes down. In some markets, for example the USA, such plants can sell this fast start-up capability on day-ahead or hour-ahead markets, thus producing additional streams of revenue. In such markets, Wärtsilä plants exemplify a “dispatcher’s dream plant” where he can choose to run during profi table hours, and avoid running at other times. It is very probable that such product features will be rewarded in the future in other markets as well.

Wärtsilä power plants can also be equipped with black start capabilities, for use to energize parts of the local grid in case of a black-out. The rugged design and advanced control systems make them ideal for power generation in areas with smaller, less stable transmission systems, where fl uctuations in voltage or frequency can occur. They can even run on “island mode” for an isolated system.

The rugged design of the engines also enables them to frequently be started quickly without any adverse affect to the maintenance schedule, or to other operational costs. This is a basic feature of a reciprocating engine, one that is nicely demonstrated with car engines. They can be started in freezing conditions and brought immediately to full load, yet have the same manufacturers’ recommended service intervals as cars used in hotter climates. There is a large amount of actual data documenting evidence of this advantage from Wärtsilä power plants in operation, showing clearly that the engine effi ciency does not change regardless of the number of starts or the load profi le.

The fact that Wärtsilä engines have minimal limitations as to the required ‘up’ or ‘down’ time, makes them even more of a fl exible system asset. Industrial

gas turbines, on the other hand, have been designed to operate at steady loads, and because of mechanical and thermal stresses, suffer from frequent starting and stopping. Their effi ciency will deteriorate, and their maintenance costs will go up.

Effi ciencyWith fl exibility being a basic requirement for these types of plants, Wärtsilä engines have the highest effi ciency of any technology that can be used on a


larger scale to provide energy resources, with fast load following and fl exible system stability. Depending on the commercial distinction of the owner, this either results in savings on fuel costs, or in higher revenues from power production. It also complements today’s environment, where we not only need to conserve the power we use, but must also generate this power with less losses.

On part load, the effi ciency curve of Wärtsilä engines remains high, in

Fig. 6 – Start-up and loading of a gas engine power plant compared to a gas turbine combined cycle plant.

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Fig. 5 – In the developing world, Wärtsilä’s fl exible power plants produce baseload electricity and simultaneously take care of grid stability and reliability.

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power generation has been limited, and will become even more so in the future.

Another advantage of Wärtsilä technology is the minimal impact of ambient conditions on plant performance and functionality. Wärtsilä engines can perform at high ambient temperatures without any detrimental impact to output or effi ciency (Figure 8). This means, for example, that the power and effi ciency is really there when you need it on a hot summer’s day. Wärtsilä plants also provide an excellent solution for high altitude applications, since the plant output remains the same up to an elevation of 2000 m (6000 ft) above sea level.

Operational aspectsModern engines are easy to maintain and can be operated without the requirement of special skills other than the training given with delivery. On ships, such engines are often maintained by the crew, including major overhauls. In multi-engine power plants, it is possible to service one engine at a time, thereby keeping most of the plant output continuously available for power generation, thus maximising plant availability.

Wärtsilä operates power plants on a long-term contract basis. Many customers opt for a long-term maintenance contract, which brings Wärtsilä specialists to the plant for major overhauls. An important part of both alternatives is remote access to the power plant’s controlling and monitoring system, enabling Wärtsilä specialists to remotely analyse plant performance. By using plant automation data, logging data and actual operational data, maintenance needs can be assessed.

Effi cient fl exibilityOperators of electrical systems, grids and power plants, have a number of demanding requirements and preferences for their power generation assets. Wärtsilä has focused its efforts on providing the most fl exible and effective power solutions on the market, to meet the complex needs and ever changing environment of modern power systems. Whether it’s a small, rural system, an industrial manufacturing plant, or a large, commercially developed nationwide grid system, Wärtsilä products are there, on duty, providing the owners with un-matched fl exibility and other benefi ts for a successful future.

fact almost fl at down to below 50% load. This is a very benefi cial feature in any load following and ancillary service application where part load operation is necessary (Figure 7).

Ambient circumstances and technological benefi tsThe turbo charged and intercooled reciprocating engine has many technological advantages over other technologies used for power generation.

One such benefi t is that Wärtsilä plants consume virtually no water if equipped with a closed loop cooling system. By using air cooled radiators for engine cooling in a closed loop system, water usage can be limited to whatever is needed for minimal tank evaporation, social areas or cleaning. The availability of water is becoming a larger and increasingly important environmental issue, and in some areas water availability for heavy industry or

Fig. 7 – The multi-unit gas engine power plant has very high part-load effi ciency.

Fig. 8 – Wärtsilä gas engines offer stable output and high performance in hot and dry conditions.

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Reliable power from renewables with assistance from reciprocating engines

Rising fossil fuel prices, decreasing security of fuel supply as well as the desire to limit greenhouse gas emissions are reasons why the EU has decided to stimulate

an increase in the use of renewable energy sources in Europe. The European Commission has recently decided that Europe has to derive 20% of its energy needs from renewable sources by the year 2020. Part of this will be achieved in the transport sector, where 10% of the fuel demand will be covered by renewables such as ethanol or methanol. The bulk of the renewable energy will be used for electricity generation and high hopes are put in wind power and photovoltaics. However, electricity generation based on wind power and solar radiation lacks the easy controllability of power output from fuel-based power generation,

Fig. 1 – Examples of the typical dynamics in electricity demand in a Scottish region (left) and in Portugal (right).

resulting in diffi culties in matching electricity production with demand.

MATCHING DEMAND PATTERN AND PRODUCTIONThe use of electricity and human activities are closely connected. Electricity is a very versatile energy source used for example for artifi cial lighting, to power production lines and public transport systems. During the night, the demand for electricity falls to a minimum, but from 7 am on weekdays many activities start up again, resulting in a sharp rise in power demand, which can be up to 180% of the minimum demand. In hotter

The need to cut greenhouse emissions is driving the move to renewable energy sources. Wind and solar power are frequently mentioned as natural alternatives to fuel-based electricity generation, but both depend upon weather conditions. Reliable reserve power capability is, therefore, necessary to ensure electricity supply.

AUTHOR: Jacob Klimstra , Senior Energy and Engine Expert, Wärtsi lä Power Plants in The Netherlands

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countries, air conditioning causes a peak in demand at noon. In colder countries, demand peaks in wintertime can be 50% higher than in summer as electricity is used for domestic heating. Figure 1 illustrates the dynamics in electricity use in a Scottish region and in Portugal.

The demand fl uctuations caused by individual users switching equipment on and off have a stochastic nature and generally do not exceed 2% of the mean momentary demand.

Network operators need to be able to control the output of the generators in a supply system to cope with these short-term fl uctuations in demand. These generators can then be used for frequency regulation, load following and as spinning or non-spinning reserve. Network operators predict the demand pattern for the next day and contract suffi cient capacity to meet the sharp rise in power in the morning and the peak in the afternoon.

Steam-based power plants typically need a couple of hours for preheating before they can deliver electricity. Their ramping-up capacity is about 2 to 3% of their

nominal power per minute. Power stations can also fail to start up or trip at full load. That is why a contingency reserve is required, which can be spinning reserve (running and on line) as well as standby reserve (non-spinning, but ready to come on line). The non-spinning reserve power has to come on line as soon as the bulk of the spinning reserve has been used. It will be clear that a generator owner has to be compensated fi nancially for such so-called system services (or ‘ancillary services’ in the North-American literature). Reciprocating engines and aero-derivative gas turbines have a ramping-up rate faster than steam based power systems and are often used for this type of services.

Generators based on hydro energy from water reservoirs can also react quickly to demand fl uctuations. Countries such as Italy and Portugal have the landscape and climate to make extensive use of hydro power, even though the available energy varies from year to year and depends upon the time of year. Existing hydro systems make it relatively easy to apply pumped storage, so that excess electricity from other sources can be used to pump water

into the reservoirs for later use. The energy effi ciency of such pumped-storage systems lies between 75% and 80%. In the EU, pumped storage capacity equals about 4% of the total installed generating capacity.

Electricity production characteristics of renewablesElectricity production from wind energy and photo voltaics depends on the local weather conditions and is largely not controllable (non-dispatchable). If the wind increases in strength, there is a high risk that the wind turbines will suddenly have to cease operation while running at rated capacity, to avoid damage caused by overspeed. To cope with these situations, the network needs spinning capacity that can instantaneously take over the load from the wind turbines. Also, if the wind speed falls drastically over a wide area, much standby reserve has to be put on line. In both cases, the network operator has to pay for these services, which can reduce the intrinsic economic value of the electricity from renewables down to almost nothing. Therefore the real economic value of the electricity produced depends p

Fig. 2 – Typical output during a year for a windmill at an average site (red) and at an excellent site (blue).

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dispatchable electricity. Land-based wind installations are considerably cheaper than offshore installations (1200– 1500 €/kW),but their capacity factor is generally just slightly above 20%.

The country with the highest relative share of wind-energy-based electricity is Denmark. In 2004, 16.3 % of the total 40.5 TWh electricity was produced by wind power. However, the capacity factor for the total installed wind power was just 24%. Assuming that on average 5% of the windmills were not available for production because of maintenance and repairs, the available wind capacity was 0.95 x 3.1 GW = 2.9 GW. Total annual net electricity generation from all sources in Denmark is 38.4 TWh, which means a time-averaged production of 4.4 GW.Comparing this with the demand patterns in Figure 1, it is easy to see that wind power in Denmark will exceed the nightly minimum weekday demand if the 2.9 GW active wind capacity is on line with a favourable wind. With a policy of unlimited grid feed in by wind power, the only solution in this situation is to export. That explains why Denmark has relatively high electricity exports compared with four typical EU-25 countries.

The problem of having too much electricity production on line is worsened in wintertime in Denmark since the demand for heating is often met by combined heat and power units. This means that even more excess electricity is produced, especially during cold, windy nights. If there are high winds, much fuel-based or hydro-based spinning reserve and back-up power has to be available in case the critical wind speed is exceeded. This is quite costly and results in spoiled fuel consumption.

On the other hand, wind speed levels are low for a signifi cant part of the year, so power plants based on fuels have to take over. As a result, the utilisation factor for conventional thermal plants in Denmark is only 37%, while the general optimum for the sector lies between 50 and 55%. Denmark also actively uses electricity imports to cover peaks in demand (see Figure 3). Denmark itself has no pumped hydro storage, but uses Norway’s storage capacity to some extent.

Without wind power that can freely feed into the grid, nuclear and coal-based power plants normally cover the baseload power generation, so that capacity factors


Fig. 3 – An illustration of Denmark’s relatively high electricity imports and exports due to substantial utilization of wind power.

on the extent to which the network operator can use it to match demand.

Photovoltaic electricity peaks normally at noon, so it is of benefi t only in situations where air conditioning requires much energy, such as in Spain and Italy in the summer. Solar power will not reduce the total installed generating capacity needed to meet the winter peak from 4 pm to 9 pm since solar irradiation is very low at that time.

Biomass-based power plants differ in this respect, since their fuel can be stored close to the power plant, making the output more dispatchable. Liquid biofuels are ideal for diesel engines that can act as spinning and back-up reserve for electricity from wind and solar sources.

Electricity from windWind speed has a stochastic character. The average wind speed at offshore locations

is normally higher than that at land-based sites, giving a higher capacity factor. The capacity factor of a windmill is the total amount of electricity produced in a year divided by the electricity that would be produced if the generator was running 100% of the time at full load. Figure 2 illustrates typical production duration curves for windmills at an average site and at an excellent site. In addition a windmill will also have downtime for maintenance.

A new offshore wind park of 110 MW near the coast of the Netherlands (Shell/NUON) is expected to have a capacity factor of 30%. The specifi c capital investment in that park is 2100 €/kW. For a commercial fi xed interest rate of 10%, the specifi c capital costs will be 8 €cts/kWh. Insurance costs as well as operation and maintenance costs will easily result in production costs of more than 11 €cts/kWh. That is rather high for non-

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of up to 85% can be reached. However, with a high amount of wind power, such as in Denmark, nuclear power especially is not attractive since it would have to be shut down during nights with much wind. The nuclear process is not suitable for this sort of operation, and it would also substantially increase the specifi c capital costs of electricity.

In summary, the stochastic character of wind energy makes it necessary to install additional dispatchable and fl exible back-up power plants that will run with a low utilisation factor. Electricity in Denmark for domestic users cost 24 €cts/kWh in 2004, twice as high as the EU-25 average. To be able to produce 16.3% of all the electricity used by wind, the wind capacity had to be 23% of the total capacity, while the total installed generation capacity had a utilisation factor of only 34.6%.

Electricity from photo voltaicsThe energy radiated to the earth by the sun exceeds the energy required for human activities many times. The challenge is in capturing the radiation. Current photovoltaic (PV) systems have an effi ciency ranging from 10 to 15%. In the Netherlands, with an average solar radiation of 115 W/m2, the energy catching effi ciency of straw is only 2% and that of trees less than 0.3%.

The main problems with PV, however, are the high capital investment of about 5000 €/kW of rated power, and a capacity factor ranging from only 10% in Denmark to 23% in the Sahara. Under standard commercial fi nancial conditions, this would result in specifi c capital costs of 58 €cts/kWh in Denmark. Moreover, Figures 4 and 5 show that the electricity production of PV systems peaks at noon while it is relatively low in the wintertime. So the capacity is not available at the peak hours after 4 pm and not at times of peak demand in the wintertime. Since its production peaks at noon, proportionately even more peaking power capacity has to be made available.

Electricity from biomass-based generationDenmark had in 2004 a total of 474 MW of electricity production capacity based on wood waste and 312 MW based on municipal waste. Together these account for 5.9% of the total generation capacity in Denmark. The utilisation

factor of this capacity was 51%, and it covered 8% of the electricity need.

These steam-based systems have the advantage that the electricity produced is dispatchable and more controllable than that based on wind and solar radiation. However, even though the fuel costs are relatively low (and even negative in the case of waste), the specifi c investment is around 3000 €/kW, resulting in specifi c capital costs of 7 €cts/kWh, with specifi c maintenance costs of 2 €cts/kWh.

These steam-based power plants lack the rapid load response needed for offering

substantial spinning reserve and back-up reserve as network services. Nevertheless, they are an attractive way of utilising the energy available in solid biomass and waste. Small-scale wood-based generators in the power range 2-5 MW are often used in forest-rich countries such as Finland and Sweden. In most cases, the most economic way to use biomass is co-fi ring in coal-fuelled power stations.

Electricity from biogas and liquid biofuelsBiogas primarily originates from

Fig. 4 – Typical variations in solar irradiation in three European cities during the year.

Fig. 5 – Solar irradiation during a typical day in summer and winter in Madrid.

8000

7000

6000

5000

4000

3000

2000

1000

0

London

Madrid

Helsinki

Aver. /day:

3092 Wh/m2

5125 Wh/m2

3068 Wh/m2

900.00

800.00

700.00

600.00

500.00

400.00

300.00

200.00

100.00

0.0000:00 04:00 08:00 12:00 16:00 20:00 00:00

hour of day

Madrid, Spain

July

January

p

Wh

/m2

per

day

So

lar

irra

dia

tio

n (

W/m

2)

Jan

Feb

Mar

Ap

r

May

Jun

Jul

Au

g

Sep

Oct

Nov

Dec

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12 in detail


sewage treatment plants and landfi lls, but digesters using farm and forest residues are also increasingly used.

Liquid biofuels are based on rapeseed, jatropha and palm oil or animal fats. Such fuels can easily be used with a high effi ciency in reciprocating engines with a power capacity of up to 18 MW. The specifi c capital investment in such decentralised installations (€/kW) is about the same as for large-scale generators. The small-scale character of these installations means that electricity can be produced close to the users so that the heat released also can be used (cogeneration), resulting in total fuel effi ciency exceeding 85%. The starting time of such installations is less than 10 minutes so that their output can serve as back-up power in the electricity supply system.

A HYBRID SOLUTION TO EFFECTIVELY INTEGRATE RENEWABLESIn the opinion of the author, solar electricity may offer interesting options in the future to tap the energy infl ux from the sun. At present, however, the specifi c investment cost as well as the amount of energy needed to produce the photo voltaic elements are far too high. Germany, for example, subsidises PV electricity with 50 €cts/kWh, which is almost 10 times as much as the costs of baseload electricity from existing power stations. This indirect way of stimulating the photovoltaic industry is counterproductive since it is a burden on the economy. It would be much better to directly subsidise extensive research into more cost-effective PV equipment.

The basic character of wind power

means that the installed wind capacity cannot be considered as controllable, and suffi cient alternative capacity is needed to at least cover the peaks in demand. Simple load shedding during conditions when the windmills cannot produce is generally not acceptable. Since wind capacity reduces the utilisation factor of non-wind capacity, it is necessary to have a back-up capacity with a low specifi c investment. In addition, the non-wind generators need to have high ramping up and ramping down rates. That is required in times when wind power covers the baseload (a maximum of 20 to 30% of the time), since then the other generators have to take care of the rapid rise in demand associated with the intermediate load on weekday mornings. A rapid response is also required in case the wind power suddenly stops because of excessively high winds.

