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Comment by bobthepanda | Hacker News Reader

Pumped hydro is actually possible to be a lot smaller and less ecologically devastating than traditional hydro.

The requirements are rarely for more than a few hours or a day or two of storage, which significantly reduces the required reservoir volume. And the only requirement is that it be at a higher elevation than the source body of water, so rather than disrupt an entire river and its migration patterns you can have it off to the side.

Because the sites are now a lot smaller and not limited to drops in elevation along rivers, you now have many possible sites; many pumped storage sites are either existing reservoirs or disused mines.

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> The requirements are rarely for more than a few hours or a day or two of storage, which significantly reduces the required reservoir volume.

That’s one of the main issues right there. You can’t just plan for the typical case. You need to account for the slightly less frequent cases as well, like 11 days straight of <20% solar/wind generation [1]. And that’s not even an extreme outlier event.

[1] https://reports.electricinsights.co.uk/q1-2021/when-the-wind...

Rare events like that can be covered by combustion turbines. First with natural gas (not used often, so little CO2 emission), ultimately with hydrogen.

Because a simple cycle combustion turbine power plant is maybe 5% of the cost per watt of capacity of a nuclear power plant, we could cover the entire grid with CT backup and not come anywhere close to the cost of powering the grid with nuclear. And because these would be used so infrequently the fuel cost would be negligible.

Example of a pumped hydro system being built in Nevada, near Ely:

https://www.whitepinepumpedstorage.com/

You can see from the image how small the reservoirs are (go to Google Maps and find the spot north of Ely up the valley; it's eye opening how tiny this all is compared the size of the state of Nevada). The initial charge is 5,500 acre-feet of water (and 600 acre-feet per year makeup water, I presume for evaporation). It stores 8 GWh of energy with a power capacity of 1 GW. The estimated economic lifespan is 75 years (conservative, since very few PHES systems worldwide have been retired.) Cost is $2.5B.

The Basin and Range province has an embarrassingly large potential for pumped hydro, due to the geography: all those intermixed linear mountain ranges and valleys. This province is also where UAMPS is trying to get utilities to buy into that cluster of six NuScale reactors. Utterly dumb, when they have practically unlimited storage at a shade over $300/kWh of capacity and could use renewables instead. Utah also has the potential for enormous hydrogen storage in Miocene salt formations near Delta (~15 TWh).

The pumped hydro projects do seem to have long build times; it would be interesting to know why that was. This one is not projected to come online until 2031. The company has 11 projects in the pipeline.

https://www.rplushydro.com/projects

Furthermore, the reservoirs can make good sites for solar PV: having power distribution already present, reducing evaporation and enhancing PV output by cooling.

> rather than disrupt an entire river and its migration patterns you can have it off to the side.

This doesn’t sound accurate.

If you have a reservoir with zero head you can’t recover potential energy because there is not.

Off river pumped hydro can still be at a higher elevation. It’s just not the entire river itself. https://iopscience.iop.org/article/10.1088/2516-1083/abeb5b

Which just means you need elevation beside a body of water. Take a look at the picture of Ludington: https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power...

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