four7. 02 Twenty 2007 - Crasmantwentyfour7.studio.crasman.fi/pub/web/pdf/magazine... · issue no....

issue no.

022007Tw

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7.

WÄRTSILÄ TECHNICAL JOURNAL

[ WWW.WARTSILA.COM ]

Cooling Indian offi cesBusiness parks welcome combined power and cooling

Tri-fl exibilityWärtsilä 50DF is a tri-fuel engine for the electricity producers

11

Better effi cienciesNew ferry concepts reduce costs and emissions

16

45

ENERGY

MARINE

Robust controlsMerging controls with heavy equipment requires design

40

Dear Reader

issue no. 02.2007 p

ECCs with ICEs . . . . . . . . . . . . . . . . . . . . . . . . . 04

Combined cycles in Pakistan and Italy . . . . 06

All together - cooling, heating and power . . 07

Cooling Indian offi ces . . . . . . . . . . . . . . . . . . . 1 1

Automation with Ethernet . . . . . . . . . . . . . . . . 12

The ultimate in fuel fl exibility . . . . . . . . . . . . . 16

Planning a national power system . . . . . . . . 21

Towards a cleaner global environment . . . . 26

Arctic sea transportation . . . . . . . . . . . . . . . . 30

Dual-fuel for LNG carriers . . . . . . . . . . . . . . . 33

Bearings for longer shaft life . . . . . . . . . . . . . 37

Reliability in industrial controls . . . . . . . . . . . 40

Cost-effective ferry propulsion . . . . . . . . . . . 45

Cutting cylinder oil costs . . . . . . . . . . . . . . . . 51

SOX emissions under control . . . . . . . . . . . . . 55

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: A new concept in ferry propulsion, p. 45.

in detail

E-mail and feedback: [email protected]

2 in detail

The possibility to have fast and easy information may be crucial for any plant or process. Wärtsilä´s power plant automation with Ethernet on page 12.

WÄRTSILÄ IS A MAIN PLAYER in an industry with a strong technology focus. As our aim is to be recognized as the Technology Leader in this industry, innovation is high on our agenda.

BEING AN INNOVATIVE COMPANY means creating a climate where people feel encouraged to develop new ideas and to develop them further. Innovation doesn’t come about by asking for it, nor by waiting for it to happen. It is a culture that is built up over the years within a company. It requires a framework wherein new ideas are identifi ed, picked up, and sponsored so that they can be further elaborated.

IN THIS CLIMATE of innovation that we strive to create, it is not the quantity of new ideas, but their quality that counts. Innovative ideas should ultimately result in product improvement, in new functionality, or even in an entirely new product that brings tangible benefi ts to our customers.

IN THIS ISSUE of In Detail we present, amongst other things, a number of new technologies and products developed by Wärtsilä.

With its unrivalled fuel fl exibility, the Wärtsilä 50DF engine has been the forerunner in market segments where there is a demand to switch between fuels to select that which is the most economical.

In the fi eld of engine automation, Wärtsilä Unifi ed Controls (UNIC) provides an advanced and reliable electronic control system for our latest generation of diesel and gas engines.

Looking into new concepts in ferry propulsion, a direct driven controllable pitch propeller, together with a contra rotating propeller behind it, offers the possibility to reduce both fuel consumption and exhaust emissions.

And in the area of materials, composite marine bearings have been developed for longer life and outstanding performance, even under severe operating conditions.

THESE ARE JUST A FEW examples of Wärtsilä innovations, and of the interesting topics that you will fi nd in this issue. And while you are reading these articles you can be sure that we are already busy working on new ideas.

Klaus Heim

Vice President, Global

Research & Development

Contributing Editor for this

issue of In Detail.

Contents

WÄRTSILÄ TECHNICAL JOURNAL 01.2007 WÄRTSILÄ TECHNICAL JOURNAL | WWW.WARTSILA.COM

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MORE ON PAGE 06 MORE ON PAGE 11 MORE ON PAGE 33

Pakistan and Italy get combined cycles

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The Attock Refi nery in Pakistan and the ItalGreen olive oil production plant in Italy have both opted for Wärtsilä combined cycle power units.

Improving working conditions in India

The International Tech Park is located in Bangalore, India. A Wärtsilä combined cooling, heating and power plant keeps the inside temperature comfortable.

Dual-fuel powering LNG carriers

When Wärtsilä introduced dual-fuel electric machinery to the LNG carrier market, orders soon followed. The British Emerald is one such ship using this technology.

MOVING NORTHNew arctic transport offers sound ice breaking properties

without detriment to open water performance. PAGE 30

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ECC with internal combustion enginesAUTHOR: Anders Ahnger , General Manager, Combined Cycles and Environment, Power Plants, Wärtsi lä in Finland

Fig. 1 – Conceptual study for hot climates. A 140 MWe ECC plant with eight Wärtsilä 18V50DF engines and a steam turbine with a direct air-cooled condenser.

The energy world is in the process of undergoing big changes. Environmental requirements are becoming more and more stringent, while the Kyoto-protocol is being implemented country-by-country, step-by-step. Authorities and governments around the world are enacting measures aimed at fulfi lling the CO

2 and other

emission targets and limits. Combined heat and power (CHP) directives striving for better primary energy utilization, economy, and savings are being published and implemented to improve general plant effi ciencies. Renewable fuels are becoming preferable to fossil fuels due to the CO

2 emission targets. At the

same time, fuel prices are high and slowly but steadily increasing. Electricity

In this article, engine combined cycle (ECC) solutions are discussed as a means of increasing electricity output and effi ciency for a plant using combined cycle techniques, based upon heat recoveries from medium-speed gas and diesel engines.

prices are also increasing, although not as directly nor as fast as fuel prices.

In order to meet these demands, the technologies used in modern power plants need to be further developed for higher effi ciencies and technical solutions, amongst other things, will require greater sophistication. All waste heat sources from the prime movers must be better utilized for secondary energy production, either for direct heat generation or for secondary power generation. Governments are engaged in ensuring that such developments are heading in the right direction.

With this situation very much in mind, Wärtsilä is studying different kinds of combined cycles and developing them further. The rising interest by power producers and plant owners, in engine combined cycles has been noted, and there is clearly an increasing awareness in utilising and recovering for re-use in, for example, additional electricity production, energy and heat that would otherwise be wasted.

Engines in combined cyclesBoth diesel and gas medium-speed internal combustion engines (ICE), also called reciprocating engines, are already from design and construction very effi cient in terms of electricity and power production. Today, we talk about a gross electrical effi ciency of up to 47%, for engine sizes bigger than about 3 MWe. This electrical effi ciency is remarkably high, even compared with large-sized power plants based on other technologies. The rest of the engine fuel input emerges in the form of heat in exhaust gases and engine cooling. In a typical CHP application, these engine waste heat sources can be utilized for valuable heat production. However, in many places there is no “heat sink” into which the waste heat can be “dumped”, and therefore, secondary power generation is preferred, as in an engine combined cycle confi guration.

The most common technique for secondary power generation is based upon a conventional steam bottoming cycle. The cycle can be defi ned as a post-

WÄRTSILÄ TECHNICAL JOURNAL 02.2007

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Fig. 2 - General fl ow diagram of a typical steam turbine system for internal combustion engines.

Exhaustgas boiler(HRSG)

Exhaust in390–410°C

Exhaust out175–190°C

Feedwater tank

Steamdrum

Make-upwater

Steam turbine wilt alternator

Condenser

16–20 bar

105°C

G

Table 1 - Performance values for various engine combined cycle plants based on ordinary, one pressure steam cycle. (Values given at ISO reference conditions, tolerance 5%)

Plant set-up Fuel Simple cycle Additional Plant output output effi ciency

MWe (gross) MWe %

6 x Wärtsilä 20V34SG Natural gas 52.3 4.8 50.73 x Wärtsilä 18V50DF Natural gas 49.8 4.7 51.86 x Wärtsilä 20V32 HFO 53.5 3.8 49.33 x Wärtsilä 18V46 HFO 51.2 4.2 50.7

engine “hang-on” type, and does not directly affect the performance or the running of the engine. Prerequisites for a modern and effi cient steam bottoming cycle are high steam pressures and temperatures. As previously pointed out, the reciprocating engine is, from basic design, already very effi cient, meaning that the temperatures of the waste heat are somewhat low for a steam bottoming cycle. Nevertheless, very high total plant effi ciencies are easily obtainable.

The main equipment in the system are: the heat recovery steam generator (HRSG), the steam turbine set with an alternator, the condenser with cooling, as well as the feed water and water treatment systems. The main heat source from the engine is the engine exhaust gas, where the temperature plays a more important role than the exhaust gas fl ow in the effi ciency

of the steam cycle. Taking a normal medium-speed engine directly from production, the exhaust gas temperature would be approximately 340–370oC for diesel engines, and 370–410oC for gas engines. Engine exhaust gas temperatures, the ambient conditions, steam condenser cooling, engine type, and the type of fuel determine the design pressures for steam generation. Usually, a single pressure steam system operates economically at 12–20 bars. The engine cooling water is used as preheating for the feed water and condensate fl ows, before being fed to the feed water treatment system.

More sophisticated steam systems with exhaust gas boilers having several pressure levels and multi stage steam turbines are possible, but seldom economical. Generally, an ECC based on a single-pressure steam system attains

a total gross effi ciency of 49.0-51.5%. With a sophisticated multi-pressure system, effi ciencies of up to 53.5% can be reached. These fi gures are valid for today’s standard engines. Even though the effi ciency from multi pressure secondary power generation is much higher, it very seldom justifi es the higher investment.

Organic rankine cycles (ORC)The organic rankine cycle (ORC), is a closed thermodynamic rankine cycle process where heat is added to the selected organic fl uid at a constant pressure in order to vaporise it. It is then expanded through a turbine, condensed under very low pressure to liquid, and fed back for heating and evaporation.

ORC manufacturers are typically focusing on heat recoveries from different low grade or low volume waste heat, such as geothermal heats, where an ordinary steam turbine cycle is unnecessarily ineffi cient and expensive, and where the investment for a comprehensive steam turbine system cannot be justifi ed. The equipment is manufactured as small compact factory-made modules, which are then delivered to site as functional and pre-tested units. The markets for such units are such that they are generally less than 5 MWe in size. From a design and construction point of view, the ORC cycle is well suited for gas and diesel engines.

The organic fl uid in the closed rankine cycle is selected according to the application and the temperature levels of the waste heat source. Using an organic fl uid is seen as being environmentally hazardous, and brings up the question of fl uid stability and toxicity. Because the organic fl uid is kept only in the primary cycle, an intermediate thermal oil circuit is usually used for transferring the heat from the waste heat source to the ORC-module.

The organic rankine cycle products of today give 8-10% additional power - even for small engine plants. Even though the organic rankine cycle has been on the market for more than 20 years, further development potential to increase the effi ciency and output remains.

Research work continuesComparing investment costs against performance, the ordinary steam turbine cycle is a stronger alternative for engine plant sizes above 30 MW, while the organic rankine cycle is well suited for

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plants below 30 MW and especially for one engine installations. The ORC cycles still have the potential for being developed to optimize the cycles and technique for reciprocating engines, and for the better use of engine cooling water.

Furthermore, from these two “hang-on” type combined cycle technologies, there are numerous research activities, developments, and studies taking place aimed at developing much more effi cient bottoming cycles. They are also looking into integrating these technologies with other combustion methods and boilers,

with ordinary supplementary fi red heat recovery steam generators, and with different kinds of “hybrid plants”, etc.

In parallel with these technologies, a lot of focus and development work is being targeted towards the engine and prime mover itself, as well as the combustion, effi cient turbo-charging with direct utilization of excess exhaust gas, and other relevant areas. Many of these are, however, not yet fully commercialized, and it is likely to take some years before they are applicable for combined cycle technologies and ordinary power plants.

Power and energy demand is growing hand in hand with economic growth, and is already an important global concern. We have many interesting years ahead of us as we strive to meet the increasing demand for better and more effi cient power and energy generation, and for environmental compliancies.

REFERENCES: - Miroslav Petrov/Steam bottoming cycles for the W20V34SG gas engine /KTH 2006.- Seminar work made by group of students at Technical University of Helsinki and Royal Institute of Technology, Stockholm/2007.

Attock Refi nery, PakistanWärtsilä will be delivering a 160 MW power plant for the Attock Refi nery Ltd site near Rawalpindi in Pakistan.

The customer is Attock Gen Ltd, a company set up specifi cally to own and operate the power plant. The main sponsors are various units within the Attock Oil Group, including Pakistan Oilfi elds, Attock Refi nery Ltd, Attock Petroleum and Attock Oil Company. The new power plant will improve refi nery operations.

The plant consists of nine Wärtsilä 18V46type generating sets with heat recovery steam generators (HRSG) on each, one 12 MWe condensing steam turbine plant, and a 132 kV switchyard. The plant is run on heavy fuel oil and will be connected to the national grid.

The combined cycle concept is intended to meet the demand for the highest possible power plant effi ciency during a lifetime cycle of 25 years. With the combined cycle confi guration, an electrical net effi ciency of 45% can be reached.

ItalGreen II in Monopoli, ItalyItalGreen is part of the Casa Olearia Italiana Group (COI), a world-leading supplier of household and commercial food oils. COI situated in Monopoli, in the heart of Italy’s Puglia olive growing region, covers an area of 100,000 m2 (24.70 acres). This facility is used for the production of extra virgin olive oil, olive oil, and the refi ning of pomace oil and various seed oils. The site has over 100 stainless steel tanks storing some 60,000 tonnes of oil, and a packaging plant for their own brand and other international household and commercial brands. The facility is one of the largest in the world with four packaging lines, one of which has a phenomenal production capacity of 11 pieces per second.

The ItalGreen II plant will burn vegetable oil, mainly imported palm oil from Southeast Asia. The economics of a biofuel plant in Italy are good, with competitive bio-oil prices and considerable government incentives to generate electricity using renewable power.

The 100 MW plant consists of six Wärtsilä 18V46 engines, each with heat recovery steam generators equipped with natural gas driven duct burners for improving the steam parameters before being fed to the condensing steam turbine of 12 MWe, giving a gross electrical effi ciency of 50%.

Green Energy, ItalyThe Green Energy plant consists of one Wärtsilä 18V46 engine running on liquid biofuel and equipped with an organic rankin cycle (ORC) for boosting electrical output and effi ciency. The engine waste heat is recovered only from the exhaust gases with a thermo-oil intermediate heat circuit feeding heat from exhaust gases to the package type ORC-unit. The ORC turbine unit generates 1.3 MWe net effi ciency in parallel with the engine and boosts the plant electrical output by 8%. The project is under delivery and will be commissioned in 2008.

REFERENCES PAKISTAN AND ITALY

The benefi ts and increased effi ciencies created through heat recovery generating capability are being realised on a global basis. Recent orders for Wärtsilä combined cycle engines refl ect this trend.

ENGINE COMBINED CYCLE REFERENCES

Fig. 1 – The Attock Gen Limited power plant with a steam turbine totalling 160 MW in Pakistan.


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Combined cooling, heating and power solutions for mega-commercial spacesAUTHOR: Nandkumar Pai , Head of Sales, Power Plants, Wärtsi lä in India

This has given rise to an unprecedented boom in real estate development, especially in its commercial segment, notably offi ce park developments catering to Information Technology/Information Technology Enabled Services (IT/ITES) and other such mega-complexes, as well as to the growing number of large commercial malls, all of which are heavy electricity consumers.

Energy requirements of commercial spacesThe energy requirement of commercial spaces can be broadly classifi ed under three broad headings: power and comfort cooling, reliability and compact layout:

n Power and comfort cooling requirements will vary from day to day and throughout the year, and are application driven. For example, a 24 hourIT/ITES facility with a built-up area of close to 2 million sq.ft. (186,000 m2),will have a more or less stable power requirement in the range of 6-8 MW throughout the day, whereas the comfort cooling requirement will see a wide range of fl uctuation from 2000 TR to 8000 TR. (TR stands for Tons of Refrigeration and is a thermal unit commonly used for measuring cooling/chilling. 1 TR = 3.5163 kW, 1 kw = 860 kcal, 1 TR = 3024 kcal). A commercial mall, on the other hand, will typically have a 12-16 hour daily operating pattern with comfort cooling peaking during weekends.

n Reliability: These facilities need 24/7 power without interruption, since

Apart from the consistent growth in its economy, in the last few years, India has witnessed a massive growth in the services-outsourcing segment, a rise in consumerism, and rapid urbanization.

they are driven by the application sensitivity such as server loads in an IT complex, business sensitivity such as retail outlets in a mall, as well as safety considerations. Hence these facilities are designed with redundancy factored in for both power and comfort cooling sources.

n Compactness in layout is quite important as it allows the real estate developer to effectively utilize the available land, and to maximize the rental space.

A facility developer has two options for meeting his energy requirements. He can choose either a conventional solution, or a combined cooling, heating and power (CCHP) solution, both of which are discussed and compared below.

The conventional solutionIn this case the power is sourced from the local state electricity board, and redundancy is built-in with 100% back-up power by installing high-speed diesel generators. Comfort cooling is provided by electrical chillers with a built-in redundancy in the confi guration. For example, for a facility with 8000 TR of design comfort cooling requirement, nine (eight working and one standby) 1000 TRelectrical chillers can be installed. The electrical chiller can be of reciprocating type, rotary screw type or centrifugal type. The fi nal combination of electrical chiller equipment varies according to operating conditions, space constraints, water availability, and so on. The specifi c power consumption of these chillers will vary from 0.9-0.5 kW/TR. Centrifugal chillers are the most effi cient at full load conditions, having a 0.55-0.65 kW/TR power: TR ratio.

Though the conventional solution would appear to be the most lucrative option with the least investment

needed, this is not always the case on account of the following:1) Poor reliability of power supplied by the Indian state utility boards makes it necessary to operate expensive diesel sets during power interruptions. In some states the power supply situation is so poor that the end customer is forced to endure power interruptions for approximately 30% of the time year round. In such cases, the effective power cost to the end user shoots up by 30-40% of the base electricity tariff. 2) Recent trends in India show that the power tariff to commercial establishments is increasing, and is in the range of 30-80% above the industrial tariff.

These factors are causing developers to evaluate setting-up their own captive power plants to cater to the energy demands of their upcoming commercial establishments.

Combined cooling, heating and power (CCHP) for commercial spacesThe CCHP solution for such commercial spaces depends, amongst other things, on the location, the availability of fuel, the operating pattern and space constraints, and every solution will be unique for a given case. For the purpose of detailed evaluation, this article is limited to a CCHP solution with natural gas as the primary fuel. However, this concept is equally applicable for liquid fuels.

The basic concept in a CCHP case will be to improve effi ciency of the solution and thereby reduce the operating cost, by using the free waste heat from exhaust gases and the hot water circuit in the absorption chiller for chilled water generation.

In an absorption chiller, the free heat from the engines is used to separate water from the absorbent i.e lithium bromide, solution. Water acts as a refrigerant. A concept diagram of an absorption

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Fig. 1 – Absorption chiller - working principle.

Coolingwater

Steam

Regenerator

Drivingheat

source

Coolingwater

30–32°C

Evaporator

Chilledwater

Condenser

Liquidrefrigerant

(water)

Concentratedsolution

Libr. + water

7°C

12°C

Table 1. – First indications in the electrical and thermal effi ciency comparison between gas turbine- and engine-based plants (see detailed analysis in Table 2).

Description Gas turbine Engine1 Electrical heat rate - kcal/kWh (nominal values)* 3000 19402 Electrical effi ciency - % 28.7% 44.3%3 TR generation TR/MW 550 2004 Useful equivalent thermal heat - kWth 1933.8 703.25 Useful electrical output kWe 1000 10006 Total kW 2933.8 1703.27 Useful heat in kcal 2,523,068 1,464,7528 Total heat input in kcal 3,000,000 1,940,0009 Effi ciency 84% 76%

* These are nominal values and considered at 35ºC ambient, since comfort cooling requirement round the year

is predominant in tropical countries, where the average ambient is in the range of 35ºC.

chiller is given in Figure 1. The detailed operating principle of an absorption chiller can be obtained, for example, from the internet, and previous Wärtsilä published articles.

Generally in a commercial space, comfort cooling (TR) constitutes about 40-50% of the overall energy requirement, i.e. of power + comfort cooling. The chilled water recovery potential through an absorption chiller of Wärtsilä medium-speed engines is in the range of 170-210 TR/MW. This means that TR recovered from the absorption chiller through engine waste heat is not suffi cient to meet the total comfort cooling loads of such facilities, and hence some amount of chilled water has to be recovered through electrical chillers.

The redundancy factor can be considered, based on the criticality of the application, by having one or two additional engines as standby. However with piped gas, which cannot be stored, as the primary fuel, one has to also consider operating the facility on an alternate fuel such as diesel. This is especially true in countries like India where the gas supply agreement one enters into with the gas supplier, provides for 15-21 days of annual gas outage. Thus, with this in mind, with pure gas engines one has to consider equivalent standby capacity through high-speed diesel sets. Alternatively, dual-fuel engines, which are a better option on account of compactness of layout and lower capital cost, could be considered.

With a dual-fuel option, gas turbines (GT) also qualify as a possible option, especially considering their potential for recovering higher TR through an absorption chiller using free exhaust gases. Generally, for such applications, considering a comparatively limited power requirement, normally less than 50 MW, and a multi-unit solution addressing the need of redundancy and load variations, industrial turbines are preferred. The TR recovery potential from a GT through an absorption chiller is in the range of 500-700 TR/MW depending upon the electrical effi ciency of the GT, i.e. the higher the electrical effi ciency, the lower the TR recovery potential, and vice versa. The energy balance from a GT is quite close to the energy balance of a commercial space. And when trying to equate the electrical effi ciency and thermal effi ciency from both options, then one can conclude that the effi ciency of a GT is better than

an engine, after recovering the total heat for TR generation (see Table 1).

With this background, it would be obvious to conclude that in such spaces GT is a better option than a reciprocating engine. However, this is not so and the fact is that reciprocating engines are the clear and natural choice because of the following factors.

Reciprocating engines, the best choice Chilled water can be generated through reciprocating chillers, screw chillers, centrifugal chillers or vapor absorption machines (VAMs). Except for absorption chillers, which need heat, all other machines consume electricity to generate chilled water output. When comparing

these machines for performance, the term coeffi cient of performance (COP) is often used, which is nothing but effi ciency (effi ciency terminology is not used as COP most of the times exceeds 1), and is defi ned as: COP= CHILLING OUTPUT/HEAT INPUT, with both the numerator and denominator measured in the same thermal unit, i.e. TR, kcal, kJ, etc.

