Industry awaits LNG developments
With both gas-fuelled and conventional four-stroke technologies currently at a mature stage, the industry waits to see whether, and when, LNG as fuel will become the norm in the markets traditionally served by medium-speed technology.
Four stroke marine engine technology seems to have reached a hiatus in its development. After a rush to clean up conventional and dual fuel engines, development has stabilised, admittedly at a peak, with a number of successful, environmentally-friendly solutions on the market from all the major designers.
Everybody in the industry now seems agreed that use of LNG as a fuel is something that is going to become widespread; it’s just a matter of when. Gas-fuelled four-stroke engines are now a mature technology, the industry turning its attention towards low speed units able to operate on gaseous fuels.
The drivers for the next stage of four-stroke gas engines are three-fold. First – and not necessarily in this order - there are the lower emission limits coming in soon. Operating on gas, four-stroke engines are able easily to meet the upcoming limits on oxides of sulphur and nitrogen and particulates, and provide a significant reduction in carbon emissions.
Second, there is cost. This is still an unknown, as the viability of LNG as fuel depends on the price differential between it and conventional liquid fuels. It is highly likely that the differential will widen, particularly as demand for distillate fuels, which will be required in order to meet sulphur limits, will drive the cost up, making LNG more attractive. There is also the prospect of tapping into large-scale sources of shale gas, which will result in cheap natural gas in certain regions. Then, if exhaust gas cleaning becomes widely adopted, which depends on the cost of residual fuels coming down as well as persuading large sectors of the industry that the technology is sufficiently advanced and reliable to justify the considerable investment, that could affect the demand for the LNG alternative. But although most of the successful scrubber installations so far have been on four-stroke engines, the solution lends itself more to deep-sea vessels powered by two-strokes.
Thirdly, and perhaps most crucially, is the bunkering and infrastructure question. Gas fuel needs to be made available where it is needed by ships – that much seems obvious. It’s often described as a ‘chicken and egg’ situation, as LNG is not likely to be adopted by most ship operators until it is available, and it is not going to be made available until the suppliers know there is sufficient demand. Until that time, use is limited to vessels operating in a distinct area, or on fixed routes, namely offshore supply ships and ferries. However, some parts of the industry are now saying that “the chickens have arrived”, quoting the fact that LNG bunkers can be easily laid on in much of Europe, where there are gas terminals near to major shipping routes, as well as in certain areas in the Far East.
Taking all these factors into account, prospects look good for four-stroke gas engines in the future, with the industry waiting to see what the next few years will bring. In fact we may be closer than we think; one engine supplier, Wärtsilä, points out that in terms of horsepower at least, gas engines already enjoy a significant share of the marine four-stroke market. The company’s large dual-fuel four-strokes currently seem to be the prime movers of choice in the LNG tanker sector, one part of the shipping market which is currently enjoying growth rather than stagnation. MAN Diesel & Turbo is attacking the same market.
These, and the smaller four-strokes, continue to do well in the offshore support and passenger vessel sectors, with gas fuelled engines increasing their penetration. The current question here is whether to go for dual-fuel or gas-only. Both solutions have their strong adherents, among end users as well as engine designers. Rolls-Royce, through its Bergen engines division, is firmly committed to single-fuel engines, either gas or diesel. Bergen has recently re-structured to become part of Tognum, alongside MTU, Tognum being jointly owned by Rolls-Royce and Daimler.
Rolls-Royce says, understandably, that a single fuel engine will always be more efficient and perform better overall, including producing fewer harmful emissions, than an engine built as a compromise between two very different fuels. Several end users, mainly in the offshore sector, agree, as we found out at the last Motorship gas fuelled ships conference, in Bergen in 2012.
Wärtsilä, on the other hand, is committed to the dual-fuel solution. The company’s most pressing argument is one of flexibility. The ability to operate on different fuels means that ships can move freely between operating areas, and are less likely to be affected by fluctuations in supply or price. In addition, the redundancy requirements applicable to many offshore support applications mean that gas systems need to be duplicated – at considerable cost, meaning that the single-fuel installations end up more costly than dual fuel. Interestingly, some of the single-fuel gas-only users have a reserve diesel genset onboard to cover these requirements. And Wärtsilä can, if necessary, supply gas-only engines, having considerable experience with spark ignition gas fuelled engines in the land-based power plant market, The company, though, does not yet see these units as being applicable to marine installations, but believes that as the gas supply question gets resolved, the situation could change.
Recently Wärtsilä’s 34DF engine became the first dual-fuel unit to receive certification of emission standard compliance from the United States EPA. As a result, Wärtsilä anticipates that market demand in the US for its dual-fuel engines will further increase. The first engines will equip the Harvey Energy, a PSV being built for Harvey Gulf International Marine, and four recently-ordered sister ships with the same engines.
