From theory to operation: A systematic loss analysis framework for fuel cell systems

This publication presents a systematic and broadly applicable methodology for analyzing efficiency losses in fuel cell systems, tracing performance from theoretical to actual (effective) efficiency. The classification of efficiency losses is conducted according to their physical and chemical origins within fuel cell systems, encompassing the DC/DC converter as the defined system boundary. The methodology delineates distinct loss categories, including those arising from entropy generation, deviations from standard operating conditions, internal current density, electrochemical activation overpotentials, membrane-associated losses, ohmic resistance, gas transport limitations, and losses due to purging events and auxiliary components (such as balance-of-plant systems). This structured approach facilitates both the quantitative assessment of individual loss contributions and the identification of interactions among different loss mechanisms, thereby enabling targeted system optimization. While the methodology is universally applicable to various fuel cell technologies, the current work exemplifies its implementation using a proton exchange membrane (PEM) fuel cell system evaluated under beginning-of-life and degraded operating states. The results highlight the influence of operational parameters and degradation phenomena on system performance. Additionally, an analysis of efficiency improvement potential reveals substantial opportunities for enhancing the overall performance of PEM fuel cell systems.