I wonder if there could be an "excess power coin" that could only be mined when there was an excess of green energy. I suppose the utilities would have to be in

I wonder if there could be an "excess power coin" that could only be mined when there was an excess of green energy. I suppose the utilities would have to be in on it to validate power delivery. Even then can't think of a way you could prove a certain block was mined with a specific allotment of energy...