[alvah]

Allow me to support the completely unsupported naysaying: https://cleantechnica.com/2024/01/16/gravity-storage-101-or-...

Cliff's Notes: any currently-considered form of gravity storage that isn't pumped hydro is orders of magnitude more expensive and more stupid than a Tesla Megapack.

Michael Barnard's abrasive tone aside, is he wrong?

[s1artibartfast]

had to look up some price comparisons.

Fengning Pumped Storage Power Station stores 40 GWh and cost 2 billion or 20 Wh/USD

Tesla megapack 2 stores 3.8 Mwh = Costs 1.5 million, or approximately 2.6 Wh/USD

It seems like pumped hydro is about an order of magnitude cheaper.

https://en.wikipedia.org/wiki/Fengning_Pumped_Storage_Power_...

https://en.wikipedia.org/wiki/Tesla_Megapack

[alvah]

That wasn’t the comparison. The comparison was every form of pumped storage EXCEPT pumped hydro vs a megapack. I’m sure you’re correct about pumped hydro though, it does seem like something we should do more of.

[s1artibartfast]

That was the comparison I felt compelled to make. I have been a big fan of pumped hydro for many years.

Contrary to what skeptics say, there are countless locations all over. [2]

There is a suitable location 3 times larger than the Chinese one I linked That could use California's sites reservoir [1] under construction as a lower basin. It would have a similar 400m head, and an upper reservoir with 3 times the capacity or 120 GWh.

https://en.wikipedia.org/wiki/Sites_Reservoir

https://re100.anu.edu.au/#share=g-e5955e35f1c7f3677ac265bcdd...

another: https://maps.nrel.gov/psh

[8bitsrule]

Here in the PNW,

"The Columbia River Gorge is a canyon ... up to 4,000 feet (1,200 m) deep [and which] stretches for over eighty miles (130 km) as the river winds westward [toward Portland]." - WPedia

Hmmm. Now I'm wondering how many reservoirs already (or could) exist above and along 80 miles of river. (No need to dig tunnels to the generators.)

[usrusr]

Exactly one reservoir (or a number of tiny ones not worth mentioning), because even all the way from Richland to Portland there is hardly any elevation drop.

[usrusr]

PS: oh, you meant reservoirs in contributory valleys left and right of the main river. Sorry about the misread, "above and along" should have been clear enough.

[usrusr]

Nice hit piece that looks like written by someone deeply invested in chemical batteries (or going mercenary for patrons who are). But his dismissal of mine shafts omits some important parts: when you have a mine, you don't just dangle a mass from an elevator winch, you fill the entire volume at the low end with ballast while discharging and get all that mass up again when charging. That's a many orders of magnitude difference in capacity versus the naive block-on-a-winch approach. And you don't just operate one winch with a Very Large Rope, you form a bucket-brigade of identical, cheap, short loops with a good handover mechanism. Or you equip the shaft with a pair of linear induction motors all the way up/down if you'd rather go solid state.

[danbruc]

Then why not pour water down the mine shaft and pump it back out? That seems a lot less complicated than transporting any kind of solid material up and down. I can think of three possible reasons - material density, loses in pumps and pipes, and potentially measure to make the mine suitable for storing water.

[usrusr]

That's what GP suggested. But unless the mine happens to be in particularly water-friendly rock or is carefully prepared for safe repeated flooding/dewatering, that would only speed up the conversion from mine to uncontrolled sinkhole. Many given up mines are expected to have active dewatering running forever, because the cost of letting them collapse or for safe filling would be so much greater than the cost of continued dewatering for the next couple of generations.

For small capacities, using water as the ballast medium would certainly be cheaper. But there's a break-even point in capacity beyond which the cost for readying the volume for water would be higher than the premium you'd have to pay for handling dry mass instead of liquid.

[friend_and_foe]

From your link:

> The alternative idea is to put a lot of sand on a single elevator with huge winches that just goes up and down in a big, deep mine shaft. This one at least has the potential to be viable.

[alvah]

Did you read the part immediately after that?

[friend_and_foe]

Yeah I did. He immediately dismisses the prospect, cuts the size of everything in half with a glorious hand wave, and then explains how that's not enough.

I don't think it's viable either FYI. Just pointing out your rebuke acknowledges the feasibility.

[HPsquared]

They aren't building it from scratch.

[alvah]

He addresses using existing mineshafts in the article.