Saw some solar lawn lights on spikes - you stick them in the ground, and supposedly they'll stay lit most of the night. It looked to me like you could cut round holes in the roof of a coop and drop them in, with the spike part removed. In other words, the solar panel part of the light would be on the roof, and the LED light part would be inside. Anyone tried this? Might be a good way to keep the girls laying in the winter.