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New hybrid-electric propulsion for large LNG carriers has five compact generating sets instead of the typical two large, 2-stroke engines and four auxiliary generating sets. Because this design saves space, the cargo capacity of a standard 174,000 cbm vessel will increase by 9000 cbm below deck. What’s more, the new design reduces equipment weight by over 40%. This means that even with more cargo, the overall vessel displacement, draft, and hull performance will be the same as current designs, enabling it to be compatible with standard large LNG terminals. The increased cargo space will lead to reduced emissions per ton mile. Although LNG carriers are designed for a speed of 19.5 kn, several sources indicate the current average sailing speed to be around 15 kn. This means that when applying the current 2-stroke solutions they are not operating optimally – and therefore, their emissions are higher. Considering the actual operating profile of today’s LNG carriers, the new, modular hybrid electric design will achieve the following, approximate savings: 10% Reduction in fuel consumption 15% Reduction in greenhouse gas emissions 20% Reduction in methane slip. The Wärtsilä 31 engine platform is highly modular and can easily be converted to use different fuels, including LNG, bio-LNG, synthetic LNG, HFO, MDO, and a variety of biofuels. The introduction of future fuels can certainly impact engine power ratings and dynamic performance. The energy storage – the vessel battery - in the new hybrid electric design will result in higher load factors and greatly reduced running hours. As a result, maintenance costs will be significantly lower. Because the vessel battery takes care of dynamic loads, the generating sets can run at high and steady state loads. The operation will be more efficient and there will be less wear and tear on the engines. Electric propulsion has been in use in many shipping segments for several decades and is highly proven technology including in the large LNG carrier segment where there are approximately 230 vessels in operation today with electric propulsion.