Fuels are certain to become scarcer during the planned life of at least 30 years for future generating equipment, so that high fuel effi ciency is very important. Power plants consisting of generators driven by reciprocating engines can have a simple-cycle electrical effi ciency of up to 45%, can ramp up to full power in 2 minutes (ramp rate 50% per minute) and start from standstill to full load within 10 minutes. Such units also have the advantage of a quite fl at effi ciency curve in the upper load range, which is attractive for offering spinning reserve. Moreover, the specifi c investments for gas-fuelled installations are only about 500 €/kW. Installations running on bioliquids can cost up to 700 €/kWh. An attractive option is the use of dual-fuel engines. Such engines can run on

renewable liquid fuels if these are available and switch over to liquid or gaseous fossil fuel when renewable fuels are not available.

The electrical effi ciency of such installations can be further improved to roughly 50% by adding a steam cycle or organic Rankine cycle. Until now, the additional investment of about 1200 €/ kWfor such a topping cycle has been considered uneconomic. However, compared with wind power it is quite attractive, since here again the ‘fuel’ is free except in the case of high-temperature cogeneration. The capacity is also more controllable than that of wind power.

As mentioned before, using substantial wind capacity will reduce the utilisation factor of other installed generating capacity. That, in turn, will result in higher specifi c capital costs for the non-wind capacity. In an honest comparison, these extra costs should be attributed to that of electricity from wind. For gas-engine-driven installations, the specifi c capital costs of electricity production will increase from 1 €cts/kWh to 1.5 €cts/kWh if the utilisation factor decreases from 55% to 35%. The difference would be at least three to six times higher for coal-fuelled and nuclear power plants (see Table 1).

Power stations based on reciprocating engines have multiple units that run in parallel. That guarantees high reliability and availability. By using engines with a unit power capacity ranging between 5 MW and 18 MW, the size of such power stations can easily match the output of wind-power parks. The power stations can be built at suitable locations, preferably close to heat users for cogeneration. Generating units at different locations can even be combined into virtual power plants. The units based on reciprocating engines should be equipped with heat recovery as much as possible. Heat storage systems may be needed to make sure that suffi cient heating capacity is available in case the cogeneration units cannot run during cold nights because much wind capacity is on line.

In conclusion, liquid biofuel-fi red and gas-fuelled power plants based on effi cient and fl exible engine-driven generators, with rapid starting and ramping up capabilities, as well as a fl at effi ciency curve in the upper load range, create cost-effective and energy-effi cient reserve power for wind stations.

Table 1. – Example of the effect of a lower utilisation factor on the specifi c capital costs of generators.

Power plant type Specifi c investment Specifi c capital costs Specifi c capital costs

55% utilisation 35% utilisationGas engine 500 €/kW 1 €cts/kWh 1.5 €cts/kWhCoal/steam 1200 €/kW 2.5 €cts/kWh 4 €cts/kWhNuclear/steam 2500 €/kW 5.4 €cts/kWh 8.5 €cts/kWh

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Wärtsilä will provide the Belgian independent power producer Renogen S.A. with a second biomass-fuelled combined heat and power plant.

Due for delivery in July 2008, the new plant is a duplicate of the existing BioPower plant already installed by Wärtsilä. Both plants are BioPower 5 CEX plants that will burn non-contaminated wood residues supplied by the local forestry industry.

The power plants are located in the municipality of Amel in the Ardennes, also called the fi rst “sustainable industrial area” in the southern part of Belgium. The new plant, just like the previous plant, will have a net electrical power output of 3.3 MWe, and a thermal output of up to 10 MWth

for district heating. The electrical output in condensing operation is 5.3 MWe. They will deliver hot water to local industrial businesses with the electricity generated being fed to the local grid. The two plants will be eligible for carbon emission credits (so called “green certifi cates”) applicable in Belgian Wallonia.

Wärtsilä will deliver the complete new plant under an equipment, procurement and construction contract (EPC). There is also a full O&M contract to cover operation and maintenance after the plant is commissioned.

The new BioPower plant, is based on the same well-proven modular concept as the earlier plant. “Wärtsilä’s modular approach brings several benefi ts to us,” says Mr Yves Crits, CEO of Renogen S.A. “The site work is minimized and delivery time is short, in addition the plant can grow with the growth of heat demand on the industrial estate,” he continues.

The modular approach also means

consistent quality owing to the factory assembly of modules and compact, but well-considered layout arrangements requiring less fl oor area for the power plant building. This proven technology results in a reliable, durable plant. The plants are also highly automated, enabling unmanned operation.

Wärtsilä’s biomass-fuelled plants are clean and effi cient. They are practical solutions for meeting the needs for renewable energy supplies with minimum environmental impact. They incorporate patented Wärtsilä BioGrate combustion technology to burn biomass fuels with high combustion effi ciency and low NOX and CO emissions. The moisture content of the fuel can be as high as 55%. The fl y ash is removed from the fl ue gases in an electrostatic fi lter.

The BioPower plant operates on a closed steam-feed water cycle separate from the hot water system. Superheated steam is generated in an effi cient water-tube boiler, and supplied to a high-effi ciency reaction-type condensing extraction steam turbine driving an alternator. The water is then heated by steam extracted from the turbine.

Wärtsilä BioPower plants are highly modular, being based on well-proven standardised components with a conservative design approach. The plants can thus be delivered and installed quickly.

The recent order from Belgian power producer Renogen S.A. for a second unit, again underscores the effi ciency of Wärtsilä’s modular BioPower energy plants.

Fig. 1 – The second Wärtsilä bio-fuelled power plant ordered by Renogen will be situated right next to the existing, identical plant in Amel, Belgium.

WÄRTSILÄ BIOPOWER PLANTS IN THE ARDENNES, BELGIUM

REFERENCES AMEL | BELGIUM

p

14 in detail

high temperature of the compressed air in the cylinder. The effi ciency of the Diesel cycle is a function of compression ratio (r=V

2/V

1) and cutoff ratio (r

c= V

3/V

2):

1 r

ck – 1

η = 1 – ----- -----------

r k-1 k(rc – 1)

The effi ciency of a Diesel cycle is lower than the effi ciency of the Otto cycle, provided the compression ratio is the same. However, because the compression ratio in a Diesel cycle is normally higher than in the Otto cycle, the effi ciency of the Diesel cycle can be higher.

center (BDC) point 1, where the piston starts compressing the gas to state 2, where the piston is at the top dead center (TDC).

The ratio of volumes V1/V

2 is called

the compression ratio (r), and the effi ciency is dependent entirely upon the compression ratio and gas constant (k):

η = 1 – 1/r k-1

Diesel cycleThe Diesel cycle describes the thermodynamic process within diesel engines. The diesel engine is an internal combustion engine, where ignition starts by injecting high pressure oil into the cylinder. Ignition occurs as a result of the

Fig. 1 - Otto cycle of spark-ignition engines.


Fundamentals of power plants

THERMODYNAMICS OF ENGINE CYCLES

Carnot cycleOne of the early engine inventions was based on a theory presented by a French engineer Sadi Carnot (1797-1832) in 1824. In his book, Carnot introduced his theory of the ideal thermodynamic cycle, which became known as the Carnot cycle.

The effi ciency of the Carnot cycle can be expressed as follows:

η = 1 – T2/T

1

Where T1 is the temperature at which

heat is taken into the cycle, and T2 is the

temperature at which the heat is taken out. The temperatures are expressed in Kelvin degrees or in absolute values. Thus 0 oC corresponds to 273 oK. The equation states that in the ideal Carnot cycle, effi ciency is dependent solely upon the two temperatures in the engine.

Otto cycleThe Otto cycle describes the thermodynamic process of a spark-ignited internal combustion engine (Figure 1). The cycle starts from the bottom dead

Power system planning will be the subject of a series of articles for In Detail magazine. The series is based on the book “Planning of Optimal Power Systems”, written by Asko Vuorinen (www.optimalpowersystems.com). The fi rst article describes the thermodynamics of power plant cycles. Why do gas and diesel engines have higher effi ciencies than gas turbines? The answer can be explained by basic thermodynamic formulas, which will be given.

AUTHOR: Asko Vuorinen , Managing Director, Modigen Ltd.

Fig. 2 - The Diesel cycle has constant pressure, when heat is added.

T

2

1

3

4

Q1

Q2

S

S1 S2

T-S Diagram P

3

2

V2 V1

V

4

1

P-V Diagram

TT-S Diagram P-V Diagram

S

1

2

p=const

p=const

Q2

Q1

3

4

S1S2

4

3

Q2

Q1

P

2

1

P= constant

V2 V1

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T-S Diagram P-V Diagram

Brayton cycleThe Brayton cycle (Figure 3) describes a gas turbine process. The effi ciency of the Brayton cycle can be evaluated using the formula η = 1 – 1/r

p (k-1)/k where r

p

is the pressure ratio of the compressor. In an ideal Brayton cycle, effi ciency is a function of pressure ratio r

p alone.

Rankine cycleWater and steam cycles are used for power generation in power plants using nuclear or solid fuels. In such plants the energy conversion machine is called a steam turbine, and the energy conversion cycle is the Rankine cycle.

A T-S diagram of the Rankine cycle is given in Figure 4. A theoretical cycle has isentropic compression from point 1 to 2. The water is then heated to its e saturation temperature (T

s), whereupon

the water is converted into steam in the steam boiler. The steam is then superheated (T

3) and the superheated

steam will expand (isentropic expansion) in the steam turbine from point 3 to 4. The steam is then condensed into water in a condenser from point 4 to 1.

Combined cyclesInternal combustion engines (Diesel, Otto cycle) or gas turbines (Brayton cycle) can be combined with a steam turbine (Rankine cycle) in order to obtain higher effi ciencies. The diesel engine combined cycle (DECC) (Figure 5) has a diesel engine as the topping cycle and a steam turbine as the bottoming cycle. The gas engine combined cycle (GECC) combines a gas engine and a steam turbine. Both cycles use a waste heat boiler, which generates steam for the steam turbine.

The benefi t of the internal combustion engine combined cycle is higher effi ciency since the waste heat generates extra electrical energy. Diesel engine combined cycles have been used in plants from 15 MW to 300 MW in size, resulting in a typical effi ciency increase of between 44% to 49% or 3–5% points. The steam turbine is designed to generate typically 5–15% of the output of the diesel engine, because the exhaust gases have a relatively low temperature (350–450 oC).

A gas turbine combined cycle (GTCC) combines gas turbine and steam turbine cycles together in a similar manner (Figure 6). Gas turbine combined cycles p

Fig. 3 - Brayton cycle with constant pressures in heat input and heat rejection.

Fig. 4 - Rankine cycle or water steam cycle.

Fig. 5 - Internal Combustion Engine Combined Cycle (DECC and GECC) power plant.

Fig. 6 - Gas Turbine Combined Cycle (GTCC) power plant.

T-S Diagram

T

T3

T2

T1

S

1

2

p=const

p=const Q2

Q1

3

4

S1 S2

4

3

Q2

Q1

P

2

1

P2= constant

P1= constant

V2 V1 V4

T

S

3

4

T3

T2

T1

Ts

1

2

S2S1

Turbo charger Exhaust

Exhaust gases

Cylinder

Air

Steam

BoilerSteam turbine

Feed water Condensate

C T 3

4

2 1

Compressor Gas Turbine

Fuel

Combustion

Exhaust

Steam

BoilerSteam turbine

Feed water Condensate

3

4

2 1

p

16 in detail

are used for 60 to 600 MW size plants. The effi ciency of the gas turbine plant rises from 30–35% in single cycle to 45–60% in combined cycle, depending on the design. Steam turbines are dimensioned to generate 40–50% of the electrical output of gas turbines.

The steam turbine is very useful for gas turbine combine cycle applications since the exhaust gases have higher temperatures (450–550 oC). This means that more waste heat in the form of steam can be recovered. In large size plants (>300 MW) very high (55%) electrical effi ciencies can also be achieved under favourable climatic conditions.

Diesel and gas engine combined cycle plants have been built more seldom, because internal combustion engines have almost the same performance as gas turbine combined cycle plants in small (<100 MW) size plants. In combined heat and power applications, gas turbine combined cycle plants and internal combined cycle plants have about the same total (80 – 90%) and electrical effi ciency (45%).

ELECTRICAL EFFICIENCY

Effi ciency defi nitionsThe electrical effi ciency of a power plant is η

g = P

g / Q

f, where P

g is the generator

output (MW) and Qf is fuel input

(MW), which is measured using the low heat values of the fuels. A typical fi gure of fuel consumption of a large diesel engine is 180 g/kWh, which includes 5% tolerance as stated in the ISO standard.

The net effi ciency of a power plant can be evaluated using the net output values of power plants η

net = (P

gen – P

aux)/Q

f. While

the auxiliary power consumption is 2% – 9%of the output, depending on the type of power plant, the net effi ciency values are lower than the generator effi ciency values. Net effi ciency is, however, the right way to measure the performance of power plants.

Actual effi ciency values of power plantsThe effi ciency values of internal combustion and gas turbines engines can be found in the engine manuals of vendors. The latest effi ciency values of two large manufacturers have been evaluated in Figure 7. The effi ciency values of large internal combustion engines are within the 40–45% range. Aero-derivative gas turbines are within

Fig. 7 - Electrical effi ciency of internal combustion engine and gas turbine power plants as a function of electrical output using low heat values.

Diesel engines Gas engines Aero-derivative GT Industrial GT


50

45

40

35

30

25

2 4 6 8 16 25 40 80 120

Output (MW)

Fig. 8 - Correction factor of ambient temperature for electrical effi ciency.

1,15

1,10

1,05

1,00

0,95

0,90

0,85

Ambient temperature (°C)

IC-engines Gas turbine

%

-30 -20 -10 0 10 20 30 40 50

Fig. 9 - Correction factor of part load operation for electrical effi ciency.

1,10

1,00

0,90

0,80

0,70

0,60

0,50

Output (%)

IC-engines Gas turbine

30% 40% 50% 60% 70% 80% 90% 100%

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in detail 17

the 35–40% range, and industrial gas turbines within the 25–35% range.

From Figure 7 one can deduce that diesel and gas engines have about the same effi ciency at the same sizes. Effi ciency fi gures for gas turbines are typically 1% point lower, if the gas turbine operates with light fuel oil. The internal combustion engines have about 10%-points better effi ciency than the aero-derivative gas turbines at 16 MW size. With larger size plants, the effi ciency difference is 5% points with aero-derivative gas turbines and 10% points with industrial gas turbines.

Correction factors for effi ciencyThe effi ciency fi gures should be adjusted according to site conditions. The basic correction factors are tolerance, ambient temperature and part load operation. The actual effi ciency during operation conditions can be obtained using the following formula: η

a = (η

g / k

t) x k

et x k

el x k

ef x k

ein x

keex,

where ηg = guarantee effi ciency

given with 5% tolerance,

n kt = correction factor for

tolerance (typically 1.05), n k

et = effi ciency correction factor

for ambient temperature, n k

el= effi ciency correction

factor for part load, n k

ef = effi ciency correction

factor for deterioration, n k

ein = effi ciency correction

factor for inlet pressure, n k

eex = effi ciency correction

factor for outlet pressure.

The tolerance comes from the ISO standard for internal combustion engines, which states that the measuring tolerance for fuel consumption is 5%. Today the accuracy of measuring fuel consumption is much better, and the effi ciencies in practical life are calculated without tolerances.

The ambient temperature correction factor for effi ciency is given in Figure 8. If the ambient temperature rises, the effi ciency drops. At 45 oC the ambient temperature correction factor for gas turbine effi ciency is about 0.92, and for internal combustion engine effi ciency about 0.99.

Calculate the effi ciency of a) Otto cycle and b) Diesel cycle, when the compression ratio r is 12 and the cut-off ratio in the Diesel cycle rc is 2. c) What will be the effi ciency, if the compression ratio of the Diesel cycle is increased to 16?

a) Otto cycle, when r = 12

η = 1 – 1/(r k-1) = 1- 1/ 12 0.4 = 63%

b) Diesel cycle when r = 12 and rc = 2

1 rck – 1 1 2 1.4 -1

η = 1 – = 1 - r k-1 k(r

c – 1) 12 0.4 1.4 (2 -1)

= 1 – 0.37 x 1.17 = 57%

Thus at the same compression rate the Otto cycle has higher effi ciency.

c) Diesel cycle, when r = 16 and rc = 2:

1 rck – 1 1 2 1.4 -1

η = 1 – = 1 - r k-1 k(r

c – 1) 16 0.4 1.4 (2 -1)

= 1 – 0.33 x 1.17 = 61%

Calculate the effi ciency of a Brayton cycle, if the pressure ratio is a) 10 or b) 16 and gas const k= 1.4.

a) If rp = 10, then η = 1 – 1/r

p (k-1)/k = 1 –1/ 10 0.4/1.4 = 1 – 0.52 = 48%

b) If rp = 16, then η = 1 –1 / 16 -0.4/1.4 = 1 – 0.45 = 55%

These fi gures can be compared with the Diesel cycle effi ciency of 61% at the 16 compression ratio, and the Otto cycle effi ciency of 63% at 12 compression ratio in example 2.1.3. They show that internal combustion engines have about 10%-points better effi ciency, which comes from theoretical cycles.

