For the past forty years, steam turbine installations have dominated propulsion and electric power generation onboard LNG carriers. The ease with which these installations can utilize boiloff gas and their apparent reliability have kept them in a position that has long been lost to diesel engines in all other segments of the shipping industry. Steam turbine installations are however not very efficient. This has a negative impact on both the ship's operating economy and its exhaust gas emissions. Exactly these issues play an increasingly important role in LNG shipping today. Initially encouraged by the latest developments in its gas engine technology, Wärtsilä started looking for more economic and environmentally friendly ways to power LNG carriers. Machinery alternatives with two- and four-stroke diesel, high-pressure gas-diesel and low-pressure dual-fuel engines, in mechanical and electric propulsion arrangements, with and without boil-off reliquefaction plants, were studied. Dual-fuel-electric installations were found to be the most attractive alternative to steam turbine installations.
The first dual-fuel-electric LNG carrier, Gaz de France Energy, will take to the sea later this year and two more dual-fuel-electric LNG carriers are on order. Further orders for dual-fuel-electric LNG carrier are expected anytime soon.