As the aviation has realized the seriousness of pollution and emission issues, people have taken efforts to use renewable energy on planes or UAVs. This paper focused on the applications of solar and hydrogen energy to UAVs. A hybrid power system, consisting of solar cells, fuel cells and lithium batteries, was discussed. To achieve the hybridization of power sources, a prototype of a power management unit (PMU) was fabricated. After the installation of a test system for synthesizing power sources, PMU and load, a series of ground tests were executed to verify the mathematical model of lithium battery and the reliability of the hardware. Ground data confirmed the feasibility of hybrid power system.

More and more attention is paid to the pollution and emission issues in aviation, renewable energy is applied on Unmanned Aerial Vehicles (UAVs). Solar and hydrogen energy were used in the hybrid power system to achieve the goals of zero-emission and long endurance. The power system was carefully designed to maximize its efficiency. The connection among solar cells, fuel cells and lithium batteries which were used in power system was discussed. The coupling relationship among propeller, motor and batteries (including solar cells, fuel cells and lithium batteries) was studied. The effects of power system configuration on system efficiency were analyzed. The results show that well-matched propeller, motor and batteries can effectively improve the power system efficiency.