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points by 8bitsrule 3 days ago | 0 comments

I'd like to see more examples of (non-hydro) Gravitational Potential Energy Storage tried out. Very large containers full of sand, for example. If you have no mountains, a deep hole will do.

"Current levelized cost of storage ranges from $150-300 per MWh for established pumped-storage systems, while newer solid-mass gravity systems estimate costs of $200-400 per MWh. These figures are competitive with long-duration storage applications but remain higher than lithium-ion batteries for shorter-duration uses."

https://eureka.patsnap.com/report-gravitational-potential-en...

[–] cowlevel 3 days ago

The amount of space needed is just gargantuan. Hydro only works because you can declare that an entire valley is now energy storage, in one fell swoop. As soon as you have to construct each unit of storage instead of letting nature do it for you, it becomes completely impractical. Yes you can store energy in a tower of concrete blocks... if you can make enough concrete blocks to fill a lake.

[–] myrmidon 2 days ago

There's some plausible concepts:

https://gravity-storage.com/technical-concept/

But battery storage is a proven technology now and the cost trends with such bespoke megaprojects are not looking promising, so I'm not holding my breath.

Burning (regenerable) metal fuel in old coal power plants is also an interesting approach:

https://www.sciencedirect.com/science/article/pii/S2666352X2...

[–] Maxion 3 days ago

AFAIK problem with all physical energy storage solutions is just one of cost.

Batteries are scheduled to become so cheap that these type of physical storage systems just won't be able to keep up in terms of cost.

Most pumped hydro projects are now put on hold as batteries have been coming down.

[–] Flere-Imsaho 3 days ago

I've recently learnt about sodium ion batteries, such as this uk company:

https://www.elevenenergy.co.uk/#sodium-ion

They are larger than lithium batteries, but potentially cheaper and better performing around temperature extremes.

[–] chickenbig 2 days ago

> Batteries are scheduled to become so cheap

Wait, you can schedule price drops?

https://www.nature.com/articles/nenergy2017110 / https://www.cell.com/joule/abstract/S2542-4351(18)30583-X make the battery takeover look like a foregone conclusion, but past performance is no indication of future performance.

Also what about the systems to turn the batteries into something useable? It is telling how cheap lead-acid batteries looked on the first paper's Figure 2, yet overall system costs were vastly higher.

[–] tim333 2 days ago

You can get a reasonable idea in the near term from the announcements of CATL and BYD who are building the things.

Like CATL announced a cost of $19 per kwh. https://electrek.co/2026/07/16/catl-sodium-ion-15000-cycle-g...

which I think is far cheaper than the prices in your links. I think they'll have a job going lower for a while as the raw materials are ~$10.

I think the actual cost to buy one now it more $40-60. The $19 is probably their target in a while.

If you spread $60 over 15000 cycles that's 0.4c per kwh stored and returned which is pretty cheap compared to what I pay for electicity (~$35c).

[–] chickenbig 2 days ago

> Like CATL announced a cost of $19 per kwh > I think the actual cost to buy one now it more $40-60.

Plus battery assembly and installation costs (inverter, grid connection).

> If you spread $60 over 15000 cycles

A 30 year lifetime (11k cycles if charged/discharged once a day). Using a 5% discount rate the cost goes up to 0.78c/kWh for the cells. The cost goes up if it can not cycle once a day, for instance intermittent source of energy or excess capacity. And the cost goes up with all the rest of the equipment involved, and round trip efficiency.

[–] Animats 3 days ago

It looks like Energy Vault, the people with the tower crane and big stack of concrete blocks scheme, gave up on that. Energy Vault is now selling large battery systems that actually work.

[–] micw 3 days ago

Thing is that you need incredible large masses in incredible heights.

Example: Lifting a 10-metric-ton stone by 36 meters stores just about 1 kilowatt-hour (kWh) of energy. This is roughly equivalent to the capacity of a small power station used for a camping trip.

[–] leonidasrup 2 days ago

This is the reason whey pumped hydroelectric energy storage (PHES) systems are so large. Gravity is quite a weak force.

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

[–] loomy7 2 days ago

To get a sense of scale, when accounting for round trip efficiency of li-ion batteries and gravity batteries, a single 18650 battery has about the same energy as lifting 100kg by 50 meters.

A single cell is about $5 in volume, while 100kg of fill dirt and rock is about $2. At this point new pumped hydro or gravity batteries don’t scale like li-ion does. This tips even more towards normal batteries when you look at sodium or other cheaper but less energy dense batteries.

[–] robin_reala 3 days ago

If you’ve got very large containers of sand you can just store energy as heat instead, especially if you’re planning to use the energy for heating eventually: https://en.wikipedia.org/wiki/Thermal_energy_storage

[–] jacquesm 3 days ago

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