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Comment by pfdietz | Hacker News Reader

The reservoirs need not be that large, at least for diurnal storage. Look at the illustration for this 1000 MW, 8 hour project:

https://www.whitepinepumpedstorage.com/

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For solar the storage really need to be seasonal.

Think 100 million times the size of that project.

24/8 * 100days * 330000Mw

Pumped hydro is not appropriate for seasonal storage. It's not an environmental issue, it's a capital cost issue. The capex per kWh of storage capacity is two orders of magnitude too high. See the comparison tables at https://www.orcasciences.com/articles/standard-thermal-copy

Well yes, but nothing is appropriate.

That's why we still burn natural gas all winter instead of storing solar.

Renewables-hydrolysed hydrogen stored in the caverns where we currently store methane is quite likely a big part of the interseasonal energy solution.

Or indeed methane generated via the Sabatier reaction using hydrogen generated from renewables - higher energy density, easier to handle, store and distribute. And it can be fed to existing gas peaker plants, a known technology.

Indeed possible and both will probably happen.

If you put your H2 hydrolysers and turbines or fuel cells near the H2 store then handlng and distribution becomes easier. Move the electricity not the H2.

The problem is where do you get the CO2. This adds complexity and cost and looks to make the economics inferior to just storing hydrogen.

I had thought that, until the technology in that link above came out. Ultra cheap thermal storage in dirt, if it works, looks much superior to hydrogen for seasonal grid storage, and has no geographical constraints. Hydrogen really wants salt formations to make cheap solution mined cavities; piles of dirt can be made just about anywhere.

Storing heat in dirt will only work if it's combined with low grade heart distribution networks.

In general though low grade heat is almost entirely worthless, all the Bitcoin miners and data centers that regularly just blow low grade heat into the air.

What? No. Here we're talking about storage of heat in dirt to be recovered as electrical energy using a steam cycle. This only requires moving the high grade (600 C) heat to the power plant itself. There is no need to move low grade heat, except the waste heat from this power plant.

That makes a really interesting case for large-scale thermal storage at high temperatures (inefficient, cheap, enormous capacity, slow response) as a complement to solar generation (cheap, intermittent), and batteries (efficient, instant response, not enough capacity).

It could be a game changer. They've been coy about what their resistive heaters are made out of, but this is looking like something that could be done anywhere in the world without high tech. If it works it could expand explosively (figuratively :)).

It also is a counter to anyone still proposing primary baseload plant construction. Why fission atoms when you can just get cheap heat from huge piles of slightly red hot dirt?

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