A fuel cell/battery hybrid power system for an unmanned aerial vehicle

A hybrid propulsion system composed of a homemade Polymer electrolyte fuel cell (PEFC) with a Lithium polymer (LiPo) battery in parallel connection was developed for Unmanned aerial vehicles (UAVs). The characteristics and performance of the system were evaluated considering its dynamic load responding capability and energy efficiency. A homemade PEFC stack composed of 36-unit cells and Balance of plant (BOP) was used to construct the fuel cell system directly connected to the propulsion system. Ten cells of a 3300-mAh 40C LiPo battery were combined with the PEFC system in parallel, and the LiPo battery was only switched on when high power was required for takeoff, acceleration and landing. The independent use of the homemade PEFC system and battery for the UAV showed a good load responding capability and a high fuel cell system efficiency of approximately 45%, which was obtained during cruising. The parasitic loss and the amount of unreacted hydrogen gas discharged outside of PEFC were nearly 3.91% and 0.89%, respectively. Results of the field test flights confirmed that the hybrid propulsion system based on the parallel connection of a PEFC system and a battery power is extremely effective in operating a UAV.