I've seen this applied in the real world, but i forget the proper name for it. Basically, in the real world buildings are being designed that can generate electricity when people walk over the specialised flooring.
I suppose this would be OP perhaps in a multiplayer setting, so you could code into it that it will only generate say 20 eu each time someone stands on it, and you can only stand on it once every 2 minutes or so.
I imagine that it would have to be hard coded for players only, as i can potentially see people luring a bunch of animals into an area filled with the generator plates.