Economic Study of Hybrid Power System Using Boil-off Hydrogen for Liquid Hydrogen Carriers

This study presents a hybrid power system comprising a fuel cell (FC) and a lithium-ion battery (LIB) for liquid hydrogen (LH2) carriers, which is expected to increase globally due to the production cost gap of green hydrogen between renewable-rich and renewable-poor countries. The LH2 carrier has a key challenge in handling the inevitably considerable boil-off hydrogen (BOH). As a target ship of a 50,000 m3 LH2 carrier with a boil-off rate (BOR) of 0.4% per day, this study employs an optimization tool to determine the economic power dispatch between the FC and LIB aimed at minimizing the lifetime cost of the ship. The BOH is used as fuel for FC during the voyage. Moreover, when the ship is under cargo loading and unloading operations at the port, the considerable surplus BOH is utilized to generate electricity and then sold to the shore grid (StG). The results indicate that 45.2% of the BOH can be utilized as fuel for the FC, and the StG system can effectively reduce the total lifetime cost by 32.0%. Further, the paper presents the outcomes of a sensitivity analysis conducted on critical parameters. This study provides new insights into the BOH issue of LH2 carriers and helps to increase the international green hydrogen market.