Use of solar cells in small scale fixed-wing UAV applications

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.