Part load operationDuring part load operation, effi ciency drops considerably (Figure 9). At 70% load, the part load correction factor (k

el) is 0.96 for internal combustion

engine and 0.92 for a typical gas turbine. The correction factor of an internal combustion engine can be approximated using the following formula:

k

el = P/(f + (1-f ) x P)

where k

el = correction factor for effi ciency

P = output in percent of full output

f = zero load consumption (ic-engines f = 0.1, gas turbines f= 0.2)

Normally the engine runs at part load for a considerable number of hours. To fi nd the weighted part load factor for effi ciency, one should defi ne how many hours at each load the power plant will be operated. The weighted effi ciency is then calculated by multiplying the hours at each effi ciency fi gure, and dividing the sum by the total number of operating hours.

In multi-unit installations, the most effective means of operation is to start-up just as many engines as are needed to run all engines at near 100% load. A ten engine power plant at 10% load, for example, can be operated by starting one engine and operating it at 100%. When11% output is required, one can start two engines and then operate them at 55% (11/20) power level. Thus the correction factor of effi ciency of a multi-unit plant can be 1.0, even at 10% output.

p

18 in detail


Lack of investment in electrical power production during the previous 25 years rapidly took its toll in the 1990s as Azerbaijan’s economy grew and electrical power demand increased. According to Marlen Askerov, Vice President of AzerEnerji, the state-owned power generation and transmission company, by the beginning of the new millennium some 50% of the older electrical generation plants were obsolete.

“This caused the cost of electric energy production to be unacceptably high, with only some 25% electrical effi ciency,” Askerov explains.

As a result, the decision was made to close six of the obsolete power stations.

This not only left a shortage of electrical supply capacity, which had to be made up for by importing power from Russia, but those power stations that remained were all located in the west of the country far from the main population centre of Baku on the Absheron Peninsular. This meant long transmission lines, with frequent localised outages and occasional widespread system failures. Many areas of the country were receiving only a few hours of electricity per day.

Governmental strategy supports utilitiesThe political stabilisation that Azerbaijan has experienced during recent years has boosted the nation’s economic growth. This development is refl ected in the 10% annual increase in the level of electricity consumption that has been typical as homes and factories become modernised, new industrial investments are realised, and machine usage rises.

Recognising that the delivery of affordable electricity and other utility services of acceptable quality is an essential element of managing the enhancement of living standards, the Azerbaijani government addressed this issue as part of its Letter of Development Policy (LDP) strategy. Essentially, the elements of the strategy are designed to support

a fi nancially viable and self-sustaining utilities sector, while providing effi cient and cost effective service to the population.

The LDP initiative provided the mechanism to strengthen the power generation and transmission infrastructure. This promised the dual benefi ts of providing reliable electricity supply while reducing, and ultimately eliminating, the need to import electricity. However, although plans for new power stations were quickly drawn up, it was very clear that the four to fi ve year timetable necessary for bringing such new facilities on line would mean continued power shortages in the meantime. “In order to address the growing industrial and private demand for electricity, it was necessary to commission additional capacity as soon as possible,” Askerov points out.

Multiple Wärtsilä plants chosen to meet short-term needs Consequently, in May of 2005 an agreement was signed between AzerEnerji and Wärtsilä for the supply of fi ve gas power plants with a total capacity of 450 MW. In short, rather than wait for a large power plant to be built and commissioned, AzerEnerji made the decision to provide multiple smaller units that could be installed relatively quickly and, most importantly, close to locations where electricity was most needed. Furthermore, they offered the option of

Azerbaijan re-energizedAUTHOR: Tom Crockford , Editor, Crockford Communications. Acknowledgement: Material from earl ier art icles by Peep Ehasalu on this subject has also been used in the preparation of this art icle.

Fig. 1 – Wärtsilä gas power plants are meeting Azerbaijan’s growing electricity needs.

Fig. 2 – The Wärtsilä power plants are all at strategically important locations.

Azerbaijan has long been energy rich. In fact, at the beginning of the 20th century the country was supplying almost half the of the world’s oil. Nevertheless, following the nation’s re-independence, Azerbaijan found itself short of electrical power capacity despite its enormous oil and gas wealth. Now, thanks to the rapid installation of fi ve technically effi cient Wärtsilä power plants, Azerbaijan is rapidly becoming once again energy self-suffi cient.

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Naxçivan90 MWm

Saki90 MWm

Xaçmaz90 MWm

Baku108 MWm

Sangachal300 MWm

Astara90 MWm


in detail 19

combined heat and power production.The sites chosen for the Wärtsilä power

plants were all strategically important locations: Astara in the southern tip of the country, Sheki between the borders with Russia and Georgia, Khachmaz in the north-eastern area of Azerbaijan near the coast, Nakhchivan close to Turkey, and Baku the capital. In order to re-vitalise the country’s energy system, an estimated total of USD 2.3 billion will be invested in building power plants and strengthening the transmission grid by the end of 2008.

The decision to build multiple smaller power stations, rather than wait for larger more conventional facilities, was not popular with everyone in the republic. As Marlen Askerov explains: “Many people, including those in the press and television, believed that this was not a cost-effective and reliable way forward. There were also concerns that this equipment could not be operated in a parallel mode.”

Nevertheless, AzerEnerji stood behind its decision – one that is now proving to be both farsighted and correct. “The move has defi nitely justifi ed itself,” adds Askerov.

Decision yields rapid benefi tsWärtsilä was able to react remarkably quickly to AzerEnerji’s needs. The fi rst of the new plants – at Astara – was delivered, installed and commissioned already in February 2006, just 9 months after the contract had been signed in the spring of 2005. The other installations followed in quick succession with the fi fth and fi nal plant – at Baku – being inaugurated in February 2007.

Apart from adding some 15% to the national grid capacity, the Wärtsilä power plants have provided a range of other important benefi ts. Each power plant consists of 10 identical 9 MW generators based on Wärtsilä 34SG gas-engine sets. The net fuel effi ciency is close to 44% under all circumstances - a marked improvement on the existing system where the net fuel effi ciency is considerably less than 30%. This translates into a specifi c fuel consumption for these new generators that is at least 50% better than that of the old system. This high effi ciency, combined with the fact that they use the natural gas that is available locally in abundance, offers the bonus of releasing substantial levels of refi nery output for both domestic consumption and export. Additionally, compared

to the old oil-fi red units, the new gas-driven plants have very low emissions.

Askerov is enthusiastic about both the immediate and the future operational advantages the new equipment provides: “The Wärtsilä units are currently operating at baseload mode to compensate for the inadequate supply situation. Later, when our large stations are commissioned, this equipment can be operated at peak mode to provide the roughly 30% of peak capacity necessary for reliable energy system operation.”

The technical superiority of the new engine-driven plants is illustrated by the innovative ‘cascading principle’ control concept. Accordingly, when power demand decreases, individual engines can be switched off allowing the remaining engines to continue running at their rated power. As more power is demanded, the idle engines can be quickly re-started. Since idle engines do not wear, maintenance costs are notably reduced. Similarly, should a single engine-generator unit fail, only 10% of the 90 MW supply is lost. Usually, the remaining engines can make up the extra load. This minimises the risk of interruptions to the electrical supply system.

Heat production also creates jobsThe fi ve new power plants are up and running and quickly helping to re-energize Azerbaijan, both literally and spiritually. After all, a nation cannot thrive if it is insecure about its electricity supply. Nowadays, refrigerators stay cool, lights illuminate the darkness, and people can watch television in the evenings. At the same time, industry can now rely on a secure power supply.

There are also other, more fundamental, reasons why the Wärtsilä equipment is benefi ting the people of Azerbaijan, even beyond supporting economic growth by helping to secure a reliable supply of electricity. The biggest benefi t is the creation of jobs. Since it is estimated that each new workplace requires an additional 1.5 kW of energy capacity, the added capacity provided by the Wärtsilä generators represents signifi cant potential job creation.

At the same time, each of these new stations also produces heat that can also be utilised to good effect. Askerov notes that the technical specifi cations of the order say that the generated heat can

be used for other purposes to improve the overall effi ciency of the plants. “Although some of these stations are in remote rural areas, even there the heat can be used for agricultural development applications such as the heating of greenhouses. This certainly helps to create new jobs, particularly as there is little industrial development in such areas.”

New order placedWhile the basic aim has been to make Azerbaijan an energy independent country, as well as to take advantage of local energy reserves, the future likelihood is that there will be suffi cient power to allow exports as well. The neighbouring countries are likely importers of Azerbaijani electricity, especially Russia with whom Azerbaijan has had long established electricity trading relations.

The on-time delivery of the fi ve Wärtsilä power plants, and the speed at which they were able to be commissioned has not gone unnoticed or unappreciated by the management of AzerEnerji. “The excellent work of the specialists that have been involved in this project, and the high quality of the equipment supplied, means that we have been able to commission all of these units in perhaps even record-breaking time,” says Askerov.

To put the scale of each installation into perspective, it is worth noting that 100 container loads of materials were shipped from Wärtsilä’s base in Finland for each of the fi ve projects. These contained not only the engines, but also pipes, screws, fi ttings down to the smallest parts, construction materials, and even the fl ooring plates. More than 500 specialists were involved in the building of the Astara station under Wärtsilä supervision.

Documentation of AzerEnerji’s satisfaction with the multiple plant solution, and the endorsement of its original purchasing decision, came in January 2007 with the announcement of a new 300 MWe multi-fuelled generating plant order. This plant, to be located 50 kilometres south of Baku, will be equipped with 18 generating sets each powered by an 18-cylinder Wärtsilä 50DF engine delivering 17 MW. Wärtsilä will also deliver the power plant design, other principal equipment and all building materials. The plant is scheduled to be fully operational by October 2008.

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20 in detail


Project execution for small power plants is often as labour intensive as for much larger plants. The specifi c investment cost of a plant, in EUR/kW, is therefore often higher for small and medium size power plants, often used for industrial applications and small independent power producers. A recent package developed by Wärtsilä, known as the PowerCube, manages to provide users with a pre-engineered power plant within a competitive cost framework, improving the Life Cycle Cost and Internal Rate of Return of such projects.

Undertaking turnkey delivery of small power plants based on just a few engines is usually not an economically viable option for industrial customers or small independent power producers (IPPs). This is because turnkey project execution for a small power plant is often as labour intensive as the turnkey delivery of a much larger plant.

The reason for this is that the required project-specifi c design, engineering and project management, has a higher impact on the overall specifi c cost of a small project. Furthermore, the economics of scale do not act in favour

of small “one-off” projects, either in producing equipment, or in site works.

What is required for the successful and economical delivery of a small power plant is a fully standardized and optimized plant that is totally modular. Wärtsilä has met this challenge with the introduction of the PowerCube.

Available in two versions, the GasCube and the OilCube are single-engine, 9 MW power plant units that have all the components and auxiliaries needed for a complete power production unit. They offer clear benefi ts for industrial, utility and IPP customers who do not

have their own construction and project-handling capabilities, but like to entrust the delivery and construction of the power plant to one responsible party.

A bigger packageThe idea of power packages is not new. In the past Wärtsilä has had standard power modules based on the Wärtsilä 200 and Wärtsilä 220SG engines. But these were based on smaller generating sets that were delivered to site as ready to install modules.

The standard power plant concepts of today are usually optimised for upwards of fi ve or six engines. Such concepts were not optimised for installations that required one to three engines. A power plant with multiple engines has common parts, such as the control room, fuel treatment system, etc. But where there is one single engine, these common parts can be more expensive than the engine itself. This results in a high price per kW.

The aim when developing the PowerCubes, was to design larger multi-functional units that were manufactured in a controlled workshop environment and would be assembled at site.

Since a 9 MW power plant unit would be too large to be transported as a single containerized system, the PowerCubes comprises a number of fully engineered and pre-fabricated modules that are essentially like a kit that is assembled at site.

This means that the customer gets a fully engineered and standardised power plant unit and does not need to spend extra money on project specifi c engineering on the main power generation equipment. The complete detailed design of the PowerCube is already existing and can thus be repeated from project to project, saving cost and time as well as securing quality of the fi nal product.

A PowerCube installation typically consists of 1-3 PowerCubes that can be installed either all at the same time or in consequent steps. It can be assembled and in operation in 2-3 months after arrival at site, with each additional Cube taking one month. This means that a 27 MW plant could be installed in 4-5 months. (See Figure 1).

Cube rootsDevelopment of the PowerCubes began at the beginning of 2006. The OilCube is based on the 20-cylinder Wärtsilä 20V32

Thinking inside the boxAUTHORS: Thomas Hägglund , Product Manager, Gas Power Plants, Wärtsi lä in Finland. Greger Kåll , Product Manager, Oi l Power Plants, Wärtsi lä in Finland

Fig. 1 – A Wärtsilä PowerCube plant can consist of eg. three combined GasCubes installed next to each other.

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diesel engine. The GasCube is basedon the Wärtsilä 20V34SG gas engine. (Figure 2 and 3).

Power plants with 1-3 engines were specifi cally targeted and Wärtsilä evaluated a number of layout alternatives. For the OilCube, major work included the development of auxiliary modules, a fuel treatment module, fuel handling equipment and other mechanical equipment. Also modelling of a new ventilation system that could achieve high effi ciency with low power consumption was done. A free-standing exhaust gas silencer was developed to reduce the amount of steelwork required for the exhaust gas stack.

For both the GasCube and the OilCube, the evaluations considered costs, technical requirements and crucially, how to minimize space requirements while allowing the equipment to be easily maintained. There was therefore a major focus on reducing the footprint of the plant.

A one engine OilCube power plant requires 85% less space compared to a standard heavy fuel oil power plant solution with the same output. The footprint of the GasCube building is merely 113 m2 per each generating set, which is comparable to or smaller than a typical gas turbine package with an equivalent power output. This opens up possibilities regarding the location of the plant. For industrial customers for example, where land is limited, the space needed for installation of a plant might be a decisive factor.

Key featuresA major feature of the PowerCubes is the integration of the radiator coolers on the roof of the PowerCube – a design feature which, in addition to reducing the footprint, improves heat dissipation from the plant. (Figure 4). In the GasCube, the exhaust silencer and stack is also integrated with the Cube and supported by the same foundation. (Figure 5).

Placing the radiators on the roof reduces the amount of piping and assembly work needed at site. It also means that no separate supports or foundations are needed for the radiators. This reduces the necessary infrastructure and reduces the number of interfaces during site assembly.

The GasCube consists of a cubicle enclosure that has the engine and generator located on a common base-frame. The inlet air module, charge air silencers, exhaust gas system and an auxiliary module are all connected to the generating set. The auxiliary module includes the gas regulating ramp, the cooling system, the instrument air system, the engine pre-heater and the maintenance water pump. All auxiliaries are located in the module. The radiators are installed on the roof of the enclosure. The only major component not located on the auxiliary module is the starting air compressor, starting air bottle and maintenance water tank, which are installed next to the auxiliary module.

Availability of clean water is a global concern and is almost always scarce in remote areas. The PowerCube does not consume any cooling water. The PowerCubes use a closed circuit cooling system and all that is needed is the initial supply of water for fi lling the closed circuit cooling system and maintenance water tank. In bigger power plants such as those based on steam turbines, for example, there may be problems related to water consumption. In such plants, there is high water consumption and the cooling system is of a completely different magnitude.

The PowerCubes have low auxiliary power consumption and de-rating. Notably, the internal auxiliary power consumption of the PowerCubes has been minimized by reducing the parasitic power needs for items like ventilation and radiator fans. This results in the GasCube having a typical net electrical effi ciency, after deduction of auxiliary consumption, of more than 44%.

De-rating is a major concern in extreme ambient conditions, especially for gas turbines operating in hot countries. The GasCube based on the Wärtsilä 20V34SG is very effi cient when it comes to de-rating. De-rating usually begins at about 35 °C. This, in combination with effi cient closed loop cooling provides a competitive edge in the market. There is an optimized single pFig. 3 – The OilCube is based on the Wärtsilä 20V32 diesel engine.

Fig. 2 – The GasCube is based on the Wärtsilä 20V34SG gas engine.

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22 in detail

circuit cooling system, which allows high output at high ambient temperatures. This ensures full power output across a wide range of ambient temperatures compared to other technologies.

The major difference between the GasCube and the OilCube is of course the fuel. The OilCube is designed to use heavy fuel oil (HFO) with a viscosity of up to 500 cSt/50 °C. Running on HFO, additional equipment is needed for fuel oil treatment.

In large power plants, there is usually steam heating of the fuel. In a single engine installation, however, a steam heating system proves to be quite expensive. In the OilCube, cooling water from the engine high temperature circuit is therefore used to partly heat the fuel, in conjunction with electrical heaters. The use of electrical heaters slightly increases


Fig. 4 – A major feature of the PowerCubes is the integrated radiator coolers on the roof.

