Energy might be another factor and important as well, so a less power hungry solution might be great
The PoW algorithm adapts itself to the globally invested computing power regularly. So it is always as power hungry as people are willing to invest electricity.
on the other side it could be very healthy to the renewables industry if all miners would be forced to use only green energy, since this would generate a significant amount of money flowing into those industries. But I don't see any technical way to really enforce that.
I don't see the need to enforce this technically. People acquire electricity through the existing economy. If it is wanted to have a larger fraction of green energy, a way to do so might be to tax energy from non-renewable sources.