this post was submitted on 22 Dec 2025
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"This giant bubble on the island of Sardinia holds 2,000 tonnes of carbon dioxide. But the gas wasn’t captured from factory emissions, nor was it pulled from the air. It came from a gas supplier.... "The facility compresses and expands CO2 daily in its closed system, turning a turbine that generates 200 megawatt-hours of electricity, or 20 MW over 10 hours."

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[–] it_depends_man@lemmy.world 36 points 14 hours ago (2 children)

Could be very high, even the waste heat from the compression could be used to achieve more compression and turbines get to above 90%, that all depends on the scales they're building this at. 70% overall doesn't seem unrealistic as an educated guess.

[–] oxbech@feddit.dk 37 points 13 hours ago (3 children)

On their website (energydome.com) they claim “75%+” round trip efficiency, so not a bad guess!

[–] sunbeam60@feddit.uk 20 points 12 hours ago (1 children)

That’s a hell of a lot better than most other systems. If true, and if scalable, this is a huge innovation.

[–] fullsquare@awful.systems 11 points 11 hours ago* (last edited 11 hours ago)

compressors, turbines (like steam turbines), piping, some of which heat-resistant (500C), container for liquid carbon dioxide, lots of plastic for the bubble, something for thermal storage, dry and clean carbon dioxide, these aren't unusual or restricted resources, don't depend on critical raw materials or anything like that

[–] fullsquare@awful.systems 13 points 12 hours ago* (last edited 12 hours ago)

Compressed air without heat recovery is more like 30%, so this is huge

Carbon dioxide can be liquefied relatively easily which is what i guess makes this efficient

[–] brucethemoose@lemmy.world 3 points 7 hours ago* (last edited 7 hours ago)

I was just about to bang out that they must lose a lot of heat from the compression. But apparently not! That’s amazing.

I’m struggling to think of systems that would significantly outperform “75%+”. Chilled superconducting coils? Those are expensive, and would fail rather catastrophically.

[–] HaraldvonBlauzahn@feddit.org 1 points 2 hours ago (1 children)

even the waste heat from the compression could be used to achieve more compression

No. Waste heat can by definition not be converted to mechanical work.

Otherwise, one could build a perpetuum mobile: Convert heat to mechanical work, use that work to generate heat, convert it to work again, and so on. You'd have a machine that generates energy out of nothing, and that's not possible because of the law of energy conservation.

[–] nooneescapesthelaw@mander.xyz 2 points 50 minutes ago

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

A recuperator is a counter-flow energy recovery heat exchanger that recovers waste heat in the supply