Wärtsilä engines were selected for the first large LNG-fuelled passenger ship in service, the Viking Grace, won which the 2013 Motorship Gas Fuelled Ships conference will be held. The company has recently concluded a five year maintenance agreement with owner Viking Line, covering maintaining and servicing the four 50DF main engines and the Wärtsilä LNGPac gas system safety valves. Under the terms of the contract, Wärtsilä will provide a range of services including engine maintenance planning, maintenance work, condition monitoring, spare parts supply, technical support, and workshop services.
MAN Diesel & Turbo offers gas-fuelled four-stroke engines to the power generation market, in both single and dual-fuel variants, but has yet to achieve any significant penetration into the gas-fuelled marine propulsion field, though it claims the market-leading position in marine four-stroke propulsion engines. The 51/60DF engine, the largest dual-fuel four-stroke on the market, has been launched with a ‘fuel sharing’ mode, which allows operation on a mixture of gas and liquid fuel, as well as gas or diesel only. This has been targeted specifically at the LNG carrier market, and last year picked up its first order, from Greek shipowner Alpha Tankers, for two newbuildings at STX in Korea. Each will be powered by a diesel-electric plant based on two 9L51/60DF and two 8L51/60DF engines, a total of 34MW per ship.
MAN diesel-fuelled engines continue to pick up orders in the ro-ro and ro-pax sectors, and have been making inroads into the offshore market. The company says its complete propulsion packages have gained a foothold in the Middle East, where it supplied engines, reduction gears, shaft alternators, CP propellers, nozzles and control systems for a pair of AHTS vessels for Topaz Energy.
The two 67m 80t bollard pull vessels are equipped for DP2 and Fi-Fi Class I operations. The twin-screw propulsion package for each vessel consists of 8-cylinder, mediumspeed MAN L27/38 engines each rated 2,720kW, horizontal offset reduction gearboxes with CPP servo oil distribution unit, and a 1,500 kW shaft alternator PTO. The gearboxes drive 18m intermediate shafting and 13metre propeller tailshafts in oil-lubricated stern tubes. The Alpha CP propellers are 2,800mm diameter ducted, and are boosted by Alpha high thrust nozzles, with length/diameter ratio of 0.6. the alphatronic 2000 propulsion Control System is configured with twin control stations on main bridge, aft bridge and engine control room, including interfaces to joystick and DP systems.
The company’s 48/60 engine, on which the 51/60DF is based, has sold more than 500 examples. This milestone was reached at the end of last year with an order for two common-rail variants to power a dredger for Saudi company Huta Marine, built by IHC Merwede in the Netherlands. The current version of the engine features, as well as a common-rail fuel system, a redesigned cylinder head where a higher fuel injection pressure resulted in improved atomisation and better combustion, ultimately reducing both fuel consumption and emission levels, and enabling IMO Tier II compliance.
More recently, MAN has picked up an order for a complete propulsion system for a new large Spanish tuna fishing vessel. The company says that this system is of interest because it comprises three high-efficiency products: a MAN 8L32/44CR engine with common rail technology, a Renk RSVL-950 gear unit, and an innovative Alpha VBS1100 CP propeller with Kappel blades and rudder bulb. This combination is claimed to increase propulsion system efficiency by some 9%, helping to decrease costs, fuel consumption, and exhaust emissions.
“This propulsion package is the most energy-efficient solution that we currently offer,” said MAN Diesel & Turbo’s Frederik Carstens, sales manager of the medium speed business unit. He cites Italian shipyard Visentini to back up this assessment; the yard having ordered a complete package consisting of two 9L32/44CR engines with CR technology, Renk gearboxes, and Alpha propellers.
Caterpillar, through its MaK division, offers both diesel and gas fuelled four-stroke engines, though, like MAN, it has yet to break into the market with its gas versions. The M46DF is a dual-fuel engine based on the M43, and is expected to be ready for first deliveries in 2014. With an output of 900kW/cylinder, MaK claims industry-leading efficiency and fuel consumption in gas mode. MaK’s diesel-fuelled engines have enjoyed a strong position in the passenger ship market, mainly through the M43, and as the M46DF is designed to have the same footprint and be easily retrofitted, MaK obviously has its sights set on the new generation of ‘green’ cruise ships. The company said at the last SMM exhibition that it intends to launch a dual-fuel engine based on its M32 family, with availability planned from 2015.
Rolls-Royce recently concluded a memorandum of understanding with Drydocks World Dubai to provide systems for LNG powered tugs for the Middle East market. The tugs, to be designed by Drydocks World’s own design team, will incorporate a range of power and propulsion equipment from Rolls-Royce, including Bergen medium speed gas engines.
