[boublepop]

You cannot have PoW running on burning a free or cheap resource, the entire point of PoW is that the resource you are burning is costly, which pushes up the amount burned to close to the break-even point.

The amount of energy consumed now is not at its current level because of some fixed power requirement of the network. It’s there due to competition. If power was cheaper miners would run their ops using more power and the only thing that would change would be more energy would be wasted.