Wärtsilä GasCube technical details

Engine type Wärtsilä 20V34SGPower, electrical 8730/8439 KWe at generator terminalsEffi ciency, electrical 46.5% at generator terminals, with engine driven pumps, ISO 3046Frequency 50/60 Hz GasCube building dimensions 19.4 m x 5.8 m x 9.1 m

Wärtsilä OilCube technical details

Engine type Wärtsilä 20V32Power, electrical 8924/8730 KWe at generator terminals Effi ciency, electrical 46% at generator terminals, with engine driven pumps, ISO 3046Frequency 50/60 HzOilCube building dimensions 22.3m x 7.65m x 9.1m

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auxiliary power consumption and special effort was made to keep this additional internal consumption to a minimum.

The OilCube has a net electrical effi ciency of approximately 43%, which is only marginally less than in a power plant that uses steam heating for fuel conditioning. The choice of using combined cooling water and electrical heating for the fuel was made based on extensive Life Cycle Cost calculations. These calculations showed clearly that the lowest cost of generation would be achieved with the chosen technology in single unit plants such as the OilCube.

The use of low speed fans in the radiator coolers is used for reducing the internal power consumption. Although slightly more expensive, they have the additional benefi t of reducing noise levels from the radiators.

A key innovation in the OilCube is the modular HFO treatment system, including fuel oil separators. In developing the OilCube, the fuel treatment system is totally integrated into the auxiliary module. There are two full fl ow HFO separators included for full redundancy.

A small intermediate fuel tank has also been included in the fuel treatment module. This eliminates the need for large fuel treatment tanks that would be needed to be fabricated on site, resulting in a substantial saving on site infrastructure. Combining the separators and the fuel tank in the same pre-fabricated module reduces the amount of pipe work required at site.

Both the GasCube and OilCube incorporate a low-voltage electrical system inside the PowerCube, including a programmable logic controller and panel-

mounted Wärtsilä Operator Interface System (WOIS). This eliminates the need for a separate control room. The control panel in the engine hall can be connected remotely to a central control room. This means the plant can be monitored and operated remotely from the customer’s control systems, or by using additional WOIS workstations whose positioning can be freely chosen. For example, the electrical distribution system and an optional WOIS station can be installed in the client’s facilities or installed in a separate building.

Main benefi tsThe PowerCube is a lifecycle-optimized solution based on Wärtsilä’s core prime movers, the Wärtsilä 20V32 and Wärtsilä 20V34SG engines. The PowerCube’s auxiliary systems have been designed with high quality components with the aim of minimising site work and auxiliary power consumption.

With a pre-designed, fully standardised product, Wärtsilä can offer a fully tested power plant of the highest quality. The high level of pre-fabrication means the plant requires minimum work on-site, thus reducing time needed for erection, reducing costs and ensuring consistent quality. Standardisation also means that spare parts for all components in the package have high availability.

Operation of the plant also benefi ts from the standardised modular design. The engine technology is fully proven and has been validated in a number of installations. Troubleshooting is easier, which has benefi ts in all parts of the operation and maintenance chain. Proven technology means that operation and maintenance requires minimum staff on-site.

With the PowerCube solution, customers know exactly what they get. Installation is fast and easy thus guaranteeing a reliable project time schedule. At the same time, further extensions to the plant can be done fl exibly. The technical risks that can arise with project-specifi c designs are eliminated and possible delays in the delivery schedule are minimised. This signifi cant reduction in risk is a defi nite advantage when seeking project fi nancing.

The benefi ts of the PowerCube mean it is now much easier for potential power producers to enter the power generation business with small and medium size projects.

Fig. 5 – In the GasCube, the exhaust silencer and stack are integrated, thereby reducing the plant’s footprint.

24 in detail

[ MARINE / IN DETAIL ]

Designs for life - from initial ship design right through to its end-of-life, Wärtsilä can guide the way

Of course, Wärtsilä has itself presented a number of innovative ship designs, such as the CODED panamax cruise ship concept and the LNG-fuelled ropax, but these have acted primarily as a catalyst for propulsion projects. These were concept designs that merely tickled and inspired the market.

But with SCHIFFKO’s integration into

the Wärtsilä network, the company can now offer owners complete ship design and newbuild consultancy services, together with the dialogue it can provide on whole ship processes, including propulsion, automation, and systems integration.

The acquisition means that Wärtsilä can, as a project partner, be even more resourceful and valuable in bringing technology concepts and solutions to the discussion table, since it is now in a position to understand the whole ship, not just the engineering products within the ship. Through the integration of SCHIFFKO designs and services, Wärtsilä can now offer customers initial

design (general arrangement), basic design (classifi cation drawings), detailed design (production drawings), as well as upgrade and conversion designs. It has the capability to oversee whole projects from the initial concept, on to the building and operation, and through to the life after sale stages.

Wärtsilä will continue to focus on SCHIFFKO’s established presence in the containership, research and special ship sectors, and will update existing SCHIFFKO designs. New designs, such as the recently introduced CV 7300 RESOLUTE (Reliable, Economic, Safe Operation, Leading Ultimate Technology

For Wärtsilä, a company synonymous with being a total ship solutions provider, the December 2006 acquisition of German ship designer SCHIFFKO can only be viewed as a logical step forward.

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AUTHOR: Magnus Miemois , Vice President, Ship Power Solutions, Wärtsi lä in Finland

Fig.1 - The recently introduced CV 7300 RESOLUTE-class containership design.

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and Engineering)-class containership design, will continue to be promoted.

The CV 7300, an 85,000 dwt, 322.34 m long vessel, capable of 25.5 kts with a power output of 62,920 kW, features the company’s state-of-the-art design and engineering capabilities. One of the most noticeable innovations of this vessel type is the modular compact deckhouse, which allows for more crew comfort and maximum weight saving (40%).

The effective mass production process for the modules means that the fabrication and assembly time is much faster than for a conventional deckhouse design, and the cost is 40% lower. The U-shaped outline of the deckhouse also enhances optimisation of cargo space. The CV 7300 can accommodate a wide range of container sizes, and facilities for temperature controlled freight are also provided.

In addition to the successful CV 1100 series, which with more than 130 vessels built is the most successful 1100 TEU container feeder design ever, the company has also released a new design, the SCHIFFKO Reefer 350XT. This is intended to meet demand for reefer container capacity. This new design can accommodate 363 high cube FEUs and 118 standard TEUs.

Wärtsilä will, in time, develop its design portfolio to include other vessel types but in the meantime, will continue to design containerships, offshore vessels and other specialist ships.

In the 1960s, SCHIFFKO was instrumental in pioneering the 3-D CAD system. Its customised software was eventually merged into the KCS group system, to become the revered Tribon ship design software – a system that will still be used following the acquisition, although other programmes will be used too for hull, outfi tting and for the piping designs system. Further software applications include the BRAVO system, FORAN 60 and ShipConstructor, as well as the general CAD software AutoCAD and ANSYS for FE-calculations. Today all design work at SCHIFFKO is done using computers, and traditional manual drafting is no longer practised.

Wärtsilä can also offer customers the latest advanced developments to the SCHIFFKO Combi System. These advancements combine a Fig. 2 – The modular, compact deckhouse of the CV 7300 containership.

larger number of integrated programs and functions for cargo handling, monitoring, control and alarm, as applicable both onboard and ashore.

The application area covers the ship’s safety operation, nautical route planning, monitoring and alarm system, ship related administration and communication, life cycle maintenance, crew training and system simulation.

Ships can now be designed that are energy effi cient, operationally effi cient, and environmentally effi cient. With Wärtsilä’s deep understanding and knowledge of energy management, which places the company in a very unique

position as a ship designer, the company has the potential to design ships that out-perform other market designs on operating costs and environmental impact.

Along with its traditional and established Wärtsilä products, the company can now offer initial/basic/detailed designs for:n Container, multi-purpose

and reefer vesselsn Fast patrol and rescue boatsn Biological, hydrographic, geophysical

and oceanographic research vessels and seismic survey vessels

n Pipe laying barges and vesselsn Crane barges and vessels.

26 in detail

can usually be met with standard marine equipment. However, we already know of new and tougher limits that will come into force in the near future. There are also an increasing number of local legislations that can be very hard to meet without changing the fuel quality, or applying extra measures to clean exhaust emissions. Most of these regulations focus on NO

X

and SOX emissions that for the most part,

have a local impact on the environment. However, industry discussions are these

days focusing more and more on the subject of climate change. This topic has quickly gained worldwide importance and recognition. In order to offset the

Wärtsilä has introduced many novel propulsion concepts for passenger vessels that can offer clear reductions in emission levels. Some have been based on of the principle of switching fuel from diesel to natural gas. In cooperation with one of the leading builders of cruise ships, Aker Yards, Wärtsilä has developed the concept of a large cruise ship operating on liquefi ed natural gas (LNG). This new concept will produce a clear reduction in almost all major emission levels.

CRUISING AND THE ENVIRONMENTThe current international regulations for ship emissions are not very stringent. They


Cruising on gas into a cleaner future

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AUTHOR: Oskar Levander , M.Sc. (Nav. Arch.), General Manager, Conceptual Design, Wärtsi lä Ship Power in Finland

The maritime industry is facing ever-increasing pressure to reduce its environmental impact. Regulations are becoming more stringent, and new authorities are establishing their own emission regulations in local areas. At the same time, the cruise business is booming and the number of cruise berths is growing rapidly. Even though cruising is a leisure business, it is also one of the most visible parts of the shipping sector. Cruise operators will, therefore, need to put more and more effort into becoming greener.

Fig. 1 – Cruising on gas into a cleaner future.

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effects of climate change, greenhouse emissions need to be reduced. The main contributors to the greenhouse effect are the CO

2 emissions formed when burning

fossil fuels. The European Union has committed to reducing CO

2 emissions

by 20%. The maritime industry will surely be forced to do their fair share to help the EU to achieve this target.

Reducing CO2The only ways for ships to reduce their CO

2 emissions are either to reduce fuel

consumption, or to switch to a fuel containing less carbon. Fuel consumption can be lowered by either reducing the power demand, or by improving the effi ciency of the power generation. There is no easy way to do the latter, for while engine technology is improving slowly, no quantum leaps can be expected in the near future. Furthermore, an improvement in engine effi ciency can often lead to an increase in other emissions, such as NO

X.

Power demand reduction offers more options for reducing emissions, but large improvements are by no means easy to achieve either. One way that propulsion power can be lowered is to adopt new innovative propulsion solutions, and to optimise the hull form. On the other hand, cruise ships also offer large power reduction potential on the hotel side. The hotel loads represent a very large share of the total energy consumption. Another possibility for achieving fuel savings is to change the operating parameters of the vessel, notably by selecting the right speed

profi le and optimising the itinerary. However, there are still limits

to the potential CO2 savings from

reducing power demand. The big CO2

reduction must be sought from other means, such as alternative fuels.

Switching to LNGSwitching from HFO to natural gas will signifi cantly reduce all important exhaust gas emissions from a ship, including a 30% reduction in CO

2 emissions. The main

reason for this reduction is the fact that the main component of natural gas (NG) is methane, which in turn is the most effi cient hydrocarbon when measuring energy content against carbon content.

By running on LNG instead of HFO, the main emissions can be reduced accordingly:n 30% lower CO

2 – Thanks to low

carbon to hydrogen ratio of fueln 85% lower NO

X – Lean burn

concept (high air-fuel ratio)n No SO

X emissions – Sulphur is removed

from LNG when NG is liquefi edn Very low particulate emissionsn No visible smoken No sludge deposits.

LNG CRUISE SHIP CONCEPTWärtsilä has, together with Aker Yards, designed a cruise ship concept using LNG as fuel. The idea is to investigate how LNG systems can be effi ciently integrated into the design, and to show how the gas will improve the performance of the vessel. The project was based upon a large cruise

ship since they will represent the bulk of the cruise ship construction market in the near future. The ship has a volume of 125,000 GT and almost 2800 lower beds.

Main Particularsn Gross tonnage 125,000 GTn Length overall 310 mn Length, bp 295 mn Breadth 40 mn Draught, design 8,6 mn Deadweight 10,000 tonn Service speed, 21.0 knotsn Lower beds (no.) 2780 n Pax cabins (no.) 1390

The cruise ship has a novel general arrangement with a large number of balcony cabins. The superstructure is split into two parts in the stern to form an outdoor garden in the centre. In the middle and forward part of the vessel, the superstructure is in one part and is narrower than the hull.

Regulations for gas installationsThe maritime industry is full of rules and regulations from different authorities with which a ship must comply. As gas as a fuel is new to passenger vessels, it raises many issues that need to be addressed as the various regulations are developed. Today, DNV is the only classifi cation society that has rules applicable to gas-fuelled passenger vessels. Norway has been in the forefront of LNG-fuelled vessel development, and has therefore also led the way in writing regulations. There are already six ferries in p

Fig. 2 – Cruise ship concept operating on LNG.

28 in detail

of diesel tanks, taking into account the lost space around the cylindrical tanks. Since cruise ships are volume-critical vessels, this poses a big challenge to the naval architect. The end result is that the cruise ship will need to be larger in order to offer the same passenger capacity.

A new location for the LNG tanks has been developed for the LNG cruise ship concept. The tanks are located in the centre of the superstructure, inside the outer row of cabins and in front of the engine casing. The tanks are located above the public space decks so as not to obstruct passenger fl ows. As is often the case with contemporary cruise ships, the technical spaces within the accommodation areas, such as the AC rooms, are located in the dark centre casing of the superstructure. The tank compartment forms a logical continuation of these technical areas. The advantage of this location is free access to open air. This provides for an ultra safe storage location. Any possible leak, even though this is very unlikely, will evaporate and disperse directly into the air. No pressure build up is possible either, since the space has an open roof that cancels any pressure increase from fi re. A stainless steel tray beneath the tanks prevents possible leaks of cold LNG to come into


operation or on order in Norway, running on LNG, as well as four supply vessels. As the IMO is also currently dealing with some draft rule proposals, the availability of governing rules is likely to improve.

LNG storageOne of the important issues addressed in the rules is the location of the LNG tanks. They are not allowed to be close to the side of the vessel, and must also be a certain distance above the bottom. This is to protect the tanks in case of grounding or collision. On the other hand, these restrictions are actually not so different from those applying to diesel tanks in new cruise vessels. However, the big challenge for LNG storage comes from the larger size of the tanks. In order to produce the same amount of energy, the volume of LNG is 1,8 times that of diesel. LNG has to be stored at -162OC for it to remain in liquid state, so this requires special tanks with good insulation. This means thicker walls that take up additional space. The most common LNG tank used in existing LNG ferries and supply vessels is a cylindrically shaped, double walled, stainless steel pressure vessel. Thus, the actual volume needed for the LNG storage compartment is about four times that

contact with the ship steel structure.Wärtsilä has also made an alternative

design, with the LNG tanks in the conventional location on the tank top down in the hull. The idea in this case would be to use International Gas Carrier code B-type low-pressure stainless steel tanks. These would be cheaper to buy and would take up less space, as they can be rectangular in shape. However, the current class rules do not yet recognise this type of tank for vessels other than for LNG carriers.

MachineryThe ship machinery consists of six 12-cylinder Wärtsilä 50DF dual-fuel engines in V-confi guration divided into two separate compartments. This gives an installed engine power of 68,400 kW. The propulsion consists of twin FP (fi xed pitch) propellers on shaft lines, each driven by a low speed electric motor.

The Wärtsilä 50DF engine has high effi ciency and can run on either gas or diesel. It uses low-pressure gas and adopts a lean burning process. The air gas mix is ignited by a small pilot fuel injection of diesel oil. The Wärtsilä 50DF engine has already been ordered for more than 52 LNG carriers with a combined

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Fig. 4 – The LNG cruise ship concept design includes a split stern-end superstructure.

Fig. 3 – Methane molecule with four hydrogen atoms for each carbon atom.

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Fig. 5 – Machinery and LNG tanks.

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output of more than 2000 MW. This represents a reliable and well proven solution for future cruise ships.

The LNG is fed from the tanks down to one of two small compartments containing a heat exchanger, which evaporates the liquid to gas, and a gas valve unit for each engine. The gas is led from each valve unit through double wall pipes, directly to each engine. There are no pumps or compressors needed. The gas is fed by the pressure in the LNG tank, which makes for a very simple and reliable system. The pressure in the tank is maintained by evaporating some of the LNG in a separate heat exchanger located in the tank room. In order to heat the LNG, the heat exchangers use a glycol water mix. For improved energy effi ciency, most of the heat is taken from the AC cold water circuit. This will actually provide chilling power for the HVAC system, thereby reducing the AC compressor power demand.

SafetyGas is sometimes wrongly considered to be a dangerous explosive. This is, however, far from the truth. Natural gas is actually a very safe fuel - especially if the installation is correctly designed. The LNG cruise ship concept represents one of the safest, and most reliable cruise ship designs.

