Thermo-economic optimization of a novel proton exchange membrane fuel cell system with a critical mode ejector

• A novel proton exchange membrane fuel cell system with an ejector has been designed. • The operating characteristics of the ejector under critical mode have been studied. • A thermo-economic approach is used to evaluate and optimize the system performance. • The system performance is optimized at an anode relative humidity of 0.3. Currently, research on the independent optimization of ejectors is relatively mature, but the study of coupling effects with proton exchange membrane fuel cell (PEMFC) systems is still insufficient, making it difficult for local optimizations to translate into system-wide synergistic improvements. This paper presents a novel hydrogen fuel cell system with an ejector, analyzing the impact of various operating parameters on the ejector and system performance under critical conditions through thermo-economic analysis. A multi-objective optimization method is used to determine the optimal operating parameters. The study shows that the anode relative humidity (RH) and backpressure differential significantly affect the mass fractions of hydrogen and water vapor at the anode outlet, with optimal system performance occurring at RH = 0.3. Reducing the current density or stack operating temperature can reduce the costs of both the ejector and the system. While current density significantly affects the ejector’s D nt and NXP sizes, it has a smaller impact on the entrainment ratio. After optimization, the system efficiency is 0.495, the cost rate is reduced to 1.759 $/h, and the ejector recirculation rate is 2.087. This study demonstrates that the collaborative optimization of critical conditions and parameters can significantly improve system efficiency while maintaining economic viability.