Abstract

For the past forty years, steam turbine installations have dominated propulsion and electric power generation onboard LNG carriers. The ease with which these installation can utilize boil-off 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 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, Wartsila started looking for more economical and environmentally friendly ways to power LNG carriers. We studied machinery alternative with two- and four-stroke diesel, high-pressure gas-diesel, and low-pressure dual fuel engines, in mechanical and electrical and electric propulsion arrangements, with and without boil-off reliquefaction plants. Dual-fuel-electric installations were found to be the most attractive alternative to steam turbine installations.
The first dual-fuel-electric LNG carrier, Gas de France Energy will go to sea later this year and two more duel-fuel-electric LNG carriers are on order, Further orders for duel-fuel-electric LNG carrier are expected any time soon.