Exergy analysis and structural optimization improving efficiency in automotive proton exchange membrane fuel cell system

Abstract

As the core power device in the transition of renewable energy, the efficient operation of proton exchange membrane fuel cell (PEMFC) relies heavily on the coordination of numerous auxiliary components, which consume significant amounts of energy during operation. This study established and validated thermodynamic models of system components from the energy and exergy perspective based on an actual stack operation data. In this model, the thermodynamic performance of the system under different stack operating conditions (current density, temperature, and pressure) is clearly defined and water transport within the stack is also considered. The results reveal that higher operating temperature can enhance the system's energy and exergy efficiency, while higher current density and operating pressure can lead to a decrease in system performance. The exergy destruction of system components is quantified, with the stack exergy destruction being the largest proportion. Auxiliary components of the air system exhibit significant exergy destruction across the entire range of operating current densities, particularly the air compressor (AC). Therefore, optimization efforts should prioritize the AC. Furthermore, based on the exergy destruction of system auxiliary components, the system is optimized and integrated, resulting in an exergy efficiency improvement of approximately 4 % or more.