For example, the COP of a centrifugal chiller consuming 0.6 kW of power for delivering 1 TR per hour of heat, will be:1TR = 3024 kcal, 1 kW = 860 kcal.Hence, the COP of the machine equals 3024/(0.6 x 860) = 5.86.

The COP of reciprocating, screw and centrifugal chillers varies from 4 to 7.


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Fig. 2 – A typical plant room lay-out for a 17 MW CCHP plant with 8000 TR of comfort cooling.

Absorption chillers,4 x 1000 TR

Electrical-centritugal

chillers,4 x 1000 TR

4 x Wärtsilä 18V32DF engines

Whereas, for an absorption chiller it is 0.65 to 1.3, depending upon whether the absorption chiller is of single-effect or double-effect (single-effect will have a COP of 0.65, whereas the double-effect COP will be almost double, a little less than 1.3). This clearly explains that an absorption chiller needs more heat input to deliver the same TR when compared with electrical chillers.

This is precisely one of the reasons why engines are the clear lead runners for combined cooling, heating and power solutions in the commercial segment. With engines, the balance shortfall in TR can be made good by effi cient electrical chillers, having a higher COP as compared to an absorption chiller. Though the

generated electrical power with engines will be higher, the overall operating cost will still be lower compared to a turbine.

This conclusion is substantiated by the calculation given in Table 2. Here is a case where the energy balance suiting a gas turbine is considered for evaluation. The numbers given below are based on a kW: TR ratio of 1000:550, and the analysis will hold good for similar ratios for a commercial facility, such as 20 MW of power and 11,000 TR of refrigeration, or 30 MW of power and 16,500 TR of refrigeration, etc.

It is evident that Wärtsilä dual-fuel (DF) engines have a far superior operating cost, even when compared with the best energy mix suiting a GT.

Hence, any hybrid solution i.e. mixes of GT and engines, cannot be better than a pure Wärtsilä engine solution.

Apart from this advantage, a mix of electrical chiller and absorption chiller reduces the overall chilled water equipment cost for meeting a given TR requirement, compared to that of a pure absorption chiller solution. Also, the design TRload is only needed during peak summertimes – say, approximately 100 hours per annum. For the rest of the year the TRrequirement is low, on an average 50-60% of design value. This automatically suits the engine case since the absorption chiller with engines act as baseload machines, while for peak requirements, the electrical chillers can be switched on and

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Fig. 3 – Indicative CCHP viability curve.

Cost of gas USD/MMBTU

0,14

0,12

0,1

0,08

0,06

0,04

0,02

0

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Table 2. – Detailed comparison of natural gas consumption between gas turbine- and Wärtsilä dual-fuel engine-based power plants.

Description Unit Gas turbine Wärtsilä dual-fuel 1 Power kW 1000 1000 2 Required TR TR 550 550 3 Chilled water recovery through waste heat TR/MW 550 200 4 Electrical chillers TR 0 350 5 Specifi c power consumption of electric centrifugal chiller kW/TR 0.6 0.6 6 Additional kW to be generated to run electrical chillers * kW 0 210 7 Total kW to be generated to meet the energy balance of the facility kW 1000 1210 8 Heat Rate of GT/DF engine ** kcal/kWh 3000 1940 9 NCV of gas at site kcal/Sm3 8500 8500 10 Hourly gas consumption Sm3/hr 352.9 276.2 11 Gas saved with engines as compared with gas turbines

* Note the actual savings are more than projected, since we have not considered the additional free chilling recovery

from 210 kW of additional electrical generation above thereby reducing the electrical TR load on the engines.

** These are nominal values and considered at 35 ºC ambient, since comfort cooling requirement round the year is

predominant in tropical countries, where the average ambient is in the range of 35 ºC.

22%

off, thereby lowering the actual electrical load on the engines and reducing the gas consumption. In the case of GT, excess TR can only be avoided by bypassing heat to the stack, which does not lower gas consumption. This will further improve fuel savings in favour of engines.

It should also be noted that irrespective of the type of chiller, electrical (vapour compression type) or absorption type,

a cooling tower is needed for supporting its operations. However, to generate the same amount of chilling (TR), an absorption chiller needs a bigger cooling tower than an electrical chiller. Although the absorption machine is quite expensive as compared with an electrical chiller of equivalent capacity, the difference in cooling tower sizes further widens the differential investment costs between

absorption and electrical chiller systems.Unlike a GT, engine life is not affected

by daily starts and stops resulting from daily load variations of a 24 hour facility or a daily on and off facility such as a commercial mall. Also, the carbon foot-print with an engine is the least amongst all fossil fuel power generation technologies, and is even lower than a CCHP gas turbine solution.

In the case of the real estate developer having land/space constraints, the entire plant room i.e. the engines, the absorption chillers, and electrical chillers, can be located in an extended basement of a commercial facility. A typical plant room plan for a 17 MW and 8000 TR CCHP plant is given in Figure 2.

Initial investments will vary based on the energy mix of a given facility. When a developer is considering engine based CCHP solutions purely from the point of view of returns on investment, then his decision will depend on two external variables such as cost of natural gas (fuel) and the equivalent power tariff from a conventional source (including the standby power cost). Figure 3 shows an indicative CCHP viability curve based on these two variables. As per Wärtsilä’s analysis, the minimum built-up area of a commercial space beyond which the CCHP solution becomes viable is about 1-1.5 million sq.ft. (90,000-140,000 m2).

Conclusion:It is evident from the above that a Wärtsilä engine based CCHP solution meets the requirements of large commercial spaces, viz.:

1) Flexibility to take care of the varying load pattern.

2) Inbuilt redundancy in the confi guration.

3) Multifuel capability to ensure a 24/7 energy requirement.

4) Compactness of layout and possibility of a basement installation.

5) Lowest operating cost amongst all alternatives.

6) Environmentally friendly on account of its carbon footprint being the smallest.

This provides the real estate developers with a serious alternative for meeting the energy requirements of commercial spaces.


in detail 11

The 69-acre ITPB is the fi rst hi-tech park of its kind in India, and is designed to provide a complete ‘work-live-play’ environment for IT and technology-related businesses. It fully integrates a practical amalgamation of offi ce, production and retail space. To date, the Park has a total built-up area of close to 2.3 million sq.ft. (214,000 m2).

ITPB currently has six multi-tenanted buildings that are fully occupied and

has land available and ready for further expansion. It is the fi rst business space facility in India to house a shopping mall and to organize regular fun and fi tness events for its occupants. The mall offers fully functional banks, ATMs, foreign exchange facilities, courier, lifestyle stores, a laundry service, a wide range of F&B outlets, medical clinic and a health club, thereby offering a wide range of conveniences to the occupants. Truly a ‘World in a Park’, ITPB houses more than 130 companies employing over 20,000 employees.

Businesses located at ITPB are involved in key growth industries, including information technology, biotechnology, electronics, telecommunications, R&D, fi nancial services, and other IT-related services.

Over 26 acres of land within ITPB has been notifi ed as IT/ITES SEZ and earmarked for further development for multi-tenanted and built-to-suit buildings.

The success of this landmark development has made the Park an iconic benchmark for other Indian states vying to set up world-class infrastructure of their own to attract investments. Since it started operations in 1997, ITPB has won accolades for its ability to attract global corporations to Bangalore.

Power to the ITPB Bangalore property is produced by a liquid fuel based Wärtsilä combined cooling, heating and power (CCHP) solution, comprising three Wärtsilä 9R32 generating 9 MW and one Wärtsilä 18V32 engine of 7.5 MW capacity, with chilled water recovered from engine waste heat totaling to 7560 kWchilling (2150 TR) through absorption chillers. The remaining comfort cooling requirement is generated through electrical chillers.

REFERENCES BANGALORE | INDIA

INTERNATIONAL TECH PARK, BANGALORE (ITPB) India has, in recent years, emerged as a key player in the global IT market. As a result, the country is attracting international investments and new, effi cient, business parks are springing up everywhere. Combined cooling, heating and power plants make for a better working environment.

Fig 1. – The International Tech Park in Bangalore, India, is powered and chilled by an effi cient Wärtsilä combined cooling, heating and power plant.

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Power plant automation – the communication highway features of a top performerAUTHOR: Niklas Wägar , General Manager, Electrical & Automation, Power Plant Technology, Wärtsi lä in Finland

Being able to take immediate proactive actions could make a vital difference to operations. The analysing and diagnostic features of Wärtsilä’s power plant automation are designed to support normal operations and maintain high productivity.

Introducing EthernetDiagnostics and all the detailed data needed in modern operating techniques require more bandwidth from communications than has earlier been available. Ethernet, the same communication media as used in offi ce networks, however, now enables automation devices to provide far more information than just regular control data. Automation has, as a result of the introduction of Ethernet, received an enormous development boost.

By introducing Ethernet and taking full advantage of the benefi ts it offers, Wärtsilä’s power plant automation solutions have been at the forefront of new technological developments that can provide real value to customers.

Today, Ethernet is more than merely the data highway used by Wärtsilä in its power plant automation solutions, it is the ‘glue’ that binds and connects the various control system devices and related diagnostics that defi ne the possibilities to interactively control the process.

Before EthernetAutomation communication solutions prior to Ethernet were based on the

RS485/RS232 types of serial bus communication with, of course, traditional wiring to the input and output modules.

The bus communications were fairly reliable, quite slow for longer distances (RS-485; (35 Mbit/s up to 10 m and 100 kbit/s at 1200 m), but very proprietary. Normally one could utilize only one type (or protocol) of communication in one cable.

Communications using serial bus were intended mostly for traditional communication of bit information and analogue values, but the bandwidth was not suffi cient for diagnostics, pictures, or even video data transfer.

Ethernet historyEthernet was invented in the early 1970s as part of a pioneering project at a company belonging to Xerox Corporation. The fi rst patent was fi led by Xerox in 1975 with the name: Multipoint data communication system with collision detection.

The big development boost for Ethernet came in the 1980s with personal computers, and communication between them based on local area networks (LANs). At that time, probably nobody realised the impact that Ethernet would have on global automation development.

The Ethernet cabling was originally based on coaxial cables, but evolved since the mid-80s to the twisted pair system. This led to the famous abbreviation RJ-45 which, although sounding like the name of a Star Wars robot, is in fact the name of the most used Ethernet connector. This RJ-45 connector is still used for the majority of all high speed PC communications to offi ce LANs and the internet where wireless (WLAN) communication is not used.

Industrial EthernetThe automation industry did not know much about Ethernet until the beginning of the 1990s. At that time it was used mainly for communication between personal computers. The fi rst PLCs with Ethernet communication came in the mid-90s, but it was not until after the turn of the millennium that one could expect to fi nd an Ethernet RJ-45 port in PLCs. Today, there is hardly any PLC manufacturer that would not have Ethernet communication as default, or at least as an option. The term, Industrial Ethernet, also became known for the use of the Ethernet protocol in an industrial environment for automation and process control.

This development has also included industrial type switches, WLAN access points, routers, and fi rewalls. It is also very common for frequency converters, and for switchgear equipment such as protection relays and power monitoring units to have direct Ethernet communication. The major difference between industrial Ethernet equipment and the normal offi ce type is the power supply arrangement, which is based on 24VDC, and a more robust design to withstand temperature variations and vibrations.

Wärtsilä’s power plant automation with EthernetSince 2003, Ethernet has been the standard communication for all the main control components in Wärtsilä’s plant automation solutions.

The actual advantages have exceeded expectations:n Increased speed, up from 9.6 kbit/s

(RS232) to 10 and 100 Mbit/s.

For any plant and process, the possibility to have fast and easy information available may be crucial if disturbances happen – either internally or from an external source.


in detail 13

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Fig. 1 – Gas plants, advanced automation layout with Ethernet connections.

Remote solutions(optional)

Hardcopylaser printer

WOIS workstation WOIS workstation WISE workstation

UNIC controller

AVR, voltage regulator

PLC or Remote I/Omodule

Power monitoring unit or Protection relay

Ethernet switch

Plant network, Ethernet,TCP/IP, Twisted pairs

Plant network, Ethernet,Fiber Optics

Remote I/O bus

Central control panel,

enginewise section

CFC011

Local aux.control panel

BJA011

Central control panel,

enginewise section

CFC021

Local aux.control panel

BJA021

Control room

Engine hall

Central control panel,common section

UNICEngine local displayEthernet gatewayEmbedded controller

CFA901

n Longer distances (even kilometres), especially with optical fi bre which is very resistant to possible interference.

n Increased performance, more devices can be connected to the same network.

n Accessibility, the devices connected can be accessed with standard components, and also accessed and even confi gured from remote locations.

n Enhanced diagnostics and troubleshooting possibilities thanks to the speed and performance.

n Possibility to confi gure a ring network, meaning redundancy.

n Several protocols for different communication needs can be used in the same physical network.

For Wärtsilä power plants, which are usually connected to power grids, one major feature built-in to one of the protocols is the clock synchronisation of the control components in the plant. At the same time, it can also be optionally synchronized to a GPS (Global Positioning System) time server, thereby ensuring

that the clock in the plant automation system is the same as in the grid substations and switchyard components.

Thanks to the clock synchronization, a time stamping or SOE (sequence of events) functionality is adapted, meaning that all the main controllers’ alarms and events in the system are time stamped at the source with high resolution, and listed in the WOISTM (Wärtsilä Operator’s Interface System) alarm list in the correct sequence.

This combination of an accurate clock on the devices and time stamped alarms and events, are of obvious help during any detailed analysis.

Ethernet advantage example 1: Grid transient analysesIn addition to the WOIS and WISETM (Wärtsilä Information System Environment) computers, and the PLCs, the switchgear protection relays and power monitoring units are also connected to Ethernet. With the introduction of the UNICTM engine automation

solutions, the majority of the engines will also have Ethernet connectivity.

The following example of device integration with Ethernet, is based on the default grid transient analyses feature consisting of:

n Protection relays connected to Ethernet with standard disturbance (also known as transient) recording confi gured, 12 channels with the most important electrical measurements recorded with 20-millisecond resolution, 4 seconds before a generator breaker trip and 4 seconds after.

n The WISE reporting platform computer checks for any possible new transient recording via Ethernet.

n Data is transferred from the protection relays to the WISE computer that automatically confi gures a data fi le in COMTRADE format, which is a commonly known format for power grid and substation measurement analysis.

n The breaker trip transient recording

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Fig. 2 – On the WISE daily maximum values display, an abnormally high generator voltage value for genset 4 can be seen on July 13, 2007. This can also be observed remotely through the Wärtsilä CBM services.

Fig. 3 – At the plant or via the Wärtsilä remote services, the high voltage can be confi rmed in the WOIS historical trends, July 13,2007 at 10:33:46

Fig. 4 – By checking the WOIS alarm and event database, the exact timestamp with millisecond resolution of the generator breaker trip can be seen, with included description (in this case with dual language). July 13, 2007

Fig. 5 – By analysing the protection relay disturbance record with the high resolution trending of the electrical measurements during the trip, the maximum voltage during the peak can be seen, in this case 16,9 kV. The time stamp is within 1 millisecond accuracy compared to the WOIS alarm list; July 13, 2007 10:33:46,258

fl ags in order to make sure that the WOIS workstation has received the alarm and event information. The time stamps of the protection relays’ trips and alarms are very accurate, to a millisecond level, since they are stamped in the relay with the fast actions that are expected from protection relays, and are, at the same time, shown on the WOIS alarm list.

The extract from the WOIS alarm list at a power plant control system factory acceptance test, shown in Figure 7,indicates the system’s high level of accuracy. This example consists of 12 gensets and the usual PLCs, and the differences in accuracies were tested by having all emergency stop circuits hardwire connected, as is typical at plants. The plant emergency push button was pressed in the common control panel, and we can see from the time stamps that the safety relay tripped immediately. There is a small delay

COMTRADE fi le is automatically stored in the WISE hard disk with the time stamp of the breaker trip time for later analysis.

n The operator can open the transient recording with the protection relay confi guration tool that is by default installed in the WISE computer. Alternatively, it can be analyzed by Wärtsilä as part of its condition based maintenance (CBM) services.

Ethernet advantage example 2: Time stamping functionalityThe SOE, (sequence of events) or time stamping functionality is often requested from power plant control systems. Wärtsilä has supported time stamping functionalities for several years, and thanks to the UNIC development and its Ethernet protocols support development, time stamping of the engine related

alarms and events is also supported.Essentially, time stamping consists

of three different features:1) Accurate clock synchronization

of the control units.2) Time stamping of the alarms and

events at the source, the control stations.3) Transfer of the time stamped data

to an HMI, (human machine interface) alarm list capable of sorting the time stamped data in correct order.

Wärtsilä is utilising the standard Ethernet protocol NTP for synchronizing the clocks on the controllers. This NTP protocol based time can also be received from a satellite GPS server should more regional or global time accuracy be requested.

Every alarm and event is time stamped in the controllers, i.e. PLC, UNIC, and in the protection relays. Necessary buffering is carried out with appropriate


in detail 15

Fig. 7 – Extract from the WOIS alarm list during a factory acceptance test of time stamping.Fig. 7 – Extract from the WOIS alarm list during a control system factory acceptance test of time stamping.

Fig. 6 – The production continues and the losses July 13, 2007 could be minimized to just a few hundreds of kWh thanks to selective protection and safe confi guration.

before the fi rst genset reacts since there are also delays in the reaction of the safety relays (<14 ms according to the manufacturer). However, from the time when the fi rst genset reacted until the last, we can see that the maximum difference is 24 ms. The differences are due to small delays in the relays, PLC cycle time, and some possible small error between the PLC time and common time as synchronized with the NTP time. We can anyhow conclude that for a 12 genset plant, a maximum accuracy variation of 24 milliseconds is a very satisfactory achievement.

Ethernet installationFibre optic communication should be selected when exceeding more than 100 metres of cable length distance. Fibre optics is excellent in harsh environments where electrical or electromagnetic interferences could be expected.

Since Ethernet is widely used in offi ce and home environments, there is always a risk of hacking, and the plant control with Ethernet should be adequately protected. However, once a strategy for the Ethernet communication has been established, with plant control, offi ce, and any 3rd party Ethernet networks separated with a fi rewall, this is not a major concern. The fi rewall can be seen as a two-way safety device since it will protect the plant control network, and also the other networks from possible hacking or computer virus attacks.

Cyber security, customer and 3rd party connectivityWärtsilä makes a point of protecting the plant control network with an industrial type fi rewall, and related confi gurations, usernames, and passwords are treated with the highest possible

security. This still means that customer or 3rd party connections are supported for transfer of plant data, but the safety procedures need to be in order. One of the supported protocols for 3rd party connections is the OPC protocol, which is supported by the majority of available HMI and SCADA solutions.

Several countries are currently defi ning national rules for so called Cyber security. This means that the infrastructure, critical plants, and processes need to comply with regulations relating to connectivity and possible threats. Wärtsilä is following this development closely and will endeavour to comply with new regulations as they are released.

Additional features comingStandard features, such as good diagnostics and the other examples described above, will certainly help our customers to maintain their own businesses in the best possible way. Nevertheless, there are still more features that will enhance plant performance, one being the effi ciency. The next step for Wärtsilä will be to implement Ethernet communication also to the frequency drives. In this way, statistics of optimal operation curves can be analyzed, and the total consumption of so called “parasitic loads”, i.e. the plant’s own consumption, can be lowered.

Another feature is further development of the Wärtsilä CBM concept to include electrical and automation equipment analysis and parameterising over remote communications. Customers with plants in very remote locations are clearly interested in having a “big brother” at Wärtsilä that can securely connect to the plant to help out with technical expertise. Ethernet related known acronyms, such as VoIP (voice over IP) and streaming (or video on demand), are to be integrated into the WOIS, WISE and CBM remote support systems.

Wärtsilä, with its quite unique experience in developing remote connections for the energy business, represents the ideal partner for enhancing the overall lifetime effi ciency and availability of any customer’s plant - even if we are not always physically present.

NOTE: This article is an in detail follow-up of the Wärtsilä TwentyFour7 1.07 article; Power Plant Automation – On-Line 24/7.

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The ultimate in fuel fl exibilityAUTHOR: Thomas Hägglund, Product Manager, Gas Power Plants, Wärtsilä in Finland

Fig. 1 – The Wärtsilä 50DF tri-fuel engine can switch smoothly from gas, via LFO to HFO and back during operation.

is based on the reliable and well-tried Wärtsilä 46 HFO engine, now with ‘tri-fuel’ capability. It is the fi rst large engine to offer such fuel fl exibility. The Wärtsilä 50DF is intended to provide high output with fuel fl exibility, low emission rates, high effi ciency and excellent reliability.

The Wärtsilä 50DF is designed to meet customer demands for a safe and fuel-fl exible engine, running on gas, LFO or HFO. While the earlier design of the Wärtsilä 50DF dual-fuel engine had the capability of switching over to HFO operation, it involved stopping the engine and changing fuel injection valves. Now, however, the fuel can be switched whilst the engine is operating.

Fuel economy is always a major concern, especially in these days of high gas prices. The ability for marine and power industry sector users to switch to the most economical fuel is, therefore, a capability that is of great value.

The latest Wärtsilä 50DF version

Design overviewThe Wärtsilä 50DF is manufactured in confi gurations from 6L up to 18V, giving 950 kW per cylinder and a total maximum mechanical output of 17,100 kW. It is designed to give the same output whether it is running on natural gas or on LFO/HFO. The engine speed is 500 or 514 rpm for use with 50 or 60 Hz applications. It also has a maximum thermal effi ciency of 47% (± 0% tolerance), higher than for any other gas engine.

The engine functions are controlled by an advanced automation system that allows optimum running conditions to be set independent of the ambient conditions or fuel.

Both the gas admission and pilot fuel injection are electronically controlled. This ensures that the correct air-fuel ratio can be set for each cylinder individually, and that the minimum amount of pilot fuel can be injected while ensuring safe and stable combustion. All parameters are controlled automatically during operation.

The individually and electronically controlled valves ensure that all cylinders stay within the operating window, avoiding knocking and misfi ring. This eliminates unnecessary load reductions and shutdowns.

OperationThe Wärtsilä 50DF can run on most qualities of natural gas. The nominal design point is a methane number of 80. It is also designed for continuous operation on LFO and HFO, without reduction in the rated output.

The Wärtsilä 50DF operates on the lean burn principle: the mixture of air and gas in the cylinder has more air than is needed for complete combustion. Lean combustion reduces peak temperatures and, therefore, NO

X emissions. Effi ciency

is increased and higher output is reached while avoiding knocking.

Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main charge. To obtain the best effi ciency and lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio and with the correct amount and timing of pilot fuel injection.

The latest development of the Wärtsilä 50DF engine, is a tri-fuel engine that is able to run on natural gas, light fuel oil (LFO) or heavy fuel oil (HFO), offering optimum fuel fl exibility. With initial installations in the marine sector, the engine is now fi nding its way into the power industry.


in detail 17

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Fig. 2 – Wärtsilä 50DF tri-fuel system.

Return fuel

Fuel injection pumps for back-up fuel operation Injection valves

Controlsystem

Pressure

Pre

ssu

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M

Pilot fuel pump unit

Pre

ssu

re

Co

mm

on

rai

l fo

r h

igh

p

ress

ure

pilo

t fu

el

Ret

urn

fu

el

Booster pump unit

Booster pump unit

Pilot fuel tank LFO

Main fuel tank LFO or HFO

Wärtsilä has developed a special electronic control system to cope with the demanding task of controlling the combustion in each cylinder, and to ensure optimal performance in terms of effi ciency and emissions under all conditions by keeping each cylinder within the operating window. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components.

Tri-fuel abilityThe main development in the Wärtsilä 50DF is in the fuel system. The fuel system has been divided into three: one for gas, one for back-up fuel, and one for the pilot fuel system. The separate connection for the pilot fuel means that pilot fuel is always present whether the engine is running on gas, LFO or HFO.

The Wärtsilä 50DF is normally started in diesel mode, using both main diesel and pilot fuel. Gas admission is activated when combustion is stable in all cylinders. When running the engine in gas mode the pilot fuel, which is always LFO, amounts to less than 1% of full-load fuel consumption. The amount of pilot fuel is controlled by the engine control system. When running the engine in back-up fuel mode, the pilot fuel is also in use to ensure nozzle cooling and to keep pilot fuel nozzles clean.

The engine can also be delivered without the back-up fuel system. In this case, the engine is started on pilot fuel with gas admission activated when the engine is up to speed. The synchronization and loading is done on gas. The pilot fuel consumption here is the same, i.e. less than 1% of full load fuel consumption.

Gas supply: The natural gas is supplied to the engine through a gas regulating unit (GRU). The gas is fi rst fi ltered to ensure a clean supply, and the gas pressure, which is dependent on engine load, is controlled by a valve located in the GRU. At full load, the pressure before the engine is 3.9 bar (g) running on gas with LHV 36 MJ/m3. For lower LHV, the pressure has to be increased. The GRU includes the necessary shut-off and venting valves to ensure safe and reliable gas supply.

On the engine, the gas is supplied through large common-rail pipes running along the engine. Each cylinder has an individual feed pipe to the gas admission valve on the cylinder

head. Gas pipes on the engine can, if requested, be of double wall design.

Diesel oil supply: The fuel oil supply to the engine is divided into two separate systems, one for the pilot fuel and the other for back-up fuel.

The pilot fuel is elevated to the required pressure by a pump unit. This includes duplex fi lters, a pressure regulator, and an engine-driven radial piston-type pump. The high-pressure pilot fuel is then distributed through a common rail pipe to the injection valves at each cylinder. Pilot fuel is injected at approximately 900 bar pressure, and the timing and duration are electronically controlled. The pilot fuel system is separated from the back-up fuel system with separate connections on the engine. The back-up fuel is fed to a normal camshaft-driven injection pump. From the injection pump, the high-pressure fuel goes to a spring-loaded injection valve of standard design for a diesel engine.

Fuel injection valve: The Wärtsilä 50DF has a twin-needle injection valve. The larger needle is used in diesel mode for LFO or HFO operation, and the smaller for pilot fuel oil. Pilot injection

is electronically controlled and the main diesel injection is hydraulically controlled. The individually controlled solenoid valve allows optimum timing and duration of pilot fuel injection into every cylinder. Since NO

X formation depends greatly

on the pilot fuel amount, this design ensures very low NO

X formation while

still employing a stable and reliable ignition source for the lean air-gas mixture in the combustion chamber.

Gas admission valve: Gas is admitted to the cylinders just before the air inlet valve. The gas admission valves are electronically actuated and controlled by the engine control system to give exactly the correct amount of gas to each cylinder. In this way, the combustion in each cylinder can be fully and individually controlled. Since the valve can be timed independently of the inlet valves, the cylinder can be scavenged without risk of gas being fed directly to the exhaust system.

Independent gas admission ensures the correct air-fuel ratio, and an optimal operating point with respect to effi ciency and emissions. It also enables reliable performance without shutdowns, knocking or misfi ring. The gas admission valves have a short stroke and utilize

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Fig. 3 – Instant change over from gas to HFO mode with the Wärtsilä 50DF tri-fuel solution.

gas to liquid fuel liquid fuel to gas

Instant ~0,5h ~0,5h

~0,1h

~80%

In the tri-fuel solution the twin injection nozzles are used also for HFO operation.The LFO pilot is in use also during the HFO operation.*The time needed to reach full load on gas depends on the duration of HFO operation.

*

Gas LFO HFO Gas LFO HFO

100%load

specially selected materials, thus providing low wear and long maintenance intervals.

Injection pump: The Wärtsilä 50DF utilizes the well-proven monoblock injection pump developed by Wärtsilä. This pump withstands the high pressures involved in fuel injection and has a constant-pressure relief valve to avoid cavitation. The fuel pump is ready for operation at all times and will switch over from gas to fuel oil if necessary. The plunger is equipped with a wear-resistant coating.

Pilot fuel pump: The pilot fuel pump is engine-driven. It receives the signal for correct outgoing fuel pressure from the engine control unit and independently sets and maintains the pressure at the required level. It transmits the prevailing fuel pressure to the engine control system.

High-pressure fuel is delivered to each injection valve through a common rail pipe, which acts as a pressure accumulator and damper against pressure pulses in the system. The fuel system has a double wall design with an alarm in case of leakage.

Seamless fuel switchingThe engine can be switched automatically from fuel oil to gas operation at loads below 80% of the full load. Transfer takes place automatically after the operator’s command without load changes. During switchover, which lasts about one minute, the fuel oil is gradually substituted by gas.

In the event of, for example, a gas supply interruption, the engine automatically and instantaneously transfers from gas to fuel oil operation at any load. Furthermore, the separate back-up fuel system makes it possible to switch over from LFO to HFO without load reduction. The pilot fuel is in operation during HFO operation to ensure nozzle cooling and to keep fuel nozzles clean. The pilot fuel consumption is less than 1% of full load fuel consumption. Switching over to LFO from HFO operation can also be done without load reduction. From LFO to gas operation, the switch can be made as described above. This operation fl exibility is the real advantage of the tri-fuel system.

Air-fuel ratio control: Correct air-fuel ratio under any operating conditions is essential to optimum performance and emissions. For this function,

the Wärtsilä 50DF is equipped with an exhaust gas waste-gate valve.

Some portion of the exhaust gases bypasses the turbocharger through the waste-gate valve. The valve adjusts the air-fuel ratio to the correct value independent of the varying site conditions under high engine loads.

Extensive validation tests on HFO have been carried out. One important issue was whether the deposits that build up in the engine after running for a long time on HFO would cause problems during gas operation. It was found, however, that quite soon after switching over from HFO to gas operation, the load could be increased rapidly and deposits were burned out quickly without problem.

Other developmentsIn addition to the tri-fuel system, there are a few other notable developments in the latest version of the Wärtsilä 50DF.

Lube oil system: One issue that arose during development work was lube oil quality. Normally gas engines are run using lube oils with lower base numbers (BN) compared to engines running on HFO. There was a question of whether the lube oil would have to be changed when switching from HFO to gas, but tests showed that the same lube oil could be used, even when switching fuel. The lube oil BN has, however, to be selected based on the sulphur content in the back-up fuel.

The Wärtsilä 50DF has an engine-driven oil pump and can be provided with either a wet or dry sump oil system, where the oil is mainly treated outside the engine. Marine engines have a dry sump and power plant engines a wet sump. On the way to the engine, the oil passes through a full-fl ow automatic fi lter unit and a safety fi lter for fi nal protection. Lubricating oil is fi ltered through a full-fl ow paper cartridge fi lter. A separate centrifugal fi lter acts as an indicator of excessive dirt


in detail 19

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Fig. 4 – The 300 MWe power plant in Sangachal will utilize the fi rst tri-fuel Wärtsilä 50DF engines.

in the lubricating oil. A separate pre-lubricating system is used before the engine is started to avoid engine part wear.

Engine cooling: The Wärtsilä 50DF also now has more effi cient coolers. The engine has a fl exible cooling system design optimized for different cooling applications. The cooling system has two separate circuits – high-temperature (HT) and low-temperature (LT). The HT circuit controls the cylinder liner and the cylinder head temperatures, while the LT circuit serves the lubricating oil cooler. The circuits are also connected to the respective parts of the two-stage charge air cooler.

The V-type engines are also available with an open interface system where the cooling circuits can be connected separately. This makes optimized heat recovery and an optimized cooling system possible. The LT pump is always in serial connection with the second stage of CA cooler, while the HT pump is always

in serial connection with the jacket cooling circuit. Both HT and LT water pumps are engine-driven as standard.

Turbocharger: The effi ciency of the turbocharger has also been improved. The Wärtsilä 50DF is equipped with the modular-built Monospex (single pipe exhaust) turbo charging system, which combines the advantages of both pulse and constant pressure charging. The interface between engine and turbocharger is streamlined with a minimum of fl ow resistance on both exhaust and air sides. High-effi ciency turbochargers with in-board plain bearings are used, and the engine lubricating oil system is used for the turbocharger. The waste-gate is actuated electro-pneumatically.

Moving into energyThe tri-fuel Wärtsilä 50DF was introduced for marine use towards the end of 2007. The tri-fuel capability is

useful in the marine industry since ships have a demand for instant changeover. For example, in LNG transportation, typically LNG carriers are run on LNG on their outward journey, but can select to use the cheapest liquid fuel (HFO) on the return journey, when all LNG has been delivered to the receiving terminal.

In the past there had not been a great demand for instant changeover in the power generation business, but there could be benefi ts. In some areas of the world there may be a need for independence of gas supply, as has been the case in parts of Eastern Europe. This offers an economical, feasible alternative if there is a lack of gas, or where the gas supply is not secure.

Building a large power plant is a major investment, and it is crucial to have a guaranteed fuel supply. Having the fuel fl exibility that would be provided by Wärtsilä’s 50DF would therefore be of huge benefi t. It would also be useful in small power plants where

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Table 1. – Wärtsilä 50DF main technical data.

Wärtsilä 50DF main technical dataCylinder bore (mm) 500Piston stroke (mm) 580Cylinder output (kW/cyl) 950Engine speed (rpm) 500, 514 Mean effective pressure (bar) 20.0, 19.5Piston speed (m/s) 9.7, 9.9Fuel specifi cation:Fuel oil Marine diesel oilISO 8217, category ISO-F-DMX, DMA and DMBFuel oil Marine residual HFOISO 8217, category ISO-F-RMA 30 – RMK 700Natural gas methane number: 80

50 Hz/500 rpm 60 Hz/514 rpm 18V50DF 18V50DF* 18V50DF 18V50DF*Electrical power (kW) 16621 16621 16621 16621Heat rate (kJ/kWh) 7616 8184 7616 8184Electrical effi ciency (%) 47.3 44.0 47.3 44.0

Heat rate and electrical effi ciency at generator terminals, including engine-driven pumps, ISO 3046 conditions

and LHV.

Tolerance 5%. Power factor 0.8. Gas methane number > 80.

* Back-up fuel LFO or HFO. LFO pilot <1% in use when running on HFO.

Fig. 5 – The Manisa power plant in Turkey with the fi rst Wärtsilä 50DF engine for a power plant installation.

the gas pressure is low, or where the gas supply is interruptible. Having to run on LFO as a back-up in such situations is uneconomical, and for countries like Pakistan, the tri-fuel engine offers interesting opportunities.

Certainly the demand for dual-fuel capability has become more important in the last few years. At the end of 2004, Wärtsilä was awarded a contract for an 84.8 MW replacement and extension of an existing diesel plant at Manisa in western Turkey. The contract was the fi rst installation of a Wärtsilä 50DF for a power plant. The installation allowed a change of fuel from heavy fuel oil to natural gas.

Meanwhile, the fi rst two Wärtsilä 50DF dual-fuel engines for Pakistan were supplied to two captive power plants at the start of 2006. Fuel fl exibility is an important factor in Pakistan as the year-round supply of natural gas cannot be guaranteed.

Now the fi rst tri-fuel Wärtsilä 50DF engines for the power industry will be used in Azerbaijan. In December 2006, Wärtsilä was awarded a contract by AzerEnerji, the Azerbaijan state electricity company, to deliver a multi-fuelled generating plant for a 300 MWe power plant to be located at Sangachal, 50 km south of the capital Baku.

The plant will consist of 18 generating sets each powered by an 18-cylinder Wärtsilä 50DF, delivering 17 MW. The plant is scheduled to be fully operational by October 2008. The engines will run primarily on natural gas (with a small

amount of pilot LFO for ignition). However, it will also be able to run on HFO if there is a problem with gas supply. It can also run on LFO and can deliver the same power on all three fuels.

The success of this innovation

has already been shown in marine applications, and now it is rapidly being applied to the power sector. This fi rst tri-fuel installation may be an indication of a trend in the region.


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National power system planningAUTHOR: Asko Vuorinen , Managing Director, Modigen Ltd.

Table 1. – Cost estimates of alternative power plants.

* CHP plant has 85% total effi ciency

Output Effi ciency Investment Fixed Variable costs (I) costs (Fc) costs (Vc) (MW) (%) (EUR/kWe) (EUR/kWa) (EUR/MWh)Oil-fi red plants - DE-160 HFO 160 43 815 94.8 85.2- DE-160 LFO 160 41 630 68.1 108.9- DE-160 LBF 160 41 815 89.8 118.2- AD GT-160 LFO 160 36 715 76.6 124.4- Ind GT-110 LFO 110 31 530 60.9 154.9Gas-fi red plants - GTCC-330 gas 330 49 1050 134.6 66.7- DF-160 gas 160 43 830 114.1 73.8- GE-160 gas 160 42 775 107.7 75.0- AD GT-160 gas 160 38 875 120.3 86.1- Ind. GT gas 110 31 645 106.8 102.1- CHP-160 gas* 160 42 (85%) 845 121.6 39.3Other power plants - Nuclear-1500 1500 35 2670 281.0 17.1 - Coal-500 500 40 1495 166.2 47.6- Biomass-160 160 34 1510 172.9 44.4- Wind-160 160 - 1200 126.0 12.0

In this second article based on his book “Planning of Optimal Power Systems” Asko Vuorinen explains how national power systems are planned.

The main target of national power system planning is to fi nd an optimal capacity mix in the system which either gives minimum costs or maximum profi ts. Minimizing the total system cost is the main method used by national utilities, while maximizing profi ts has been the preferred goal for private companies.

GENERATION COST EVALUATION

AssumptionsThis analysis has been made at an ambient temperature of +30oC at a site to be 100 m above sea level. The assumed power

system has a 10 GW peak load and 52 TWh electricity consumption. The alternative power plants include nuclear, coal, gas, oil and renewable technologies.

Oil-fi red plantsOil-fi red plants include heavy fuel oil (HFO), light fuel oil (LFO), and crude liquid biofuel (LBF) diesel engine plants. The HFO diesel engine (DE-160) plant has ten Wärtsilä 18V46 diesel engines. The HFO and LBF diesel engines will operate more than 1000 h/a and have been equipped with SCR denox-systems. The LFO and LBF diesel engine plants utilize twenty Wärtsilä 20V32 diesel engines.

The gas turbine plants can use only LFO and can be built using either aero-derivative or industrial gas turbines. The aero-derivative gas turbine plant includes four 40 MW turbines. The industrial gas

turbines have one 110 MW turbine. The LFO-fuelled plants are assumed to operate less than 1000 h/a without denox-system.

Gas-fi red plantsGas-fi red plants include a gas turbine combined cycle (GTCC-330), a gas engine (GE-160), an aero-derivative gas turbine (ADGT-160) and a dual-fuel engine plant (DF-160). The GTCC-330 plant has two 110 MW gas turbines and one steam turbine. The output of the plant at site conditions is 330 MW. The aero-derivative gas turbine plant (ADGT-160) has four 40 MW turbines. The industrial gas turbine (Ind. GT-110) plant has one 110 MW gas turbine.

The gas engine plant (GE-160) has twenty Wärtsilä 20V34SG engines. The dual-fuel plant (DF-160) has ten Wärtsilä 18V50DF engines. The combined output of the two plants is 160 MW. The combined heat and power production plant (CHP) has twenty Wärtsilä 20V34SGgas engines, and a heat recovery boiler with a bypass in each of the boilers.

Other plantsOther power plants analyzed include nuclear, coal, biomass and wind power plants. The nuclear plant has one pressurized water reactor (PWR) and a 1500 MW output.

The coal-fi red plant has a fl uidized bed boiler and one reheat steam turbine with supercritical steam values and an output of 500 MW. The coal-fi red plant includes both desox- and denox-systems. The 160 MW biomass plant employs a steam plant, which is fi red by sawdust, bark, and crushed wood.

Capital cost evaluationCapital costs of power plant alternatives have been evaluated using the formula CC = FCR x I, where CC = capital costs, FCR = fi xed charge rate and I = investment costs (Table 1). Investment costs include turnkey plant costs and owner’s costs

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Fig. 1 – Optimum generation mix with all options open.

Case 1: All generation options accepted

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

Ind. GT

Diesel eng.

Gas eng.

GTCC

Coal

Nuclear

Fig. 2 –Optimum generation mix without nuclear plants.

Case 2: Nuclear plants not accepted

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

Ind. GT

Diesel eng.

Gas eng.

GTCC

Coal

Nuclear

including interest during construction.Capital costs have been evaluated using

a 25-year lifespan and 8.1% discount rates. The fi xed charge rate (FCR) is then evaluated based on the formula FCR = (r(1 + r)n)/((1 + r)n – 1), where r = costs of capital and n = lifespan of the power plant.

Operation and maintenance costsFixed operation and maintenance costs (Fom) include plant operating personnel, taxes, insurances, and other services. Variable operation and maintenance (Vom) costs include maintenance costs, as well as material and waste costs. Material costs include materials for denox- and desox-systems and lubricating oil. Waste costs include nuclear waste handling and the costs of CO

2-emission allowances.

Fuel costsFuture prices of fuels have been evaluated by calculating linear trends from the historical values from 1994-2005. It is then assumed that these trends will continue during the 25-year operation time of the power plants between the years 2011–2035.

Levelized prices of fuels have been evaluated by discounting future pricesof fuels to the start of operation: liquid biofuel (LBF) 45.6 EUR/MWh, lightfuel oil (LFO) 36.3 EUR/MWh, heavyfuel oil (HFO) 25.7 EUR/MWh,26.5 EUR/MWh, coal 7.6 EUR/MWh and nuclear 4.0 EUR/MWh.

Generation costsGeneration costs (Gc) of alternative power plants can be evaluated using a tariff formula Gc= Fc/t + Vc, where Fc = fi xed costs, t = full power hours and Vc = variable costs. The parameters of the tariff formulas are given in Table 1.

The optimization starts by studying the lowest cost alternatives for each full power hours (t) range. The break-even costs of peaking plants can be found when the costs of a light oil-fi red industrial gas turbine plant (Ind. GT-160) and a diesel engine plant (DE-160) are at the same level, which is at 157 h/a. Thus diesel engines are the most economical above 157 hours, and industrial gas turbines when t is below 157 hours. It should be noted, however, that industrial gas turbines are seldom used in peaking applications, since they cannot be started up in 10 minutes, which is the requirement

for peaking plants in most systems.The break-even costs of a diesel engine

plant (DE-160) and a natural gas-fi red gas engine plant (GE-160) can be similarly found at 1170 hours. When annual operating hours are less than 1170 hours, the diesel engine yields the lowest costs. Gas engines are the most economical at levels above 1170 hours. Diesel and gas engines can meet the 10 minute start-up requirement.

Similarly, break-even costs for a gas

engine and a gas-fi red combined cycle plant are at 3240 hours. But the break-even costs between a gas engine plant and a coal plant are at 2140 h/a. Thus, a gas engine plant has the lowest costs between 1190 and 2140 hours annually. The gas turbine combined cycle plant has higher costs than the coal plant. The break-even costs of a coal plant and a nuclear plant are then at 3760 hours, while the break-even costs of biomass steam plants and LBF diesel engine plants are at 1125 hours.


in detail 23

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Fig. 3 – Optimum generation mix without nuclear and coal plants.

Case 3: Nuclear and coal plants not accepted

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

Ind. GT

Diesel eng.

Gas eng.

GTCC

Coal

Nuclear

Fig. 4 – Optimum generation mix with renewable plants.

Case 4: Only renewable power plants accepted

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

LBF-diesel

Biomass

Wind

Table 2. – Lowest cost ranges of power plants.

Power plant Full power hours (h/a)LFO GT plant 0 - 157LFO diesel plant 157 - 1170 Gas engine plant 1170 - 2140Coal plant 2140 - 3740GTCC plant (without coal) 3240 - 3740 Nuclear plant 3740 - 8760Gas-fi red CHP plant 770 - 5800

The lowest cost for plants at different operation times have been given in Table 2. It should be noted that a gas-fi red CHP plant is the lowest cost alternative throughout almost the full range. A CHP plant can be used only if the heat load is needed for district heating, cooling, or industrial process needs.

MINIMIZATION OF POWER SYSTEM COSTSThe goal of optimization is to minimize the total generation costs of the national power system. Four cases have been studied as follows:

Case 1: All generation options accepted (nuclear)The optimum power generation mix in the system, if all of the above options are open, has been evaluated in Figure 1. The duration curve segments have been fi lled so that all available plants will be operating only during hours of lowest costs given in Table 2. The baseload would be generated using nuclear power plants, the intermediate load by coal-fi red plants and gas engines. The peak load would be generated using light fuel oil-fi red diesel engines and gas turbines.

Case 2: Nuclear plants not accepted (coal)If nuclear power plants are ruled out for whatever reason, coal-fi red plants would replace them (Figure 2). In this case, about 97% of the electricity in the optimum system will be based on coal. The peak load generation would be the same as in Figure 3.

