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Comment by hgomersall | Hacker News Reader

I've been pondering the question of what happens if you change the design requirements to say, 20 charge/discharge cycles in total, then use it over seasonal timescales. Can you get the price so low that you can scale up enough battery storage to buffer a whole season?

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I don't think anyone's cracked that yet. There was a YC startup trying to do stuff with iron oxide. (https://www.canarymedia.com/articles/batteries/gigantic-form...)

And proposals using aluminium but again not in action.

Also zinc air https://inc42.com/startups/sthyr-energy-aims-to-tame-169-bn-...

the trouble is it's easy enough to propose such things but hard to be economically competitive with existing solutions. My guess is sodium ion will get cheap because the ingredients are cheap and there's a lot of money going into mass production which will bring the cost of that down over time.

There's an ancient non electrical seasonal solar storage practiced in Austria and such places where they grow tree and then chop them into logs for the winter but it's a bit labour intensive.

I've been thinking about Polysulphide-Air for this. There are certainly engineering questions, but on the face of it it looks like it might be tractable. I think the trick is to view it like a winter base-supply, and treat it like a power station that runs when solar is less.

Even if you have an entire season's worth of capacity, your inputs and outputs still cycle per-day. You're still cycling charge and discharge every day, you're just doing it in a very small band within the overall capacity.

This still causes wear on the battery, and it can be better or worse depending on chemistry. The only way to get around that is if you disconnect all inputs, throwing away all the excess solar/wind power and supply exclusively from battery for the entire season.

There's no real benefit apart from like a standby power supply for a cataclysmic event where all other power sources including the sun become nonviable. You just won't ever use the full capacity of the battery, so most of the resources to build it will be wasted.

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