Decarbonisation of the shipping industry: Thermodynamic analysis of a Cryogenic Carbon Capture system coupled with LNG-fuelled SOFC

The global effort to achieve net-zero greenhouse gas (GHG) emissions by 2050 requires all industrial activities to actively transition to carbon-neutral energy consumption in the near term. The maritime industry, as both a crucial enabler of global trade and a notable contributor to GHG emissions, faces a particularly complex yet relevant decarbonisation challenge due to its heavy reliance on fossil fuels for ship power generation. While various solutions are under investigation, carbon capture technologies are gaining interest as a near-term mitigation strategy, and in recent years, solid oxide fuel cells (SOFCs) have been increasingly studied for their potential as efficient ship propulsion systems. The present study examines the performance of a novel integrated system for ship propulsion, that couples a cryogenic carbon capture unit with an SOFC fuelled by liquefied natural gas (LNG). A key focus of the research is to assess the contribution of LNG regassification in cooling the exhaust gases to cryogenic temperatures, thereby reducing the power demand of the capture system, which, without any internal thermal integration, relies on an external cryogenic refrigeration system. The system is modelled using the Aspen Plus software, with multiple simulations conducted to analyse its operating conditions and evaluate the overall system efficiency. The proposed configuration maximises internal thermal integration while achieving 99.5% CO2 capture rate in the flue gases. A sensitivity analysis is performed to examine the impact of key SOFC operating parameters – temperature, fuel utilisation and current density – on the overall system efficiency. The findings indicate that while LNG regassification provides some benefits within the thermal integration framework, its contribution to reducing the cooling demand of the cryogenic system is only marginal. This highlights an opportunity for further research to explore the system’s performance with alternative fuels. The results demonstrate that the system’s overall efficiency is comparable to the typical values for conventional internal combustion engines, while having nearly zero emissions. The additional power consumption required for the cryogenic refrigeration system is offset by the inherently higher electrical efficiency of the SOFC, leading to increased net electrical power output. Ultimately, the integrated system represents a promising opportunity to achieve a more efficient and cleaner power generation for ship propulsion.