The machinery is fully redundant with all systems divided into two or more compartments. Not only are the power generation and propulsion divided into two parts, but so also are the comfort systems. The engine rooms contain gas detectors that will detect even the tiniest gas leak. The ventilation is also increased to avoid any build up of gas. This is in fact, one of the more important features of gas safety principles. There will never be a build up of any large quantities of gas. All gas pipes are double walled or enclosed in a separate duct. The space between the pipes are ventilated and equipped with gas detectors. Any gas detection will lead to an automatic shutdown of the gas supply. The

Fig. 6 – LNG bunkering from a barge.


4,5

4,0

3,5

3,0

2,5

2,0

1,5

1,0

0,5

0,0

Diesel LNG (10 bar)

Energy content equal

Tank room Tank Fuel

Fig. 7 – LNG storage volume.

Volume relative to MDO

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ship will then switch to diesel operation to allow for uninterrupted power supply. Only the amount of gas that is consumed will be evaporated and brought into the engine rooms. The rest will be in liquid form in the LNG tanks located in the separate tank compartment, isolated from any machinery. Safety is also enhanced by the location of the tanks, above the ship and with free access to open air.

A signifi cant advantage of LNG storage is that in liquid form, natural gas cannot ignite. It is simply too cold. Also, when it has evaporated into gas form, it is still very diffi cult to fi nd the right mixture of gas and air to allow it to burn. Furthermore, the ignition temperature of the air gas mix is much higher (600oC) than that of diesel. There are no surfaces in the engine room hot enough to ignite gas. Gas is also lighter than air, so it will quickly disperse upwards in case of a leak. This means that the potential burning matter disappears by itself, unlike an oil leak that will fl ood the fl oor areas and stay there until it is manually removed, or has burned away.

GAS OPERATIONRunning a ship on LNG instead of marine diesel oil (MDO) or heavy fuel

oil (HFO) will mean some changes to the philosophy behind the operation. Gas does not have the same availability as diesel, and the bunkering arrangements need to be thought out in advance.

Availability of gasNatural gas is, nevertheless, available in many places. However, most of the gas is distributed in pipelines and is therefore in gas form. Ships need LNG and this is not available in as many places. Access to LNG is easiest in areas relatively close to LNG receiving and export terminals. Today, there is no existing infrastructure for LNG supply to ships, but it can be arranged with trucks, small LNG carriers and barges. There are a number of LNG terminals close to all major cruise areas. Since a cruise ship would be such a big LNG customer, most gas suppliers would certainly be ready to provide the gas needed. However, the cruise operator would most likely need to make a long- term contract with the gas supplier. This has the benefi t of providing good predictability of coming fuel costs.

Ship performanceThe performance and economics of the

LNG cruise ship have been compared to those of a conventional cruise ship. This comparison shows a slight increase in costs. The larger vessel and the LNG system increase investment costs. On the other hand, the LNG cruise ship has lower fuel costs, partly due to the lower energy consumption. A small increase in ticket rate can still be expected. However, this is very marginal and a small price considering the signifi cant improvement in emission levels. If the alternative would be to switch from HFO to MDO, the cost increase would be signifi cantly higher.

CONCLUSIONSThe LNG cruise ship concept shows that LNG is a very interesting option for cruise ships of the future. It offers signifi cantly lower emission levels that cannot be reached with any other existing technology. The introduction of gaseous fuels calls for some small changes to the ship, but they can be effi ciently handled by applying novel design solutions. In particular, a new location for the LNG tanks high up in the vessel could offer an ultra safe solution. Introduction of LNG as a marine fuel is a big step towards a cleaner and more sustainable cruise business.

Fig. 8 – Emission comparison between a conventional cruise ship and the new ship with dual-fuel engines.

120

100

80

60

40

20

0

HFO DF

% CO2 NOx SOx

CO2 -30%

NOx -85%

SOx -99.9%

32 in detail


Wärtsilä R&D is responding to increasing concern about particulate emissions

Particulate emissions are assumed to be a contributory factor in causing asthma, allergies, and various other human health problems. In the marine industry, abatement remedy choices are limited due to the quality of the typical fuel used. At the same time, the measurement method currently applied by marine legislators, is not adequate to deal with residual fuels.

Campaigners have often cited combustion sources, including diesel engines, as being contributory factors to ill health. In making this claim, they point to the increase in hospital admissions for bronchial infection and disease.

Studies have shown that smaller sized particulates show a stronger correlation between ambient concentrations and health symptoms than larger ones. Smaller particulates are considered more likely to penetrate deep into the human lung. The most minute of these particles may even move into the blood stream. The chemical composition of the particulate may signifi cantly contribute to the biological effect. However, the real mechanism causing such adverse health effects remains unknown.

The particulate is made up of randomly agglomerated carbonaceous spherules, which build up into a highly branched three-dimensional structure. Various hydrocarbons, ash and sulphur compounds are all associated within this structure. Due to the complexity of the particulate, it is impossible to give a satisfactory general defi nition, since the characterization depends, to a large extent, on the measurement method used. It can be defi ned, for example, in terms of opacity, fi lter blackening, particle number, size or mass.

Due to increasing concern regarding

particulate emissions, and with tighter emission regulations anticipated, Wärtsilä is devoting a substantial part of its R&D activities to a better understanding of the subject. This work covers formation and size distributions, the infl uence of engine specifi cation, environmental and biological effects, and other aspects relating to diesel particulate emissions.

Wärtsilä studyIn a study carried out by Wärtsilä, presented at the International Council on Combustion Engines (CIMAC)

in Vienna, in May 2007, it was found that typically between 50 and 70% of the particulate composition consists of compounds that are related directly to the quality of residual fuel oil, i.e. the sulphur and ash content of the fuel, and cannot be reduced by improved combustion. Consequently, typically only about 30–50% of the particulate composition can be affected – thus even a signifi cant improvement in engine combustion will not necessarily result in any major reduction of particulate emissions.

After formation inside the cylinder,

p

AUTHOR: Göran Hellén , Head of Exhaust Emission Control , Engine Performance, Research & Development, Wärtsi lä in Finland

Fig. 1 – Example of simplifi ed number and mass size distributions of particulates of diesel exhaust.

Fig. 2 – An example of typical exhaust particulate composition at high engine loads when operating on high sulphur residual fuel. • Sulphuric acid, sulphates and water

fraction – a result of sulphurous compounds in the fuel.

• Ash – a result of ash in fuel. • Soluble Organic Fraction (SOF) and

Soot – typically a result of incomplete combustion of fuel and lube oil.

10 100 1000

Number distribution

Mass distribution

Particle diameter (nm)

Medium speed diesel(operation on residual fuel oil)

Sulphuric acid, sulphates, water 60%

Soluble organicfraction (SOF) 20%

Soot 10%

Ash 10%

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the nanometre-sized primary particles coagulate to form larger particulates to which are attached, as the exhaust gas cools, hydrocarbons and sulphates.

Secondary particulates can be formed outside the engine combustion chamber as a result of the absorption and condensation processes. This means that the particulate composition and size distribution in the engine exhaust duct is completely different to that reaching the human respiratory tract.

Particulate abatementThe abatement measures for diesel particulates can be divided into three categories – the improvement of fuel and lube oil quality, improvement of the engine combustion process, and exhaust gas cleaning.

Examples of engine measures for improving combustion include advanced fuel injection properties, such as advanced rate shaping with common rail technology, and improved combustion chamber geometry including swirl and squish.

Traps and oxidation catalysts, used for

exhaust gas cleaning in truck engines, are unsuitable for use with residual fuel- operated big diesel engines, due to the high sulphur and ash content of the fuel.

For engines running on residual fuel, an Electrostatic Precipitator (ESP) is a viable option, but their size makes marine applications impractical. While exhaust gas scrubbers are potential options for the future, no demonstrated working solution for the onboard scrubbing of particulates, exists on the market today. The particulates reducing potential of scrubbers is still, therefore, unclear. However, Wärtsilä is currently evaluating such a technology with the aim of introducing it on the market.

Common rail technologyWärtsilä has, nevertheless, already improved the combustion process of its marine diesel engines. Consequently, by improving the fuel injection properties as implemented in the company’s common rail fuel injection engine technology, particulate formation has been reduced, especially at low engine loads. Fuel rate

shaping, increased fuel injection pressure and advanced injection timing are all used.

Whatever methods are favoured by, or indeed available to the ship owner, particulate measurement systems are an inevitable legislative requirement. But there are various methods approved by various administrative bodies, and most of them have widely differing results. Often the results are not comparable, and the establishment of correlations between results is often impossible because emission regulations are based on different measurement methods. This is due to regulators defi ning particulates in different ways.

Measurement challengesThere are several direct measurement methods (without dilution), used for measuring particulates from all types of land-based stationary industrial sources, including diesel and gas engine power plants; the ISO 9096 method; the US-EPA Methods 17 and 5, and US-EPA Methods 201 and 202.

The ISO 8178 method (with dilution) is the standard applied to most marine emission regulations, although it should not be used together with high sulphur fuel.

According to ISO, the sulphur upper limit for application of this method (ISO 8178) is 0.8%, while according to CIMAC Recommendation (23/2005), the upper limit is 0.05%. The dilution conditions are crucial to the measurement result. Various dilution ratios and strategies, dilution air temperatures, and humidities can be used, and all affect the measurement result substantially. The reproducibility of measurement results with the ISO 8178 standard, when operating on typical marine fuels, is often poor. Furthermore, by an improper choice of the dilution and measurement settings within the permitted requirements of the standard, it is possible to manipulate the measurement results signifi cantly. For achieving repeatable results, and enabling comparison of results with land-based stationary industrial sources, Wärtsilä recommends that direct measurement methods are used.

Table 1. – Means to reduce particulate emissions.

Reduction of particulate soot fraction

Increased fuel injection pressure and boost pressureOptimized combustion chamberCommon rail with split injection/ multiple injectionChange to fuel quality with reduced content of aromatics and asphaltenes

Reduction of soluble organic fraction (SOF)

Faster rate of injection pressure decay at end of fuel injection Reduction of leakages from turbocharger turbine seal, exhaust valve guides and fuel injection nozzles

Reduction of particulate sulphuric acid/water fraction

Reduced fuel sulphur contentReduced lube oil sulphur contentReduced lube oil consumption

Reduction of particulate ash fraction

Reduced fuel ash content Reduced lube oil additives (containing ash components)

Particulate exhaust cleaning

Dry electrostatic precipitator (not applicable in marine installations)Scrubber technology (particulates reducing potential is still unclear)

34 in detail


Next steps in exhaust emissions control for Wärtsilä low-speed engines

With the IMO (International Maritime Organisation) emissions control regulations now in force, discussion in the marine industry has turned to the next steps in reducing air pollution from shipping. At Wärtsilä, various emissions control measures have already been developed or are in the course of development, including tuning fl exibility, water injection, exhaust gas recirculation, selective catalytic reduction (SCR), fuel fl exibility, reduced cylinder oil feed rates and high-effi ciency waste heat recovery.

Since May 2005, all sea-going ships built after January 2000 have had to comply with the emissions control regulations set out in Annex VI of the MARPOL 73/78 convention. These regulations set limits on exhaust emissions for nitrogen oxides (NO

X) and sulphur oxides (SO

X).

The NOX limit is set according to a

function of nominal engine speed and SO

X emissions are restricted by a global

cap of 4.5% on the sulphur content of fuel. In addition, fuels with no more than 1.5% sulphur may be used in SO

X emission control areas (SECA).

Work at IMO has since progressed with consideration of the next steps in further reduction of NO

X and SO

X emissions,

together with controls for other engine emissions including carbon dioxide (CO

2) and particulate matter (PM).

The next step to lower NOX emissions

levels is expected for the year 2011, known as IMO Tier 2, and discussions have been started at IMO to defi ne the size of the step. Reductions in NO

X emissions

to between 10 and 30% less than the current IMO limit have been proposed.

A further step, to an IMO Tier 3, is

also being discussed for around 2016, with NO

X levels of 40–80% less than

the IMO Tier 2 limit being discussed.These target maximum emission

levels provide the engine industry with clear objectives on which to focus research and development resources.

The fi rst approach to reducing NOX

emissions is to extend the internal measures that are already employed to comply with the current IMO limit (which can be regarded as IMO Tier 1). These include increased compression ratio, delayed injection timing and adapted exhaust valve timing, as well as different fuel nozzles. The measures are applied in various combinations according to the degree of NO

X reduction necessary for

the specifi c engine type and its rating point. These measures are simple and effective yet have no detrimental effect on engine reliability and have only minimal effect on fuel consumption. Extending these measures as Low-NO

X

Tuning in Wärtsilä RTA low-speed

engines can result in further reductions in NO

X emissions to perhaps 5% below

the IMO Tier 1 limit while incurring a fuel penalty of some 2 g/kWh greater BSFC (brake specifi c fuel consumption).

In Wärtsilä RT-fl ex engines, their electronically-controlled common-rail fuel injection systems are capable of various injection patterns. These can be employed as a Low-NO

X Injection

option which would be expected to reduce NO

X emissions to perhaps 15–

20% below the IMO Tier 1 limit.

‘Wet’ techniquesIt has long been well known that introduction of water into the combustion chamber reduces NO

X

formation. Of the various possible ‘wet’ techniques for doing this, water-fuel emulsion is the longest studied.

Flexibility in engine setting in RT-fl ex common rail engines makes it easier to adapt them to the requirements of emulsions. With the current pumping

p

AUTHORS: David Brown , Manager, Marketing Support, Wärtsi lä in Switzerland. Rudolf Holtbecker , Manager, Engine Perfor-mance Technologies, Wärtsi lä in Switzerland

Fig. 1 – Injection characteristics for three different fuel injection patterns which can be obtained using the Wärtsilä RT-fl ex common rail fuel injection system. In pre-injection and triple injection, the three injectors in each cylinder operate in unison, while for sequential injection the three injectors operate in turn separately.

Pre-injection

-20 0 20 40 60

Triple-injection

-20 0 20 40 60

Sequential injection

-20 0 20 40 60

Needle lift

Pressures:

Fuel rail

Cylinder

Injection

Crank angle, degrees

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in detail 35

capacity in RT-fl ex engines, it should be possible to reduce NO

X emissions to some

20% below the IMO Tier 1 limit.

Direct water injectionAnother technique for introducing water into the combustion process for lowering NO

X emissions is to inject

the water directly into the combustion chamber separately from the fuel. Under development for Wärtsilä low-speed engines since 1993, this direct water injection (DWI) technique directly reduces cycle temperatures and thus NO

X formation. It enables the water to

be injected at the right time and place to obtain the greatest NO

X reduction.

The water is handled by a fully independent, second common rail injection system under electronic control. It offers the possibilities of injecting very


large amounts of water. The quantity of water injected could even be more than 100%, that is a 1:1 ratio of water to fuel.

With DWI, the water and fuel can also be injected with different timings. For example, the water can be injected in parallel with the fuel or before the fuel during the compression stroke. An RT-fl ex common rail engine with DWI could be provided with fuel injection that is optimised separately for when water injection is turned on or off.

DWI has been tested on the full-scale research engine in Winterthur, Switzerland. With about 70% water, DWI has been shown to be capable of reducing NO

X emissions down to around 8 g/kWh,

or to some 50% below the IMO Tier 1 limit. The associated fuel consumption penalty was in the range of 5g/kWh or less.

Although the DWI system operated for

numerous hours on the research engine without problems even when running on heavy fuel oil, the tests were by no means suffi cient for assessing its performance under service conditions. Accordingly, shipboard tests with DWI are to be started in summer 2007 in one cylinder of an 8-cylinder Wärtsilä RT-fl ex96C engine in a containership under normal service conditions. These tests are being carried out under the EU-funded research project HERCULES in collaboration with the shipowner.

Whichever ‘wet’ technique is employed, consideration must be particularly given to the logistics of providing suffi cient fresh water on board ship.

Combining water injection and exhaust gas recirculationAlthough DWI can be applied alone, it can be applied in combination with internal exhaust gas recirculation (EGR), as in WaCoReG (water-cooled residual gas) by which we expect to obtain up to 70% reduction in NO

X emissions below

the IMO Tier 1 limit. This would bring NO

X emissions down to about 5g/kWh.

Exhaust gas recirculation reduces NOX

formation at source by reducing the oxygen available in the engine cylinder and increasing the heat capacity of the cylinder charge. With internal EGR, the purity of gas in the cylinder at the start of compression is decreased by reducing the height of scavenge ports to reduce the scavenge air quantity fl ow.

Internal recirculation normally increases the thermal load of the engine, so water injection is applied to reduce temperature levels, thereby keeping thermal loads much the same as when running without internal EGR.

Selective catalytic reduction (SCR)When reductions in NO

X emissions of

80 % or more below the IMO Tier 1 level are required, the currently available solution is aftertreatment of the exhaust gases by selective catalytic reduction (SCR). This can provide up to 90% reduction in NO

X emission levels.

