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Comment by guelo | Hacker News Reader

I don't know why this article keeps using the word 'massive'. 20MW is tiny at utility scale. For comparison the typical pumped-storage station has 1,000-3,000MW capacity.

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Pumped-storage exploits pre-existing landscape features. Battery storage is essentially building storage from scratch in places where no favorable geological features exist.

How much would digging a mineshaft, a bedrock cavern and a lake or additional caverns just to pump water up and down cost?

When weighted against cost and expected lifetime, it may not make sense to do this over e.g. solar + molten salt.

Except that utility-scale thermal solar + molten salt doesn't exactly have a good track record so far. It'd be great if it lived up to expectations...

80 MWh is massive for a battery. MW are a measure of power, not energy. You mean MW-h. It's incorrect to say something has a MW capacity when discussing energy storage.

> MW are a measure of power, not energy. You mean MW-h. It's incorrect to say something has a MW capacity when discussing energy storage.

He's quoting TFA,

> With a capacity of 20 MW/80 MWh

It would seem sensible that the system has both metrics: a total capacity of storage, and a total rate at which it can supply that storage to things connected to it.

Further, my understanding is that the parent you're responding to is correct: pumped-storage hydro tends to have much greater generation rates; Wikipedia lists an example of 360MW.

Batteries have inherently high MW per MWh so you can usually ignore the power capacity. But that's not true with everything. Both numbers are important.

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