Case 3: Nuclear and coal plants not accepted (gas)If both coal and the nuclear fuel plants are omitted, coal plants would be replaced by gas combined cycle plants (Figure 3). The generation mix would consist mainly of gas-fi red plants. This would mean that 97% of generation would come from natural gas.

Case 4: Only renewable power plants acceptedFinally, if all nuclear and fossil-fi red plants were replaced by biomass, liquid biofuel and wind energy plants, the optimal generation mix is given in Figure 4. Wind power is only available in baseload, but would need a lot of back-up power. In this case only 10% of wind

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Fig. 6 – Wind and liquid biofuel (LBF) mixed power system. Wind power plants produce the baseload and LBF power plants produce the peak and intermediate load.

Case 6: Wind and LBF diesel

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

LBF-diesel

Wind

Fig. 5 – Nuclear and liquid biofuel (LBF) mixed power system. Nuclear plants produce the baseload and LBF plants produce the peak and intermediate load.

Case 5: Nuclear and LBF diesel

12 000

10 000

8000

6000

4000

2000

0

(MW

)

(h/a)

5 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 8760

LBF-diesel

Nuclear

power can be considered as available capacity during peak load. The system would need regulating reserves of about 20% of wind capacity (2600 MW), which can be built using LBF engines.

Optimal capacity mixThe optimum power generationcapacity in megawatts in the 10,000 MW system has been evaluated in Table 3. Case 1 (nuclear) would have the lowest generation costs of 63 EUR/MWh. Case 2 (coal) has the second lowest costs at 77 EUR/MWh. The total costs of cases 3 and 4 will be 90 EUR/MWh and 83 EUR/MWh respectively.

MAXIMIZATION OF PROFITSIn free electricity markets, the shareholder value of a utility company depends on the profi t. Thus private investors try to maximize profi ts by building a system in which the electricity prices are high but the electricity generation costs are lowest.

Competitive electricity prices in the power system should be based on the variable costs of the marginal plant during each hour. Prices of electricity based on marginal costs of the marginal power plant in cases 1, 2, 3 and 4 respectively will be asfollows: 43.9 EUR/MWh, 61.2 EUR/MWh,80.3 EUR/MWh and 52.8 EUR/MWh.Incomes and net profi ts have been evaluated for each case in Table 4.

Maximum profi ts can be found if prices are based on the most expensive variable costs 100% of the time, but most generation takes place using low variable cost nuclear plants. Highest net profi ts are obtained with nuclear/LBF (Case 5, Figure 5), in which electricity prices are always 118.6 EUR/MWh, but total costs are lower.

Case 6 (Figure 6) shows wind power producing the baseload and an LBF diesel plant producing the peak load. In this instance, the price of electricity is always 118.6 EUR/MWh, corresponding to the marginal costs of LBF diesel plants. Costs of power generation correspond to the variable costs of wind power (12 EUR/MWh).

SUMMARY AND CONCLUSIONSThe capacity mix of a national power system can be optimized by evaluating the generation costs of alternative power plants at site conditions using levelized prices of fuels. There are two methods of

optimization: to minimize the generation costs or to maximize the profi ts.

The lowest costs can be obtained by employing nuclear and CHP plants for the baseload having 60% of the capacity. The coal-fi red plants and gas engine plants in the intermediate load with 15% of the capacity. Peak load plants should be fi lled by diesel engines and industrial gas turbines having 25% of the capacity.

If the system is planned with the goal of maximizing profi ts, then the baseload should be fi lled with nuclear plants or wind energy plants having 40-50% of the total capacity. The intermediate and the peak load should be fi lled with liquid biofuel plants having 50-60% of the capacity. In this case, the price of electricity will be high and generation costs will be low.


in detail 25

Table 3. – Optimal power generation capacity (MW).

Alternative Case 1 Case 2 Case 3 Case 4 Nuclear Coal Gas Renewable- Nuclear 6 200 - - -- Coal 700 7000 - -- Gas combined cycle - - 6500 -- Gas engines 700 800 800 -- LFO diesel engines 1 500 1400 1650 -- LFO gas turbines 1 500 1400 1650- Wind turbines - - - 13,000- Biomass steam turbines - - - 4300- LBF diesel engines - - - 7700Total 10,600 10,600 10,600 25,000Average costs EUR/MWh (63.3) (76.6) (90.1) (82.8)

Table 4. – Net profi ts of alternative 10,000 MW power systems.

Case Price of Incomes Costs Net profi t electricity (MEUR) (MEUR) (MEUR)

(EUR/MWh)

1) Nuclear 43.9 2276 3286 - 1008 2) Coal 61.2 3173 3972 - 7983) Gas 80.3 4193 4677 - 4844) Renewable 52.8 2750 4294 - 15445) Nuclear and LBF 118.6 6167 3980 2186 6) Wind and LBF 118.6 6167 4674 1493

RETRACTION – IN DETAIL 01, 2007Fundamentals of power plantsFigure 8 on page 16: The ambient temperature correction factor curves for electrical effi ciency for gas turbines and internal combustion engines had changed place by mistake. This is how the correct fi gure should look:

Thanks go to Sami Myllyviita from Wärtsilä in Finland and Bo Svensson from Diesel & Gas Turbine Worldwide magazine for noticing.

Ambient temperature (°C)

1,15

1,10

1,05

1,00

0,95

0,90

0,85

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

IC-engines

Gas turbines

The need of ancillary services was not evaluated. In the real world the operation and regulation reserve requirements tend to increase the share of fl exible power plants. In the optimal system, about 30-40% of capacity should be fi lled by gasengines, light fuel oil-fi red diesel enginesand gas turbines. Additionally, thepeaking power plants should be capable of being started up in ten minutes. The infl uence of ancillary services will be described in detail in future articles.

NOTE: The first article in the series “Planning of Optimal Power Systems” was published in In Detail issue 01, 2007. Please visit www.optimalpowersystems.com for more information.

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Striving towards a cleaner global environment

AUTHOR: Johan Boij , Chairman of the Euromot Working Group (WG) Stationary Engines

Performance Standard 1: Social and Environmental Assessment and Management SystemPerformance Standard 2: Labor and Working ConditionsPerformance Standard 3: Pollution Prevention and AbatementPerformance Standard 4: Community Health, Safety and SecurityPerformance Standard 5: Land Acquisition and Involuntary ResettlementPerformance Standard 6: Biodiversity Conservation and Sustainable Natural Resource ManagementPerformance Standard 7: Indigenous PeoplesPerformance Standard 8: Cultural Heritage

Table 1. – IFC Performance Standards.

The Kyoto Protocol (fi rst stage 2008 – 2012) and the European Union’s (EU) Emission Trading Scheme (ETS) (the fi rst stage began 1 January 2005 with the second stage due to start on 1 January 2008) are aimed at reducing anthropogenic greenhouse gas (GHG) emissions. One means towards the achievement of this target is to utilize energy more effi ciently in power production. The World Bank Group continues to update its performance standards on social and environmental sustainability, and the Environmental, Health and Safety (EHS) Guidelines are a part of this package. The EHS Guidelines contain the performance levels considered to be achievable at reasonable cost in new facilities using existing technology.

Leading international investment banks have made an agreement with the IFC (International Finance Corporation, the private sector arm of the World Bank Group) to follow guidelines based on IFC’s environmental and social standards and thus adopted the Equator Principles. These principles apply to projects having a capital cost in excess of USD 10 million. Many other fi nancial institutions (via environmental and other policies) are also using the World Bank Group guidelines in addition to national norms in their projects. Consequently, the World Bank’s EHS guidelines have in practice become the minimum environmental standard in global power plant projects.

The engine manufacturing industry has in the updating process of the EHS

A global requirement today is to fi nd clean and more effi cient power production processes. The Kyoto Protocol and IFC/World Bank Guidelines are the reference sources being increasingly used in international business today.

Guidelines been active via Euromot (The European Association of Internal Combustion Engine Manufacturers). The EHS draft papers have been commented upon (drafts were posted by the World Bank/IFC on the internet for a 60 days comment period) in several Euromot Position Papers (also available on the internet). Additionally, a delegation from Euromot met with IFC/Worldbank representatives in Washington during 2007, at which the engine industry gave its’ reaction to the Guideline drafts.

THE WORLD BANK GROUP’S ENVIRONMENTAL AND SOCIAL STANDARDSIn February 2006, the International Finance Corporation (IFC) completed a rigorous updating of its standards. The eight performance standards are intended to establish the conditions that the client is to meet throughout the life of an investment, and are listed in Table 1.

Social and environmental considerations are considered integral parts of good business practice, and responsible businesses can create value for all parties

involved while helping to promote long-term profi tability and investments. Every effort should be made to ensure that investments do not harm people or the environment, and if negative impacts are unavoidable, these should be minimized and mitigated appropriately.

The EHS Guidelines are included in Performance Standard 3. These are technical reference documents with general and industry-specifi c examples of Good International Industry Practice (GIIP). Performance Standard 3 asks the client to adopt Best Available control and process Techniques (BAT) that are feasible and cost effective. Aspects to be considered in the choice of pollution abatement control measures are:

Technical feasibility: This considers factors such as local infrastructure, commercial markets, etc. in the selection of control technologies, such as the availability of reagents and water if required by the treatment method, and the local availability of maintenance and other services.


in detail 27

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Table 2. – Stack emissions for engine plants*** (unit mg/Nm3 (15% O2) or as indicated). Nm3 is at one atmosphere pressure and 0°C.

Fuel PM SO2 NOX

(Particulate matter) (Sulphur dioxide) (Nitrogen oxides as NO2)

Liquid 50 - 100* 1.5 - 3%* Bore < 400 mm 1460 - 1600 ** Bore ≥ 400 mm 1850Gas N/A N/A SG (spark ignited): 200 DF (dual-fuel): 400 GD (compression ignition, gas diesel): 1600

Financial feasibility: The incremental cost of the control technique over the projects’ investment, operating and maintenance costs, and whether such incremental cost could make the project non-viable. The used technique should not produce secondary wastes that cannot be accepted (handled) by local environmental capacity and infrastructure.

Operational feasibility: Addresses operational reliability and local conditions, considering the availability of trained personnel with suffi cient technical and fi nancial resources.

In other words, the chosen pollution control and process technology is to be practical, cost-effective and suitable for the project within the local context.

ENVIRONMENTAL, HEALTH AND SAFETY (EHS) GUIDELINESThe previous guidelines version was adopted in July 1998. On 30 April 2007, a new updated version of the EHS Guidelines was published on the Internet [1]. These new guidelines were developed as part of a two and half year review process. However, six (out of totally 63) of these guidelines are still in the review/comment stage. In contrast to the previous ‘static’ document, it is intended that the new EHS Guidelines will be a ‘living’ document subject to regular updating.

The EHS Guidelines are to be used as a technical source of information

during the project appraisal activities. When host country regulations differ from the levels and measures presented in the EHS Guidelines, the project is expected to achieve whichever is the more stringent. If, in view of specifi c project circumstances, less strict levels are appropriate, a full and detailed justifi cation for any proposed alternative is needed as part of the environmental assessment (EA). In practice, this kind of deviation (“variation”) is only possible with certain IFC fi nanced projects.

The new guidelines incorporate the General EHS Guidelines and 62 specifi c Industry Sector Guidelines. The General EHS and Thermal Power Guidelines are “joint guidelines” and are intended to be used together with relevant industry sector guidelines. Combustion source emission guidelines associated with steam and power generation activities from sources with a capacity of less or equal 50 MW

th = fuel input, are addressed in the

General EHS Guidelines, and for larger power source (>50 MW

th) emissions,

in the Thermal Power Guidelines. By this approach, the EHS Guidelines are technique specifi c with their own technique specifi c emission limits for boilers, gas turbines and engines in line with present worldwide trends towards progressive regulations.

For power plant projects, the General EHS and Thermal Power Guidelines are the primary reference focus. The Thermal Power Guidelines document is

still in the review stage, but is expected to be published for commenting upon in autumn 2007. For some types of project, such as oil pipe pumping stations, other guidelines, notably the Onshore Oil and Gas Development document, will also be of interest.

GENERAL EHS GUIDELINESThe General EHS Guidelines [2] contain numerous cross-cutting environmental, health and safety issues potentially applicable to all industry sectors (during plant construction, operations phase, and plant demolition) such as: stack emissions, ambient air quality, noise, hazardous materials management, etc. It is intended for small combustion processes between 3 MW

th and 50 MW

th.

Stack emissionsIn Table 2 the stack emissions for an engine plant are given. It should be noted that in the General EHS Guidelines, 15% O

2 is used as the oxygen reference

point for the emission concentration values. This is the case also in USA, India and the European Union’s (EU BREF) Reference Document on Best Available Techniques for Large Combustion Plants document. For a bigger stationary engine, 15% O

2 is close

to “actual” conditions and is thus logical. The performance of a secondary fl ue gas abatement process (if used), is best described if the emission concentration is expressed close to actual conditions.

In contrast to the old guidelines, where the same emission values applied regardless of stationary engine type or the fuel (liquid/gas) in use, in the new General EHS Guidelines the limits are differentiated for different engine types and fuels used. As regards the fi ndings in Table 2:

n PM (particulate) and SO2 levels

refl ect quite well the existing fuel infrastructure around the world. Limits can, in most cases, be met by an appropriate liquid fuel choice (primary measure).

n NOX: For a number of years already,

the engine industry has been working intensively to make engines more environmentally friendly, especially concerning NO

X emissions.

* If justifi ed by project specifi c justifi cations (economic feasibility, environmental capacity of site).

** If justifi ed to maintain high energy effi ciency.

*** Higher performance levels should be applied to facilities in urban/industrial areas with a degraded air-shed

or close to sensitive areas.

Emission guidelines are applicable to plants operating more than 500 hours per year and to those with an annual

capacity utilization factor of more than 30 percent.

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Table 3. – US EPA Primary NAAQS (only the most relevant pollutants listed).

Pollutant Average time GLC (ground level concentration), microgram/m3SO2 Annual 80 24-hour* 365NO2 Annual 100PM-10 Annual - 24-hour** 150PM-2.5 Annual 15 24-hour*** 35Ozone 1-hour** 235 (0.12 ppm) 8-hour**** 157 (0.08 ppm)

* Not to be exceeded more than once per year.

** Not to be exceeded more than 3 times in 3 consecutive years. Ozone level limit applies only in limited areas.

*** 98th percentile of concentrations in a given year, averaged over 3 years.

**** 3 year average of annual 4th highest daily maximum 8-hour concentrations.

Table 4. – Noise level (beyond property boundary (one hour LAeq dB(A)).

Time Residential, institutional, Industrial, educational commercial07:00 – 22:00 55 7022:00 – 07:00 45 70

Liquid fuel:o < 400 mm bore engines: In order to

reach the prescribed emission levels for a four-stroke engine, the latest engine development version with enhanced “Miller-concept” (a primary measure with higher pressure ratios) is to be utilized. The NO

X-level of 1460 mg/

Nm3 has a drawback in respect of its higher heat rate compared to the 1600 mg/Nm3 level. The IFC/World Bank allows the higher NO

X-level if

energy effi ciency is improved, and the impact of the Kyoto Protocol spirit can thus be seen in this limit. For a two-stroke engine to comply with the set NO

X-level the only option

today is to apply a secondary selective catalytic reduction (SCR) technology.

o ≥ 400 mm bore engines: Most current four-stroke engines are to be injection retarded or equipped with a “water addition (wet) method” in order to reach the prescribed NO

X-level. For

two-stroke engines a wet method such as a fuel water emulsion system or a direct water injection system is to be used. As a consequence, the heat rate will increase. Future four-stroke and two-stroke engine generations are expected to reach the NO

X-level

without an increased heat rate.

Gas:® SG (spark ignited): The engine

is tuned to reach the NOX-level

(lean-burn concept used).® DF (dual-fuel, low gas pressure): The

engine is tuned to reach the NOX-

level (lean-burn concept used).® GD (high pressure gas (compression

ignition) diesel): The engine is tuned to reach the NO

X-level.

n In degraded air-sheds or sensitive areas, secondary fl ue gas abatement methods, such as the SCR (for NO

X abatement),

for instance, might be needed - especially for liquid fi red engines. In the Environmental Assessment (EA), the assimilation capacity of the surrounding environment should be evaluated to establish the emissions levels that can be accepted from a power plant.

n Stack emission testing is carried out on an annual basis.

The emission limits in Table 2 give, in general, a good representation of

BAT for an engine power plant, taking into account the existing fuel, reagent infrastructures, etc., around the world, and the latest technical developments.

As stated previously, the emission levels given in the General EHS Guideline are only intended for rather small power plants (≤ 50 MW

fuel input = thermal => power

plant output typically about 20-23 MWe).

The Thermal Power Guideline draft (for bigger power plants > 50 MW

th) is still

unpublished and its required emission values are not known at this time.

Ambient Air Quality (AAQ)By applying national legislated standards, or in their absence the current WHO (World Health Organization) Air Quality Guidelines or other internationally recognized guidelines (such as the federal

US EPA (Environmental Protection Agency) National Ambient Air Quality Standards (NAAQS) or the relevant European Council Directive 1999/30/EC, Directive 2002/3/EC), emissions to the surrounding area should not result in pollutant concentrations that reach or exceed relevant ambient quality guidelines and standards. The federal US NAAQS are shown in Table 3.

The US EPA has also regulated the allowed PSD (Prevention of Signifi cant Deterioration) increments of the emissions. For example, for SO

2 the allowed PSD increment

in a class II (almost the entire USA belongs to this class) area is about 25% of the 24-hour value. At the EU level, no general increment rule is given, and the total ground level


in detail 29

concentration (GLC) in an area is to be below the stipulated limit level.

Euromot has recently (June 2007) made known to IFC/WB the problems associated with the general increment rule of 25%, as suggested by IFC/WB in the General EHS Guideline with notable reference to the WHO AAQ Guideline levels. A misinterpretation of this might lead to AAQ levels that are 1800% stricter than comparative levels allowed in the USA. No general “universal” increment rule should be given for application in context with different AAQ Guidelines. Only fi gures stipulated by the specifi c AAQ norm should be used (if given). The AAQ Guidelines by WHO are not intended to be strictly applied as a legislative norm without considering local circumstances. Further information regarding these matters can be obtained from documents [3] and [4] given in “internet sources” below.

AAQ levels are cumulative and refl ect all polluters in an area, existing topography, weather conditions (wind direction, speed), stack height & confi guration, and so on, and need therefore always to be calculated on a case-by-case basis. Stack height should be according to Good International Industry Practise (or Good Engineering Practise (GEP)), this is further described on page 16 of the General EHS Guidelines.

Ground level Concentration (GLC) calculations should be handled by third party environmental experts with suffi ciently advanced calculation programmes (in order to get percentiles excluded etc.).

NoiseThe current World Bank Thermal Power – Guidelines for New Plants 1988 levels, for the noise level beyond property boundary are maintained. These are shown in Table 4.

Design measures to achieve noise levels include, among other things:n Silencers on the exhaust gas and

inlet air side of the plant.n Noise absorbing material in

the walls and the roof.n Low noise radiator type.

In the General EHS Guideline, noise limits for various working environments (heavy industry, open offi ces, control

rooms, etc.) are also given. The recommended noise level for control rooms (45-50 dB(A)) is, for example, very strict, and corresponds to the level applied in the control rooms of nuclear power plants. Such strict requirements should not be applied on a stationary (reciprocating) engine power plant, considering the different complexity of such plants and the different risks involved. This has also been commented upon in the Euromot position papers [3] and [4], and a counter proposal of 65-70 dB(A) has been offered.

Liquid effl uent limitsIn the General EHS Guidelines, no limit values are given for liquid effl uent. In the new guidelines, liquid effl uent limits can be found in the Industrial Guidelines, and it is expected, therefore, that power plant values will be included in the Thermal Power Guidelines. Euromot has stressed the importance of having smaller power plants with a relative small effl uent stream treated more leniently than big thermal power plants [3] and [4].

Other pointsIt should be noted that the new EHS Guidelines went immediately into effect on April 30, 2007 when they were published, replacing previously published documents in Part III of the Pollution Prevention and Abatement Handbook and on the IFC website. Euromot has, in position papers [3] and [4], referred to this challenge. Some other aspects (such as an interruption of gas supply, etc.) needing clarifi cation are also listed in the above mentioned Euromot papers.

WORK CONTINUESEuromot’s work in commenting upon the EHS Guideline proposals has been interesting and intensive. The co-operation between different engine manufacturers has been constructive, and such industry co-operation is important in order to present third parties with a general common picture of the development status of techniques in this kind of work.

The fi nal version of the General EHS Guidelines as BAT describes an engine power plant rather well. However, some critical items (explained above) remain, and Euromot has recently given feedback on these to the IFC/WorldBank. The updating mechanism of the documents is still unclear.

As previously mentioned, six guideline proposals are still in the comment or review stages. The Thermal Power (for power production plants > 50 MW

th)

is one of these. This means that there is still a lot of work to be done before the complete World Bank Group EHS Guidelines package is fi nalized.

Via Euromot the European engine industry actively supports the environmental development work done by WB/IFC, US EPA, EU and other organizations/countries, and brings together the accumulated knowledge of the engine industry in this important work.

INTERNET SOURCES:[1] http://www.ifc.org/ifcext/enviro.nsf/Content/EnvironmentalGuidelines

[2] http://www.ifc.org/ifcext/enviro.nsf/AttachmentsByTitle/gui_EHSGuide-lines2007_GeneralEHS/$FILE/Final+-+General+EHS+Guidelines.pdf

[3] http://www.euromot.org/download/news/positions/stationary_engines/WB_EHS_guidelines_euromot_position_back-ground_paper_290607.pdf

[4] http://www.euromot.org/download/news/positions/stationary_engines/WB_EHS_guidelines_euromot_position_paper_290607.pdf

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DAPPB – a new concept in arctic sea transportationAUTHORS: Oskar Levander , General Manager, Conceptual Design, Ship Power, Wärtsi lä in Finland and Tuomas Sipilä , Project Engineer, Conceptual Design, Ship Power, Wärtsi lä in Finland

Fig. 1 – New ice breaking barge concept.

Fig. 2 – Barge with open water pusher.

Analysts are suggesting that as much as 25% of the world’s remaining undiscovered natural resources lie beneath the Arctic ice. Since global warming has reduced the existing ice cover, there is now real potential for the opening of commercially attractive sea transport routes in the region. This, in turn, is furthering the development of specialized vessels that offer clear operating advantages in such conditions. Wärtsilä, together with Aker Arctic, has developed a novel hybrid concept for use in heavy ice conditions.

