Enhanced Performance of PEMFC Systems for Aircraft Application Through Altitude-Adaptive Control Strategies

Abstract

The development of powertrains for next-generation regional aircraft utilizing polymer electrolyte membrane fuel cells (PEMFCs) represents a promising pathway to decarbonizing the aviation sector. However, the operation of PEMFC systems under high-altitude conditions is associated with significant performance losses, primarily due to reduced ambient pressure. Therefore, a comprehensive understanding of fuel cell system behavior under these variable conditions is crucial to develop optimized operational strategies tailored to aircraft applications. This study presents an experimental investigation of a 12 kW PEMFC system operated in a temperature-controlled low-pressure chamber. Using statistical design of experiment, a parameter study is conducted to evaluate the influence of cathode stoichiometry, stack temperature, and pressurization while operating the system at different cell voltages under high-altitude conditions. The ambient pressure is varied between 1000 hPa and 500 hPa, thereby simulating altitudes of up to 5574 m in accordance with the “International Standard Atmosphere”. Empirical models derived from the measurement data allow a deeper understanding of the PEMFC system's behavior under altitude conditions and enable the optimization of operating parameters to maximize performance during flight. The results emphasize the necessity of pressure-adaptive temperature control to ensure effective water management. Moreover, the net power gain due to cathode pressurization is found to be highly dependent on the compressor efficiency. At higher efficiency values, pressurization becomes increasingly advantageous, particularly under low ambient pressure conditions. However, increased pressurization also results in higher hydrogen consumption due to greater mass loss during purging, indicating the need for adapted purge control strategies. Overall, these findings underscore the importance of both pressurization as well as the implementation of altitude-adaptive control strategies to enable the application of PEMFC systems in aviation with maximized efficiency and performance.