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Comment by ben_w | Hacker News Reader

> the unsolved-at-scale technical problems with grid energy storage

What are these problems, exactly? I see videos and news stories about grid batteries being successfully deployed for short term management and how pumped hydro is basically a big cheap gravity battery, but I'm not a civil/electrical engineer, so I accept there could easily be elephants in the room here.

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It’s just scale. Those batteries and pumped hydro stories seem big. Relative to your house, they are. Relative to the grid as a whole, they are small.

That doesn't answer the question. What exactly is the problem that needs to be solved?

Scaling up capacity of the storage. There aren't that many sites that are geologically feasible for pumped storage (and it destroys a local ecosystem by flooding and draining it repeatedly) and batteries need rare earth metals (not actually that rare but environmentally toxic to produce).

We need O(100x) current production to fully switch away from hydrocarbons. That's a lot of reservoirs or a lot of cobalt that have to be mined.

Globally the potential pumped storage resource is far larger than would be needed. You might be confused by assuming the pumped hydro has to be on existing rivers.

http://re100.eng.anu.edu.au/global/

Cobalt already eliminated from half of new Tesla batteries: https://electrek.co/2022/04/22/tesla-using-cobalt-free-lfp-b...

False. You have been corrected on this point before. Please stop posting what you know are falsehoods.

Can't say I remember ever interacting with you before, but either way this doesn't meet the HN standards of civility/graciousness.

> batteries need rare earth metals

"Rare earths" are a column (edit: ha ha see below) in the periodic table, and are not used in batteries.

Some types of electric motors use rare earths, others do not.

Here's a primer: https://blog.ucsusa.org/josh-goldman/electric-vehicles-batte...

"Rare earths" are actually the lanthanides plus scandium and yttrium [1], not one column of the periodic table. Good information otherwise!

[1] https://en.wikipedia.org/wiki/Lanthanide#Etymology

Ha ha busted! Thanks. As an astronomer I think everything beyond He is a metal.

I don't understand why people don't talk about the water usage involved in pumped hydro when the vast majority of the Western United States is dealing with record low water levels + sinking due to groundwater usage.

Pumped hydro doesn't use up the water. It goes back and forth between the lower and the upper reservoirs. Some evaporates, for sure, but that's a tiny fraction of the water that would be evaporated cooling a NPP of the same power output.

Furthermore, putting floating solar on the reservoirs would eliminate much of the evaporation.

And, when it is used for storage, it is at higher altitude, so evaporates less.

Sure it doesn't use water, but it's still taking water out of the ecosystem. Why is that not considered when we have record low water levels.

PV can be used to desalinate sea water as well as pumping it up to the top of the reservoirs. It's also possible to extract energy from fresh water as it mixes with sea water to improve the system efficiency, but I don't want to even guess if that's better or worse overall than just cleaning the water and reusing it.

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