Sea-Cargo AS has ordered the first ships in the world to be fuelled solely with liquefied natural gas (LNG), and also have a simple mechanical drive propulsion system. On delivery from the Bharati shipyard in India in 2010 they will operate on a ten- day round trip service covering Baltic, Norwegian and British ports, bunkering gas fuel at one location. The new 132.8m long Sea-Cargo vessels will be able to carry 5,600 tonnes of cargo on a draught of 6m, with up to 94 teu of containers on deck and 1,140 lane-metres of RoRo capacity.
The vessels are a major breakthrough, both in the application of LNG fuel for merchant vessels, and in the way the simple Rolls-Royce solution works. An important end result will be a very large reduction in emissions compared with a similar ship using liquid fuel. CO2 emission will be reduced by about 20%, NOx by about 90%, particulates negligible and sulphur oxide emissions will be zero.
The Bergen B35:40V12PG main gas engine uses the Rolls-Royce lean burn combustion technology that is the key to obtaining a very high thermal efficiency and good control in a gas-fuelled engine. It is classed for the load/speed operational pattern that comes with mechanical coupling to a controllable pitch propeller. Consequently a simple single engine propulsion system has been possible in the Sea-Cargo RoRo vessels - conventional in all but the fact that LNG is the fuel.
Cold liquid gas will be stored in two insulated flasks forward of the engine room, in a ventilated enclosure offset to one side to clear a vehicle ramp. This space will also house the evaporator system that converts to liquid into a low pressure warmed gas and supplies it to the gas engine which turns the propeller through a reduction gear and also supplies the vesselís electrical load by means of a generator driven off the gearbox.