SCR technology is already well-established, involving the metered injection and mixing of urea solution into the exhaust gas fl ow before the catalyst unit. With low-speed engines, the SCR unit is arranged between the engine’s exhaust manifold and the turbine inlet of p

16

14

12

10

8

6

4

2

00 20 40 60 80 100

NOx emissions, g /kWh

Water/fuel ratio, %

50% NOx reductionachieved

Fig. 2 – CFD simulation of the combustion process with (left) and without direct water injection (DWI) indicates the levels of NOX. These pictures show that the water is sprayed directly into the area of highest NOX concentration. The NOX concentrations are calculated for 12 degrees crank angle after the start of fuel injection.

Fig. 3 – The NOX emissions measured in the Wärtsilä RT-fl ex research engine at one engine load point when using Direct Water Injection for different water-fuel ratios in a common rail system. The testbed results show that 50% reduction in NOX is possible with 70% water.

NO_mass_fraction

2.0e-03

1.5e-03

1.0e-03

5.0e-04

0.0e+00

36 in detail


the turbocharger. This location is chosen to ensure suffi ciently high exhaust gas temperatures for the catalyst process.

At present, SCR is only being applied in special cases. For example, three Ro-Ro paper products carriers delivered in 1999/2000 are powered by single 7-cylinder RTA52U engines equipped with SCR equipment. Their NO

X

emissions are just 2 g/kWh or less.If an RT-fl ex common rail engine is

equipped with SCR then the engine could be optimised for the lowest possible fuel consumption using the full fl exibility of the RT-fl ex concept, leaving the SCR to ensure minimum NO

X emissions.

Reducing SOX emissionsThe only possibilities for reducing SO

X

emissions are either to burn fuels with lower sulphur content or to treat the engine exhaust gases. At present, SO

X

emissions are restricted by limits on the sulphur content of marine fuels. Annex VI of MARPOL imposes a global cap of 4.5% on the sulphur content of fuel and specifi es that fuels with no more than 1.5% sulphur may be used in SO

X emission

control areas (SECA) such as the North Sea, English Channel and the Baltic.

Further global reductions in fuel sulphur content together with further SECAs have been proposed and local emission control limits, such as in the European Union and California, are being imposed. As a solution various bodies have suggested a global switch to distillate fuel for all ships but for both low-sulphur fuels and distillate fuels there are logistics obstacles in the availability of these fuels and limitations in refi nery capacities. Wärtsilä RTA and RT-fl ex engines run satisfactorily on low-sulphur fuel oils (sulphur less than 1.5%) and on distillate fuels.

The use of low-sulphur fuel oil or distillate fuel are preferrable for both DWI and SCR as these NO

X control techniques

are both sensitive to fuel sulphur.The alternative of fl ue-gas scrubbing,

whereby sea water is sprayed into the engine exhaust gases to wash out the SO

X

gases, is being developed by specialist companies and shipboard trials are underway. Flue-gas scrubbing takes advantage of the natural alkalinity of sea water to buffer the acidity of SO

X gases.

In 2006, Wärtsilä initiated a two-year programme to test a scrubbing plant. The project will study the equipment’s

performance in realistic applications, to identify any diffi culties in utilising such scrubbing equipment onboard ships and to design complete exhaust gas cleaning system compliant with IMO requirements and other regulations. The project will investigate the effect of scrubber design on performance, lifetime and economy, the effect of scrubbing equipment on engine performance, installation requirements, discharge water criteria, ecological impact, etc.

Countering global warmingPublic and political attention regarding emissions are now focused on their effect on global warming and the need to counter it by cutting the global emissions of ‘greenhouse’ gases such as CO

2.

The Kyoto Protocol concerning ‘greenhouse’ gases came into force in February 2005. IMO, as the responsible body for shipping under the protocol, is already addressing the subject.

For shipping, CO2 emissions are

a function of the fuel consumed by ships’ engines. Yet shipping is the most effi cient form of transport. It carries about 90% of world trade by volume. At the same time, it has been estimated that shipping generates 1.4–1.8% of world CO

2 emissions.

Over past decades, the shipping industry

has achieved signifi cant improvements in engine fuel effi ciency, propellers and hull designs, and is using ships with larger cargo-carrying capacities. The result has been reductions in both fuel consumption and exhaust emissions with respect to tdw-mile of freight transport.

The gains in transportation economy have been achieved by more than improvements in marine diesel engines. Most has been gained by optimising the ship design and its operation, even the overall transport system. For example, it can be shown that large ships need less fuel to transport a unit of cargo (tdw-mile or TEU-mile) and therefore discharge less emissions. Furthermore large ships can be operated faster than smaller ships for the same fuel requirement in terms of tdw-mile or TEU-mile. Similar benefi ts are obtained in terms of reduced air emissions.

Although signifi cant gains in fuel consumption have been achieved over the years – BSFC has been cut by about 19% over the past 40 years – the laws of physics restrict any further reductions. Though further fuel consumption improvements of a few % may be achieved with large diesel engines themselves, the greatest gains in fuel effi ciency will no doubt be gained, as before, in further improvements in ship design, economies of scale and optimisation of sea transport.

Yet there are two possibilities for making worthwhile improvements in fuel effi ciency and thus emissions – exhaust heat recovery for a Rankine cycle and turbocompound. They are the only technologies that are commercially available today which provide both lower fuel consumption and lower exhaust emissions, including lower CO

2 emissions.

Waste heat recovery with turbocompoundThe High-Effi ciency Waste Heat Recovery system developed by Wärtsilä combines exhaust heat recovery with turbocompound to deliver up to 12% of the engine shaft power as electrical power for shipboard services and additional ship propulsion.

The waste heat recovery (WHR) plant follows the well-established concept of passing the exhaust gases of the ship’s main engine through an exhaust-gas economiser to generate steam for a turbine-driven generator. The quantity of energy that can be recovered from the exhaust gases

p

Fig. 4 – Arrangement of an SCR plant (cylindrical vessel at the top) between the engine’s exhaust gas manifold and turbocharger on a Wärtsilä low-speed engine. This indicates the relative space requirement for the SCR plant.

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gas power turbine, and a shaft motor.These ships have since been surpassed

by the 11,000 TEU “Emma Mærsk” class. They are each powered by a 14-cylinder Wärtsilä RT-fl ex96C engine of 80,080 kW supported by two shaft motors, and have a High-Effi ciency WHR plant with an 8.5 MWe turbogenerator.

For lower-powered vessels in which the payback period for the investment in a full WHR system with shaft motor could not be justifi ed, there is still the possibility of installing a WHR system with turbogenerator to supply only the ship’s services at sea.

For example, a 29,400 kW seven-cylinder Wärtsilä RT-fl ex84T engine in a VLCC could be equipped with a WHR plant able to deliver just over 1000 kWe. This would enable the tanker to operate without running its auxiliary engines while at sea. It would save more than 1400 tonnes of fuel a year, with corresponding savings in all types of air emissions, especially CO

2.

Reduced cylinder lubricating oil usageReduction of the usage of cylinder lubricating oil has been recognised as a promising means of reducing both hydrocarbon (HC) and particulate matter (PM) emissions as it did for automotive engines in cars, trucks, etc.

In the past, the recommended guide feed rate for cylinder lubricating oil in RTA and RT-fl ex engines was 1.37 g/kWh (1.0 g/bhph) though higher feed

is maximised by adapting the engine to the lower air intake temperatures that are available by drawing intake air from outside the ship (ambient air) instead of from the ship’s engine room. The engine turbochargers are matched for the lower air intake temperatures thereby increasing the exhaust energy.

At the same time, today’s high-effi ciency turbochargers have surplus capacity at the engine’s upper load range when matched for ambient air intake. Thus about 10% of the engine’s exhaust gas fl ow can be branched off in a turbocompound arrangement to drive a power turbine which is incorporated in the turbogenerator package.

The overall result of the new concept is that the quantity of energy recoverable in an exhaust-gas economiser and in the power turbine is increased without affecting the air fl ow through the engine. There is thus no increase in the thermal loading of the engine and there is no adverse effect on engine reliability.

The fi rst such plants entered service in six 7500 TEU “Gudrun Mærsk”-class containerships from June 2005 onwards. During sea trials and in operation, the plants’ performances have exceeded expectations. The vessels have 12-cylinder Wärtsilä RT-fl ex96C common rail main engines, each of 68,640 kW output. The heat recovery plant includes a 6 MWe turbogenerator set with both a multi-stage dual-pressure steam turbine and an exhaust-


rates were often employed by ships’ engineers. Then in 2003, after good experience with the latest piston-running design measures, the guide feed rate was reduced to 1.1 g/ kWh, or 0.9 g/kWh with appropriate monitoring. Both recommendations were for engines equipped with the accumulator cylinder oil system that has been long employed in Wärtsilä low-speed engines.

In 2006, the new Pulse Lubricating System (PLS) was introduced which allows guide feed rates to be reduced to 0.7 g/kWh of cylinder lubricating oil. With electronic control, PLS provides more accurate metering and timing, and better distribution of the cylinder oil to allow such lower feed rates.

Measurements have shown that if the cylinder oil feed rate is reduced by 0.8 g/kWh, particulate matter emissions fall by up to 40%, and hydrocarbon emissions by up to 20% at engine full load.

Towards the futureFrom the above developments, it can be seen that we are ready to meet the challenges of reduced emission levels for Wärtsilä low-speed engines. Reductions of about 15% in NO

X

emissions can be obtained by further adaptation of existing internal measures while around 50% reduction can be achieved with more elaborate measures, especially when combined with the fl exibility of Wärtsilä RT-fl ex engines. Yet greater NO

X reductions will most

probably involve SCR aftertreatment. Benefi ts in terms of less emissions will also come from the greater use of low-sulphur fuels and also of distillate fuels such as marine diesel oil though exhaust gas scrubbing is a possibility.

The main contributions to lowering CO

2 emissions will no doubt come

from further optimisation of ships in terms of their design and operation. Yet it must not be forgotten that there will be a signifi cant role for high-effi ciency WHR plants, especially for larger ships which justify the extra cost of shaft motor systems to aid propulsion.

The choice of emissions control measures and technologies applied in future shipping and the speed of their application will be largely dependent upon the new limits imposed in legislation such as IMO amendments to Annex VI of the MARPOL 73/78 convention.

NOx control technologies

NOx emissions, %

Basis, IMO Tuning

Low-NOx Tuning

Low-NOx Injection

Water-fuel emulsion

RT-fl ex + emulsion

Direct Water Injection

WaCoReG

SCR

WHR

-

-5%

-20%

-20%

-30%

-50%

-70%

-90%

-11%

0 20 40 60 80 100

-18 -2 0 +2 4 6 8

NOx

gain BSFC, g/kWh penalty

Fig. 5 – Summary of typical changes in NOX emissions and specifi c fuel consumption (BSFC) for various emissions control technologies.

38 in detail


The fi rst stage in the development process was to analyse those factors that had an impact on the life of the seal ring, in order to identify performance targets for the new seal system. The analysis focused on the following critical factors:

n Contact with water or contaminated oil,n Peripheral speed,n Radial load,n Heat radiation,n Foreign objects.

As a result of this work, the concepts for the Airguard system were identifi ed as follows:n Complete separation of the oil and

seawater to be achieved by providing an air seal chamber in the aft seal.

n A consistent radial load on the seal rings to be achieved via automatic pressure control from an air control unit, which by regulating the pressure in each of the aft seal chambers, provides a constant rate of airfl ow.

n Inboard collection of automatically drained water and/or oil from the air chamber.

n A maintenance free operation with simple troubleshooting measures.

With the Airguard system, compressed air is blown into the air chamber between

The Airguard seal system continues to be upgraded, even after 20 years

The Airguard oil-pollution-free seal system was originally developed some 20 years ago. It came as one of the company’s many responses to the environmental regulations and restrictions that have continued to affect the marine sector since the 1980s. The fi rst Airguard system was installed in 1988. Market demands, however, continue to change and so development work continues.

p

AUTHOR: Andy Edwards , Regional Sales Manager for Northern Europe, Seals & Bearings, Wärtsi lä in the U.K.

Fig. 1 – Airguard 4AS-B aft seal assembly.

Fig. 2 – Pressure balance of Airguard 4AS-B and 3AS.

4AS-B 3AS

about 0,015MPa

about 0,015MPa

4AS-B’s Oil pressure in #2-#3 seal chamber is about 0,015MPa higher than 3AS’s oil pressure

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Spacer ring

#2-seal ring

Holes for air supply and drain#1-seal ring

#0-seal ring

P-ring

Air escaping holes

in detail 39

the typical piping diagram for the 4AS-B.With the 3AS-B, the sealing system

is more simplifi ed. Instead of the closed system, pressurised oil tank, an open system with a gravity tank is employed as in conventional seal systems. The structure of the aft seal unit for the 3AS-B is exactly the same as with the original 3AS. The pressure balance of the 3AS-B and a typical piping diagram are shown in Figure 4 and Figure 5 respectively.

The advantages of the 3AS-B sealing system over that of the 3AS system are as follows

n Open circulation system for the sterntube oil.

n The pressurised oil tank is not required.n Checking and adjusting of the

sealing system’s pressure balance is no longer necessary.

against oil spillage. All seal rings run on a shaft liner to avoid grooving and wear to the propeller shaft. The seal is supplied as a cartridge, which includes the shaft liner, and is ready for installation without need of any further assembly work.

Other than the additional seal ring on the aft side, the 4AS-B system is essentially very similar to the original 3AS. However, the fact that the system now has two seal rings to the seawater side means that there is greater reliability in resisting foreign particles, such as sand and shell fragments. Seal performance life is also extended. Normally, the #3 seal ring is stored as a spare seal for the #2 seal ring due to continuous oil fl ow under the lip, which is the same as in the 3AS.

The structure of the aft seal on the 4AS-B, and the pressure balance in the seal and sterntube are shown in Figure 1 and Figure 2 respectively. Figure 3 illustrates


seal rings #2 and #3, at a pressure slightly greater than that of the exterior seawater. The differential pressure between the air in the air chamber and that of the seawater is automatically maintained at a constant level by a fl ow controller located in the engine room. Air fl ows into the seawater underneath seal rings #1 and #2,causing these lip rings to be raised slightly from the liner. This results in greatly reduced wear to the seal ring and liner. As a function of the air pressure in the air barrier chamber, the sterntube oil system is maintained at a slightly higher pressure than the air pressure. Therefore, under all conditions – including loaded draught, ballast draught and heavy waves, the optimum lowest operating pressures for the entire system are maintained.

Since its fi rst installation in 1988, the exceptional reliability of this Airguard 3AS sealing system has proven itself with more than 600 installations on many different types of vessel. This performance reliability also made it suitable as the seal device for the contra rotating propeller (CRP) propulsion system, with which VLCCs are equipped. In this application, the seal unit consists of two parts; the sterntube seal and the contra rotating seal, and must be capable of operating under very severe conditions. The liner is mounted on the forward propeller, and the seal casing on the aft propeller. Thus the liner and seal casing rotate in opposite directions, resulting in a higher sliding speed between the lip seal rings and liner, and in greater eccentricity than is possible with conventional seal devices.

The 4AS-B and 3AS-B sealing systemsNevertheless, market demands for cost reductions and system simplifi cation, together with the fact that container ships are being built with ever-increasing load capacities, meant that development work on the Airguard system has been ongoing. The 4AS-B and 3AS-B sealing systems are a result of this continued development work.

By adding an extra lip seal to the seawater side of the 3AS, even greater reliability has been made possible, a fact that has been proven in endurance tests. This is the basis of the 4AS-B system, whereby the seal arrangement has two lip seals facing and sealing off the seawater side, and two others facing the sterntube oil side to provide active double security

Fig. 3 – Typical piping diagram of Airguard 4AS-B aft seal.

L.O. tank unit

Air

Oil

Slight amount of air is leaked from here.

Air control unit

Float switch

Air source(Control Air)

Needle valve Stern tubeL.O. pump unit

Draincollection unit

Pump

Filter

Flow meter

Cooler

Stern tube

Aft seal

p

40 in detail

[ MARINE / IN DETAIL ]p

With this simplifi ed system, although the air pressure changes according to the seawater pressure as with the 3AS, pressure control of the sterntube oil has been eliminated and the oil circulation is now a constant pressure system. Therefore, the differential pressure of the #2 seal ring changes with the change in draft. The performance of the 3AS-B seal in dealing with the changes in differential pressure has been verifi ed in rotation tests.

In the case of the 3AS-B system, the limitation for draft changing is below 5m, as indicated in Table 1, while the circumferential speed at the seal sliding area is required to be below 6m/sec, as shown in Table 2.

There are, therefore, three types of Airguard sealing system currently available; the 3AS, 4AS-B and 3AS-B. Depending upon the required specifi cation, the particular Airguard type needed can be selected by using Table 3, although it should be noted that the 3AS and 4AS-Bare suitable for all types of vessel.

Fig. 4 – Pressure balance of Airguard 3AS-B. Fig. 5 – Typical piping diagram of Airguard 3AS-B aft seal.

about 0,015MPa

L.W.L.

B.W.L.

#15/R #25/R #35/R #45/R #55/R

Differential pressure of #2 seal ring changesdue to the change in draft.

