New CO2 Battery Stores Solar Power for 24 Hours

A startup called Energy Dome has built a giant battery that stores renewable energy using carbon dioxide gas. The battery is a huge white dome, about the size of seven soccer fields, filled with 2,000 tons of CO2. When solar or wind power is available, the gas is compressed into liquid and stored in tanks. When electricity is needed, the liquid is warmed, turns back into gas, and spins a turbine to generate power. This cycle can repeat endlessly.

Why does this matter? Solar and wind are cheap but only work when the sun shines or wind blows. Storing that energy for later is key. Lithium-ion batteries, like those in phones and electric cars, are great for short storage (up to 4 hours) but get expensive for longer durations. Energy Dome's system can store power for 8 to 24 hours and is about 10-15% cheaper than lithium-ion for 8-hour storage. That means utilities can use more renewable energy, even at night or on calm days, reducing reliance on fossil fuels.

The first commercial plant opened in Sardinia, Italy, in 2025. It can power 18,000 homes for 10 hours. Energy Dome has plans for 30 gigawatt-hours of storage worldwide, including a deal with Google for a plant in Ireland by 2028. The technology isn't perfect: it's less efficient than lithium-ion (70% vs 90% roundtrip efficiency) and some versions use natural gas, which emits greenhouse gases. But it's a promising step toward a cleaner, more reliable energy grid.