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Comment by not_wyoming | Hacker News Reader

Relatedly, I've read a couple of neat articles on using mine shafts as gravity batteries: https://bigthink.com/the-future/coal-mines-gravity-battery-e...

Major footnote here that I'm wayyyy out of my wheelhouse on this stuff, so there may be reasons that this doesn't work. I invite correction if that's the case so we can all learn some stuff :)

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Gravity batteries have horribly low energy densities. There's usually a better option.

I'd say that there is always a better option. Can someone point to a case where a gravity battery would definitely be better than all the alternatives?

Pumped hydro is a form of gravity battery. It doesn't have great energy density, but it has fantastic power density and responsiveness. That's where its strength lies. We have also probably already built most of the ones that could possibly be built.

Closed loop pumped hydro can be built anywhere there's a hill, there's tons of available expansion capacity there

There are 86 large pumped storage sites in the world. It does work, but you need the right geography. You need two good reservoir sites at considerably different levels close to one another. That's somewhat hard to find.

https://www.volts.wtf/p/whats-the-deal-with-pumped-hydro

David Roberts

Yeah, we have a lot of hills. And that's it. So, other than that, you could plop one of these down almost anywhere.

Erik Steimle

That's correct, yeah. You need some proximity, obviously, to transmission and load.

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