What is the feasibility of solar powered drones? From my understanding, solar panels are becoming more and more efficient, in terms of weight vs energy captured, and in terms of surface area vs energy captured.
What I am interested in is whether solar panels could be placed on different sized drones (small civilian quadcopter and MQ-9 Reaper), and provide enough solar power to keep the aircraft aloft indefinitely (under a theoretical condition of an "endless sunny day").
If this is not possible, are there are realistic changes that can be made to make it possible, while still keeping the core functionality of these two different drones intact?
For the purposes of this question, instead of focusing on a 100% solar powered drone, we can assume that fuel can be carried for takeoff/climb to loitering altitude, at which point is can switch to 100% loiter.