Energy storage is the deus ex machina solution that's always thrown around when real engineering concerns about the problem of electricity sources whose output you cannot control are presented. I might as well flip your argument on its head: if it was as easy to store energy as you propose, then electricity prices would never become negative.

Government is an abstraction that might make us blind to the fact that political decisions are made and enforced by actual people. The more economic power that crypto currencies amass, the bigger a threat they become to big government's taxing abilities, yes. Granted. But at the same time it also affords its supporters more lobbying power. I think governments face a prisoners dilemma in this regard: most governments might be better off if they all banned crypto currencies. But even better off if only their neighbors banned them and they allowed them, so they would get an influx of people and businesses making money in this sector, and they could tax these individuals. Think e.g. Crypto Valley in Switzerland, or Bitcoin enthusiasts visiting (or moving to?) El Salvador. And we all know how the Prisoner's Dilemma plays out in the long run: to the detriment of its actors.

And to you last points: ask modern day Venezuelans or North Koreans whether it's a waste to have sound money that can't be inflated by the whim of self-serving autocrats. Or ask a German citizen that was alive 100 years ago if sound money is a waste of resources.