Experiments on maximizing hydrogen utilization and efficiency in a PEM fuel cell system

Abstract

Maximizing hydrogen utilization is crucial for improving the efficiency of proton exchange membrane (PEM) fuel cell systems. Ideally, all supplied hydrogen reacts within the fuel cell. However, nitrogen and water back-diffusion necessitate periodic purging of the anode recirculation path. Excessive purging leads to hydrogen losses, while insufficient purging increases side reactions, lowering fuel cell voltage and directly reducing efficiency. This study investigates optimizing both hydrogen utilization and stack efficiency by adjusting purge valve actuation in a PEM fuel cell system. Results show that reducing purging from the reference increases hydrogen utilization by 0.79% points to 98.2%, resulting in efficiency improvement of 0.72% points to 47.21% based on higher heating value. Moreover, adjusting the purge valve actuation is the sole method for controlling the hydrogen stoichiometric ratio in ejector-based anode recirculation systems. Therefore, precise purge valve operation is critical for maximizing both hydrogen utilization and PEM fuel cell efficiency. • Experiments conducted on a PEM fuel cell system between 30 and 130 kW stack power. • The purge valve sets the hydrogen concentration in the anode recirculation path. • Purge valve is only way to set stoichiometric ratio in ejector recirculation. • Optimal purging improves hydrogen utilization and efficiency in PEM fuel cells. • H 2 reacted in fuel cell with ejector: 98.5% stationary, 98.2% transient operation.