The Double Acting Ship (DAS) concept, developed by Aker Arctic

With high oil prices feeding interest in exploiting the natural resources of the Arctic, the development of new, highly specialized sea tonnage for use in such harsh environments is becoming increasingly relevant.

and based on the principle of the ship operating stern fi rst in ice is, of course, indicative of the type of developments being made in ice-going ship technology.

Yet this new concept is not without shortcomings. The diesel electric propulsion arrangement of the DAS concept, for instance, is relatively expensive compared with a conventional mechanical propulsion confi guration, and the electrical transmission losses are high. The stern shape design is also a compromise between good ice-breaking capability, water infl ow to the propellers, and course stability.

Another relevant ship transport concept that has been around some time is the pusher-barge concept. It offers clear advantages with regard to effi cient use of crew and machinery. On the other hand, it is a complicated system that attains its biggest benefi ts when transporting goods with long cargo

handling periods, such as bulk cargos. The new arctic transport system

developed by Wärtsilä and Aker Arctic, however, combines the advantages of both concepts. It offers sound ice breaking properties without detriment to open water performance, at a lower investment price for the entire ship fl eet.

DAPPB conceptThe Double Acting Pusher Puller Barge system (DAPPB) is based on the principle of a barge being pushed by a dedicated pusher tug in open waters. When the combination comes to the ice edge, the open water pusher is replaced by a specially designed ice breaking tug, or puller, that pulls the barge through the ice. The principle could be applied to a range of different arctic ship types, such as LNG carriers, general cargo, and container vessels. However, the market offering the biggest potential is likely to be that of arctic oil transportation.

The propulsion arrangement consists of two electrically driven azimuthing propulsors located in the forward part of the puller unit. This enables the propellers to eat through rough ice, while at the same time fl ushing the hull behind it to reduce ice friction.

The ice puller benefi ts from a diesel-electric machinery system that has steerable propulsors to optimize ice-breaking performance. The cost of the machinery is of course high, but it is only used in ice conditions where the good features can reap maximum benefi ts.

The open water pusher, on the other hand, is not designed for ice breaking at all, and can therefore utilize conventional machinery. With a bulbous bow optimized for low resistance in open water, the pusher barge is propelled by a single CP propeller mechanically driven by one or


in detail 31

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Pusher

Fig. 3 – Machinery confi guration for open water pusher.

Barge

WÄRTSILÄCP Propeller

WÄRTSILÄ 6L46

WÄRTSILÄ 6L46

WÄRTSILÄ 6L20

WÄRTSILÄ 6L20

WÄRTSILÄ 6L20

6300 kW

6300 kW

1020 kW

1020 kW

1020 kW

WÄRTSILÄBow thruster

Fig. 4 – Machinery confi guration for ice puller.

PullerBarge

WÄRTSILÄ 6L46

WÄRTSILÄ 6L46

WÄRTSILÄ 6L20

6300 kW

6300 kW

1020 kWWÄRTSILÄ

Bow thruster

Electrical pod 8500 kW

WÄRTSILÄ 6L46 6300 kW

WÄRTSILÄ 6L46 6300 kW

Electrical pod 8500 kW

two diesel engines. This offers a very low cost solution with low transmission losses.

Since the ice-strengthened barge and pusher can be designed purely for open water use, performance is comparative to a conventional vessel, although construction costs for the pusher barge would be more expensive than for a normal ship. However, if conventional ice-going ships are used on a route with both ice and open water, the ship will not be optimum in all situations. The longer the open water transit, the more money and energy will be wasted with a purely ice-going ship.

Reduced costsThe DAPPB concept meanwhile uses the expensive ice puller during ice operation only. For the long open water leg, the open water pusher takes over and the operating costs are lower. Ideally, there are many more open water pushers than there are ice pullers in the fl eet. This means that compared to a fl eet of dedicated ice-going tonnage having expensive machinery needed in ice, total investment costs can be signifi cantly reduced.

Crewing has also been taken into account. Experienced crew for ice operation is a scarce commodity in today’s markets, but with the DAPPB transport system, only ice-experienced crew for the ice pullers is required. The open water pushers do not need specialized crew.

Another benefi t of the DAPPB concept is the possibility to actually optimize the ice puller for ice breaking. There is no need to take open water operation into consideration. For example, the bow can be made wider than the rest of the hull to allow for better turning in ice.

Design showcaseTo showcase the features of the new concept, Wärtsilä and Aker Arctic have designed an Ice-Class 1A Super tanker of 70,000 dwt based on the DAPPB principle. The main difference compared to a conventional tanker hull is the aft opening for the pusher and puller units. Because of this opening and the lack of propulsion machinery, the barge will fl oat at even keel also in ballast. The ballast capacity corresponds to that of a conventional tanker, but in order to keep the size of the pusher and puller units as small as possible, the fuel tanks are located in the cargo barge, as are all cargo handling and pumping systems.

The barge is equipped with one small auxiliary engine for generating the electrical power when disconnected from the pusher or puller unit.

The design criteria for the pusher arelow investment and operating costs. Ice class is not required for the pusher sopropulsion machinery and the hull can be of “standard” low cost design. Thedraught selected is relatively high – 9 mto maximize propeller diameter and propulsion effi ciency – but is still lower than that of a conventional ice-going tanker. The service speed of the pusher-barge combination in open water is 15 knots based on a power output of 11 MW at the propeller. The total

installed propulsion power of the pusher unit is 12.6 MW – signifi cantly lower than the power normally required in ice-going tankers – based on two medium-speed diesel engines connected to one shaft to increase redundancy.

A controllable pitch propeller is required in order to achieve smooth thrust control during unit change operations. As typical for oil tankers, three auxiliary engines are utilized for electrical power generation, although a gearbox equipped with PTO and shaft generator can provide additional electricity production. The total installed power in the pusher is about 16 MW.

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Fig. 6 – Pusher change at Murmansk.

Fig. 5 – Operation routes.

Ice pullerThe ice puller, which is intended to pull the barge when operating in ice covered waters, incorporates the offshore loading facilities. This is benefi cial as only a small number of ice pullers, rather than all the barges, need to be equipped with this facility. However, the ice class required for the puller barge does need to be at least equal to the ice class of the cargo barge, and the size of the puller needs to be bigger compared to the pusher barge, due to heavier machinery and also due to a heavier hull requirement that features a wider aft section.

This extra beam allows the puller to open a channel that is wider than the dimension of the cargo barge, which further enhances the capabilities of the Double Acting concept. Consequently the ice performance should be the same or better as for the reference Double Acting Tanker (DAT): 3 knots in 1.2 m ice thickness.

The ice puller has a machinery arrangement similar to that of other DAT tankers featuring diesel-electric propulsion with diesel generators and azimuthing podded propulsors. Diesel-electric propulsion offers good torque characteristics for the propellers that are required in ice conditions, and electrical steerable propulsors provide excellent steering and reversing capabilities.

The propulsion power, based on four medium-speed main gensets and one smaller genset for harbour use, is also equal to that of a DAT for the same operation area: 2 x 8.5 MW. Total installed power is about 26 MW.

Comparative studiesDuring comparative studies, the DAPPB was compared to a conventional 70,000 dwtDAT concept with equal cargo capacity. Three different operational routes were simulated to evaluate the economy of the concept: 1) the Varandey-terminal in the Barents Sea to Murmansk, 2) the Varandey-terminal to Rotterdam and 3) the Varandey-terminal to Port Fourchon in the US.

The simulation, based on equal amounts (12.5 Mton/year) of annually transported oil with fl eets of both concepts, found that as the cargo capacities of the DAT and oil barge are the same, the loading and unloading times are also the same. Service speeds in open water and in ice are set to be equal for both alternatives. The difference in operation is only the pusher and puller change that requires time and a sheltered location in which to make the change. This will slightly increase distance to be travelled for the DAPPB. As the annual transported amount and vessel size is fi xed, the calculated fl eet sizes will be decimal numbers, the needed fl eet sizes

are rounded up to the next integer.

ResultsThe economy of the concepts is compared as required freight rate (RFR) per cargo ton. Three different winter conditions for the ice part of the voyage are calculated: no ice, 50% ice and 80% ice. Simulation results showed economical feasibility for routes 2 and 3, although, as expected from the start, route 1 (Varandey to Murmansk) seemed not to be commercially feasible.

On route 1, the main idea of the DAPPB system – to change to pushers in open water - cannot be utilised, since there is only ice operation.

However, when the operation route contains ice and open water conditions, better economy is predicted for the DAPPB concept compared to DAT concepts. On route 3, the DAPPB concept was found to be more economical and the difference in calculated freight rate was more than USD 4/t lower than for the DAT vessel. On an annual basis the savings can be in excess of USD 50 million.

The best features of both Double Acting and pusher barge systems can be combined to create a new concept that shows better economic sense than existing solutions. The DAPPB system represents an attractive solution for transportation tasks where both open water and ice conditions occur and the longer the open water part is, the greater the benefi ts. However, the concept still requires some development with regards to connection units and hull form optimization, and the concept should of course be tailored for an operator’s specifi c logistic chain.


in detail 33

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Dual-fuel-electric LNG carrier machinery: when a concept becomes realityAUTHOR: Marco Andreola , General manager, LNG Business, Solutions, Ship Power, Wärtsi lä in Finland and Giulio Tirell i , Project Engineer, Solutions, Ship Power, Wärtsi lä in Finland

Fig. 1 – The British Emerald is the latest ship to be delivered with Wärtsilä 50DF dual-fuel engines.

During the past forty years, the LNG carrier market has been dominated by steam turbine machinery, which ensured a high level of reliability along with low maintenance costs.

Wärtsilä took a step forward by introducing the new dual-fuel-electric machinery concept, and the market’s feedback was quite clear: the time for the establishment of a complete new concept had come.

The main triggers for this change in the LNG carrier machinery standard were, and still are, a very high effi ciency over the whole output power range, the use of cheaper and cleaner fuel, and the lowest emission levels among all prime movers.

All these factors, along with many others as, for example, easy installation and maintenance, contribute considerably towards reducing vessel operating costs and, therefore, increased profi ts.

Furthermore, the Wärtsilä concept has other distinguishing aspects; the vessels’ management requires a crew with standard knowledge of diesel installations, there is a high redundancy of the whole power generation plant (giving a superior level of safety), and there is complete fuel fl exibility, given the option of running the engines on gas, HFO and/or MDO.

In December 2006, the fi rst vessel, the Provalys, to be powered by a dual-fuel-electric plant, was delivered to Gaz de France by Alstom Chantiers de l’Atlantique. The same shipyard later

Since Wärtsilä fi rst introduced the dual-fuel-electric machinery concept for liquefi ed natural gas (LNG) carriers, more than 200 engines, with a total output of almost 2000 MW,have been contracted. To date, sixteen engines have started their duty onboard the new generation of LNG carriers.

supplied two other vessels, the Gaz de France energY and the Gaselys, to the same shipowner. At the end of June 2007, Hyundai Heavy Industries Co. Ltd delivered the fi rst vessel built in Korea for BP Shipping, the British Emerald.

Different engine confi gurations were selected for each vessel according to its size and operational requirements: Gaz de France energY, a 75,000 m3-MedMax class ship, is powered by a plant consisting of four six-cylinder Wärtsilä 50DF dual-fuel engines, with a total installed power of 22.8 MW; Provalys, Gaselys and British Emerald are all 155,000 m3-class LNG carriers. Different engine confi gurations were selected: Provalys and Gaselys adopted three twelve- and one six-cylinder Wärtsilä 50DF dual-fuel engine each, while British Emerald opted for two twelve- and two nine-cylinder Wärtsilä 50DF dual-fuel

engines. Both these engine confi gurations have an aggregate power of 39.9 MW.

Being the fi rst to be delivered, Gaz de France energY, Provalys and Gaselys have accumulated a signifi cant amount of data. British Emerald has only recently ended sea trials and detailed information is not yet available. For this reason, all the material presented here refers to the experience of the Gaz de France vessels.

SEA TRIALSThe ships’ sea trials have been the fi rst step in collecting data since the entire machinery installation could fi nally be tested simultaneously, monitoring the interactions of the different equipment.

The capacity of the whole propulsion system, including the gas feeding system, was tested setting both working conditions and power request changes,

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12 000

10 000

8000

6000

4000

2000

0

Ru

nn

ing

ho

urs

10.10.06 29.11.06 18.1.07 9.3.07 28.4.07 17.6.07 6.8.07

Commissioning Start of operations

energY - gasenergY - MDO

Fig. 2 – The running hours of ‘Gaz de France energY’.

7000

6000

5000

4000

3000

2000

1000

0

Ru

nn

ing

ho

urs

10.9.06 30.10.06 19.12.06 7.2.07 29.3.07 18.5.07 7.7.07


Provalys - gasProvalys - MDO

Fig. 3 – The running hours of ‘Provalys’.

up to severe and extreme levels. The capacity for absorbing a sudden

increase in power demand by the engines and gas feeding system was tested. Engine speed and gas feeding pressure were set as sensitive factors for the fi nal evaluation of the test.

The bow thrusters - with a total start peak up to 2200 kW per unit - were simultaneously connected to the grid while the engines were running at a signifi cant load. The engines’ load increased signifi cantly in a couple of seconds during which no changes in the engines’ speed were detected. In other words, they were easily absorbing the change in load. A reduction in gas feeding pressure, correlated to the increased gas quantity request, was barely visible and the system re-established the parameter at the settled level within a few seconds.

A load rejection test was performed in order to check the power management system’s response, excluding one by one the generators from the grid, and so eliminating their contribution to the power production. With all engines running at the same time, generator breakers were opened in sequence, and the load re-distributed on the engines still connected to the grid. At each step, after having opened a breaker, a small load increase on the other engines was reported. At the same time a gas pressure increase was noticed, getting higher every time the following breaker was opened. The gas pressure increase was related to the fast closing of the pressure regulating valve in the gas valve unit (GVU). This event produced a counter peak in the gas pressure. The smaller the number of engines running on gas connected to the grid, the higher the gas pressure peak becomes. In this respect, every time an engine is disconnected, the others contribute a higher percentage to the total gas consumption, resulting in a higher gas pressure peak. In any case, the deviation of the gas pressure from the optimum value was defi nitively irrelevant. The engine load increase, related to a higher gas quantity demand, was reducing the transition phase to an irrelevant level.

Another similar type of test was performed while the ship was manoeuvring: engines were connected to and disconnected from the grid, increasing and decreasing the requested power in a continuously varying sequence. The

engines’ reaction was to exactly fulfi l the power demand at any time during the testing; no signal of concern was registered from the whole system.

During the endurance test, the propulsion system was subject to heavy loads for a prolonged period of time. The “constant power mode” was applied, meaning that a constant load was maintained on the propulsion motors while the motors’ speed was free to change in order to absorb the variations in torque, coming from the propeller.

The result was that the whole propulsion chain behaved perfectly, clearly showing that all equipment had been dimensioned correctly, matching both the propulsion power requirements and ancillary loads.

The crash-stop test is defi nitively one of the most challenging tests during sea trials. As in all other cases, during this test the engines were also running on gas, maintaining this fuel mode throughout the entire duration of the trial. Results prove that the system reacts immediately to the variation in power requirements, and the


in detail 35

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Fig. 4 – The running hours of ‘Gaselys’.

7000

6000

5000

4000

3000

2000

1000

0

Ru

nn

ing

ho

urs

18.1.07 7.2.07 27.2.07 19.3.07 8.4.07 28.4.07 18.5.07 7.6.07 27.6.07 17.7.07 6.8.07


Gaselys - gasGaselys - MDO

Fig. 5 – Total running hours for Gaz de France’s three LNG carries.

12 000

10 000

8000

6000

4000

2000

0

Ru

nn

ing

ho

urs

9.11.06 9.12.06 8.1.07 7.2.07 9.3.07 8.4.07 8.5.07 7.6.07 7.7.07 6.8.07 5.9.07

Pro

valy

s b

egin

of

op

erat

ion

s

ener

gY

beg

in o

f o

per

atio

ns

Gas

elys

beg

in o

f o

per

atio

ns

energY - gasenergY - MDO

Provalys - gasProvalys - MDO

Gaselys - gasGaselys - MDO

propeller speed ramp reached zero rpm value in only twenty seconds, counting from full speed ahead. When the torque ramp reaches the maximum astern torque value, the mode automatically changes to “constant speed mode”. This improves the response of the system, reducing to the minimum value the time required by the vessel to reach speed zero. In this case, the propeller speed is kept constant and the variation of torque is absorbed by the power variation of the propulsion motors.

A ramp test was performed starting from

zero propulsion power and setting the power request to the maximum level. The dual-fuel-electric machinery installation demonstrated its advantage compared to other machinery alternatives, such as steam turbine machinery and low-speed diesel engines, by reaching maximum propulsion power in around twenty minutes.

Dual-fuel-electric LNG carriers in operationThe Provalys has been in operation for more than half a year now. Together

with the other dual-fuel-electric LNG carriers, it has accumulated a relevant amount of running hours, giving Wärtsilä and the operators a signifi cant amount of service experience.

The vessels performances have proved that the engine confi gurations and, therefore, the power request prediction, properly match the power demand.

For the 155,000 m3-class vessel, the sailing mode requires three twelve-cylinder Wärtsilä 50DF dual-fuel engines to operate constantly at around 75 to 85% load, while the six-cylinder Wärtsilä 50DF dual-fuel engine can be in standby mode. During cargo loading or unloading, the ships still operate in gas mode, being the required power provided only by the smallest dual-fuel generator.

Running the dual-fuel generators in gas mode, utilizing as much as possible the natural boil-off gas (N-BOG) evaporating from the vessel’s cargo tanks, is a common LNG carrier management practice. All the dual-fuel-electric vessels are predominantly operating in gas mode, and no serious setbacks have been encountered in providing the requested amount of energy. As is normal, these plants need some adjustments during the very fi rst operating phase of their lives.

Both laden and ballast voyages are performed in gas mode. One of the Gaz de France vessels encountered some problems at the very beginning of the fi rst laden voyage: most probably, the combination of exceptionally poor gas quality (high level of nitrogen) and unfi nished fi ne-tuning of the low duty compressors, did not allow the engines to run at full load. The tuning of the compressors and the continuous reduction in the amount of nitrogen during sailing, fully solved the problem in less than one day. Engines tolerate a nitrogen content higher than 22% as usually the load level remains below 85%. No impact on the schedule had been recorded.

Scheduled maintenance has been the main reason to stop the engines, and although some minor component failures have been reported, none of the engines have encountered any systematic failures. The fact that the vessels have been consistently able to run according to their assigned schedules confi rms the fl exibility of dual-fuel-electric installations.

So far, roughly 40,000 running hours have been accumulated by the Wärtsilä

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Typical effi ciency (relative)

100%

100% load

100%

80%

HFO Gas Gas(DF engine) (steam

turbine)

(Wärtsilä DF engine operating on HFO resp. gas)

(Steam turbine operating on gas)

Typical specifi c CO2 emissions (relative)

Infl uence of fuel typeLNG: MethaneHFO: Residual fuel oil

100%

HFO(DF engine)

10-15%

Gas

NOx (relative)100%

HFO(DF engine)

~0%Gas

SOx (relative)

100%

HFO (DF engine)0-5%

Gas

Particulates (relative)

Fig 2. – Comparison of typical specifi c NOx, SOx and particulate emissions – infl uence of fuel type.

Fig 1. – Comparison of typical specifi c CO2 emissions – Wärtsilä DF dual-fuel engine versus steam turbine - infl uences of process effi ciency and fuel type.

50DF dual-fuel engines on the three Gaz de France vessels. The plants are running almost continuously on gas, and the total running hours in gas mode have reached 25,000 running hours (63% of the total amount of running hours). The ratio between the running hours on gas and the total running hours will increase, with the vessels being operated only on gas.

Before ship delivery, the engines accumulated running hours almost entirely in diesel mode, during commissioning there was no gas onboard. The only running hours accumulated in gas mode during the commissioning were those connected with the gas trials.

Once the vessels loaded their fi rst LNG cargoes, a signifi cant increase of running hours has occurred, as can be seen in the graphs. As a result, running hours on diesel mode indicate a settled value. The Provalys graph shows that the running hours on gas required a longer period to turn into a linear increasing trend. In fact, the Provalys suffered a shaft line problem and was forced to unload the cargo and move gas free to a dry-dock facility. During this period, the vessel ran at a reduced speed in diesel mode only. Provalys is now running continuously on gas and the number of running hours in gas mode has almost reached the same amount as those performed in diesel mode.

British Emerald, the latest ship to be delivered with dual-fuel-electric machinery, has performed all sea trials in both diesel and gas mode successfully. The vessel is currently sailing to the terminal to take its fi rst cargo.

In the next few years, many more LNG carriers with dual-fuel-electric machinery featuring Wärtsilä 50DF dual-fuel engines will be delivered, and many more LNG carrier newbuildings with dual-fuel-electric machinery are on the drawing board. Presently, engines for 52 dual-fuel-electric LNG carriers have been contracted.

Wärtsilä dual-fuel engines are not new tothe marine industry. Two Wärtsilä 32DF dual-fuel engines are in operation on the FPSO Petrojarl 1 and one on the Sendje Ceiba. Four Wärtsilä 32DF dual-fuel engines are in operation on the dual-fuel-electric offshore supply vessel Viking Energy and four on Stril Pioneer. Further dual-fuel engines are on order for application on FPSOs and aboard offshore supply vessels.

The dual-fuel (DF) engine represents a real low emission solution. By switching to gas fuel a major step in environmental soundness can be achieved.

In gas operating mode the specifi c CO2 emissions are typically reduced by 20% compared to heavy fuel oil (HFO)/marine diesel oil (MDO) operation. The corresponding reduction in NOX is 85-90%, with SOX and particulate emissions almost eliminated. The specifi c CO2 emission reduction with the Wärtsilä 50DF engine operating on gas compared to a steam turbine alternative is 30-40%.

The reduced CO2 emissions are a result of high hydrogen/carbon ratio of gas compared to HFO/MDO and the high shaft effi ciency of the Wärtsilä DF engines.

The lean burn premixed combustion process provides very low NOX emissions. SOX and particulate emissions are practically eliminated due to the very low pilot injection - only about 1% of the total energy input comes from pilot fuel (source of sulphur and ash).

A comparison of typical specifi c emissions can be found in Figures 1 and 2.

