This giant bubble The island of Sardinia contains 2000 tons of carbon dioxide. But the gas did not come from factory emissions or be extracted from the air. It came from the gas supplier and lives permanently inside the dome system, performing the environmentally friendly task of storing large amounts of excess renewable energy until it is needed.
Developed by a Milanese company. Energy domeThe bubble and its surrounding equipment showcase a first-of-its-kind “CO2 battery,” as the company calls it. The installation compresses and expands CO.2 Every day, in its closed system, it rotates a turbine that produces 200 megawatt-hours of electricity, or 20 MW in 10 hours. And in 2026, copies of this plant will begin to appear around the world.
We mean this literally. It only takes half a day to blow a bubble. Construction of the rest of the site takes less than two years and can be built almost anywhere there is 5 hectares of flat land.
The first to build it outside Sardinia will be one of India's largest energy companies. NTPC Limited. The company plans to complete construction of the CO2 battery sometime in 2026 at the Coogee Power Station in Karnataka, India. Meanwhile, in Wisconsin, utilities Alliant Energy received permission from the authorities to begin construction of another power plant in 2026, which will provide electricity to 18,000 homes.
AND Google love the concept so much so that it plans to rapidly deploy this capacity across all of its key data centers in Europe, the US and Asia Pacific. The idea is to ensure electricity consumption data centers with 24/7 clean energyeven when the sun doesn't shine and the wind doesn't blow. The Energy Dome partnership, announced in July, marks Google's first long-term investment energy storage.
“We scanned the world looking for different solutions,” says Your Enoasenior manager of energy strategy at Google, in Paris. The challenge the tech giant faces is not only finding a long-term storage option, but also making sure it fits the unique characteristics of each region. “So standardization is really important, and that’s one of the things we really like” about the Energy Dome, she says. “They can really plug and play it.”
Google will prioritize locating Energy Dome projects where they will have the greatest impact on the environment. decarbonization and grid reliability, as well as a place where a lot of renewable energy can be stored,” says Anda. The facilities may be located near Google's data centers or elsewhere on the same network. The companies did not disclose the terms of the deal.
Anda says Google expects to help the technology “reach a mainstream commercial stage.”
Creative approaches to long-term energy storage
All this excitement is based on the only full-size, grid-connected Energy Dome plant in Ottana, Sardinia, which was completed in July. It was built to help solve one of the biggest challenges of the energy transition: the need for grid-connected storage that can provide power for more than 8 hours at a time. This concept, called long-duration energy storage, or LDES in industry parlance, is key to maximizing the value of renewable energy.
When there is a lot of sun and wind, sunny and wind power plants tend to produce more electricity than the grid requires. Therefore, saving surpluses for use when these resources are in short supply makes sense. LDES also improves network reliability by providing redundant and supplementary power.
The problem is that even the best new grid storage systems on the market are mostly lithium-ion batteries – provide only 4 to 8 hours of storage. This is not enough time to last through a whole night, several cloudy and windless days, or the hottest week of the year when energy demand is at its peak.
After the CO2 leaves the dome, it is compressed, cooled, turned into a liquid and stored in pressure vessels. To release energy, the process is reversed: the liquid is evaporated, heated, expanded, and then fed through a turbine, which generates electricity. Luigi Avantagiato
Lithium-ion battery systems could be made larger in size to store more energy and last longer, but systems of that size are generally not economically viable. Different grid scale chemical composition of batteries and approaches to them are in development, such as sodium, iron-air and vanadium redox flow batteries. But energy density, costs, degradation and financing complications have challenged the developers of these alternatives.
Researchers have also experimented with storing energy using air compression, heating blocks or sand, use of hydrogen or methanol, water pressure deep undergroundand even suspending heavy objects in the air and dropping them. (The creativity of LDES is impressive.) But geological constraints, economic viability, efficiency, and scalability have hampered the commercialization of these strategies.
A proven option for grid-scale data storage ispump hydraulic systemin which water is pumped between reservoirs at different heights, operates for decades and can store thousands of megawatts for days. But these systems require specific topography, a lot of land, and can take up to ten years to build.
