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A novel reversible proton exchange membrane fuel cell system that is based upon micro-sized membrane and electrode assemblies is discussed. The resulting micro-fuel cell has a reduced size and mass due to an improved design of the bipolar plates and current collectors. Bipolar plates often contribute over 75% of the fuel cell stack mass and volume in traditional fuel cell and electrolyzer designs that results in power densities near 0.1 kW/kg and 0.1 kW/liter. The micro-sized membrane and electrodes allow us to minimize the size of the gas-channels that feed reactants to the electrodes. Physical Sciences Inc.’s (PSI) micro-design approach minimizes stack features resulting in power densities greater than 1 kW/liter and specific power densities greater than 1 kW/kg.

Developing unmanned aerial vehicles (UAVs) with an electric propulsion system that combines photovoltaic modules with an energy storage system has been an ongoing goal of the aeronautics community. A closed-loop energy storage system using a fuel cell and electrolyzer will enable the UAV to operate at high altitudes (> 20 km) and for mission durations over a year. However, the specific energy of the energy storage system must be increased beyond present 150W-hr/kg levels. A high capacity fuel cell and electrolyzer unit under development at Physical Sciences Inc. (PSI) is aiming to improve the energy storage capability to values much greater than 500 W-hr/kg.