Range of ship draft 3AS, 4AS-B 3AS-B

Change below 5m A AChange more than 5m A N.A.

Table 1. – Suitable condition 1: Range of draft changing on ship.

Max. Liner rotation speed 3AS, 4AS-B 3AS-B

Below 6m/s A AMore than 6m/s A N.A.

Table 2. – Suitable condition 2: Liner rotation speed.

A: Available N.A: Not available

Type of ship 3AS, 4AS-B 3AS-B

LNG / LPG CARRIER A AVLCC / ULCC A N.A. *1

TANKER 50,000 DWT A ACONTAINER CARRIER A N.A. *CAR CARRIER A AREEFER A ABULK CARRIER >50,000 DWT A N.A. *1

BULK CARRIER 50,000 DWT A APRODUCT CARRIER A ARO-RO A ACHIP CARRIER A A

Table 3. – Referable guidance for selection of Airguard system.

<=

<=

A: Available N.A: Not availableA*: Available with draft changing below 5m

*1 : Draft changing more than 5m

Air control unit

Stern tubeL.O. gravity tank

Float switch

Air

so

urc

e(C

on

tro

l Air

)

Needle valve Stern tubeL.O. pump unit

Draincollection unit

Pump

Filter

Stern tube L.O. sump tank

Flow meter

Cooler

Stern tube

Aft seal

Air

Oil

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in detail 41

Automation capturing the market

It was in 1946 when Aker Kvaerner Power and Automation Systems (AKPAS) established its fi rst electrical workshop in Norway. The company soon became a major supplier of electrical products to the local shipbuilding community. It also absorbed the development into automation technology, a process that has gained increasing acceptance within the marine and offshore industries since the 1980s. Today, automation technology is an instrumental part of all shipbuilding and offshore activities.

Wärtsilä’s evolvement into a total systems solution provider gained pace with its March 2006 acquisition of AKPAS. During that same year, the company also formed an alliance with Emerson Process Management, and these two moves have fi rmly established Wärtsilä as a total systems supplier and integrator.

From its factory in Stord, Norway, Wärtsilä has delivered a range of power distribution systems for large oil tankers, and has been instrumental in developing a variety of systems and solutions during the 30 years since the arrival of automation technology. In the 1990s, the activities were developed to deliver more complete power and automation solutions to both the ship and offshore segments. Vessel control systems were introduced to meet a burgeoning demand in the ship sector, while the decade ended with the development and delivery of fl ow line electric heating systems to the offshore industry.


AUTHORS: Arne Birkeland , President, Wärtsi lä in Norway and Ove H. Wilhelmsen , General Sales Manager, Wärtsi lä in Norway

p

Wärtsilä’s evolvement into a total systems solution provider gained pace when it in March 2006 acquired Norwegian company Aker Kvaerner Power and Automation Systems. The company’s latest automation systems for ships and offshore applications, are serving to continue a long tradition.

The automated centuryReal advances in automation systems technology, however, have been witnessed during this fi rst decade of the 21st century. Wärtsilä has continued to play a leading role in this development with, for instance, a series of low voltage frequency converters and variable speed drives designed to meet environmental and performance related targets. The innovative Low Loss Concept (LLC) for diesel electric propulsion systems (see separate article on page 43), is one such prime example.

Developed in close co-operation with ship owners and designers, the patented LLC offers a low voltage system with high effi ciency, enhanced redundancy, and very few components. Thus, instead of a typical 6.6 kV medium voltage power generation and distribution system, a 690 V low voltage LLC would negate the need for large propulsion transformers.

The concept also benefi ts from low harmonic distortion, high redundancy and increased safety, so that in the case of failure in one of the switchboard segments, all propellers would continue to turn. Additionally, for a 22 MW power system all components, except for generators and motors, can be placed in a central switchboard room to free up more space for cargo, tools and equipment. LLC can also be applied to FPSOs, offshore platforms, and drilling rigs.

Strategic allianceThe company’s strategic alliance with Emerson Process Management has enabled Wärtsilä to increase its scope of product offerings. Global marine, as well as offshore oil and gas customers, can now be supplied with complete integrated systems covering power distribution and automation, detailed engineering, electrical analysis and equipment.

Wärtsilä can now also supply the market with high-performance power plant and process automation systems that incorporate leading technologies from both companies. Dedicated engineering teams are able to develop turnkey solutions

Fig. 1 – The Aker H6-e is the world’s largest drilling rig.

42 in detail


by collaborating throughout the entire chain, from front-end engineering and design (FEED), through to commissioning and operation. The delivered solutions can include diesel and dual-fuel engines, generators, power distribution systems, electrical drives, thrusters, motor control centres, and safety and automation systems including metering, valves and instrumentation of the complete vessel.

Through combining the inherent know-how and experience of the two companies, FPSO project owners can now receive project management and system integration services that minimise their schedule and integration risks.

FPSO ConversionsThe fi rst collaborative project of the alliance was for the FPSO BW Enterprise of BW Offshore. The work involved power distribution with high- and medium-voltage motor control centres, safety and automation systems including digital process automation, metering stations, instruments and valves. Additionally, Wärtsilä has developed integrated solutions for FPSO conversions, such as the Siri FPSO project, and has cultivated a unique range of products and core technologies for power applications with integrated control systems.

The ability to supply a complete system, including FEED studies and project execution, from a single source is a considerable advantage,

p

particularly in fast-track projects.

One project, one companyFor extensive and engineering-intensive projects, where 30,000 engineering hours are the norm, Wärtsilä will provide an integrated engineering team to install, integrate, interface, and commission all safety, automation, power generation, and distribution systems and fi eld equipment. The company is capable of managing the entire project, from feasibility concept through to asset management and optimisation.

For integrated system solutions, deliveries include generators, UPS systems and electrical motors from third-party vendors, as well as the automation systems for ballast, cargo, power management, fuel oil consumption, sea and fresh water cooling, heavy fuel oil transfer, lube oil and other necessities. The customer, however, does not need to be concerned with interfaces, since all systems are integrated and based on the same integrated automation systems (IAS) technology. Customers need to deal with only one supplier, which simplifi es and speeds up the entire project.

For example, MPF Corporation contracted Wärtsilä to supply and manage the integrated system project for its new multi-purpose fl oater. The scope of supply is extensive: eight 7200 kVA diesel engines and generators; eight 5500 kW thrusters; electrical engines and VSDs; a complete

power distribution system, including 11 kV low voltage switchgears; distribution boards, transformers and UPS; an integrated control system, emergency shut down system (ESD), fi re and gas system (F&G), dynamic positioning (DP) and thrusters control; plus all commissioning and start-up routines.

Linking solutionsWithin an integrated Wärtsilä automation package there are several levels of functional complexity. The simplest is an alarm and monitoring system, which is essentially an extended part of the engine and propulsion control system. This allows classifi cation requirements for the supervision and monitoring of critical components, to be met.

Functionality can be developed into a fully integrated automation system, including tank level monitoring, cargo handling, pump control, fi re protection systems, cooling systems, bridge alarm supervision, and power management.

Power managementThe power management system (PMS) is really a group function that comprises the control and surveillance of electrical power production and consumption. It is a separate system, but can also form part of the vessel’s automation system. This allows for a number of possibilities to integrate various dedicated control systems from third-party suppliers, such

Fig. 2 – The Multi Purpose Floater (MPF) is a new and unique concept for oil & gas exploration and fi eld development.

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REFERENCES PSV VIKING GAS AVANT | NORWAY


as DP, navigation and communication.The integrated automation system is an

overall vessel automation system (VMS), which enables the operator to have access to, and supervision of all systems onboard, from one single interface.

Remote input/output units and local controllers can also be installed in the switchgears communicating with the PMS controllers, so that in the case of a system blackout, the PMS provides a blackout restart of generators, and restores power with minimal downtime.

When Norwegian shipowner Eidesvik Offshore takes delivery of its PSV Viking Gas Avant from the Westcon shipyard at Ølen, in southwestern Norway later this year, it will be the fi rst LNG-vessel to utilize Wärtsilä’s novel Low Loss (LLC) propulsion concept.

Eidesvik Offshore, a major Norwegian shipowner, has fi ve ships under construction as part of an extensive fl eet renewal programme. The shipowner expects to take delivery of the fi rst vessel in the series, the Viking Gas Avant, from the Weston shipyard in September 2007.

The Viking Gas Avant newbuild will combine four 2010 kW 6-cylinder in-line Wärtsilä 32DF dual-fuel engines. Viking Gas Avant will be an LNG-powered vessel with a strong environmental profi le. For instance, it will utilise Wärtsilä’s selective catalytic reduction technology to reduce emissions, even at engine loads above 28%. Additionally, the clean effi ciency of the dual-fuel engine and the use of gas as a fuel, will reduce NOX emissions by up to 75%. The four Wärtsilä 32DF engines will also afford a 20% reduction in CO2 emissions.

Additionally, the ship will be fi tted out with an electric propulsion and advanced vessel automation system designed to save fuel and installation costs, reduce the amount of space required for component installation, and deliver greater redundancy.

“One example of the savings is that traditionally you need many large transformers. But our system eliminates the transformers in the propulsion lines, thus negating the need for huge and heavy components, as well as their associated

equipment and utilities. This reduces investment costs, operational costs, and the space required for the equipment onboard,” says Projects and Operations Director of Wärtsilä in Norway, Arne Stenersen. Since there are no transformers/converters in the propulsion spaces, more cargo space is available.

In a traditional system the propulsion drives consist of transformers, variable

speed drives, and electrical motors. The purpose of the transformers is to establish an electrical phase shifted input voltage to the variable speed drive, in order to reduce the overall total harmonic distortion (THD) of the system.

In a conventional system, each propulsion line needs a transformer that is sized for maximum propulsion power, but the LLC combines the phase-shifted windings, and establishes an electrical phase shift between the switchboards by the LLC-unit. The propulsion lines are supplied from each side of the LLC-unit, and the THD is below 5%. The two LLC-units supply all propulsion units, as well as the 450 V system.

In the case of main switchboard failure,

normally half of the propulsion power will be out of operation. The Wärtsilä LLC, however, has a ring feeding switchboard so that only 25% of the power and all propellers can continue to turn. The main power to the propulsion motors is supplied directly from the generators to the variable speed drives, thereby reducing losses by 10-15%.

Due to the short circuit limitation capabilities of the LLC-units, more power can be produced and larger propulsion lines can be supplied by the system.

Vermund Hjelland, Director – Technology & Development, Eidesvik Offshore ASA, explains that the concept was selected for its effi ciency. “We can reduce electrical losses by 3%, and this means good fuel savings and less pollution,” he says. “The system also provides improved HSE performance through fewer components, lower pollution, and higher system redundancy”.

Ostensibly, the concept challenges traditional methods and designs of electric propulsion systems. This is because of its greater appeal in having fewer components, lower losses, higher redundancy, and being easier to install and operate. Wärtsilä can also provide low-voltage systems for propulsion systems up to 30 MW, and a medium-voltage system where preferable or necessary.

Wärtsilä is currently working on a number of FPSO, drill rig and supply vessel contracts, almost all of which will be installed with electric propulsion, power distribution and automation systems from Wärtsilä.

Offshore automationIn addition to the VMS that Wärtsilä delivers to the shipping sector, the company also offers process automation and safety automation systems to the oil and gas sector. For this latter application, an added safety automation system (SAS) is included. A PMS and a power distribution control system (PDCS) used by the electrical operators of an oil and gas unit, are part of the package, and are designed to provide the capability of controlling, operating and

maintaining all electric consuming units.The SAS includes features, such as

emergency shut down; process shut down; fi re and gas; process control; valve, measurements and metering. It normally interfaces with drilling operations, thrusters control, DP, telecommunications, and other utilities. All VMS are supplied with web technology developed by Emerson/Wärtsilä, known as Delta V, to offer a ‘total’ automation system on a common technology platform.

EIDESVIK OFFSHORE GEARING UP FOR LOW LOSSES WITH VIKING GAS AVANT

44 in detail


Smoke-free cruisingThe 294 meter long M/S Coral Princess spends the winter season in the Caribbean, before sailing the

waters of Alaska and the west coast of the USA from May to September. Here, environmental restrictions can be demanding, and in Alaska a smoke-free operation is mandatory.

The 1970 passenger Coral Princess has been in service for about four years. Her two 16-cylinder, Wärtsilä 46 common rail (CR) engines in V-confi guration have now accumulated more than 30,000 running hours each. In addition to the M/S Coral Princess, there are today seven cruise ships in operation using Wärtsilä 46 CR engines, and one of them is the famous and elegant Queen Mary II.

p

AUTHOR: Arne Lundkvist , General Manager, Technical Services Network Companies, Wärtsi lä in Finland.

Fig. 1 – The M/S Coral Princess is powered by two 16-cylinder Wärtsilä 46 common rail engines that have already accumulated more than 30,000 running hours each.

Smokeless operation has rapidly become a requirement for marine vessels, especially for cruise ships. Just prior to Christmas 2002, a new cruise ship was delivered from the Chantiers de l’Atlantique shipyard in France with the fi rst smoke-free diesel machinery. How are the common rail engines doing today?

Introducing new technology is always demanding. This is especially so for a cruise ship where the demand on the availability and reliability of the machinery is high. However, as a result of several years of experience with numerous installations, we can attest that both the availability and reliability are extremely high on all Wärtsilä CR engines.

Smoke-free engine operation was already achieved at the engine factory tests using both FSN and Ringelaman measurements. Nevertheless, although the engine settings had been tested and tuned to smoke-free operation on all loads during various

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Common rail engine – how are you today? Wärtsilä medium-speed common rail engines exceeds 540,000 running hours

in detail 45


laboratory tests, under certain operating conditions, the fuel used in the Caribbean area was still causing visible smoke.

However, thanks to the customised setting engine tuning features of the CR engine, by simply changing a few parameters within the engine control software, the problem was overcome and operation using Caribbean fuel types was also made smoke-free.

Last but not least, the reliability and the lifetime of the components are today well on a par with a conventional diesel engine.

Experiences with Wärtsilä 46 CR fuel injection equipmentThe common rail is built using one accumulator per two cylinders. The accumulators are connected to each other with small-bore pipes to eliminate pressure waves in the rail. All visual leak indicators are also integrated into the accumulators. Except for some minor leakages in the beginning, the accumulators have performed very well.

The fuel injection pump is operated by a double cam. Each fuel pump feeds one common rail accumulator, while the fl ow to the pump is controlled by a fl ow control valve. Cavitation is sometimes a risk in any fuel injection pump, especially with newly-introduced designs. The simplifi ed fuel pump element used in the common rail pump has, however, been totally free from cavitation from the very beginning. This has also been verifi ed in all pump service inspections.

Based on our experiences so far, the

service lifetime of the common rail injection pump is expected to be far longer than for a conventional pump. Figure 2 shows a pump plunger at the 24,000 hr inspection. No cavitations or any wear could be detected when making measurements and inspections. The pump tappet is of a proven design, and has been used for many years in conventional fuel injection pumps. It has also worked exceptionally well with common rail injection pumps.

The common rail fuel injection valve is perhaps the most important part of the common rail injection system. The common rail system is designed with a triple function to prevent fuel entering the combustion space when it should not. The three step function includes: 1) the nozzle seat, 2) the shuttle valve and 3) the fl ow fuse.

Initially, the lifetime expectancy of the shuttle valve seat gave cause for concern. The material used at that time was hardened steel, and because of that choice of material, there was a certain amount of fl ow erosion. Although the seat maintained its functionality, the gradual erosion of material led us to conclude that its lifetime was not acceptable. Today the seat is made of tungsten-carbide, and this design more than meets lifetime expectancy criteria.

Upon inspection following 9221 running hours, the latest design version of the shuttle valve has been found to be in excellent condition, see Figure 3. The injection nozzle is also in excellent condition with no cavitations found during

inspections. The service interval and the lifetime of the nozzle are also longer than for conventional equivalents. See Figure 4.

Experiences with engine control and automationThe automation system used for current Wärtsilä CR engines comprises an injection and rail pressure control system, which is incorporated within the standard engine alarm and monitoring system. Thus this automation package is also easy to install on existing engine retrofi ts, as are too the fuel injection components.

Surprisingly, the major challenges with the fi rst versions were cable and connector problems on the so-called manufacturing friendly cable harness system. This cabling system was swiftly replaced with a more traditional point to point type of cabling that withstands oil-, heat-, and mechanical stress. This cabling uses as few connectors as possible.

Today, our policy is also that military type connectors should be used only where service friendliness is seen as being as important as reliability. Therefore, engine speed and engine phase detection sensors, the fl ow control valve-solenoid, common rail pressure sensors, and the common rail pressure relief/safety valve solenoid are connected directly to the input/output in the control modules. Hence there are no vulnerable connection points, and the Electromagnetic Compatibility (EMC) type of metal cable glands at each cable provide excellent disturbance protection. Sensor reliability has been infl uenced by problems related to previously used connectors. In short, very few common rail related sensors have failed.

