Comparative study on air-cooled fuel cell stacks with metal and graphite bipolar plate designs for unmanned aerial vehicles

The proton exchange membrane fuel cell (PEMFC) power source is a promising solution for the unmanned aerial vehicles (UAVs) to extend the flight endurance. However, the light weighted PEMFC stack design with improved performance remains a critical challenge for the UAVs applications. In this study, two air-cooled PEMFC stacks based on metal and graphite bipolar plates are designed respectively to optimize the fuel cell power density with comparative tests and simulations under varied operating conditions. The designed metal and graphite stacks could reach the power densities of 1189 W/kg and 792 W/kg, of which the graphite one is integrated in a hybrid power system for the UAVs and operated for a flight test with ∼45 min. Validated by the experiment, a three-dimensional coupled model is developed to comparatively study the internal performance and thermal behaviors of the two stacks. Compared with the graphite stack, the metal one outputs higher voltage by 4 %, weighs lighter by 31 % and improves air forced thermal dissipation with enhanced water retention ability. The proposed model and comparative analysis reveal the mechanisms of stack performance variation under different designs and operations, which are beneficial for the optimization of UAVs fuel cell power system.