PoW has its legitimacy​ and will have a future, in my opinion. When you look towards the characteristics of money you will find out that PoS, PoA, etc... is good for other things. Hayek predicted in the 70s that there will be a natural competition between these exchangeable​ goods.

Decentralisation is the key. They can cut off the energy and network - Miners will find their way. If this happens with renewable energy - great! - maybe regulation is better than expected. Protection of scarce resources​ is a good move I guess.