Comparative analysis of a hybrid propulsion using LNG-LH2 complying with regulations on emissions

This study proposed a liquefied natural gas (LNG)-liquid hydrogen (LH2) hybrid propulsion system for a 267,000 m3 LNG carrier to be compliant with the energy efficiency design index (EEDI) requirement for CO2 emissions from ships in the near future and evaluated the system with regard to the aspects of the EEDI, hybrid fuel ratio, installation area, safety, and economics. The system design parameters were adjusted to satisfy the EEDI of Phases 4 and 5, which were less than the current EEDI requirement by 14% and 28%, respectively. The propulsion power of 6 MW should be generated in Phase 4 from hydrogen that accounted for 3% of the total mass of LH2 and LNG fuel. The CO2-free power generation in Phase 5 was increased to 13 MW, corresponding to 6% of the total fuel mass. The LH2 price was $2.0/kg and $2.4/kg for Phases 4 and 5, respectively, to gain an economic competitiveness against the conventional LNG-based propulsion system.