Can you give a quick rundown why "the crane thing" could not ever have worked, and what exactly it was, separate from the "condominium for concrete blocks", which seems to be what is described in the Wikipedia article, but also uses cranes?
As a non-mechanical engineer, it's not obvious to me.
They might still not execute well, but the idea is sound. What is different? They use a single weight, up to thousands of tons. It is suspended in a disused mineshaft, up to a kilometer deep, protected from weather. The one weight just goes up and down, i.e. it has just two moving parts, the weight and the winch. Winches are extra-mature technology.
They are talking about sealing the shaft and compressing hydrogen into it. And, maybe storing heat there, besides. Both ideas are also simple, but they don't have to work for the product to be viable; if they do work, they add value. My impression is they added those so their solution could seem more "innovative": the weight in the shaft, by itself, is a sure thing, so probably missed out on some long-shot seed subsidies. Funding in the energy sector is not well aligned.
They will probably need to figure ways to get their cost lower. Batteries are approaching $200/MWh, with people expecting that to hit $100. Certain chemistries ("Form") are quoting $20, but are probably over-optimistic. 50 years operation with no degradation could beat a nominally cheaper system that needs the expensive part replaced regularly.
Water is 1kg/L. Concrete is 2.4kg/L. Therefore, the volume of concrete lifted is 40% the volume of water you would need to store the same amount of energy.
Replacing that water with concrete, you get $2.1 billion dollars. Which, ya know, actually compares favorably with the $4 billion (2022 $) that the pumped hydro facility costs.
But then you have to remember that the pumped storage facility has like a half-dozen or dozen pumps, and that probably made up a big fraction of the cost.
The equivalent lifting block thing would have... like thousands or tens of thousands of the motor/generator devices. I can't imagine the cost.
> like thousands or tens of thousands of the motor/generator devices. I can't imagine the cost.
? The number of motor/generator pairs is proportional to the charge/discharge rate of the system. I'm not saying that because I'm an insider or have any special knowledge, I'm saying that because nothing else makes sense. So the question is whether it's cheaper to maintain a bunch of cranes and miles of steel cable and pulleys or a water generator and pipes. And then things like how each responds to earthquakes and thunderstorms (water probably wins in the latter, but the former is a little more complicated).
You also need hundreds of motors to shunt the blocks from their penthouse apartments to the elevators and back.
Hydro power dams and generating stations have been through thousands of serious earthquakes, worldwide, over more than a century. A condo penthouse packed with concrete blocks? Not so much. We have a lot of experience with earthquakes and stone blocks stacked high without mortar. The name for those is "ruins".
It doesn't work if there is any wind at all. Even with a dome over, it could store only a pitifully minuscule amount of energy. There are lots of YT vids about how stupid it is.
Compare to e.g. https://news.ycombinator.com/item?id=31736539 . Somehow people are unable to do even the most trivial reasoning about cost, where energy storage is involved: expensive stuff is expensive. Utilities will buy what is cheap to build, cheap to use, cheap to maintain, and reliable. NRGV checks zero boxes.
(Hydrogen and ammonia synthesis equipment will not be super-cheap, but its output burns in gas peaker turbines, and can be sold for hard cash.)
Even NRGV dropped the crane thing like a hot potato the moment they got their IPO cash.
As a non-mechanical engineer, it's not obvious to me.