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Bubble with 2 thousand tons of CO2 becomes a giant battery in Italy, attracts Google and places Sardinia at the center of the new race for energy storage.
In the region of Ottana, in Sardinia, a huge white inflatable dome has come to represent one of the most unusual bets of the energy transition. Instead of using chemical cells, the structure stores carbon dioxide and turns it into the central element of a system designed to store electricity and return it to the grid when renewable generation loses strength. The project was developed by the Italian company Energy Dome and gained international projection after Google announced, on July 25, 2025, a long-term partnership and investment in the company.
The declared goal is to support commercial long-duration storage projects in markets where the company already operates and needs to expand the use of carbon-free energy.
Clean energy storage has become the major bottleneck of the energy transition
The expansion of solar and wind energy has brought a challenge that the electric sector is still trying to solve on a large scale.
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Generation increases when there is sun and wind, but demand grows at times that do not always coincide with this supply, especially in the late afternoon, at night, and during periods of low renewable production.
It was at this point that the CO2 battery came onto Google’s radar. In the official announcement of the partnership, the company stated that Energy Dome’s technology can store clean energy surpluses and return them to the grid for 8 to 24 hours, covering a range above the more common short storage today.
In practice, this places the solution in a segment seen as strategic for power grids and large energy consumers. The focus is not just on storing electricity for a few hours, but on maintaining a more stable supply when renewable production has already decreased and demand remains high.
How Energy Dome’s CO2 battery transforms gas into electricity
The system’s operation is based on a thermodynamic cycle. When there is excess energy in the grid, electricity is used to compress the CO2, cool it, and convert it into liquid, storing energy in this process.
When the grid needs power again, the process is reversed. The liquid CO2 is heated, returns to a gaseous state under pressure, and passes through a turbine, which then generates electricity to return to the system.
At the Ottana plant, this cycle was scaled to deliver 20 MW of power and 200 MWh of energy, equivalent to 10 hours of continuous discharge. The installation is the company’s first full-scale unit and has become the main commercial showcase of the technology.
Closed system keeps CO2 inside the plant and reduces pressure on critical minerals
One of the key points of the technology is that carbon dioxide is not continuously released into the atmosphere during normal operation.
IEEE Spectrum reported that the gas used in the installation came from a supplier and remains within a closed system, alternating between liquid and gaseous states to fulfill the energy storage function.
This detail changes the role of CO2 within the project. The plant was not presented as a carbon capture system but as an electrical storage solution that uses the gas as a working fluid, converting a classic symbol of the climate crisis into an operational component of a clean energy infrastructure.
Another strong argument from Energy Dome is the reduced dependency on critical raw materials. According to Google, the technology avoids the use of scarce minerals as a central part of storage and can help increase grid flexibility without repeating part of the pressure that currently falls on global chains linked to conventional batteries.
Google accelerates the global visibility of the long-duration battery
Google’s announcement changed the commercial and political weight of the Italian project. The company reported that its partnership with Energy Dome is its first commercial agreement for long-duration storage and will support multiple global projects with this technology.
This movement is relevant because it links the CO2 battery to a concrete demand from large electricity consumers, such as data centers and digital operations that need clean energy more regularly throughout the day and night.
The search for carbon-free supply 24 hours a day, 7 days a week is one of the central pillars of Google’s energy strategy.
The commercial expansion has also already started to take off. IEEE Spectrum reported that projects derived from the Sardinia plant have advanced in markets like India and United States, showing that Energy Dome’s proposal has already entered a phase of international replication and is not limited to the Italian project.
Ottana became the main proof that the technology can move from pilot to market
The Sardinia unit helped take the CO2 battery from the experimental field to the commercial stage.
On December 19, 2024, Energy Dome announced with ENGIE an offtake agreement for the 20 MW/200 MWh plant in Ottana, consolidating the facility as a market asset and not just a technical demonstration.
In the official statement, the company stated that the plant was designed to provide electricity equivalent to about 14,000 homes during a continuous period of 10 hours. This data reinforced the plant’s position as one of the most concrete references for long-duration storage with CO2 at grid scale.
The IEEE Spectrum also reported that the dome houses 2,000 tons of CO2 and that the plant began operations in July 2025. With this, Ottana has come to concentrate almost all the elements that the sector seeks to observe before betting on a new technology: scale, real operation, commercial contract, and interest from major energy buyers.
Advantages and points of attention of the new CO2 battery
The main strength of the technology lies in the combination of long-duration storage, use of known industrial equipment, and less dependence on critical minerals.
This package helps explain why Energy Dome moved out of the niche of experimental solutions and began to be observed by utilities, investors, and tech giants.
At the same time, global expansion still needs to be confirmed in practice in different markets. Scale storage projects depend on licensing, grid integration, construction schedules, financing, and consistent commercial performance after entering operation.
Even with these requirements, the Italian plant has already achieved a rare feat. It turned a CO2 bubble into a symbol of a new technological race and put Sardinia at the center of the debate on how to store clean energy in sufficient volume to keep the grid supplied when the sun sets and the wind weakens. in Wisconsin capable of serving the equivalent of 18,000 homes