Wärtsilä recently gained an important offshore order with a contract to design a series of four multi-purpose PSVs for Armada Offshore of Malaysia. The vessels will be built at Fujian Mawei Shipbuilding in China by a subsidiary of Nam Cheong Limited, Malaysia's largest OSV builder. In additiona to vessel design, Wartsila will supply the complete power generation system, the propulsion system, the automation system and the Low Loss Concept (LLC) electrical system. In another offshore contract, Wärtsilä is to supply an integrated power, propulsion and positioning system for a DP3 offshore accommodation rig being built at Cosco (Qidong) Offshore in China, which is building the vessel for Singapore based Axis Offshore. Scope of supply includes the power generation and propulsion systems, plus electrical, automation and safety systems.
Hyundai Heavy Industries of Korea has recently gained type approval for its home-grown 35,300bhp HiMSEN H46/60V engine from classification societies ABS, BV, CCS, DNV, GL, KR, LR, NK, and RINA. The company says that completion of the type approval process of the IMO Tier III compliant HiMSEN H46/60V expands its medium speed marine engine line-up to cover output from 780bhp to 35,300bhp.
HiMSEN stands for Hi-touch Marine and Stationary Engine, a concept first introduced by HHI in 2000. Since then, some 7,200 units have been manufactured, mostly for land-based power plants, but also for marine applications, with configurations between five and 20 cylinders.
“The rated power of medium speed engines varies depending on ship size and power generation capacity. With the development of the high power HiMSEN H46/60V, Hyundai Heavy is well positioned to swiftly respond to the demand for high power marine engines for ship propulsion and power generation,” said Kim Jong-suk, senior vice president of the HHI engine and machinery division.
Of course, not only the actual propulsion system contributes to greater efficiency and cleaner ships. Auxiliary systems have a part to play as well, and Alfa Laval points out that its products have contributed to the advanced environmental credentials of NCL’s latest class of cruise ships. The first of the pair, Norwegian Breakaway, has recently been delivered by Meyer Werft of Germany. Alfa Laval says its new PureDry heads up an extensive range of environmental and energy-efficient equipment on board.
The PureDry waste fuel recovery system makes this the first cruise ship to benefit from MARPOL rule MEPC.1/Circ.642. Under this new legislation, it is permitted to recover and re-use the HFO fraction of waste oil as fuel for the diesel engines. PureDry makes this possible through unconventional high-speed centrifugal disc-stack separation technology. It has only two moving parts, the outer bowl and a separator insert, which rotate at slightly different speeds. Instead of a conventional bowl aperture or hydraulic discharge system, a patented, spiral-shaped device called the XCavator transports the separated solids to the base of the machine, where they exit into a container below.
According to Alfa Laval, PureDry requires no process water and leaves only non-pumpable ‘super-dry’ solids that can be landed as dry waste. Waste oil volumes are thus reduced by 99%, leaving around 5kg to-15kg/day of solids for disposal. The separated water, with an oil content <1,000ppm, is pumped to the bilge water tank as part of an integrated waste oil and bilge water handling system.
The company claims that the HFO recovered in the process can represent up to 2% of total fuel consumption, which NCL estimates as a saving of about €100,000 annually for Norwegian Breakaway at current bunker costs. “
In order for waste oil recovery to work, the traditional single waste oil tank has to be divided into one tank for fuel oil and one tank for lube oil. On Norwegian Breakaway, this was done at the design stage, following a successful demonstration onboard Silja Symphony, which has a test system installed. The result, according to Alfa Laval, is that the ship comfortably clears the EEDI demands.
In addition to PureDry, the environmental scope of the Alfa Laval delivery for Norwegian Breakaway includes the PureBilge treatment system which achieves, in real-life conditions, 0-5 ppm oil content without chemicals, adsorption filters or membranes. PureBilge will be used in conjunction with PureDry as part of an integrated waste oil and bilge water handling system.
Also aboard Norwegian Breakaway will be PureBallast, Alfa Laval’s chemical-free ballast water treatment system, high-speed separators with Alcap technology, as well as two Aalborg OM-TCi boilers, with optimised thermal design aiming for lower fuel consumption and a total efficiency of 89-92% depending on boiler load conditions. After Norwegian Breakaway’s main engines, four Aalborg XW waste heat recovery boilers will recover heat energy for use in steam production. Waste heat will also be involved in the generation of fresh water, for which Norwegian Breakaway will employ the Alfa Laval Multi-Effect Plate (MEP) evaporator. Typical electrical energy consumption for the MEP evaporator lies between 1.3 and 3.0kWh/m3, thanks to an optimised pump configuration and the application of a frequency-controlled motor on the sea water pump. Further savings are possible with the MEP unit because it only needs to be cleaned once per year with the help of non-toxic agents.
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