They built a small plant in Sardinia, but I can't find any information on what it cost to build or operate.[1]

I'm skeptical of their cost claims. Turbines aren't cheap and compared to batteries, they require significant maintenance. And while you can increase energy storage by increasing the size/number of CO2 tanks, the only way to increase power output (or "charging" speed) is to add more/bigger compressors and turbines.

There's also the issue of volumetric energy density. Wikipedia says that compressed CO2 storage has an energy density of 66.7 watt-hours per liter, though it's unclear if that's before or after turbine inefficiencies.[2] And that's the density in a compressed tank. It doesn't count the volume of the low pressure dome, which is many times larger. For comparison, lithium batteries are 250–700Wh per liter depending on the chemistry. Specific energy (energy per unit mass) is better than lithium ion, but since these are fixed installations, mass isn't a major concern.

Considering their claims are for a theoretical full scale plant, and that the numbers are already worse than batteries (75% efficiency, lower volumetric energy density, $200/kWh), I'm not optimistic. This technology might have niche uses, but I don't see it competing with most lithium battery installations.

That said, I hope I'm wrong. The more energy storage solutions we have, the better our future will be.

1. https://www.energy-storage.news/energy-dome-launches-4mwh-de...

2. https://en.wikipedia.org/wiki/Compressed_carbon_dioxide_ener...