The battery that stores energy with CO2 instead of lithium
An Italian company stores solar electricity by compressing carbon dioxide.
In central Sardinia, a huge dome full of carbon dioxide works as a battery to store solar energy.

Milan-based startup Energy Dome developed the so-called "CO2 Battery." During the day it uses surplus grid electricity, usually solar, to compress and liquefy CO2, which is stored in steel tanks. CO2 can be liquefied at high pressure and ambient temperature, something air does not allow. The heat from compression is kept in thermal storage units.
When electricity is needed, the process reverses: the liquid is heated, turns back into gas and, before returning to the dome, spins a turbine. According to the company, it is a closed loop that returns 75% of the energy used for charging to the grid.
Renewables need long-duration storage because sun and wind are not always available. Energy Dome says its system stores energy for up to 10 hours at half the cost of lithium-ion batteries, using common industrial components. Its demonstration plant had already been running for two years.
Key facts
- 200 MWh plant under construction in Ottana, Sardinia.
- Estimated lifespan of 30 years without degradation, according to the company.
- Combined funding of 60 million euros from the EIB and Breakthrough Energy Catalyst.
- Cost and efficiency figures come from the company itself.
The company plans to replicate the Sardinia module in other parts of the world.
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