Design optimization and techno-economic assessment of integrated BOG reliquefaction and fuel-supply systems for ammonia-fueled very large ammonia carriers

초록

This study proposes an integrated cargo-subcooling and liquid-fuel supply system (SC–LFSS) for an 88,000 m3 ammonia (NH3)-fueled very large ammonia carrier (VLAC), in which the cold NH3 fuel serves as a heat sink for the CO2 cycle that subcools the cargo. It is compared with vapor-compression (VC), Linde–Hampson (L–H), and subcooling (SC) boil-off gas (BOG) management configurations with a standalone fuel supply system. All configurations were optimized by a genetic algorithm to maximize the cargo-management coefficient of performance (COP) under a common cooling duty of 224.39 kW. At 75% engine load, SC–LFSS required 90.88 kW (COP 2.469), 18.21% less than L–H, the best alternative, and showed the lowest exergy destruction on a common boundary including fuel conditioning. Its advantage depended on engine load: with the operating conditions re-optimized at each load, the COP fell below those of VC and L–H at 25% load, and the COP weighted by an assumed E3 load profile was 2.317. With the load-weighted power and component-wise equipment sizing over the evaluated loads, the 20-year life-cycle cost of SC–LFSS was 12.31 million USD, 9.2% lower than that of L–H. These results show that cargo–fuel thermal integration can improve the energy and economic performance of onboard BOG management for ammonia-fueled VLACs, despite a performance penalty at low engine load. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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