> If someone had an unlimited cheap source of green energy, it would actually make Bitcoin less secure as it goes against proof of work - proof of work literally requires an “expensive” operation, exchanging work (energy) for security. This actually makes Bitcoin incompatible with green energy..

Huh? The bitcoin protocol Proof-of-Work (PoW) doesn't take energy cost into account at all. PoW simply looks to see which chain is the longest, and it takes that to be true. Miners get to add their block by doing enough computations to find the correct nonce, depending on the network's current difficulty target. But Bitcoin, strictly speaking, could care less what a miner pays for energy.

Having said that, miners have huge incentives to minimize their energy costs, as paying too much puts them our of business. And that incentivises them to find the cheapest energy sources, which are more often than not renewables.

Green energy doesn't affect bitcoin's security, but it can help miners' bottom line.