AI-rewritten: This is a summary of an article from MIT Technology Review, rewritten by AI (Qwen, running locally) to make it easier to read. The facts come from the original article – read it for the full story.

---

Energy Dome addresses the need for long-duration energy storage by using compressed carbon dioxide gas in massive grid batteries that can deliver power for up to 24 hours. While solar and wind are becoming cheaper sources of electricity, their supply varies with weather patterns. Energy Dome stores about 2,000 metric tons of carbon dioxide inside a white dome the size of seven soccer fields. When energy is available, compressors turn the gas into a liquid stored in carbon-steel tanks, generating heat kept in proprietary thermal storage material. To generate power, the system releases the gas, warms it with stored heat to turn it back into a gas, and runs it through a turbine.

The company states its technology is roughly 10% to 15% cheaper than lithium-ion batteries for eight-hour systems and offers better economics for longer durations up to 24 hours. Energy Dome turned on its first commercial plant in Sardinia, Italy, in 2025 with a capacity of 200 megawatt-hours, enough to power about 18,000 Italian homes for 10 hours. Its plants currently have eight or 10 hours of capacity and use existing equipment like compressors and storage tanks. However, the company admits its process has a roundtrip efficiency of about 70%, compared to roughly 90% for lithium-ion batteries.

Energy Dome plans to build many more projects totaling 30 gigawatt-hours of storage, with some expected online by the end of the decade. A signed deal in June 2026 involves building a 200 MWh plant in Ireland for Google, expected to come online in 2028. Some versions of the system pair carbon dioxide batteries with natural gas turbines to improve efficiency but result in greenhouse-gas emissions. Despite lower efficiency than lithium-ion, Energy Dome aims to scale faster due to its use of commercially available components.