Hybrid Solid Oxide Fuel Cell and Internal Combustion Engine Propulsion System for Maritime Decarbonization: Energy and Environmental Assessment

The maritime sector plays a crucial role in global trade but remains a significant contributor to greenhouse gas emissions, accounting for approximately 3% of global CO₂. In alignment with the International Maritime Organization's goal of achieving carbon neutrality by 2050, this thesis investigates the hybridization of Solid Oxide Fuel Cells (SOFCs) with Internal Combustion Engines (ICEs) fueled by natural gas for maritime applications. Conducted within the framework of the SOFFHICE project — a nationally funded collaborative project between Politecnico di Torino, the University of Genova, and the University of Bologna — this study assesses the feasibility and performance of a hybrid SOFC-ICE system considering the power demand profile of an existing short-sea ferry as case study. Three propulsion system configurations are evaluated: (1) a conventional ICE-only system, (2) a hybrid SOFC-ICE system with independent SOFC operation, and (3) an advanced hybridization approach where SOFC anode exhaust gases enhance ICE efficiency. A detailed thermodynamic and electrochemical model of SOFC is developed, integrating the Balance of Plant assessment to accurately represent real-world performance under nominal and partial load conditions. The ICE efficiency is modeled using real operational data, while CO₂, NOₓ, and CO emissions are assessed based on hourly fuel consumption. Additionally, a battery storage system is investigated to store excess energy, improve power distribution, and compensate for the SOFC's slow ramp rates. The reference scenario assumes a SOFC sized to cover the vessel’s baseload power (available 24/7), with the ICE supplying the additional power required for maneuvering and cruising. Results indicate that SOFC-ICE hybridization significantly reduces fuel consumption and emissions, achieving up to a 20% reduction in daily fuel use compared to the ICE-only baseline. Furthermore, port operations benefit from over a 60% reduction in emissions, demonstrating the potential of SOFCs to mitigate environmental impact in coastal areas. The findings suggest that SOFC-based hybrid systems represent a viable pathway for maritime decarbonization, especially for vessels with stable power demands.