The most vulnerable part in the electronic system has, as expected, been the drive electronics, i.e. the injector solenoid control module that uses high current/high voltage. The high electrical current required by the fi rst generation injector solenoids as used on the Wärtsilä 32, decreased the lifetime of the drive electronics. The cylinder control module that we use today is performing well. This we achieved after lowering both current levels of the Wärtsilä 32 injectors, and increasing the current limits of the output stage electronics.

Engine operators are provided with a high performance tuning and troubleshooting tool: the WECSplorer. With WECSplorer, engine parameters are p

Fig. 2 – A pump plunger at the 24,000 hr inspection with no detected cavitations or wear.

46 in detail


made accessible for performance tuning, as for example, in exhaust temperature and cylinder pressure balancing. If there is a need for troubleshooting, a parameter trending capability down to millisecond level can be made, which facilitates tracking of fast events.

The tool also provides full control over software/parameter backup. Since the latest and most accurate software is downloaded to a new onboard spare part module, fl exible spare part handling is made possible. If technical assistance is needed, WECSplorer recorded data packages can easily be exported and sent to Wärtsilä for evaluation and remote troubleshooting. Remote online connection is also possible over Ethernet/LAN connection.

The fl exibility of the computer control system allows easy use of different running parameters for different fuels, and for operation in different ‘multiple map’ areas.

Engine availability and performanceCruise ships operate in very demanding environments, regardless of whether we look at it from an availability and reliability point of view, or from an exhaust gas emission point of view.

With twin diesel electric machinery and one gas turbine, the cruise ship Coral Princess, like its sister ship the Island Princess, requires high reliability and

availability of the diesel engines, especially with rising fuel prices. The diesel engines are used for all cruising operations, and are supplemented by gas turbine power when high cruising speeds are required. Typically the diesel engines accumulate more than 7000 running hours a year.

The engines are operating well below the primary target of the exhaust gas smoke level, ensuring a smokeless start-up and operation under all loads.

Wärtsilä common rail engine portfolio in service Today the common rail technology is available in both medium- and low-speed Wärtsilä engines, with the medium-speed engines being the Wärtsilä 20, Wärtsilä 32, Wärtsilä 38, and the Wärtsilä 46 types.

Wärtsilä 32 CR engines are installed in different types of ships, for propulsion in smaller vessels and as auxiliary engines in the large ships such as containerships, tankers and others. The fi rst Wärtsilä 32 CR engine was installed as an auxiliary engine in the containership M/S Axel Maersk in 2003. This auxiliary engine has today logged more than 13,000 running hours. The Wärtsilä 38 CR can be found as main engines in cruise ships and yacht carriers. The latest addition to the Wärtsilä CR engine portfolio is the Wärtsilä 20 engine, the fi rst of which will

begin operating as an auxiliary engine, parallel to the Wärtsilä 38 CR main engines, in a yacht carrier later this year.

Altogether, 42 Wärtsilä common rail medium-speed engines are currently in operation, and have accumulated more than 540,000 cumulative running hours.

Reliable technology supported by a dedicated service networkThe common rail technology is now well established on the marine market. Wärtsilä CR engines have also been selected in the building of a number of new vessels during recent years. While most have been cruise ships, other types of vessel are also increasingly turning to this technology. Special tools and test benches have been developed to facilitate common rail maintenance.

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Fig. 3 – The latest design version of the shuttle valve is in excellent condition after more than 9220 running hours.

Fig. 4 – The service interval and lifetime of the CR nozzle are longer than for conventional equivalents.

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In fact, while traditional fuel valve opening is simply controlled by a set spring, operated by the peak fuel pressure from the fuel pump, in a common rail (CR) engine the fuel valve is a complex component, the opening of which is controlled by a digital control system (WECS 7500 or UNIC C3). It is also possible to continuously set the injection timing and duration depending on the engine speed, load, and other parameters in order to optimize engine performance and emissions. Therefore, the traditional fuel valve test benches, utilised for any engine type and brand, cannot be used for this specifi c CR engine. Hence the need for a new generation of innovative maintenance tools.

Wärtsilä Services fi rst designed and tested a preliminary experimental prototype, which was then further developed into an integrated and compact test bench, paying particular attention to ease of operation and installation, in selected Wärtsilä Services workshops.

The test bench is made up of three units, the driving and testing unit, the control cabinet with measuring unit, and the hydraulic unit. It can operate with both 50 and 60 Hz power supply. Wärtsilä 46 and Wärtsilä 38 CR fuel pumps, fuel valves and fuel accumulators can be easily tested on the bench, and are fi tted to it by means of a complete set

Common rail technology calls for dedicated test bench

of adaptation kits and cams. Additional kits are under development to extend the bench operation for the entire range of traditional medium-speed Wärtsilä engines fuel pumps and fuel valves as well. One of the advantages of the Wärtsilä Services bench is that fuel valves can be tested using exactly the same control as the one fi tted on the engine, i.e. WECS 7500 and not a generic bench digital control.

The fi rst two benches are already in operation in Wärtsilä workshops in Fort Lauderdale (USA) and Trieste (Italy). This supports the maintenance needs of Carnival Corporation fl eet ships. Other locations will be fi tted with the bench starting with one in Wärtsilä in Germany and one in Wärtsilä in Korea.

Further development of a high-technology adaptation kit is already underway in Italy to test Wärtsilä low-speed RT-fl ex engines fuel valves as well.

AUTHOR: Guido Barbazza , Vice President, Services, Wärtsi lä in Italy

The delivery of the fi rst Wärtsilä common rail engines (Wärtsilä 46 and Wärtsilä 38) and the subsequent engine base growth, has highlighted the need for a new service and maintenance concept for common rail components and devices, for which the traditional way of working, its procedures and tools, are not suitable. One need was related to the maintenance and testing of the fuel valves.

Fig. 1 –The new fuel valve test bench driving unit.

Fig. 2 –Operating the test bench.

48 in detail

Compared to the indirect measurements of a conventional oil mist detector, direct continuous monitoring of the crankpin bearing temperature permits earlier detection of crankshaft malfunctioning. This prevents major failures to these critical, high cost engine parts, protects against direct consequences on the operational availability of the engine, and avoids extra costs related to unplanned expensive maintenance operations. To be able to continuously detect and monitor the temperature of rotating crankpin bearings in an accurate and reliable


Engine safety enhanced with wireless temperature monitoring

manner, special technologies that had not been previously developed satisfactorily for diesel engines, are required.

Wärtsilä has recently developed such technology, and an innovative wireless temperature-sensing device is currently being promoted and installed by the company. The operating principle of this system is to directly measure the temperature of the connecting rod big end bearing using a temperature sensor fi tted as close as possible (within a few mm) to the bearing surface.

This temperature monitoring system is based on patented, Surface Acoustic Wave (SAW) radar technology, which has been proven to be the most reliable technology for real-time wireless temperature monitoring. The Signal Processing Unit (SPU) generates a radio wave pulse, which is picked up by the stationary antenna.

This then converts the radio wave into an acoustic wave, and sends it to the rotating sensor. This acoustic wave propagates along the surface of a SAW chip fi tted with multiple refl ectors, thus permitting the sensor to refl ect a pulse train; the time delay between echoes depends on the temperature of the SAW chip.

The wireless temperature sensors are installed in the rotating connecting rod big end. The stationary antennas are screwed to a custom designed bracket fi xed inside the engine block in such a way, that the sensors and antennas pass within a fi xed distance of each other at each rotation of the engine crankshaft.

The signal is then transmitted via a thin cable passing through the engine block, to the SPU fi xed to the engine, and from there to the control room cabinet placed in the engine room.

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AUTHOR: Lenardon Lorella , Special Projects, Services, Wärtsi lä in Italy

Recently developed technology has enabled Wärtsilä to introduce wireless temperature-sensing capabilities that can signifi cantly lower maintenance and repair costs.

Fig. 1 – Wireless temperature monitoring enables continuous measuring of the crankpin bearing temperature.

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Alternatively, it can also be connected to the main automation system.

Under normal operating conditions, the temperatures of the crankpins and connecting rod big end bearings vary within a specifi c value range, which is determined for each installation. A temperature increase is therefore signalling the beginning of a malfunction.

Thanks to the wireless temperature monitoring system, it is now possible to measure in real time the temperatures

with high precision. This allows any temperature increase of specifi c bearings to be monitored, and for the alarm to be raised so that the engine can be slowed or shut down before the deviation from predefi ned values leads to failure or breakdown.

Grimaldi Group in Naples goes for WärtsiläThe Grimaldi Group in Naples, one of Italy’s most important ship owners, has

for the past fi ve years, been operating a management and maintenance strategy policy of prevention and safety as regards the propulsion systems of its fl eet.

In spring 2006, the Grimaldi Group decided to install a Crankpin Wireless Temperature Monitoring System to one of the 12-cylinder, in V-confi guration Sulzer ZA40S main engines powering its “Eurostar Roma” ferry. The purpose was to test this prevention device and its ability to detect in advance possible failures of the engine crankshaft bearings and related components. Following successful completion of these tests in summer 2006, the Grimaldi Group made the decision to install the wireless system to “Eurostar Roma’s” other three Sulzer ZA40S main engines. The system was also installed on the two 8-cylinder, in-line Sulzer ZA40S engines on the company’s “Fides” and “Spes” vessels.

The preparatory work for the installation of the wireless system includes drilling the engine block, installing the antenna support, and drilling the connecting rod big end upper part in order to install the sensors. Wärtsilä’s knowledge of the design and vibration behaviour is critical for the determination of the position and characteristics of the hole.

The best time to perform work on the connecting rod big end is during a major overhaul when the dismantled

Fig. 2 – Installation drawing showing wireless sensors fi tted within the crankcase.

Fig. 3 – Big end bearing wireless sensors and their fi xture bracket.

p

50 in detail

[ MARINE / IN DETAIL ]p

connecting rod big ends can be drilled or replaced with ready-drilled new ones. The installation of the wireless system on the Grimaldi Group vessels was planned and executed during scheduled overhauls, and according to the specifi c needs and schedules suitable for each vessel.

For Grimaldi’s M/V Spes, the work was executed in two phases. The drilling of the connecting rod big end upper part and the engine block was completed during dry-docking, while the installation and commissioning of the wireless system was carried out at sea.

Taking advantage of Wärtsilä’s large service network, the fi rst phase was carried out by Wärtsilä in Greece. The drilling of the connecting rod was done in the workshop, while the drilling of the engine block was carried out onboard during the ship’s overhaul.

The dry-docking was carried out as planned, and Grimaldi’s M/V Spes was again ready for sailing as scheduled by the customer.

On the engine of Grimaldi’s “Eurostar Roma”, the connecting rod big ends were replaced with new ones already drilled. The remaining part of the job was carried out at sea or during operative calls. Other installations of wireless temperature monitoring systems are planned by Wärtsilä in Italy during this current year. Some will be carried out using an exchange set of connecting rod big ends during fast stops.

The versatility of Wärtsilä Services allows customers to easily install the latest technologies without hindrance to operating schedules.

Retrofi t packages, for which many customers including the Italian Navy have expressed interest and commitment, will soon be available as well for GMT 420 and 230 engines. Within Wärtsilä, wireless temperature monitoring of big end bearings is available for a wide range of engine types (see Table 1) for both marine and power plant installations. Although the operating principle is the same for all engine types, the sensors and their positioning, the antenna supports inside the engine block, and the vibration stability are specifi cally designed and checked for each engine type.

Fig. 4 – Detection times of crankpin failures by temperature monitoring and oil mist detecting.

Fig. 5 and 6 – The Grimaldi Group’s M/V Spes is equipped with an 8-cylinder, in-line Sulzer ZA40S engine fi tted with the wireless temperature monitoring system.

Table 1 - Engine types that can be equipped with the wireless temperature monitoring system.

400

300

200

100

1 2 3 4 5 Min

°C

Oil mist

Big end bearingtemperature

Cu

ttin

g t

he

oil

sup

ply

Ala

rm f

rom

tem

per

atu

re s

enso

r

Ala

rm f

rom

oil

mis

t

Alarm limit

[ M

AR

INE

/ I

N D

ET

AIL

]

Wärtsilä 32, 38A, 38B, 46, 50DF

Wärtsilä Sulzer Z, ZA, ZAS

Wärtsilä GMT 230 and 420

Wärtsilä Nohab F20, F30, 25, 25SG

Wärtsilä Stork 240, 280, 410, 620

Wärtsilä Deutz Marine D350, D358, D501, D510, D511, D528, D536, D540, D545,

D620, D628, D645, D816,

in detail 51


In-place machining repair cannot remedy the problem when a crankpin has been exposed to severe overheating and subsequent surface hardening. When this occurs, machining becomes diffi cult because of the hardness of the metal and, if the hardness depth exceeds the maximum undersize limit for a given pin, traditional reconditioning methods are not possible. In this case the crankshaft has to be scrapped and replaced with a new one. The resulting replacement work and long lay-up time leads to elevated costs, which can increase drastically if a replacement crankshaft is not available when needed.

This is, unfortunately, a fairly frequent occurrence today. There is a very high demand for components for the booming shipbuilding and engine manufacturing industries, and this in turn leads to extended delivery times from overbooked suppliers. Not surprisingly, customers have been demanding a solution to this problem, which until Wärtsilä’s recent intervention, had not been addressed satisfactorily.

Bringing the furnace to the siteThe idea was to carry out stress release heat treatment on the hardened pin. This involved placing heating devices,

temperature sensors and insulation mats on the pin without dismounting the crankshaft, in other words practically “bringing the furnace to the site”. It meant performing a controlled ‘heating – steady temperature – cooling’ cycle to reduce the pin hardness to its drawing specifi cations.

While this procedure produced satisfactory results, there were some challenging drawbacks. These related to occasional cases of deformation and misalignment of the treated shafts, and the process was, therefore, kept as a limited release for a while.

However, customer requests for a solution to this problem continued to increase, so this repair process development was given a more technological/determinist approach. A common team, established last year by Wärtsilä in Italy and Wärtsilä in Finland, combined their know-how, technical workforce and resources to bring this procedure to continuous utilisation.

The fi rst step was to issue a common technical procedure for the process. Next, several tests were performed by Wärtsilä in Italy on a test engine using sophisticated measurement devices and strain-gauges to carry out detailed checks. This process also enabled the behaviour of the treated crankshafts to be monitored for hardness drops, process repeatability, stress release, and for deformations/elongations of the crankshaft. Specifi c procedures were then developed to make and maintain the crankshaft free from constraints and abnormal loads during the heat treatment by dismantling and removing some specifi c engine parts, thus permitting free elongation and contraction to take place. The outcome of these intensive internal research and development actions was that solid technical specifi cations and guidelines for safe commercial operations could be issued. This enabled the process

to become a part of the daily working routine within Wärtsilä, resulting in very high customer satisfaction.

Wärtsilä in Italy is the knowledge centre for in-place crankshaft heat treatment, using in-house original technology and Wärtsilä’s own competent personnel and tools. A development process is ongoing to clone this activity for selected network locations.

During the past few years, Wärtsilä has succeeded in creating a worldwide organisation capable of in-place machining of crankpins for any engine brand, type or size. The team operates using its own specialised personnel, and utilises innovative, custom-designed tools. Today, Wärtsilä teams in Sweden, Italy, Singapore, and elsewhere, are operating with success in this fi eld, supporting and satisfying customers’ needs.

AUTHOR: Guido Barbazza , Vice President, Services, Wärtsi lä in Italy

Fig. 1 – Fitting of heating elements around the crankpin.

In-place crankshaft repair with heat treatment

90°W 45°W 0°

75°N

45°N

0°

45°S

45°E 90°E 135°E

WÄRTSILÄ NETWORK

...

WÄRTSILÄ TECHNICAL JOURNAL | WWW.WARTSILA.COM in detailThe information in this magazine contains, or may be deemed to contain “forward-looking statements”. These statements might relate to future events or our future fi nancial performance, including, but not limited to, strategic plans, potential growth, planned operational changes, expected capital expenditures, future cash sources and requirements, liquidity and cost savings that involve known and unknown risks, uncertainties and other factors that may cause Wärtsilä Corporation’s or its businesses’ actual results, levels of activity, performance or achievements to be materially different from those expressed or implied by any forward-looking statements. In some cases, such forward-looking statements can be identifi ed by terminology such as “may,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “potential,” or “continue,” or the negative of those terms or other comparable terminology. By their nature, forward-looking statements involve risks and uncertainties because they relate to events and depend on circumstances that may or may not occur in the future. Future results may vary from the results expressed in, or implied by, the following forward-looking statements, possibly to a material degree. All forward-looking statements made in this publication are based only on information presently available in relation to the articles contained in this magazine and may not be current any longer and Wärtsilä Corporation assumes no obligation to update any forward-looking statements. Nothing in this publication constitutes investment advice and this publication shall not constitute an offer to sell or the solicitation of an offer to buy any securities or otherwise to engage in any investment activity.

Documents

four7. 01 Twenty 2007twentyfour7.studio.crasman.fi/pub/web/pdf/magazine+pdfs/ID0107-W… · Test bench for common rail technology . . . . Wireless temperature monitoring . . .