Altitude Testing of Fuel Cell Systems for Aircraft Applications

Fuel cells may help aircraft meet increased electrical power demands while mitigating environmental, safety, reliability, and cost concerns. A potential application is to replace a conventional aircraft battery with a fuel cell system. An opened system altitude chamber has been developed to evaluate fuel cell system performance in flight altitudes. The altitude test methods have been validated by successfully obtaining fuel cell performance data that match fuel cell manufacturer data. Trends in temperature, cooling fan speed, airflow, and fuel flow at various loads and altitudes up to 5000 ft have been observed. Electrical power quality in steady state and transient loading has been determined insufficient to meet the aircraft power quality characteristics of MIL-STD-704E. Further development is needed to properly regulate voltage and obtain sufficiently quick responsiveness. Low pressure hydrogen storage using metal hydride canisters have been tested at altitude and for endurance. Current test results indicate that fuel cells operate best for aircraft applications when pressurized and used primarily for steady state loads.