Hybrid Fuel Cell – Battery System as a Main Power Unit for Small Unmanned Aerial Vehicles (UAV)

This paper describes designing procedure of an unmanned aerial vehicle (UAV) supplied with a commercial AEROPACK hybrid system consisting of a fuel cell stack and a battery pack. During preliminary tests, the following characteristics of the hybrid system were investigated: voltage-current dependences, stability of performance for various loading and H2 sourcing (pressurized cylinders or chemical source of H2), interaction between fuel stack and battery pack in supply of propulsion system and consumption of hydrogen fuel as a function of loading. It was shown that during a continuous current loading up to 5.5-6.0 A, the current withdrawn from the AEROPACK system comes almost exclusively from the fuel cell stack, only at higher loadings it is complemented from the battery pack. These tests enabled us to determine the thermal efficiency of the fuel cell stack and estimate the expected time of flight with different H2 sources, covered without the need to refuel. A small, high-pressure composite cylinder appeared to be useful only for short test flights of UAVs, whereas longer missions require using a cartridge with chemical fuel. The preliminary tests of the propulsion system (a propeller-motor-hybrid power unit) were done in the laboratory ground facilities. Unfortunately, the first tested type of motor (Hacker C50 13XL brushless) appeared to be too large and powerful for the UAV prototype. A search for a more appropriate electric motor with lower power and smaller dimensions and further adoption of the propulsion system are described in the paper. Finally, successful test flights of the UAV prototype equipped with AEROPACK hybrid system are presented.