CO2 batteries that store grid energy take off globally

Posted by rbanffy 12/21/2025

CO2 batteries that store grid energy take off globally(spectrum.ieee.org)

370 points | 311 commentspage 3

Ayanonymous 12/23/2025|

I’m new to the idea of grid‑scale energy storage technologies, but this was a really clear and interesting introduction to how CO₂ batteries could help with long‑duration renewable energy storage. It’s exciting to see new approaches that might make solar and wind power more reliable and affordable. Thanks for sharing!

readthenotes1 12/21/2025||

Does pure-ish CO2 have advantages over regular air or the freon-like substance used in air conditioning?

How much energy us used to purify and maintain the CO2?

ajb 12/21/2025||

These days CO2 is actually quite commonly used in air-conditioners as a refrigerant, R-744. Fluorinated gases like Freon are being phased out due to being even worse for global warming.

mark-r 12/21/2025||

I thought it was ozone depletion, not greenhouse effects, that led to the fluorinated gas phaseout?

ajb 12/22/2025||

The original ones yes. They are already banned - but the next generation of fluorinated refrigerants are apparently ok for the ozone layer but have a greenhouse effect. That's my understanding anyway, I'm far from an expert.

Edited to add: https://en.wikipedia.org/wiki/Kigali_Amendment has some information on this.

analog31 12/21/2025|||

It's easy to liquefy, so it has a density advantage over air, and would be bad if released but not super bad.

3eb7988a1663 12/21/2025||

Suffocation seems like the most relevant concern in the event of a catastrophic leak.

1123581321 12/21/2025||

It is a necessary risk. Oxygen is dangerous when heat is involved, and its low critical point is harder to work with than co2.

cogman10 12/21/2025||

It's pretty cheap to acquire a boatload of and, assuming you don't get it directly from burning fossil fuels, there's really no environmental harms of it leaking into the atmosphere. [1]

[1] https://en.wikipedia.org/wiki/Carbon_capture_and_storage

zahlman 12/21/2025||

> CCS could have a critical but limited role in reducing greenhouse gas emissions.[6] However, other emission-reduction options such as solar and wind energy, electrification, and public transit are less expensive than CCS and are much more effective at reducing air pollution. Given its cost and limitations, CCS is envisioned to be most useful in specific niches. These niches include heavy industry and plant retrofits.[8]: 21–24

> The cost of CCS varies greatly by CO2 source. If the facility produces a gas mixture with a high concentration of CO2, as is the case for natural gas processing, it can be captured and compressed for USD 15–25/tonne.[66] Power plants, cement plants, and iron and steel plants produce more dilute gas streams, for which the cost of capture and compression is USD 40–120/tonne CO2.[66]

... And then for this usage, presumably you'd have to separate the CO2 from the rest of the gas.

LikeBeans 12/22/2025||

I wonder how does it compare to hoisting a concrete (or something heavy) block up a pulley system as an energy store? When you need the energy you let it slide down pulling some steel cable that turns a generator, or multiple cables into multiple generators. Or even a cascade of concrete blocks at different heights as a space saver.

cenamus 12/22/2025||

Probably extremely poorly, as that's basically pumped hydro on _tiny_ scale. The amount of mass/water that fits into storage lakes is insane

LikeBeans 12/22/2025||

Good point. I was thinking more about areas without much water and a large field of poles each hoisting several blocks. Sort of wind turbines but without the blades.

sowbug 12/22/2025||

The article does address that.

...and even dangling heavy objects in the air and dropping them. (The creativity devoted to LDES is impressive.) But geologic constraints, economic viability, efficiency, and scalability have hindered the commercialization of these strategies.

rbanffy 12/22/2025||

I have one concern: what if the container bursts? CO2 is heavier than air, and a sudden pressure decrease will cool it down further, so it'll hug the ground. What would be a safe distance for the people around the plant to live without the risk of being asphixiated in an accident?

ragebol 12/22/2025|

The article mentions > If the worst happens and the dome is punctured, 2,000 tonnes of CO2 will enter the atmosphere. That’s equivalent to the emissions of about 15 round-trip flights between New York and London on a Boeing 777. “It’s negligible compared to the emissions of a coal plant,” Spadacini says. People will also need to stay back 70 meters or more until the air clears, he says.

So: 70 meters

gosub100 12/22/2025||

> or more

I guess it just depends on how much oxygen you really need.

alexchamberlain 12/21/2025||

Would this be effective at smaller volumes? Could it get down to say the size of a washing machine for use at home?

lambdaone 12/21/2025||

Very unlikely. All the technologies involved work best at scale; for example, the area-to-volume ratio of the liquid gas storage vessel is a critical parameter to keep energy losses low.

rgmerk 12/21/2025||

Also, parasitic losses in engines tend to be proportionally lower as the engines get bigger.

Compare the thermal efficiency of marine diesel engines to their automotive equivalents, for instance.

kumarvvr 12/22/2025||

The turbines would have to spin at very high speeds at those sizes to be efficient.

ursAxZA 12/22/2025||

It might function as a kind of cogeneration-style buffer, but CO₂ still gets emitted in manufacturing and maintenance — and I’m not sure the volumetric efficiency is all that compelling.

Still, if we ever end up with rows of these giant “balloons,” the landscape might look unexpectedly futuristic.

laurencerowe 12/21/2025||

> Energy Dome expects its LDES solution to be 30 percent cheaper than lithium-ion.

Can see how this could scale up for longer storage fairly cheaply but on current trends batteries will have caught up in cost in 2-3 years.

Smoosh 12/21/2025|

Aren’t CATL already producing sodium-ion batteries for about 60% the cost of lithium-ion for equivalent capacity?

laurencerowe 12/21/2025||

Yeah. Maybe this tech will have a place for week-long storage and be a good buffer for wind power but I hard to see the economics working for daily cycling.

kogasa240p 12/21/2025||

Been hearing about this project for years, nice to see that it's gaining traction! Only question is that if they use captured Co2 initially or if they have to produce it.

SwtCyber 12/22/2025||

The real question for me isn't the physics so much as ops over 20–30 years: maintenance, leakage, real-world efficiency after thousands of cycles

pkphilip 12/22/2025|

Wasn't there a plan to use concrete blocks as energy storage medium by pulling them up a little bit at a time when there is surplus power?

jvanderbot 12/22/2025|

Sure, some people have proposed that, but if you calculate how much has to be lifted to get 20 MW stored (or so), it gets pretty ridiculous pretty quickly. Like "Lift the largest aircraft carrier 20 meters" silly. You have some pretty severe size/mass issues.

It makes more sense to use water + a dam, but then again, we like to use water for things besides energy storage, and we're talking about a _lot_ of water.

This gas bag is effectively the same as water+dam, except the pressure is from the tanks and the compressor creates it, vs pumping uphill to create pressure.

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