LOW EMISSIONS WITH WÄRTSILÄ DUAL-FUEL ENGINES


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Bearings for longer shaft lifeAUTHOR: Tim Biswell , Product Development Director, Seals and Bearings, Propulsion, Wärtsi lä in the United Kingdom

Fig. 2 – Railko’s 200 mm test rig.Fig. 1 – Sternsafe bearing installation.

Composite marine bearing materials are non-metallic and have been specially designed to cope with extremes of operating conditions: loads, speeds, temperature fl uctuations, dirty conditions, etc, and depending on the application and grade, these thermosetting resin laminates can operate dry, partially lubricated, or fully lubricated in oil or seawater.

The bearings offer signifi cant advantages in terms of reduced vessel through-life operating costs. These include reduced maintenance, improved reliability, and less wear to shaft materials. The key to their success, however, lies in the high technology composite material, the excellent R&D work, engineering design, and skilful manufacturing and

Following the acquisition of the Railko Marine business in July 2007, Wärtsilä now is the leading developer and manufacturer of high performance composite bearings.

assembly. They are applied as propeller shaft bearings, rudder bearings, steering gear and deck machinery bushes.

Composite bearings Composite rudder bearings have been developed over a number of years to take the pressures and stresses inherent in rudder assemblies, and to provide continued performance under the most arduous conditions. One of the most advanced materials for rudder bearings is the CY160LS material, a fi lament wound material with high compressive and impact strength and a proven ability to resist fatigue shock damage, thus ensuring long bearing life.

The use of composite oil-lubricated stern tube bearings was introduced more than thirty years ago with the WA80H material. Today, thousands of ships worldwide have demonstrated the product’s exceptional performance benefi ts, such as the ability to operate in a seawater/oil emulsion or pure

seawater under emergency conditions. The material is also “kind” to shafts and will not seize, as metallic bearings can. A low modulus of elasticity and reduced wear and tear, together with a reduced weight for ease of handling, are other advantages. The bearings themselves can be easily machined and are available either press fi tted or resin bonded to reduce shipyard costs. CY160LS, the fi rst-generation of non-asbestos oil-lubricated bearings, manufactured using an asbestos-free reinforcement impregnated with a phenolic resin, offers high compressive strength, impact strength and wear rate, to deliver a long bearing life on the 300 vessels to which it has been applied.

Sternsafe developmentThe latest technology for oil lubricated stern tube bearings, however, is SternsafeTM. Developed in conjunction with a major shipowner and Classifi cation Society to meet the latest industry demands, this technology is based on

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Fig 3. – Bearing wear after 100 hours in gritted seawater.

50mm Journal test rig – Testing in gritted seawaterBearing wear rate – DTI

NF22 (Railko) RG22 (Railko) Elastomeric

CY160LS (Railko) Rubber

1.201.101.000.900.800.700.600.500.400.300.200.100.00

mm

0 10 20 30 40 50 60 70 80 90 100 110

Table 1. – Test conditions.

Metric units Imperial units

Sleeve: Stainless steel EN ISO 316 AISI 316Sleeve diameter 50.8 mm 2 inchShaft rotation: 55 rpm 8.8 m/min 28.9 ft/minBearing load 2500 N 550 lbfBearing pressure 0.48 N/mm 69 psi 4.8 kg/cm2

PV rating 42 kg/cm2. m/min 2000 psi. ft/minLubricant fl ow rate 7.5 litres/min 1.65 lmp. gallons/min 120 US gallons/hourLubricant tank capacity 88 litres – agitated

Fig. 4 –Elastomeric bearing wiped.

a composite material with a newly developed, improved bearing surface, which incorporates all the benefi ts of the existing products but with increased strength and durability. Sternsafe can also operate with some environmentally friendly bio-degradable oils.

The fi rst vessel fi tted with Sternsafe was the container ship Maersk Antwerp. This retrofi t was completed in April 2002 and the vessel has now completed over fi ve years of uninterrupted service. Sternsafe has since been fi tted to almost 100 ships covering a wide range of different shiptypes, with every possible shaft size operating under a variety of operating conditions.

In addition to this, Wärtsilä has recently

supplied what is thought to be the world’s largest composite stern tube bearing. The bearing, which is designed to suit a shaft of over 1000 mm in diameter, is now operating successfully on fi ve vessels in a series of what is reported to be the world’s largest container ships.

Water-lubricated systemsAlongside its oil-lubricated sterntube seals and bearings, Railko water-lubricated systems have also formed part of the company’s product portfolio for over forty years, supplying more than 30 of the world’s navies. Extensive independent end-user testing of the shaft bearing materials has been undertaken by several navies, all of whom consequently

adopted the systems for use in surface and submarine fl eets. Wärtsilä’s acquisition of Railko also includes the company’s sophisticated laboratory that has been at the forefront of bearing technology for nearly half a century.

Advanced 50 mm and 200 mm propeller shaft bearing test rigs have been used to confi rm the performance of the non-asbestos NF21/22 material intrinsic to the water lubricated stern tube bearing system. The material allows the system to offer a signifi cant reduction in the shaft speed at which the point of hydrodynamic operation is achieved. As a result, bearing friction and wear are reduced dramatically. Service wear measurements predict that a bearing life approaching 90 years could be possible.

In order to compare materials in current use, an arduous test programme was devised to analyse the performance of various bearing materials, in highly abrasive conditions, against stainless steel counter face materials.

Substitute seawater was used with silica particles added. The grit used was equivalent in particle size and shape to that found in the UK Portland area at a concentration accepted by the UK Ministry of Defence to be representative of aggressive British coastal water.

Bearing up to testsTo accelerate the comparative test, the concentration was increased by a factor of 10. The grit was kept in suspension in the


in detail 39

Fig. 5 – Rubber bearing shaft after 800 hours. Fig. 6 – NF shaft after 2000 hours testing.

seawater by means of a stirrer agitating the solution in the supply tank.

A pump was used to deliver the gritted seawater to the bearing and re-circulate it back to the tank. The fl ow rate for each of the test bearings was set at 7.5 l/m. Interestingly, the pump did not survive the fi rst set of tests. Test conditions can be seen in Table 1. The initial testing comprised running each material under the stated conditions for a period of 100 hours, measuring the bearing wear rate at 20 hour intervals.

As can be seen from the results in Figure 3, even though all the materials were tested under the same conditions, there was a spread of wear results. Most materials performed well over this time period with the exception of the elastomeric material, where signifi cant bearing wear and smearing occurred, and scoring on the shaft liner was noted. For consistency, all bearings were tested with the multi-axial groove confi guration; this tested the performance of the bearing material and not the design.

The second phase took the two best performing materials, Railko NF and rubber, testing them over a period of 2000 hours. Initially the rubber material performed well in comparison to Railko NF, but over time the wear rate increased rapidly. The rate of wear was such that the test on the rubber material was stopped at around 850 hours.

The tests showed that that there was signifi cant scoring on the shaft on the

rubber bearing when compared to the original shaft condition. This was caused by the silica particles becoming embedded in the rubber material. These particles then scored the shaft resulting in the typical failure mechanism of this type of material. The “gramophone” effect created on the shaft cannot maintain a hydrodynamic water fi lm, resulting in shaft to bearing contact. This greatly accelerates the bearing wear, leading to extensive “run-away” wear down.

Railko NF materialBy contrast, the Railko NF material, with its standard bearing design, exhibited a more linear (steady state) wear result. The test in this case was continued to 2000 hours. The bearing was still capable of further operation. It is worth noting that the Railko NF bearing took almost twice as long to reach the same wear down level as the rubber bearing.

As can be seen from Figure 6, the shaft sleeve was not heavily worn. As Railko NF is relatively harder than rubber, the material does not allow abrasive particles to embed in its surface, therefore maintaining a hydrodynamic water fi lm and greatly increasing both bearing and shaft sleeve life.

The NF21/22 material working in conjunction with gunmetal journal has over 25 years of proven service as a water-lubricated propeller shaft bearing in both naval and commercial vessel applications. In addition, based upon the additional

recent test work completed, Wärtsilä can confi dently offer its standard water-lubricated bearing material with its standard design – for both deep water and dirty river water conditions.

The compatibility of NF and stainless steel liners provides a durable system with long bearing life and extended shaft life. Railko bearings can readily replace rubber or elastomeric bearing materials and can be supplied as fi nish machined bearings, for press-fi tting into the stern tube or bracket, or in tube form for fi nal machining in the yard.

The addition of the Railko bearing materials to the existing Wärtsilä seals and bearings portfolio enables Wärtsilä to offer fully cost-effective seal and bearing package solutions for both water and oil lubricated systems, placing the company in an excellent position to satisfy shipowner demands for a totally environmentally friendly propeller shaft system.

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UNIC – The reliable solution for robust industrial controlsAUTHORS: Johan Pensar , Head of Automation, Engine Management and Automation, 4-stroke Appl ication Center, R&D, Wärtsi lä in Finland and Mårten Storbacka , General Manager, Engineering, Ship Power, Wärtsi lä in Finland

The operation of modern 4-stroke machinery installations is largely dependent upon advanced embedded electronic control. This is true not only for obvious engine types, such as the Wärtsilä spark ignited (SG) and dual-fuel (DF) gas engines and

To merge advanced embedded control with heavy industrial equipment in a safe and reliable way requires unique design solutions that include some unconventional strategies not commonly used in the industry.

the common rail (CR) engines, but also for conventional mechanical diesel engines and their auxiliary equipment. All are today benefi ting from advanced control for safety, supervision and performance. Wärtsilä Unifi ed Controls (UNICTM) provides a reliable electronic control system for rugged industrial automation needs.

With requirements for performance and functionality on the increase, the use of electronic controllers is increasing in most areas of technology. With “smart” control, it is possible to measure and control machinery better, faster and with less equipment than

ever before. The possibilities offered by smart control are also continuously evolving, allowing more data to be retrieved from the same measurements as before, better performance achievements from the same actuators, and more logical and simpler ways for the operator to handle the machinery.

Wärtsilä’s large reciprocating diesel and gas engines have, during the last decade, undergone a generation change in terms of control, whereby mechanical and hydraulic devices have gradually given way to electronics and software. With its excellent control, the system providing the utmost reliability is UNIC.


in detail 41

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Fig 1. – UNIC scalability for engine applications.

UNIC C3- EFIC engines

CR, DF, SG

UNIC C2- Mechanical

diesel injection

UNIC C1- Mechanical

diesel injection

Basicenginecontrol

Basicenginesafety

Enginemonitoring

Basicenginecontrol

Basicenginesafety

EFIC,combustioncontrol

Enginemonitoring

Basicenginecontrol

Basicenginesafety

LDU

LCP

ESM

MCM

PDM

IOMIOM

Booster

Ethernet

Integratedinterface

IOM

IOM

Generator

Combomodule

Misc.equipment(fi eldbus)

Fig. 2 – Machinery control concept based on the UNIC technology.

UNIC Reliability is the fundamental design requirement for the UNIC system. However, in order to support different applications and usage, the fl exibility and scalability of the system are also very important. These not only allow the system to be applied to all types and sizes of engines, but also allow the use of the rugged embedded control in related applications, depending on need. This is also refl ected in the system name, UNIC, Unifi ed Controls, where a unifi ed embedded control platform is emphasized. For 4-stroke diesel engines, this fl exibility is then translated into automation products in a scalable way.

Different engine applications are covered by different system variants, UNIC C1 to C3, with the hardware, software and functionality scaled accordingly. The same features as used in the basic systems are also reused in the more complex ones. In order to achieve this scalability, the system is bus-based, where functionality can easily be added, and the system extended to cover more complex demands.

The UNIC system is not applicable to engine controls only, but is widely applicable to rugged applications. Various development projects utilizing the UNIC technology are also planned. Based on its close contacts with the market, Wärtsilä selected the UNIC platform to meet market demands for ship machinery controls. Advantages of the integrated approach include:

n A common interface with vessel integrated automation systems for engines, pipe modules, feeder/boosters and other related machinery equipment.

n Real time diagnostics for trouble shooting and accurate time-stamping for cause and effect analysis.

n “Hot swapping” and auto confi guration of control modules that reduce the system’s off-line time to a minimum.

n Common spares, common tools, common service personnel, training etc.

n Flexibility in the technology used.

In general, UNIC represents a common platform that suits low-end traditional seafaring as well as future high-tech solutions, prolongs the lifetime and availability of control components,

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Hardwiredconnections

Loadsh.CAN

LDU

LCP

ESM

MCM

PDM

Ethernet

CCM CCM

IOM

Fig. 3 – UNIC bus design and main components.

Fig. 4 - The ComboModule as a machinery controls example.

and has the same expectations as engine automation components.

A total integrated machinery concept is pictured in Figure 2, where the ComboModule is a complete pre-packaged skid with all essential engine related auxiliary equipment, Figure 4.

ReliabilityFor demanding applications like marine propulsion and industrial power generation, reliability is an obvious requirement. Reliability is commonly associated with fundamentals such as safety and the commercial feasibility of the operation. Reliability, however, also impacts other factors such as ease of use, service schedules, skill requirements, and so on, all with far reaching consequences.

From the very beginning, UNIC has been designed with the sole purpose of providing excellent reliability, even during the most extreme conditions. This is an essential element in meeting the demands of challenging industrial environments. This reliability has been achieved by using some rather unique designs and solutions that are not readily available elsewhere [1][2].

One example is the sensors. Sensors, being relatively inexpensive and available off the shelf, are often somewhat neglected when designing engine control systems. In practice, however, the reliability of the sensor is extremely important to the system. This is partly due to the number

of sensors on an engine, but also because the sensors are typically mounted in diffi cult locations and are frequently in direct contact with hot surfaces, vibrating components, and aggressive chemicals.

When evaluating sensor failures, it is clear that one of the main causes is actually not the sensor itself, but rather the connector mounted on the sensor. In UNIC, all sensors have been redesigned for utmost reliability by removing the connector, and instead using a fi xed attached cable, a fl ying lead, that connects directly to the electronics. As a result of this design, the reliability of the numerous sensors on the engine has been signifi cantly improved.

Other components that heavily infl uence reliability are the connectors and cables. So called wire harnesses with a lot of connectors, unshielded wires, and numerous fragile plastic parts, as commonly used in the automotive industry for example, are not used. Instead, the wiring concept is based on rugged point-to-point cables that are very robust and easy to repair and replace in the fi eld.

Reliability is also a result of proper design and mounting of the electronics. By using over specifi ed electronics with integrated diagnostics, mounted on vibration dampers in metallic junction boxes, the lifetime of the electronics can meet even the most stringent requirements.

As large diesel or gas engines typically

are in operation some 8000 hours per year for 20 to 30 years, it is clear that the expected lifetime for the electronic components will also need to be quite long. For UNIC components, a lifetime of at least 50,000 operational hours has been the design target.

PerformanceThe performance of modern diesel and gas engines is heavily dependent upon advanced electronic controls. Even conventional diesel engines benefi t from the advanced electronic speed control provided by the UNIC C1 system, where the algorithms provide optimal load acceptance with proper protection for over-fueling. The result is good performance with reduced smoke, especially during start and transient situations. The UNIC C1 system is also available with an integrated start/stop system, minimizing the external systems needed for engine operation.

Conventional diesel engines can also be equipped with embedded monitoring as provided by the UNIC C2 system, where fault tolerant safety functions guarantee the system’s high availability, while simultaneously providing proper protection. Advanced signal diagnostics avoid spurious false alarms, while alerting the operator to possible failures


in detail 43

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Application modules

Durationcalculation

Cylinderbalansing

Cooling control

Air/Fuel ratiocontrol

HT actuatorcontrol

LT actuatorcontrol

Knock control

Ignitioncontrol

Fuel scheduler

MFI demandcontrol

MFI control

PFI control

MCC pressure control

PCC pressure control

MFI demandload estimation

MFI timingcontrol

Speed/loadcontrol &reference

control

Miscellaneousmath etc.functions

PFI pressure control

CR pressure control

Air bybass control

Slow turning

MFI timing rackcontrol

DF main control

SG main control

CR main control

DI main control

DG main control

Engine specifi cconfi guration

TPU: injection,ignition..

CAN driver &protocols:

WE-CAN+CANopen

Enginediagnostic log

DSP interface

Hardware I/O

System API

Normal &conditional Safety

TVM

DC & Filters

Ext. comm.protocols:

ModbusProfi bus

Systemservices

Turbo speedmeasurement

Speed & phase measurement

Miscellaneous

uC-OS/IIRTOS

System software

Fig 5. – Software library structure.

in, for example, the sensors. The bus-based communications also reduce the complexity of external systems for engine monitoring and control.

On a common rail diesel engine or gas engine, the UNIC C3 system provides optimal performance with advanced control algorithms for the fuel injection. Algorithms adapting to existing fuel properties, multiple maps for various fuels for example, direct cylinder pressure analysis, and functions such as split injection, allow these engines to deliver the utmost performance possible. The UNIC C3 system also contains advanced diagnostics that easily detect upcoming failures on components such as gas valves or fuel injectors, and which analyze the combustion process and engine behaviour. This ensures that engine performance is maintained, even in varying conditions.

Operation and maintenanceThe UNIC system provides new possibilities to optimize the operation and maintenance of a fl eet’s engines and machinery. Standardized components across the whole Wärtsilä portfolio means streamlined spare parts logistics, while guaranteeing that spare parts are available immediately all over the world. The same spare parts are relevant to different Wärtsilä products, thus minimizing

stock requirements, while the common system design allows operators and maintenance personnel to effi ciently service any type of Wärtsilä unit.

The service tool used for UNIC systems is common, and the standardized modular design makes it easy for operations and maintenance personnel to learn and operate different types of installations.

With the standardized design, it is also easy to modify installed engines for, amongst other things, different types of fuels, as market demands require. In addition to new engines, it is also possible to retrofi t older engines with different UNIC variants when the need for modernization arises, thereby also bringing the same UNIC system benefi ts to an existing engine base.

The advanced bus-based communication to UNIC C2 and C3 engines also allows good opportunities for increasing operating effi ciency, since remote supervision with, for example, accurate time-stamping features, is readily available. The engines are also ready for direct connection to the Wärtsilä condition based maintenance (CBM) system, and support also remote access from the maintenance tool, allowing tuning and fault tracing - even via a remote connection. CBM extensions to machinery will also be available.

Software and confi gurationThe software platform is focused on a reliable end product. Modularization and object oriented programming approaches are fundamentals in the design. Reliability and effi ciency require more, however, and the UNIC modular application platform is based on a total lifecycle approach to provide such effi ciency and reliability.

Functionality for various applications is provided by a pre-tested functions library. The designer can, from this library, select the required functionality - speed/load control, fuel injection control etc. - and based on his input, the system confi guration is generated. The confi guration also includes details on, amongst other things, selected control modules, I/O, scalings, and communication. From the confi guration, the software package is created. The quality of the software is ensured as it is fully based on pre-tested modules. Detailed reports on various functions can also be generated by the confi guration, detailing such items as safety functions, communication, and partitioning, as needed for integrating the engine and machinery with the external systems.

To create the individual software modules, UNIC provides the software developer with the fl exibility to use the

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Fig. 7 – Circuit board with capacitor broken loose during HALT tests.

Fig. 6 – Flying-lead sensor.

method best suited to the project. In addition to common C programming, the development can also be done using advanced simulation and modelling tools, where the functionality can be modelled and simulated together with a process model until perfected. By this virtual engineering step, it is possible to develop, test, and validate the functionality much more effi ciently than in a conventional development cycle, while at the same time guaranteeing high quality software. From the model, the control module is automatically generated and transferred to the module library, and is thus available for further designs. The modelling – simulation – control development cycle has also been thoroughly investigated [3].

Eventually, UNIC will also provide the possibility to program software modules using common IEC 61131 tools, providing the possibility for fi eld programmable functions where needed.

Parameters and maps needed to adjust the controller for the actual process are fully independent from the software. The service tool allows stand-alone parameterization of the controllers, which remains unchanged even during software updates. Varying tunings for different conditions can also be provided by so-called calibration sets, where the tuning information for a particular condition (e.g. fuel quality) or component (e.g. turbocharger type) can be handled as an independent entity.

Testing and validationA key element in attaining good reliability and life expectancy in a system, is thorough testing and validation. In the testing and validation phase, any weakness is observed and corrected before reaching the manufacturing stage. For the UNIC system, advanced world-class validation methods have been developed, where both hardware and software are exposed to the most demanding test methods before release.

A particular problem when designing systems for very long lifetime expectancy, is the fact that there is no way to test the system under normal running conditions for the expected lifetime. As the design lifetime exceeds 50,000 hours, real-life testing would take many years.

The method introduced with the UNIC system has been based on accelerated stress testing, commonly

referred to as highly accelerated lifetime testing (HALT). The method exposes the device to a number of different simultaneous stress factors, like multiple-axis vibrations and shocks, temperatures, temperature cycles and humidity, and operational stresses like supply voltage variations and high driver currents. The HALT testing is considered to be the current state-of-the-art in terms of reliable hardware design, and is commonly used also, for example, in the aerospace industry.

Typical weaknesses that can be observed in the tests are often of a mechanical nature – components breaking loose due to vibrations or temperature cycling. For example, Figure 7 shows where a capacitor has broken loose due to vibrations. The design could, in this case, be improved by adding glue to bind the component to the circuit board.

Testing and validation is also important for reliable software design. A key factor is the modularized software, where all software modules can be pre-tested. Therefore, the system designer can confi gure the engine and machinery

controls from pre-tested modules with the confi guration tool, where on-line error checking assists him in the confi guration.

All engine and machinery control software is tested also in a software validation environment where the correct functionality of the software is verifi ed by automatic regression testing. This signifi cantly speeds up the testing, from weeks of manual testing to some days of automatic testing. By this testing, the software released is verifi ed to be working to specifi cation.

The model based software development also allows far-going dynamic testing of the control algorithms already in the design phase – by simulation on a desktop computer. By thorough dynamic simulation, the resulting dynamic control algorithms are error free already when going to installation tests, and require only proper parameterization for the real process.

UNIC’s unique position UNIC has a unique position in the market for embedded controls. The system, which has been gradually introduced on Wärtsilä 4-stroke engines since 2005, is robust – providing many years of service in demanding conditions, as well as being fl exible and scalable for use in any type of application. The system not only provides new engines with better control, higher performance, and increased reliability, it also supports both old and new installations during the full lifecycle. It offers opportunities to follow market demands for fuel fl exibility, increased effi ciency, and optimal operations and service. The system fl exibility also allows for streamlining, not only on the engine, but also, for example, of the total machinery installation.

