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Comment by zizee | Hacker News Reader

Context for your context: Bath County resevoir is descrbed as "largest battery in the world", and cost the equivilent of 4 billion dollars (in 2021 $), occupies 265 acres of land, and has a capacity of around 14,000,000 m3 of water.

I'm curious to see how the costs compare. My understanding is pumped hydro storage gets cheaper at scale. If my math is correct, 24GWH of storage at $4 billion dollars^ is $167 per kilowatt hour. What do these batteries cost to install at scale at the moment? What are they predicted to cost in the next 5, or 10 years?

^ does the 4 billion include the cost of land? Probably not important, even at an "expensive" 200k an acre, that's only 50ish million extra in costs.

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Even putting costs aside it seems like it could be unlikely that such a thing could be built at all today. Flooding huge swaths of ecosystems is no longer in vogue and dam removal is picking up in pace. When was the last major scale hydroelectric dam built in USA?

Edit: looks like the information is here somewhere in the national dam inventory: https://nid.usace.army.mil/#/dams/search/&viewType=map&resul...

But I am very tired and must sleep so I will not query.

It's worth noting that pumped hydro, and the dams that are getting torn down for environmental these days, often look very different.

Usually the dams that are getting torn down, block the entire river, and thus fish from passing up or downstream of the dam. (Fish ladders exist but are not particularly effective.)

Pumped hydro may sit by the side of a river, but otherwise not obstruct the flow, and so that is not a major issue. (Example rendering: https://cdn.forumcomm.com/dims4/default/3ac369d/2147483647/s...)

Huh, that is a really important point, and totally changed my perspective on pumped storage projects. Very cool, thanks for sharing.

Interestingly, it’s also becoming somewhat common to dam off (concrete-fence-off?) the entire top of a hill somewhere for pumped hydro. Essentially the opposite of what you’d do for a hydropower installation.

It also makes a lot more sites interesting.

[https://www.sciencedirect.com/science/article/pii/S254243512...]

Also, pumped storage tends to be smaller, in that it’s meant to provide a certain level of discharge for hours or days. So the reservoirs can be a lot smaller.

This paper says something around $350/kwh

https://www.nrel.gov/docs/fy21osti/79236.pdf

My feeling is a big advantage for batteries over pumped hydro is utilities can can locate them on existing land they own and have use permits for. So quietly spend money today and reap the benefit immediately without having to fight Nimby's and the Sierra Club.

And batteries are perfect for grid stabilization.

Pumped hydro can amortize over 50-100 years. In a true renewable grid, you will get over 50,000 cycles from the same dam (with some turbine replacements).

EDIT: numbers..

Thermal degradation will likely take it out before 100 years, but odds of wearing out next gen sodium ion batteries by cycling are pretty slim https://natron.energy/product/

How much labour is involved in the upkeep/operation vs a battery bank?

I think that there are pros and cons of each, we'll end up with a mix of lots of different solutions.

Costs for LFP are around $350/kWh and about half consists of BOS like inverters, charge control cooling, fire control, etc.

10-20% YoY drop in manufacturing cowts is pretty likely, although demand will keep up with production and lithium extraction capacity so this might just turn into profit in the short term.

Sodium ion is presently scaling, which should remove most of this raw material limitation by late 2020s. Additionally the lower volumetric capacity, higher coulpmbic efficiency and higher thermal stability should reduce cooling and fire control.

TL;DR Some/most people expect it to drop each year similar to what solar did. I expect prices to be stable for 2-4 years while anyone with a lithium mine or existing production builds a small ocean of cash to swim in and then crash abruptly to <$80/kWh

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