Characteristics of an air-cooling PEMFC power system across different altitudes

Air-cooling proton exchange membrane fuel cells (AC-PEMFCs) with high energy density, simple structure, and environmental friendliness are considered viable power sources for aircraft. In this work, a 1.3 kW AC-PEMFC stack is utilized in a designed environmental chamber to investigate its performance from sea level to 3000 m. Constant-altitude experiments are conducted at 500 m intervals to assess the steady-state performance, while flight-mission simulation experiments with four power-load time intervals are conducted to explore the dynamic response. Power, temperature uniformity, and voltage consistency of the AC-PEMFC, with efficiency of the AC-PEMFC power system, are evaluated in both experiments. Constant-altitude experiments reveal a 7.6% power reduction per 1000 m increase in altitude, with lower temperature uniformity yet better voltage consistency. The flight-mission simulation experiments show that the power at 3000 m decreases significantly compared to that in the constant-altitude experiment, ranging from 10.9% to 13.5%. Besides, the extremely short loading intervals cause a noticeable decrease in temperature uniformity and a high voltage fluctuation rate during loading stage. Based on temperature uniformity and voltage fluctuation evaluations, the optimal loading interval is 20–30 s, balancing durability, dynamic response, and fuel efficiency. Furthermore, while altitude increase shows minimal influence on the electrical efficiency of the studied AC-PEMFC under constant operating voltage, it enhances the DC-DC's energy conversion efficiency while maintaining efficiency variations below 1% in both steady-state and dynamic conditions. This work provides comprehensive performance data of an AC-PEMFC at different altitudes, which lays the foundation for the applications of AC-PEMFCs in low-altitude aircraft.