REFERENCES

[1] J. Pensar, “Design of Engine Control Systems for Large Heavy Duty Applications”, SAE World Congress 2007, Detroit, paper 2007-01-1598, 2007.[2] J. Pensar, “Engine Management and Automation – Keeping Pace With Changes”, CIMAC Congress 2007, Vienna, paper 187. [3] A. Saikkonen and T. Kaas, “High-LevelLanguages in Low-Level Programming – A Case Study on the Use of Symbolic Programming and Simulation in the Development of Embedded Controls” proceedings of Automaatio 05 Seminar Days, Helsinki, Finland, pp. 183-188, 2005.


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

Fig. 1 – New ferry design with clear economic advantages.

and a contra rotating propeller behind it mounted on a pulling mechanical thruster. The machinery has been confi gured to keep the initial cost low by avoiding expensive electric pods and drives, and by going to a simple mechanical drive of the forward propeller using a large bore main engine. A novel machinery and cargo ramp arrangement has been developed to facilitate also very large main engines, which are too high to fi t under the main deck.

Both fuel consumption, and therefore also exhaust emissions, can be reduced by more than 10% with this new concept. Overall, the new concept offers a very attractive economic solution that represents state-of-the-art propulsion technology, while relying on well proven and reliable components.

STRIVING FOR LOWER FUEL CONSUMPTIONDuring the last couple of years, the shipping industry has witnessed a signifi cant increase in fuel prices. The price has fl uctuated both up and down, but is in general at a much higher level than in

Wärtsilä is conducting continuous development to meet the need for lower power demand and fewer emissions. In striving for these goals, Wärtsilä has during recent years proposed a number of innovative propulsion solutions for ferries. The latest in this series of ferry propulsion development concepts is presented herewith.

By combining the positive experience and very high propulsion effi ciency of the podded contra rotating propeller (CRP) concept, with the advances in thruster technology and ship design, a new propulsion machinery concept has been developed. The concept features a direct driven controllable pitch (CP) propeller,

The demands for lower bunkering costs and reduced greenhouse emissions have become two of the main drivers in the fi eld of ferry design. In competing with other modes of transport, the existing well-proven solutions might not be the most effective.

the past. Expectations are that prices will remain high and may continue to increase. This has led to a situation where the fuel cost has become even more signifi cant to the total operating costs of a ferry.

At the same time, the public is focusing more and more on climate change, and the pressure on the industry to reduce greenhouse emissions is becoming ever more evident. The EU has set a target to reduce CO

2 emissions

by 20%. The shipping industry must be ready to meet this challenge.

Both of these factors emphasize the increasing importance of fuel effi ciency. Low consumption has, of course, always been a target to strive for, but these latest developments mean that ship owners not only should, but indeed have a real incentive in seeking low consumption solutions.

Looking beyond the conventionalThe conventional large displacement ferry machinery used today is usually based on twin shaft lines, with twin

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Fig. 2 – CRP RoPax with fi xed ramp in the centre to the upper cargo deck.

Fig. 3 – Annual fuel and lube oil costs. (HFO=230 EUR/ton).

Twinshaft

Fuel

an

d lu

b o

il co

nsu

mp

tio

n c

ost

s (T

EU

R)

8000

7000

6000

5000

4000

3000

2000

1000

0CRP Thruster

Wärtsilä 7RT-fl ex60CRP ThrusterWärtsilä 8L64

CRP ThrusterWärtsilä 16V46

Lube oil cost

Fuel oil costs

CP propellers driven by two or four medium-speed diesel engines. This arrangement has proven itself as both functional and reliable. However, the shortcoming to this propulsion set-up is that the long shaft lines below the hull, together with the other appendages, give rise to high resistance. Therefore, if an alternative solution that eliminates the need for shaft lines can be found, lower power demand could be achieved.

The appendage resistance of a ferry can be as high as 10-15% of the total resistance. Furthermore, the risk of pressure side cavitation at low speed operation is always apparent with CP propellers, which are needed in this type of mechanical propulsion. The engines are also run at low load while manoeuvring and during slow speed operation. This is not desirable from the point of view of engine performance.

Ferries need good manoeuvring characteristics since they have frequent port calls and while in port, need short turnaround capabilities. Twin shaft lines with twin rudders offer quite good manoeuvring performance, but some ferries still need more side thrust than can be generated with the rudders alone, so additional tunnel thrusters are installed in the stern. Single screw arrangements are quite rare in modern ferry tonnage.

Medium-speed 4-stroke diesel engines dominate the ferry market. Only very few ferries have 2-stroke diesel engines, which are otherwise the most common type of engine in large cargo vessels operating over long distances on the open sea. The popularity of the 2-stroke engine for cargo vessels is based upon its low maintenance demand, low fuel consumption and on its reputation for high reliability.

The main reasons why 2-stroke engines are not used in ferries is because the large cross head engines do not fi t beneath the main cargo deck. This means that there would need to be an engine trunk on the main cargo deck to house the 2-stroke engine. This trunk would interfere with cargo handling over the stern, and would reduce the available lane meters (freight capacity). Space is a design issue for ferries as they are considered to be volume-critical, rather than weight-critical vessels.

As ferries need twin screws in most cases for manoeuvring purposes, and to allow some degree of redundancy,

they actually need to have at least two engines. Twin large 2-stroke engines would effectively close up the entire main deck in the stern of the vessel and make cargo handling almost impossible. This fact further contributes to the reasons why we have not seen many ferries with 2-stroke main engines.

ADVANCED PROPULSION CONCEPTS FROM WÄRTSILÄIn recent years, Wärtsilä has put forward a number of new propulsion concepts for ferries. These include, Podded CRP, Wing Pods and Wing Thrusters [2, 3, 4, 5]. These all have one important feature

in common in that they have gone away from the traditional twin shaft line set-up, and instead use a propeller mounted on the centre line skeg combined with either one or two azimuthing propulsors.

The Podded CRPThe Podded CRP concept features a contra-rotating propeller on an electric pod located directly behind the main propeller in the centre line skeg. The pod propeller is of the fi xed pitch (FP) type, while the main propeller is of the controllable pitch (CP) type. Compared to a conventional vessel fi tted with twin screws, the Podded


in detail 47

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Fig. 4 – X-ray view of a vessel showing the new concept with a large main engine.

CRP confi guration offers better hydrodynamic effi ciency. This is mainly due to the following reasons:

n The resistance of the single skeg hull form with a single pod is lower than that of a twin screw hull with two shaft lines.

n The aft propeller takes advantage of the rotative energy left in the slipstream of the forward propeller when it rotates in the opposite direction.

n The skeg offers a more favourable wake than a shaft line, resulting in better hull effi ciency (η

H).

The improvement in propulsion effi ciency is clear, but the level of improvement depends on the vessel in question. The reduction in power demand at the propeller measured in model tests, has usually been in the range of 10-17% better effi ciency compared to twin screw vessels. Even higher values have also been reported [6].

The Podded CRP concept has actually been applied in two fast Japanese ferries, and the benefi cial features of the concept have been verifi ed in actual operating conditions.

Japanese ferries showcase effi cienciesThe fi rst ferries featuring Podded CRP propulsion, the Hamanasu and the Akashia, entered into service in Japan in 2004. These two ferries are operated by the Shin Nihonkai Ferry Line, and were built by Mitsubishi

Heavy Industries. The ferries have a service speed of 30.5 knots and a top speed of 32 knots. The ship features a CODED machinery with two 12-cylinder Wärtsilä 46 medium-speed engines in V-confi guration, driving a CP propeller, two similar Wärtsilä 12V46 engines driving the generators, and one smaller genset for use in port. The total installed propulsion power is 42.8 MW, with 17.6 MW on the pod and 25.2 MW on the forward propeller (41/59 power split). The ships have been performing very well. A comparison with conventional ships in the Shin Nihonkai Ferry fl eet shows that a 20% reduction in fuel consumption can easily be reached. This does not take into account the fact that the new ships are 1 knot faster and take 15% more cargo [1].

Market slow to take advantageThe Podded CRP concept has proved itself in two full scale applications and has delivered better fuel savings than estimated. However, to date we have not seen any surge in new orders. At the same time, there have been plenty of orders for conventional ferry concepts. One has to ask, therefore, why it is that ferry owners are not taking advantage of the opportunity for fuel cost savings.

There is probably not one conclusive answer to this question, but one can speculate as to the possible reasons. One fact is that the CRP is still a rather new concept, despite its operational track record stretching back almost 3 years.

Most ferries are ordered in Europe and not all owners have concrete feedback regarding the performance of the Japanese vessels. The ferries on order have also been designed for lower speeds than the two existing CRP vessels. The question among owners is of course, how big the savings will be for a slower vessel.

One of the most important reasons, however, is still likely to be cost. The investment cost of a CRP ferry is higher than for a conventional twin shaft ferry. In particular, the electric pod is expensive and increases the investment costs. Nevertheless, it is easy to show that the CRP will pay for itself within a reasonable timeframe [2, 3]. A higher initial price though, can still be a critical item for owners trying to fi nance the ship in the fi rst place.

Another aspect of the cost issue is the sister ship effect. It is always more expensive for a shipyard to build a prototype vessel, such as the CRP vessel would be, rather than a repeat vessel. Even though many of the ferries on order today seem to be of a new design, they are often based on, and have many similarities to a previous ship. This makes it increasingly diffi cult for the introduction of any new designs.

NEW CONCEPT OFFERS LOWER INVESTMENT COSTSWärtsilä has developed a new concept that is relying on the good features of CRP propulsion, while at the same time attempting to overcome some

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Fig. 5 – X-ray view of a vessel showing new engine locations.

of the current shortcomings.The new concept features a Contra

Rotating Propeller pair with the forward propeller mounted on the centre line skeg, and the aft propeller on a pulling-type steerable mechanical thruster located directly aft of the forward propeller. When looking from the outside, this set-up looks very similar to the existing CRP arrangement with an electric pod. It also acts in the same way hydro dynamically. However, the difference is on the inside of the thruster. The electric motor is replaced by a mechanical drive system with two 90° bevel gears.

The most obvious benefi t of this is that it allows for fully diesel-mechanical machinery, while at the same time signifi cantly lowering investment costs.

Savings achieved via new machinery arrangementThe novelty of the new propulsion concept is in the machinery arrangement that makes it both practically feasible for a ferry and also economically superior to all other machinery alternatives on the market today.

The aft thruster is driven mechanically by a medium-speed diesel engine

located in the centre of the vessel above the shaft line of the forward propeller. This means that the engine is located higher up than where normally situated in ferries. The engine compartment penetrates the main deck.

The forward propeller is driven in the traditional manner by one or two engines. The engines are located in the centre of the vessel at tank top level.

The machinery forms a very compact package that is higher than normal, but much narrower. The machinery can also be pulled further aft than in a twin shaft vessel, since the single skeg hull form allows the reduction gear to be located further aft. The thruster engine, because of its high location, is also very far aft.

Machinery also suitable for large main enginesThe new machinery arrangement also provides some new options when it comes to engine selection. The narrow and high machinery is well suited for a large main engine that is higher than normally. The main engines could be, for example, a 2-stroke engine or the very largest medium-speed engine

on the market, the Wärtsilä 64.The new arrangement effi ciently

overcomes some of the problems associated with high engines in ferries. With a conventional propulsion solution, two large engines would close up the entire beam of the main deck. Since the engines in the new proposal are behind each other, two engines will not take up more than two lanes on the main deck. This is only one more than anyway occupied by the normal engine casing. This means that only very few lane meters are lost on the main deck. In addition, the shorter engine room allows for a longer lower cargo hold, which compensates for the lost lane meters.

Cargo arrangement is also innovativeAn innovative cargo deck arrangement goes hand in hand with the new machinery concept. A wide ramp from the stern of the vessel to the upper cargo deck can be located on top of the machinery. The fi xed two-lane ramp above the engines will utilize the space on the main deck, that would otherwise be lost to the machinery compartments, effi ciently. In this way, the entire beam


in detail 49

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Fig. 6 – Relative machinery equipment investment costs.

Twinshaft

Mac

hin

ery

inve

stm

ent

cost

(%

)

CRP, Thruster Wärtsilä 7RT-fl ex60

CRP, Thruster Wärtsilä 16V46

120

100

80

60

40

20

0

Steering

Propulsion train

Electric system

Gensets + generators

Propulsion engine

- 500,000 EUR

Fig. 7 – Annual machinery related costs.

Twinshaft

An

nu

al c

ost

s (T

EU

R)

10,000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0CRP Thruster

Wärtsilä 7RT-fl ex60CRP ThrusterWärtsilä 8L64

CRP ThrusterWärtsilä 16V46

Assumed fuel price:HFO 230 EUR/ton

*Maintenance cost assumptions: Spare parts onlyCalculation period 15 years

**Capital cost assumptions:Calculation period 12 yearsInterest rate 8%

- 6% - 3% - 9%

- 865,000 EURMaintenance costs*

Lubricating oil costs

Fuel oil costs

Annual extra capital cost for larger ship**

Annual capital costs**

of the vessel can be used for loading. The two centre lanes lead directly to the upper cargo deck without any interfering with the loading operation on the main deck. There are three lanes to the main deck on each side of the centre ramp and engine casing. The new cargo arrangement is of course, best suited for ports with only single level loading.

NEW SHIP DESIGNS MADEA few new ferry designs have been made using different machinery solutions. One design is of a ferry with conventional twin-screw machinery, while all the other

have a CRP propulsion arrangement but with different main engines. The fi ve machinery alternatives studied are:

n Twin shaft, 4 x Wärtsilä 9L38n CRP, 7-cylinder

Wärtsilä RT-fl ex60 + Wärtsilä 8L38n CRP, Wärtsilä 16V46 + Wärtsilä 8L38n CRP, 2 x Wärtsilä 8L46

+ Wärtsilä 8L38n CRP, Wärtsilä 8L64 + Wärtsilä 8L38

The vessels are designed to offer thesame capacity and performance:n Lane meter 2400 m

n Payload 5150 tonn Speed 24 knots (15% SM, 85% MCR)

The ship design is kept similar, but the main dimensions are varied to offer an optimized solution. This provides the ideal way by which to compare different machinery alternatives.

It would be wrong to start with a certain hull and then see how much cargo can be fi tted into it after the machinery is in place. This is, however, the method often used for similar machinery comparisons, but it represents the wrong approach. It means that one or more of the alternatives are not optimized.

The method used here is to start from the mission of the vessel, and then design a ship to meet this mission. Of course, the principle behind the design process should be similar to arrive at comparable end results.

RoPax particularsThe ferry represents a contemporary RoPax vessel with 2400 lane meters for cargo and day facilities, for a limited number of passengers. The main dimensions are presented in Table 1.

The CRP ferry with a main engine below the main deck can have the same dimensions as the conventional twin shaft ferry and still offer the same cargo capacity. There is some reduction in lane meters by way of the thruster engine compartment. However, this is compensated by a larger lower cargo hold made possible by the shorter engine room.

The CRP machinery option with a high main engine going through the main deck, and with the ramp above the machinery, cannot offer the same cargo capacity, unless the length of the ship is increased.

MACHINERY COMPARISONSThe different machinery options have been compared with each other as follows:

WeightThe CRP machinery option shows an advantage when it comes to weight. Even with the low speed engine, the weight is at the same level as with conventional twin shaft machinery.

Power demand and fuel consumptionThe power demand of the vessel has been calculated and compared with results from

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Table 1. – Main dimensions of the RoPax ferry.

Twin shaft CRP 2-stroke CRP Wärtsilä 16V46Length, oa 186.0 191.9 186.6 mLength, bp 170.0 175.1 170.0 mBreadth 27.7 27.7 27.7 mDraught, design 7.0 7.0 7.0 mDepth 10.0 10.0 10.0 mGross tonnage 28,500 29,000 28,500 gtDeadweight 6700 6600 6600 tonPayload 5150 5150 5150 tonLWT 12,000 12,300 11,900 tonDisplacement 18,700 18,900 18,500 tonLanemeters 2410 2420 2410 m

Fig. 8 – New ferry with mechanical thruster CRP propulsion.

previous CRP model tests that Wärtsilä has been involved in. The delivered power demand of the CRP propulsion is about 9.5-11% lower than that of the twin-screw option. The larger saving is achieved with the option having the lower Wärtsilä 46 medium-speed engines, as their weight is 400 tons less, due to the lighter machinery and the small ship.

However, fuel consumption also depends on the transmission losses, as well as the specifi c fuel oil consumption in each operating mode. The mechanical thruster has higher transmission losses than a conventional shaft line owing to the two bevel gears. On the other hand, this represents only 25% of the total power. The main engine in the CRP options is of a larger type than in the twin shaft vessels. This gives lower SFOC. The total annual fuel consumption is shown in Figure 3. It can be seen that the CRP option (Wärtsilä 16V46) offers the lowest fuel and lube oil costs. The annual fuel and lube oil cost saving with the CRP is about 11-12.5%.

Investment costsThe investment cost of each machinery alternative has been estimated based on equipment offers, and is shown in Figure 6. It can be seen that the CRP machinery with the smaller medium- speed main engine offers the lowest machinery equipment investment costs.

In addition to the machinery, other building costs need to be assessed as well. This has been done with a system model of each vessel. The CRP alternative with the low-speed engine is about 2 MEUR more expensive than the other options, since its hull is about 500 gt larger than the others.

Total machinery related costsThe total annual machinery costs are shown for each alternative in Figure 7. The annual operating costs are calculated based on an assumed operating profi le. The investment costs are turned into annual payments over an assumed 12 year period with 6% interest.

All of the CRP options indicate clear savings compared to a conventional twin shaft vessel. The CRP option with the Wärtsilä 16V46 medium-speed engine is the most economical, with an annual saving of about EUR 850,000.

THE NEW CRP CONCEPT OFFERS A COMPETITIVE SOLUTIONThere is increasing demand for the ferry industry to begin focusing on greenhouse emissions. At the same time, high fuel prices also call for a clear reduction in fuel consumption. A new propulsion machinery concept based on CRP propulsion with a mechanical thruster, can offer a more than 10% reduction in both fuel consumption and operating costs. The nice feature of this concept is that it does not need to be more expensive than a conventional solution despite its superior performance. The investment costs can actually be cheaper depending on main engine selection. The unique arrangement also allows for effi cient cargo handling, despite a small penalty in lost lane meters on the main deck. This can however be compensated by increasing the ship size.

This fact is taken into account in the comprehensive economic comparison performed showing that all CRP options indicate clearly superior overall performance. The lowest total cost level is for the CRP concept with the Wärtsilä 16V46 main engine. It has an annual

saving of up to EUR 850,000. All in all, the new concept offers a very competitive solution that is a step in the right direction towards a cleaner ferry business.

REFERENCES[1] Anderson L. - Wärtsilä Corporation, ‘Hybrid CRP pods for large Japanese ferries’, Marine News - Wärtsilä Customer Magazine nr 1-2005, March 2005, www.wartsila.com[2] Levander O., Sipilä H., Pakaste R., ‘ENVIROPAX ferries make promising progress’, Marine News - Wärtsilä Customer Magazine nr 1-2005, March 2005, www.wartsila.com[3] Levander O. - Wärtsilä Corporation, ‘Combined Diesel-Electric and Diesel Mechanical Propulsion for a RoPax Vessel’, Marine News - Wärtsilä Customer Magazine nr 3-2001, December 2001, www.wartsila.com[4] Levander O. - Wärtsilä Corporation, ‘Wing Thrusters propelling the next generation of ferries’, The Scandinavian Shipping Gazette, September 23rd , 2005[5] Levander O. - Wärtsilä Corporation, ‘Novel propulsion machinery solutions for ferries’, World Maritime Technology Conference, London, 6-10 March 2006[6] Praefke E., Richards J. and Engelskirchen J. - HSVA and Blohm+Voss, ‘Counter rotating propellers without complex shafting for a fast monohull ferry’, Presentation at FAST 2001, Southampton UK, September 2001


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Cutting cylinder oil costs without a break in serviceAUTHOR: Jürgen Gerdes , General Manager, Service Sales, Wärtsi lä in Switzerland

Cylinder oildaily tank

Filter andmeasuring unit

Dosage pump

Lubricator

FCM-20ALM-20

Servo oil supply unitServo oil supply unit

Lubricating oil drain tank

Fig. 1 – Arrangement of the Retrofi t Pulse Lubrication System on one cylinder of a Wärtsilä low-speed engine.

Pulse Lubricating Systems have quickly become popular as retrofi ts for Wärtsilä RTA and RT-fl ex low-speed engines, and since summer 2006, complete systems have been ordered for more than 80 engines.

After-sales service is more than just supplying spare parts. Wärtsilä offers a complete range of products and proactive services to help customers get the best results from their engines. Wärtsilä’s centre for 2-stroke engines in Switzerland provides customers

with original equipment manufacturer (OEM) spare parts, tools and consumables, together with performance optimization, modernization, and operational support services.

Customers are moving their focus more and more to performance optimization, especially towards upgrades or retrofi ts that result in immediate fuel or lubricating oil savings.

For example, since March 2004, the price of cylinder lubricating oil has increased by some 250% with an average cost today of about USD 1700 per tonne. Thus, on a 12-cylinder Wärtsilä RTA96C engine with a 68 MW output, even a modest cut of just 0.3 g/kWh in the cylinder oil feed rate can result in annual savings of more than USD 200,000. Therefore, it was decided in early 2006 to accelerate development of the new, electronically-controlled Pulse Lubricating System (PLS) to make it available for retrofi tting to RTA and RT-fl ex engines.

PLS cuts cylinder oil consumption without compromising piston-running reliability by accurately metering and precisely timing the oil delivery, and improving the distribution of cylinder lubricating oil to an engine’s cylinder liners. It enables the guide feed rate for cylinder lubricating oil to be cut to 0.8 g/kWh in Wärtsilä RTA and RT-fl ex engines retrofi tted with PLS.

When, during the SMM exhibition in Hamburg at the end of September 2006, the Retrofi t Pulse Lubricating System (RPLS) was offi cially announced it attracted much interest from shipowners. The fi rst retrofi ts were already on order before the announcement, and by the end of August 2007, orders for more than 80 complete engine installations had been received, amounting to 850 cylinders. By mid-August, 16 engines of both RTA and RT-fl ex types had been successfully retrofi tted, while the fi rst orders had also been booked for RTA84C and RTA84T engines.

The fi rst retrofi t went into service at the beginning of September 2006. By mid-2007, the RPLS had been released for RTA96C, RT-fl ex96C, RTA84C and RTA84T engine types while further engine types will be added during 2008.

