... I think there are still many countries where plenty of hydroelectricity is available however cost per unit is high compared to china.
Those countries include Canada and Iceland, who turned out to be not very keen on miners. Local authorities have to take the risk of energy shortage into consideration.
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That proposal by Cobra was more for the centralization problem of mining than energy Usage. Its a concern as he points out that with such concentrated mining power, an entity like Jihan's Bitmain can cause major upheavals. Though, I think such a scenario is unlikely because they would also be damaging themselves.
I'm aware that Cobra's proposal wasn't related to energy waste issues, but there's no reason we couldn't solve 2 problems with one solution.
As for Jihan - sure, his future profits are heavily dependent on success of Bitcoin, but that's not enough to stop caring about decentralisation. There's always a risk he could get co-opted by MSS (Chinese counterpart of CIA).
The value of bitcoin comes from the securtiy provided by miner's POW. If they decide to shift that security then its a MAD scenario. Not much chance that it'll happen.
How secure was the PoW when gHash pool exceeded 50% of hashpower at one point?
How less secure would PoS/PoW hybrid be?
In my opinion, no PoW change is needed and the energy issue can, in fact, provide a corrective measure for centralization. ...
It could in a way, ie. if countries with the cheapest energy allow mining but introduce cap on its energy usage. That would enforce geographical decentralisation. But the implications of miners having to ask for special permissions (licenses) to mine (which would likely include home-miners) don't sound very great.
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I think that eventually miners will have to generate their own electricity.
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Well, that would solve the problem. At the end of the day, it doesn't really matter if BTC mining consumes 99% of global energy, as long as it's not damaging to environment and as long as other industries/individuals don't have to compete for scarce electricity.
And after a PoW change, "CPU/GPU farms" will surely emerge - huge datacenters dedicated to mining. It would have maybe some practical advantages - CPU's don't need a specialized industry and thus mining hardware could be re-used - but no energy-efficiency change at all.
I think you're talking about alternative to SHA256 here, not about PoW alternative. CPU/GPU mining is still Proof of Work.