I thought I'd seen it all but some braniacs over in Idaho have come up with a way to tap infrared energy.
Nightime solar panals
Actually I was thinking about something similar this week. With all the ambient electromagnetic bouncing around would it be possible to capture it for reuse? Think of it as recycled energy. Reason I thought of this is because when I was a kid I had a tiny crystal radio. You powered it by putting two allegator clips on the harp of the nearest lamp hence using the power bleed from the lamp. It only received one station but you didn't need to buy batteries.