A hybrid-electric propulsion system for an unmanned aerial vehicle based on proton exchange membrane fuel cell, battery, and electric motor

Most Unmanned Aerial Vehicles (UAV) currently use propulsion systems based on gas turbines or internal combustion engines. However, such systems cannot be used in all sizes of UAVs. To perform a high- endurance mission, a UAV must have an efficient propulsion system and aerodynamic. On the other hand, batteries have a low energy density, which therefore increases the UAV's weight and imposes penalties on the system. Using fuel cells as the main source of power generation in the UAV propulsion system can increase flight endurance and have reasonable fuel consumption. The aim of the present work is introduce and investigate of a new electric propulsion system based on electric motor, proton exchange membrane fuel cell (PEMFC) and battery for a small UAV. Two different battery discharge strategies are compared for propulsion system design. In addition, static optimization is applied to determine the appropriate size of the various components of the propulsion system. It was found that, the required power at the theoretical endurance speed is about 42.13% lower than that at the actual endurance speed. In addition, the required hydrogen rate and PEMFC area to provide the required power in the proposed hybrid propulsion system are 55.7 g/h and 0.09 m(2), respectively. Moreover, the payload weight (with lithium-ion polymer battery) for two battery discharge strategies was 0.71 and 1 kg, respectively. The sensitivity analysis is also used to determine the parameters affecting the final performance of the propulsion system.