Energy Dome bets on carbon dioxide for grid storage

Energy Dome is developing long-duration grid storage that uses carbon dioxide to absorb excess power from renewables and dispatch it when electricity demand rises. Its system compresses carbon dioxide into a liquid, stores the heat created during compression, then uses that heat to turn the liquid back into gas and drive a turbine.

The company’s plants center on a large dome covering about the size of seven soccer fields and holding about 2,000 metric tons of carbon dioxide. Unlike compressed-air storage that often depends on underground caverns, the design uses commercially available equipment such as compressors and carbon-steel tanks, which could make it easier to deploy in different regions.

Energy Dome turned on its first commercial plant in Sardinia, Italy, in 2025. The facility has a capacity of 200 megawatt-hours, enough to power about 18,000 Italian homes for 10 hours. The company estimates its technology is roughly 10% to 15% cheaper than lithium-ion batteries for an eight-hour system, with better economics for longer-duration systems of up to 24 hours.

Challenges remain. The process returns about 70% of stored electricity to the grid, compared with roughly 90% for lithium-ion batteries, and Energy Dome has only one commercial project operating. It has plans for 30 gigawatt-hours of projects across five continents, including a June 2026 deal with Google to build a 200 MWh plant in Ireland expected to come online in 2028.