Analysis of the Dynamic Response of a Proton Exchange Membrane (PEM) Fuel Cell Under Variable Load Scenarios

The dynamics and transient response of fuel cell systems are critical aspects, especially in commercial applications where an immediate response to fluctuating power demands is required. This study presents experimental results obtained from evaluating the dynamic behavior of a 1.2 kW Ballard Nexa fuel cell, subjected to various operational disturbances, including startups, shutdowns, step load increases, irregular and constant loading, and system purging operations. The variables analyzed include voltage, current, and temperature, both in individual cells and in the entire system. The results indicate that the temperature exhibits an attenuated response with an arc-like evolution, but with an upward trend correlated with the increase in the demanded current. Meanwhile, when multiple load steps are applied, the system exhibits rapid responses in both cell and stack voltages, with transient overshoot and undershoot peaks whose magnitudes increase proportionally with the applied current. Regarding the purge system, tests show that its activation improves operational efficiency, resulting in approximately 0.3 V of voltage increase per operation. Furthermore, it is observed that the purge frequency increases with higher external load levels, suggesting a direct interaction between energy demand and active waste gas management in the system.