EMEA News
Rolls-Royce Claims Advantages for Single-Fuel LNG Tugs Over Dual-Fuel
Rolls-Royce says its single-fuel liquefied natural gas (LNG) propulsion systems, used in a tug boat now undergoing sea trials, offer efficiency advantages over dual-fuel engines, industry news site the Motorship reports.
Rolls Royce said the equipment used by the Borgøy,built at Turkey's Sanmar shipyard for Norwegian operator Buksér og Berging (Buksér), is simpler and less prone to methane slip than dual-fuel systems.
The engines can operate on gas of 70 methane number, rather than at least 80 methane number, as dual-fuel engines demand.
They emit only 5 grams per kilowatt hour (g/kWh) of methane at 25 percent load, and only 4g/kWh at 100 percent, compared with 40g/kWh at 25 percent and 6g/kWh at 100 percent for dual-fuel engines, according to figures from Norwegian research institute Marintek.
The tug is one of two that Buksér has ordered for use at the Kårstø gas terminal, under contract to the oil company Statoil, and the second is due to be delivered in 2014.
Buksér said it costs 40 to 50 percent more to buy a gas-fuelled tug than a conventional one, but LNG is expected to become cheaper than diesel over time, reducing operating costs.
Norway also provides tax benefits to support the reduction in emissions produced by the use of LNG.
Johan Sperling, vice president of Jensen Naval Architects and Marine Engineers, said last month that most orders for vessels with LNG capacity involve dual-fuel engines, which can operate on diesel if gas is not available, but he said some low-horsepower vessels like tugboats use the single-fuel LNG engines.
