Hybrid marine power systems: techno-economic and environmental optimisation of alternative fuel pathways

This paper offers a comprehensive optimisation tool for the design and assessment of hybrid maritime power systems that combine internal combustion engines, fuel cells, and battery energy storage systems. Using a surrogate-assisted NSGA-II algorithm, the framework concurrently reduces operational expenditure, CO₂ emissions, and life cycle cost assessment. Under constant technical criteria, including system weight and volume, with and without waste heat recovery, four fuel pathways—diesel, LNG, methanol, and ammonia—are evaluated. The results reveal considerable economic and environmental differences compared to the diesel baseline: LNG increases LCCA by 0.5 % (€1.2M) and global warming potential (GWP) by 2 % (1752 kg), while acidification potential (AP) and aerosol formation potential (AFP) decrease by 91 % (914 kg and 1118 kg, respectively). Methanol reduces LCCA by 14.3 % (€35.3M), GWP by 36 % (35,540 kg), and AP/AFP by 81 %, offering a cost-effective and environmentally balanced solution. Ammonia eliminates GWP, AP, and AFP, though with a 10.7 % (€60M) increase in LCCA, demonstrating its potential for long-term decarbonisation. The findings show clear Pareto fronts for every fuel, suggesting that the possible design area is significantly influenced by fuel type. The framework offers practical guidance for designing energy-efficient, low-emission vessels, aiding in sustainable marine energy transitions.