4E(Energetic, Exergetic, Economic, and Exergoeconomic) analysis and optimization of fuel utilization in a methane-fueled cascade SOFC system with a fuel regenerator

This study aims to evaluate the performance of a novel cascade solid oxide fuel cell (SOFC) system that integrates a fuel regenerator and features a parallel stack configuration for emergency stability and to enhance operational flexibility and independent stack control. At 80 % fuel utilization for both stacks, the system achieves a maximum electrical efficiency of 66.14 %, which is 10.86 % and 6.67 % higher than those of the single-stage and anode off-gas recirculation (AOGR) SOFC systems, respectively. Exergy analysis was used to identify the location and magnitude of irreversibility within the system. The results helped optimize energy utilization in the proposed system and enabled direct comparison with conventional configurations. Among the three systems, the AOGR configuration showed the least overall exergy destruction. In the cascade system with a fuel regenerator, the catalytic combustor exhibited the highest component-level exergy destruction, followed by the external reformer, air pre-heater 1, and the fuel regenerator. The levelized cost of electricity (LCOE) was evaluated to assess the system's economic feasibility. Exergoeconomic analysis converted exergy losses into cost metrics, identifying key inefficiencies in specific components. This approach supports system optimization by linking thermodynamic losses with economic performance. At 75 % fuel utilization, the LCOE of the proposed system was calculated to be 0.218 $/kWh. Both SOFC stacks showed high exergoeconomic factors of 98.3 % and 98.8 %, whereas the catalytic combustor and air pre-heater 1 had the lowest value of 11.95 %.