''the cost of mining one bitcoin would be 100 times greater than now but only half as many bitcoins would be mined that year''

I think you're fundamentally wrong thinking in these terms.

Higher price of bitcoin =/= higher energy consumption

What increases energy consumption is 'new' hash rate joining the network, and this happens because NEW miners are joining (or because old ones are increasing their power). NOT the other way around (higher price increases difficulty).

BTC mining algorithm adjusts itself to 'print' new blocks at 10 min/ block rate. All the other factors don't matter. If it isn't profitable to mine, some miners will shut down their machines & vice versa.

Eventually miners will have (even more) optimized machines, and renewable energies will play a huge role in the future.

Hope it helps :)

Cheers