CO2 batteries check a lot of boxes that other approaches don't. They do not require special topography like pumped hydraulic reservoirs. They don't need critical minerals as do electrochemical and other batteries. They use components for which supply chains already exist. Their expected service life is almost three times longer than lithium ion batteries. And adding size and capacity significantly reduces the cost per kilowatt-hour. Energy Dome expects its LDES solution to be 30 percent cheaper than lithium-ion.
China took note. It is reported that China Huadian Corp. and Dongfang Electric Corp. build CO2Energy storage facility in Xinjiang in northwest China. Media reports show renders domes, but give wide range of storage capacities— including 100 MW and 1,000 MW. Chinese companies did not respond to IEEE spectrumrequests for information.
“What I can say is that they are developing something very, very similar. [to Energy Dome’s CO2 Battery] but quite large-scale,” says Claudio SpadacciniFounder and CEO of Energy Dome. Chinese companies “are good, they're super fast and they have a lot of money,” he says.
Why is Google investing in CO2 batteries?
When I visited the Energy Dome plant in Sardinia, CO in October2 it had just been pumped out of the dome, so I could look inside. It was massive, monochromatic and practically empty. An inner membrane that retained uncompressed CO.2collapsed all over the floor. There were a few pockets of gas left behind, causing the off-white sheet to bulge in spots.
Meanwhile, the translucent outer dome let in some daylight, creating a creamy glow that enveloped the vast space. Without a structural frame, the only thing that kept the dome upright was the slight difference in pressure between the inside and outside air.
“This is incredible,” I told my guide. Mario TorchioDirector of Global Marketing and Communications at Energy Dome.
“That's true. But that's physics,” he said.
Outside the dome, a series of machines connected by undulating pipes move the CO.2 from the dome for compression and condensation. First, the compressor creates a gas pressure from 1 bar (100,000 pascals) to approximately 55 bar (5,500,000 Pa). The thermal energy storage system then cools the CO.2 to ambient temperature. A condenser then turns it into a liquid, which is stored in several dozen pressure vessels, each the size of a school bus. The entire process takes about 10 hours, and upon completion the battery is considered charged.
To discharge the battery, the process is reversed. Liquid CO2 evaporates and heats up. It then enters a gas expander turbine, which is similar to a medium pressure steam turbine. This drives a synchronous generator, which converts mechanical energy into electrical energy for the grid. The gas at atmospheric pressure is then released back into the dome, filling it until the next charging phase.
Energy Dome engineers are testing a drying system that constantly maintains the optimal level of dryness of CO₂ gas in the dome.Luigi Avantagiato
This is not rocket science. However, someone had to put it together first and figure out how to do it cost-effectively, which Spadaccini says his company has achieved and patented. “The way we seal the turbomachinery, the way we store the heat in the thermal energy storage, the way we store the heat after condensation… can really reduce costs and improve efficiency,” he says.
The company uses pure, purpose-created CO2.2 instead of getting it from emissions or the air, because these sources contain impurities and moisture that break down the steel in machines.
What happens if the canopy is punctured?
On the other hand, the Energy Dome facility takes up about twice as much land as a lithium-ion battery of comparable capacity. And the domes themselves, which are about as tall at the top as a sports stadium and longer, can stand out in the landscape and cause some NIMBY pushback.
What if a tornado comes? Spadaccini says the dome can withstand winds of up to 100 mph. If the Energy Dome could get half a day's warning of severe weather, the company could simply compress and store the CO2.2 “In the tanks and then deflate the outer dome,” he says.
If the worst happens and the dome is breached, CO2 emissions would be 2,000 tons.2 will enter the atmosphere. This is equivalent to the emissions of about 15 round-trip flights between New York and London. Boeing 777. “This is negligible compared to the emissions from a coal-fired power plant,” Spadaccini says. People will also have to stay 70 meters or more away until the air clears, he said.
Is it worth the risk? The companies lining up to build these systems seem to think so.
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