The efficiency concerns here are valid. For comparison, modern lithium power stations are hitting 90%+ round-trip efficiency pretty consistently now.

The mechanical complexity is what worries me most - CO2 phase changes, compression/decompression cycles, heat exchangers...that's a lot of potential failure points compared to solid-state lithium cells. When researching portable power stations (I used gearscouts to compare $/Wh across different capacities), even budget lithium units are getting surprisingly cost-effective. We're seeing <$0.30/Wh for some models now.

That said, if Energy Dome can achieve reasonable $/kWh at grid scale without the lithium supply chain constraints, the efficiency trade-off might be worth it. The real question is whether the mechanical complexity translates to higher maintenance costs that eat into any capex savings.

https://gearscouts.com/power-stations

With the energy source (presumably solar/wind) being "free," efficiency isn't the most important thing. But the whole thing sounds sort of "Rube Goldberg" even if it works, batteries or supercapacitors or something like that are probably going to be a lot more reliable.

It's sort of like arguing for going back to steam engines because we've got a new way to boil water.

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...

The storage of CO2 as a liquid means less pressure then a high pressure gas.