Energy Dome and the EIC Accelerator: Storing Power in a CO2 Dome

Energy Dome, a Milan company founded in 2020 by CEO Claudio Spadacini, builds the CO2 Battery, a long-duration energy store that compresses carbon dioxide from an inflatable dome into liquid and later expands it through a turbine to generate power. Its EIC application promised a round-trip efficiency of 75% "without degradation over time", a capital cost of €183 per kWh for the first plant falling to €103 at 50 plants a year, and a lifetime of more than 30 years, using "only steel, water and CO2", according to CORDIS.

The European Innovation Council granted €2,500,000 towards a €3.95 million project from February 2023 to March 2025. The final report says Energy Dome developed a new sealing system for commercial-scale turbomachinery, tested a turbine in July 2023 that proved "completely gas-tight", and adapted a gas-turbine compressor to run on CO2, preparing "for full technology validation in the next few months". The first full-scale plant, 20 MW and 200 MWh at Ottana in Sardinia, was completed in July 2025, IEEE Spectrum reported. The same month Google announced a partnership and an undisclosed investment, its first in long-duration storage.

Where Energy Dome Stands Now

India's NTPC expected to finish a CO2 Battery at its Kudgi plant in Karnataka in 2026, and the US utility Alliant Energy was cleared to start building one in Wisconsin, IEEE Spectrum reported. In July 2026 Energy Dome agreed with SEC, Victoria's state-owned energy company, to build a 20 MW/200 MWh plant in the Latrobe Valley, and said its global pipeline exceeds 30 GWh with projects in the United States, Italy, Ireland and India, according to its announcement. ENGIE signed an offtake agreement for the Ottana plant in December 2024. In June 2026 Spadacini was named Innovator of the Year at the Reuters Events Energy Industry Awards.

The Technology: A Bubble and a Turbine

The dome at Ottana holds 2,000 tonnes of CO2. To store energy, the gas is compressed, cooled and liquefied in pressure vessels; to release it, the liquid is evaporated, heated and expanded through a turbine, IEEE Spectrum explains. The plant stores 10 hours of power at 20 MW, longer than the 4 to 8 hours typical of grid lithium-ion systems. Energy Dome expects its storage to be 30% cheaper than lithium-ion.

What the EIC Project Promised, and What CORDIS Shows

The project funded the engineering for commercial-size machines: leak-free sealing, turbine testing and a full-scale CO2 compressor. By the end of the project the compressor was being prepared for validation, and the first full-scale plant was completed four months later. The efficiency and cost figures in the application are Energy Dome's own and have not been published from independent measurement at Ottana. CORDIS lists the project as closed.

1. Gas-tight turbomachineryDeliveredTurbine test, July 2023.
2. Full-scale compressorDeliveredOttana, 2025.
3. Commercial rolloutUnder wayIndia, US, Australia.
4. 75% efficiency, €183/kWhUnverifiedNo independent data.

The Money

Energy Dome's €55 million Series B closed in two tranches in 2023, co-led by Eni Next and Neva SGR, with CDP Venture Capital's EU-funded Green Transition Fund in the second tranche, according to the company. Google's investment in 2025 was undisclosed. Whether the EIC Fund invested under the blended award, and Energy Dome's revenue, are not public.

What Cannot Be Checked

Why Europe Should Care

Long-duration storage is what makes wind and solar dispatchable, and Energy Dome's machines use steel, water and CO2 rather than critical minerals. The EIC paid for part of the engineering that took the technology to full scale. The first plant outside Sardinia is due in India, IEEE Spectrum reported; in Europe the company lists further projects in Italy and Ireland.

The Verdict

Energy Dome and the EIC have not been asked for comment for this article. It is based entirely on public records and published statements, linked throughout.