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LordHeini

Sure you can always get the big option but that does not mean it is feasible.

What does it cost to dig and maintain a 1.5km deep shaft?

I found is something around 8000-10000$ per meter. I can buy a whole lot of batteries for that.

This technology just does not scale since mgh always holds true.

Unlike flywheels where you get w^2.

Just making the wheel out of carbon fiber and making them go fast, squares the amount of energy you can store.

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batteries don’t last as long as a hole. some holes already exist.

Meaningfully deep holes in the ground require some maintenance as well.

One of the biggest is groundwater removal. Behind that would be the maintenance of shoring materials in the face of earthquakes, and ensuring that it remains straight in the face of earth movement.

yup it's feasible. It does scale. Here are two links to research that support the feasibility and cost effectiveness of underground gravity storage.

https://www.storage-lab.com/gravity-based-storage https://www.osti.gov/biblio/6517343

$8000 to dig a 1m hole sounds very high - that's months of someone's salary. Surely the best drilling machines can beat the cost of paying someone with a shovel for a month?

But mostly they won't be digging the holes, they will be using shafts left over from earlier mining operations.

That is what i found:

https://minewiki.engineering.queensu.ca/mediawiki/index.php/...

Honestly i would have thought it to be more expensive.

At higher depths the ground pressure is enormous and you need a lot of bracing.

Then there is water management, air, transportation of the dug out material...

When there is rock you usually need blasting or gargantuan drills which i am not sure even exists in the required diameter.

OH come on, I'm sure you can imagine the complexity of digging grows as the depth grows. the first meter would cost 100$ the second 150$, the 3rd 200$, the fourth 500$ the fifth 550$, the sixth 600$, etc.

Those prices are probably only true once you go deep enough to require permits, ground water management and all the other complications of very deep holes.

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