Evaluation of solar powered systems in small scale UAV designs

Abstract: Unmanned Aerial Vehicles (UAV) also know as drones are becoming increasingly present in modern societies. Despite their versatility and success in many areas, small scale UAVs which are nearly always battery powered and therefore have limited flight endurance. To aid the low energy density of electrochemical batteries, solar cells can be used to generate additional electrical power onboard. Researchers have successfully designed and flown solar powered UAVs for durations exceeding 24 hours yet photovoltaics are rarely seen in commercial fixed-wing UAV designs. Numerical simulations based on both aerodynamic and electrical performance estimates show a significant increase in endurance when applying solar power systems to most types of conventional small scale UAVs. These predictions are tested by converting a RC model sailplane into an autonomous solar UAV prototype, equipped with 14 Maxeon C60 Gen3 monocrystalline solar cells. Both mechanical and electrical integration proves to be challenging as the necessary speciality components are difficult to obtain. Use of more generic components results in the solar array covering the wings being fragile and less efficient than expected while the power system lacks compatibility and features to enable battery charging. This shows that the are significant practical problems to be solved in order to successfully implement solar power systems in existing designs and achieve the performance benefits predicted. Use of high performance thin-film solar cells would likely mitigate most of the difficulties for a quick UAV conversion while monocrystalline cells are only feasible in a purpose-built solar UAV design.