This is basically false (some miners might do this but they're a minority). Almost all bitcoin mining happens in China, and happens in an area where a large fra

This is basically false (some miners might do this but they're a minority). Almost all bitcoin mining happens in China, and happens in an area where a large fraction of grid power comes from coal. Using excess power doesn't work well for bitcoin mining because the power draw is constant: miners are generally not powered on or off over the coarse of a day: they're turned on and not turned off until they're decommissioned.