Retrofi t installationA retrofi t is especially attractive to shipowners if it can be undertaken without disturbing commercial operation of the

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Fig 2. – Schematic of the RPLS.

Cylinder oil tank

Alarmmonitoring

system

LubricatorCylinder

Filter WECS CAN bus

Power supply

ALM-20

Dosage pump

Junctionbox

Mainbearing

oilCylinder oil

Servo oil

Servo oil return

Servo oilsupply unit Servo oil

overfl ow

Pressuresensors

vessel. Wärtsilä’s two-stroke center and the Wärtsilä services network are thus working in close co-operation to minimize the required installation time so that RPLS can be retrofi tted in a ship while on passage and during a normal port stay. For example, Wärtsilä in Korea is manufacturing all pipework and other mechanical parts. Before dispatching the material to the vessel, it is prefi tted on a dummy in the Wärtsilä workshop in Noksan, South Korea, to verify that the work is correct.

RPLS is an independent system with few connections or interfaces to other systems, and utilizes the engine’s existing cylinder liners. Thus preparation and installation are easy and fast. All equipment, including prefabricated piping, is supplied with installation and commissioning work being undertaken by Wärtsilä service engineers.

To a substantial extent this material can be installed during the voyage, thereby considerably reducing the port time required for fi nishing the installation and for the commissioning. Installation of controls, pumps, wiring, and interface connections to remote and alarm monitoring systems, is executed during the voyage. Ample attention is paid to commissioning, fi ne adjustment and the running-in of the RPLS in port and during a confi rmation voyage.

The whole retrofi t and commissioning on the fi rst vessel, the 7500 TEU container ship “COSCO SHENZHEN” with a 12-cylinder Wärtsilä RTA96C main engine, could be completed in fi ve steps without interrupting the vessel’s schedule:

1. Pre-inspection in Hong Kong on 22 June 2006.

2. First installation trip from Hong Kong to Yantian during 26–27 August. Installation work continued in Yantian and during the Pacifi c crossing to Long Beach (USA), arriving there on 9 September.

3. The second and fi nal installation period in Long Beach during 9–11 September, included piston-running related modifi cations.

4. The commissioning was carried-out while on passage from Long Beach to Oakland, where on 13 September the fi nal inspection was also carried out.

5. Finally, on her ‘maiden’ passage to China, measurements and documentation of the RPLS performance were carried out.

Working principleThe basic principle of the Pulse Lubricating System is to deliver metered quantities of cylinder lubricating oil under pressure at precise timing exactly into the piston ring package, from where it is evenly distributed around the circumference of the cylinder liner.

The RPLS is based on a lubricating module for each cylinder with a dosage pump and monitoring electronics, which delivers pressurized cylinder lubricating oil to newly developed lubricators (formerly known as quills) that fi t existing cylinder liners of the Wärtsilä RTA and RT-fl ex engine types.

Each lubricating module is equipped with two separate supply lines – for cylinder lubricating oil and servo oil. A separate servo oil supply unit is needed to drive the lubricating module for RTA engines, whereas on RT-fl ex common rail engines, the servo oil is taken from the servo oil common rail through a pressure reducing valve.

Once the Wärtsilä Engine Control System (WECS) switches the 4/2-way solenoid valve in the lubricating module

to the open position, servo oil fl ows to the drive side of the central piston of the dosage pump in the lubricating module. As the central piston is actuated, it feeds cylinder lubricating oil from the lubricating oil supply to the metering ducts, and then discharges it from the lubricators at high pressure. The cylinder oil is accurately supplied at defi ned positions of the working piston whose position is constantly detected by the control system from the reference signal given by the crank angle sensor. At the end of the lubrication work cycle, the directional valve in the lubricating module directs the servo oil to the return-fl ow side of the central piston of the dosage pump, which then returns to its initial position. The metering chamber is fi lled again with cylinder lubricating oil to be ready for the next lubricating cycle.

A separate servo oil supply unit is provided for RTA engines. It includes two gear pumps, one supplying the lubricating module with servo oil taken from the main engine oil system, with the second pump as a standby. The oil supply unit also includes a pressure limiting and safety valve, pressure gauge, pressure sensor, and


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Fig. 3 – The RPLS lubricating module with lubricator connections and associated electronics for eight lubricators.

Fig. 4 – One of the nine container ships managed by E.R. Schiffahrt, which have been completely retrofi tted with the Pulse Lubricating System. The ships are powered by Wärtsilä RTA96C low-speed diesel engines.

Shut-off valve for servo oil

Relief valve for servo oil

To system oil drain tank

Cylinder oil inlet

Shut-off valve forlubricating oil

Pressuresensor

Cylinder oil outlet to

lubricators

Venting plug for cylinder oil

Venting plug for servo oil

4/2-way solenoid valve

Diaphragm accumulator

shut-off valve. For RT-fl ex engines, servo oil is drawn from the engine servo oil system through a pressure reducing valve by which the oil pressure is reduced from 200 bar to 50 bar. The reduced pressure is monitored by pressure transmitters directly connected to the alarm system; the pipes are SOLAS compliant. The reduced pressure can be adjusted and its level is shown on an analogue pressure gauge.

The lubricating module for each cylinder consists of a dosage pump, a 4/2-way solenoid valve, monitoring electronics, pressure sensor, and diaphragm accumulator on a base plate. The timed lubricating module feeds a predefi ned metered quantity of cylinder oil at high speed to the lubricators at the precise timing ascertained by the engine control system. Part of the control oil fl ow from the servo oil line is routed to the 4/2-way solenoid valve. At the same time, the load-dependent cylinder lubricating oil needs of the respective cylinders are ascertained by the engine control system, which sends a corresponding signal to the monitoring electronics of the lubricating module. The ALM-20 (Advanced Lubricating Module) checks that the dosage pump is working correctly. The ALM-20 communicates with the master control unit through a redundant bus system, sends the signal to the 4/2-way solenoid valve, and processes the data from the pressure transmitter.

The redesigned lubricator delivers the cylinder oil radially as compact oil pulse feeds exactly into the piston ring package, from where it is equally distributed around the circumference of the cylinder liner. The lubricators (up to eight) are arranged around the liner in one row to ensure an excellent distribution of the cylinder oil on the cylinder liner. The vertical distribution is governed by the lubricating oil injection timing as a function of the crank angle.

A generously dimensioned 40-micron cylinder lubricating oil fi lter is arranged before the lubricating modules. It effectively removes any particles of dirt, thereby ensuring reliable operation of the lubricating modules. A 12 litre buffer tank is provided with a scaled sight glass that enables cylinder oil consumption measurements of up to fi ve litres. The buffer tank also allows the fi lter to be changed while the engine is running. When the fi lter is dirty, the integrated sensor gives a signal on the excessive differential pressure.

Ph

oto

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rdca

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Fig 6. – Specifi c diametrical liner wear, mm/1000 running hours, in one cylinder of the 12-cylinder RTA96C engine of the “COSCO SHENZHEN” at the second inspection at Long Beach: measurement taken fore–aft and port–starboard.

Specifi c diametrical liner wear, mm/1000 hours

Distant down from joint face, mm

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0.000 0.020 0.040

Fore – AftPort – Starboard

Fig. 5 – Excellent service experience with the RPLS revealed by the piston ring pack in an RT-fl ex96C engine after running with a cylinder oil feed rate of 0.8 g/kWh during shipboard trials.

Control and monitoring of the Pulse Lubricating System is provided by the WECS engine control system, which is based on the system used on Wärtsilä RT-fl ex common rail engines. The Advanced Lubricating Module (ALM-20) units communicate with the master control unit (FCM-20) by means of a redundant bus system. All control modules have a redundant power supply. When a lubricating pulse is initiated by the engine control system, the monitoring electronics associated with the respective lubricator activate the 4/2-way solenoid valve. The lubricating pulse is triggered electro-hydraulically as the pressure sensor sends a check signal to the ALM-20. When the pressure is within the programmed range, the local signal confi rms that the lubricating cycle was executed as specifi ed. If, for instance, no correct lubricating cycle is ascertained owing to a fault such as a lubricator blockage, a shortage of lubricant, a lack of hydraulic drive power or a faulty shut off-valve position, a local fault signal is sent to the WECS engine control system. The redundant SSI bus connecting the FCM-20 to the crank angle sensor is part of the retrofi t package. The crank-angle sensor is mounted on the intermediate

shaft and has built-in redundancy.From the outset, considerable

thought and design work was put into developing a cost-effective lubricating system that can deliver the shortest possible payback time. This required that the RPLS is able to be retrofi tted in the minimum working time on board ship with cost-effective components.

Experience with RPLSSince the fi rst retrofi t, the “COSCO SHENZHEN” has been visited by Wärtsilä engineers several times, and the cylinder lubricating feed rate was reduced within two weeks to the target level of 0.8 g/kWh from its original setting of 1.36 g/kWh. The operating results have been very good during the 6000 running hours so far accumulated.

“With its improved capability and considerable cost savings, this new cylinder lubricating system is a notable performance improvement to the Wärtsilä engines, and we look forward to rapid completion of the series of nine retrofi ts”, said Willem Dekker, Chief Operating Offi cer, of E.R. Schiffahrt GmbH & Cie KG, the Hamburg manager of “COSCO SHENZHEN”, after reviewing the service results at the end of 2006. In the meantime, the whole RTA96C-engined fl eet of E.R. Schiffahrt has been successful retrofi tted with RPLS.

Overall, experience with RPLS has been successful, and excellent liner and piston ring conditions have been recorded since the earliest tests. Before the fi rst commercial installation, trials had been carried out both on the Wärtsilä research engine in Winterthur, and on shipboard engines.

The fi rst RPLS test started on the research engine in June 2003. Shipboard testing began with an RTA58T engine in September 2004, and later with an RT-fl ex96C engine. Shipboard testing has accumulated more than 20,000 running hours. Throughout, the outstanding performance of the RPLS was confi rmed, with all testing being at or below the guide feed rate of 0.8 g/kWh.

The Pulse Lubricating System is now established as a worthwhile retrofi t for Wärtsilä RTA and RT-fl ex engines, and it offers ship owners and operators substantial savings in operating costs without disturbing the normal operating service of their ships.


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SOx scrubbing of marine exhaust gasesAUTHOR: Torbjörn Henriksson , Propulsion and Appl ications Expert, Technical Service, Wärtsi lä in Finland

When Ship type Area % Act19.5.2006 All Baltic SECA 1.5 Marpol11.8.2006 All Baltic SECA 1.5 EU11.8.2006 Passenger ships All EU 1.5 EU11.8.2007 All North Sea + English Channel SECA 1.5 EU22.11.2007 All North Sea + English Channel SECA 1.5 Marpol1.1.2010 All All EU ports 0.1 EU1.1.2010 Inland waterway vessels All EU inland waterways 0.1 EU1.1.2012 16 Greek ferries Greek ports 0.1 EU

Table 1. – A summary of existing SOX emission regulations.

For the commercial implementation of marine scrubbers to become viable, there are a number of challenges to be faced. These include the return on investment with fuel prices as they are at present, the need to clarify rules relating to the discharge of wash water, the certifi cation process, and the absence of reference installations. Wärtsilä has combined it’s long experience of developing and delivering SO

X scrubbers for stationary

diesel power plants with it’s specifi c expertise in marine system design, and has now produced in-depth feasibility studies for several selected ship types.

Existing SOX emission regulations Currently, the most important legislation, particularly for ship operation in Europe, is covered by the Marpol Annex VI Act and the new EU directive. Table 1 shows a rough summary of these regulations.

New legislation governing SOX emissions of ships affects ship design and operation. If the vessel operates in areas where SOX emissions are controlled, compliance can be achieved by using low sulphur fuel, or by cleaning exhaust gases using SOX scrubbers, or by a combination of both.

Additionally, the California Air Resources Board (CARB), for example, has adopted regulations for auxiliary diesel engines and diesel-electric engines in ocean-going vessels within regulated California waters (24 nautical miles from California). The limits are 0.5% of sulphur in the fuel from 1.1.2007, and 0.1% of sulphur from 1.1.2010. Exhaust gas abatement is an alternative.

Locally, ports and local authorities for example in Sweden, offer reductions in port and fairway fees depending on the sulphur content in the fuel being used.

Future regulations under discussionThe clear goal of the IMO and EU is to further curb the emission of sulphur oxides. The work on revising MARPOL Annex VI is actively being pursued at the IMO, and an expert group has been nominated. Decisions are expected during 2008.

Six alternatives are presently being discussed. Four of them include more stringent requirements for certain regions, while the other two alternatives focus on unifi ed SO

X-limits that would

be applicable globally on all seas. One option is to use distillate quality

everywhere. However, while this would certainly simplify many things, it has met with considerable objections based

upon its drastic impact on shipping and the oil industry, and the increased CO

2-emissions at refi neries.

The fi ve remaining alternatives are more “goal-setting”, specifying the required emission performance, but leaving the solutions to the industry. In these scenarios, exhaust gas cleaning is also considered as being an economically feasible alternative to using much more expensive fuel. The low-sulphur fuel price premium is expected to grow due to reduced sulphur limits and to the fact that regions with more stringent requirements are being geographically extended.

SOX SCUBBER REGULATIONSThe IMO and the EU are being urged to produce a consolidated approach to reasonable wash water discharge criteria and a unifi ed geographical defi nition.

The development of legislation is presently considered to be the most important means of ensuring the successful introduction of exhaust gas cleaning on ships. Here again decisions are expected during 2008.

IMO scrubber certifi cationThere are already some regulations stipulating performance, verifi cation, and certifi cation issues for SO

X-scrubbers.

IMO Resolution MEPC.130(53) requires a SECA Compliance Plan (SCP) describing methodology for compliance by each ship using scrubbers rather than low-sulphur fuel.

Similarly to the NOX regulation

requirements for engines, the scrubber (Exhaust Gas Cleaning System-SO

X,

or EGCS) shall be delivered with a technical document, the EGCS-SO

X

Technical Manual (ETM), outlining the nominal capacity, type of combustion units, operating limits (gas temperature, sea water alkalinity etc.), maintenance, and survey procedures to ensure proper operation etc. Upon successful approval of the ETM and demonstration of performance, a SECA Compliance

56 in detail

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100%

50%

0%pH 14

SO2 reduction

Fig 1. – Scrubber SOX-reduction versus pH of the scrubbing water.

Fig 2. – Alkalinity of the Baltic Sea.

Longitude (°)

Lati

tud

e (°

)

Alkalinity

Open sea alkalinitySurface data (0...15m)Data from 2001-2005

Certifi cate (SCC) will be issued. During operation, scrubber maintenance

should be recorded in a dedicated “EGCS-SO

X record book”, or alternatively

in a Planned Maintenance System. Maintenance and survey procedures of monitoring systems are documented in an “Onboard Monitoring Manual (OMM)”.

IMO wash water requirementsMarpol Annex VI stipulates that “waste streams shall have no adverse impact on ecosystems based on criteria of port State”. While this may sound obvious, countries have been slow in defi ning their criteria. This is soon expected to change, as IMO Wash Water Guidelines will be available (approval expected in 2008).

EU regulationsEU Marine Fuels Sulphur Directive (2005/33/EC) includes provisions for the testing and installation of emission abatement technologies.

The European Commission is responsible for establishing criteria for the use of scrubbers in enclosed areas. Similarly, ships utilizing scrubbers are required to be fi tted with continuous emission monitoring equipment. It is hoped that the EU will harmonize this requirement with the provisions of IMO Resolution MEPC.130(53), which offers both unit approval (scheme A) and continuous monitoring (scheme B).

National regulationsFor authorities it is diffi cult to get a full picture of the composition and quantity of scrubber wash water, and what is “effl uent” and what is “residue”. This is fully understandable, as little information is publicly available, and several scrubber technologies exist with considerable variation in this respect.

Some countries adjacent to SECA areas have then defi ned certain coastal zones, within which the discharge of scrubber wash water is currently not permitted (in contrast to the discharge from inert gas scrubbers on tankers).

ALKALINITY, PH AND SALINITYThe driving factor for sulphur acid neutralization, and therefore SO

2-

reduction, is the water alkalinity. Such alkalinity is to some extent

available in sea water, but it can also be added artifi cially in the


in detail 57

p

Fig 3. – Sulphur removal from exhaust gas by fresh water scrubbing, Wärtsilä scrubber system layout.

Closed loop works with freshwater, to which NaOH is added for the neutralization of SOX.

Exhaust gas

Fresh water

Water treatment

Cooling

Process tank

Holding tank

Closed loop=

Zero dischargein enclosed area

Scrubber

pHpH

Source: Finnish Institute of Marine Research

NaOH unit

Seawater

form of an alkaline chemical. Alkalinity does not refer simply to

pH, but to the ability of water to resist changes in pH. Buffering materials are primarily bicarbonate, carbonate, but also consist of hydroxide, borates, silicates, phosphates, ammonium, sulphides, and organic compounds. Total alkalinity, AT, is the sum of all these.

Salinity describes the salt content of water. The salinity of ocean water is approximately 3.5%-weight. Water can have high alkalinity and zero salinity depending on the calcium concentration.

Alkalinity in natureOcean alkalinity is usually constant and high; approximately 2200-2300 µmol/l.

Alkalinity in coastal areas, ports, rivers and estuaries is mainly affected by the different drainage areas of the infl owing rivers, resulting in large variations in the chemical quality. Rivers running through soil rich in carbonates will be high in alkalinity. For example, the northern rivers of the Baltic Sea run through granite bedrock resulting in low alkalinity, while the southern rivers run through calcite bedrock resulting in high carbonate concentrations with consequently high alkalinity (see Figure 2).

In general, the alkalinity in the Baltic Sea is lower than normally in sea areas because of the minimal exchange of water through the Danish straits.

At low alkalinity levels the seawater scrubber can still operate, but it leads to lower cleaning effi ciency and to low effl uent pH fi gures.

SOX scrubbing technologies for marine applicationsWärtsilä has an impressive reference list of delivered SO

X-scrubbers for stationary

plants, and has consequently accumulated vast experience of scrubbing technology. Based on this background, Wärtsilä has concluded that there are two different technologies worth further development for marine applications, namely sea water (“open loop”) scrubbing, and fresh water (“closed loop”) scrubbing with an added chemical (typically caustic soda).

As ships have sea water available in unlimited quantities, sea water scrubbing may appear to be the obvious choice. There are, however, some limitations involved in this concept, which will be discussed below.

SEA WATER SCRUBBINGThe main benefi t of a seawater scrubber is simplicity; it requires neither additional chemicals nor fresh water for operation. Instead seawater alkalinity, or buffering capacity, is used to neutralize the exhaust gas sulphur. In order to maintain high effi ciency, a seawater scrubber needs a high fl ow of seawater with an adequate level of alkalinity.

FRESH WATER SCRUBBINGThe fresh water scrubber is a good alternative if high effi ciency cleaning is needed, or as a means of avoiding seawater alkalinity issues. In such scrubbers, a caustic soda (NaOH) solution is used to neutralize sulphur compound.

Fresh water scrubber cleaning effi ciency is typically higher than 90%. A fi gure as high as 97% can be specifi ed for generator engines to reach an equivalent of 0.1% fuel sulphur, as will be required in, for example, EU ports and California (see Table 1). Thus, engines will always be able to run on conventional HFO.

The power demand for pumps is very low, between 0.5 and 1% of the engine in question.

System layoutThe fresh water scrubber system layout is shown in Figure 3. The main principle is as follows:

The washing solution is pumped

from the process tank through a system cooler to the scrubber. From the scrubber the washing solution returns to the process tank by gravity.

NaOH is fed to the system via a small feed pump. Topping-up of fresh water is needed to the extent that the evaporated or discharged water is not fully compensated by the humidity in the exhaust gases (from engine combustion).

A small portion (the “bleed-off”) of the scrubbing water fl ow is directed to the treatment unit. The treated effl uent is either discharged overboard or collected in a clean bilge water tank or other suitable holding tank. This feature is unique, as the system can periodically be operated in a “Zero Discharge Mode” i. e. with no discharge of wash water overboard.

The captured contaminants (sludge) are transferred to the existing vessel’s sludge tank.

The process tank can be large enough to temporarily hold some bleed-off for periods when the scrubber is running but the treatment plant is not, or vice versa.

Caustic sodaThe typical commercial solution is a liquid with a concentration of 50%. It has a density of 1.52 t/m3 and a pH of 14. It solidifi es at 12°C, and is typically transported warm.

The caustic soda can be bunkered

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Fig 4. – Wärtsilä scrubbers in a RoPax (longitudinal section).

605040605040

Original Converted

Scrubber 1

Scrubber 2

Process tank

Scrubbingwatercooler

Fig 5. – Wärtsilä scrubbers in a RoPax (transverse section).

Original Scrubber

from trucks via fi lling connections in the bunker stations. The storage tank can be of normal shipbuilding steel.

Based on price fl uctuations of caustic soda during the last 20 years, the cost is between 0.5 and 4% of the fuel costs.

Exhaust gasThe exhaust gas plume in traditional wet scrubbers has a high relative humidity. Wärtsilä’s marine scrubber includes a feature to minimize the water vapour of the plume, as well as the water lost to the atmosphere and, therefore, the need for topping-up water.

As the scrubber provides noise attenuation, it can replace the existing silencer. Attenuation of high frequencies is inherent in the scrubber design, while lower frequencies are taken care of by a suitable geometry considering the emission spectrum of the engine in question.

As a separate silencer is not needed, the overall back pressure of the exhaust gas system can be maintained within acceptable limits.

Retrofi ts and newbuilds Scrubbers can be fi tted on newbuildings as well as on existing ships.

On newbuildings there is full freedom to locate components. It is also possible to specify a “readiness for later retrofi t of scrubbers”. Wärtsilä can provide information relating to matters such as space allocation etc. (see Figures 4 and 5).

On existing ships the funnel may not be large enough. In such cases the funnel geometry can be modifi ed, but it is also possible to fi t the scrubber itself outside the funnel, with the other equipment inside.

As an example, a scrubber for an 8400 kW engine is 8.0 meters high, 2.9 meters in diameter, and the weight in operation is 13.4 tons.

CONCLUSIONWith more stringent regulations looming in the future, SO

X-scrubbing is being

seen as an increasingly attractive way of minimizing operational costs by using HFO in an environmentally sound way. The interest of shipping companies is steadily increasing, and authorities are working actively to develop corresponding regulations.

NOTE: For more information, please contact us at [email protected]

WÄ

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TOMORROW THEY’LL BE DRESSEDFOR THE SAHARA.

If you need lifecycle care on land, at sea - or even in it – call us. This is the kind

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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.

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