Do you actually need an ornithopter? Why not just make it a powered glider (small pusher prop). The wing supports could be made of conductive materials, or infused with small wires, and the thing could just buzz along close to the wires. If you get it right, you could get more juice than you output, and when you get enough stored charge, just fly high and glide down, find updrafts, etc until power is low again and go buzzing some more.