Modelling of a hybrid propulsion system based on SOFC (Solid Oxide Fuel Cell) and ICE (Internal Combustion Engine)

The maritime industry is under pressure to meet decarbonization goals due to its significant emissions, including sulphur and nitrogen oxides. These emissions have harmful environmental and health impacts. To tackle these challenges, two main solutions are emerging: the use of alternative fuels (e.g., ammonia, methanol, hydrogen) and the development of efficient technologies like Solid Oxide Fuel Cells (SOFCs), which generate power without combustion. Hybrid propulsion systems, which combine fuel cells with internal combustion engines (ICEs), offer a potential solution for reducing emissions and improving energy efficiency. This study examines the integration of SOFC technology with an ICE in three configurations for the RoPax vessel Anna Mur, which operates with a steady, low-load profile. The configurations are: 1) an ICE-only system, 2) a hybrid system with SOFC and ICE, and 3) an advanced integration where off-gases from the SOFC are recycled into the ICE. Daily power curves and emissions for each configuration were modelled. Results indicate that Configuration 2, combining the ICE with SOFC, significantly reduces emissions and increases overall system efficiency compared to the ICE-only system. However, Configuration 3 offers only minimal gains in efficiency, with a higher level of complexity, making it less suitable for this specific case. A sensitivity analysis was conducted to optimize SOFC size and operational profiles. The findings show that using SOFCs can reduce emissions in port by 63% and daily emissions by approximately 1.2 tons. SOFCs are highly efficient at handling lower loads and can also use alternative fuels, making them a promising technology for future maritime applications. However, in this case study, the added complexity of an integrated system does not justify the minor emission reductions achieved, suggesting that a simpler hybrid solution might be more appropriate. In conclusion, integrating SOFCs into maritime propulsion systems can significantly reduce emissions and increase efficiency, particularly for vessels with steady load demands like the Anna Mur. Although the integrated system provides some benefits, the complexity may outweigh the gains for certain operations. Future studies should explore scalability and economic feasibility to support broader adoption of SOFCs in the maritime sector, contributing to decarbonization efforts.