CHARACTERIZATION OF A 20-KW FUEL CELL SYSTEM FOR ULTRALIGHT AVIATION UNDER STATIONARY AND DYNAMIC OPERATION

The urgent need to reduce greenhouse gas emissions has renewed interest in hydrogen-based propulsion, with proton exchange membrane (PEM) fuel cell systems emerging as a promising solution for small aircraft. This work presents an experimental characterization of a 20-kW rated, liquid-cooled PEM fuel cell system conceived for integration in a modular hybrid-electric powertrain for ultralight aviation. The system includes a two‑stage compressor, humidifier, liquid-cooling loop, and hydrogen recirculation, and is tested under both steady-state and dynamic load profiles representative of flight operation. Measured quantities comprise stack voltage, temperature, section-wise cell voltages, hydrogen and air mass flow rates, compressor operating points, and auxiliary power consumption, enabling the evaluation of voltage efficiency, global efficiency, stoichiometric ratio, and hydrogen utilization factor. Results show that, while the stack maintains a voltaic efficiency above 60% in the explored current range, global efficiency is significantly reduced by parasitic loads, highlighting the critical impact of balance-of-plant components on the achievable net power and flight endurance in aviation applications. In particular, compressor power alone reached up to 7% of stack power and hydrogen consumption exceeded the theoretical demand by about 32% over the test. The dynamic analysis highlights the strong coupling between thermal control, air management, and fuel utilization, and underlines the need for improved BOP control logic to maximize endurance and reliability in aviation applications. The study provides an experimentally validated basis for subsequent altitude extrapolation and control strategy development for hybrid-electric aircraft.