In the middle of Sardinia, the Italian island known for its blue seas and hard cheeses, the long-duration energy storage company Energy Dome is developing the world’s first full-scale carbon dioxide long-duration storage facility.
And as of December, the company has a signed offtake agreement for the project, with the French utility company Engie.
The facility covers five hectares, and is round and white — reminiscent of the white domes that cover tennis courts for professional tournaments. Once operational, it will be equipped with a 20-megawatt (200-megawatt-hour) battery unit, capable of providing electricity back to the island’s grid for a continuous 10-hour period. When the grid has a surplus of renewable energy from solar and wind, Energy Dome stores it through a thermodynamic process that uses liquefied carbon dioxide.
The company was founded in 2020, it built a commercial demonstration facility in 2022, and it’s now about to commission its first utility-scale plant. The speed with which it chased commercial validation is key to being successful when it comes to FOAKs, according to Ben Potter, Energy Dome’s chief operating officer.
“You want to build your FOAK plant, but at the same time you want to be getting customer feedback as soon as possible,” he said. “Going through product-market fit is extremely challenging, and the faster you do it, the better. I think many people wait too long, but you want to get validation quickly.” Energy Dome initially built a demonstration project in 2022, also in Sardinia. But the new plant, which is being built right nextdoor, is the company’s first utility-scale commercial unit; it expects it to be up and running within the next few months.
According to Energy Dome, once operational, the project “will be the only operational energy storage asset in the global market with a 10-hour discharge duration and a signed commercial offtake agreement, apart from existing pumped hydro projects.”
The offtake agreement
Per the offtake agreement’s terms, Energy Dome owns and operates its Sardinian plant on behalf of Engie, which will provide the company with fixed, predictable payments. Engie is responsible for coordinating the plant’s dispatch — meaning deciding when to charge and discharge the battery.
It’s a version of the tolling agreements that are common in infrastructure financing, and allows Energy Dome to take on the technology and funding risk of the project, while passing the market risk onto the customer.
“What we’re trying to do here is eliminate risks,” Potter said. “So we will take funding risk, we will take technology risk… but we won’t take market risk. The off-taker has to deal with the wholesale markets, deal with arbitrage issues, and with merchant issues.”
The company selected Engie through a competitive process, partly because of the “very good chemistry” between the two teams. “When you are at first-of-a-kind, and moving to nth-of-a-kind, it’s important to learn and have a partner who’s going through that journey with you,” Potter said.
This kind of risk distribution paired with the long-term nature of the offtake agreement is essential to Energy Dome’s energy-storage-as-a-service business model — and an attractive feature for funders looking to invest in first-of-a-kind technologies. In December 2023, Energy Dome raised roughly $60 million from Breakthrough Energy Catalyst and the European Investment Bank to build the plant.
‘We’re not reinventing the wheel’
Potter describes the company’s technology as mechanical energy storage, “with a thermal twist.”
“We have an electric motor which takes the power from the grid,” he told Latitude Media. “Then we pressurize CO2 gas and we liquefy it. When the carbon dioxide is pressurized, condensed, and liquefied, that’s when, as a thermal energy storage system, we’re fully charged.”
Then, when there’s more demand than supply and power prices are higher — at night, for example — Energy Dome evaporates the liquefied gas. The company pushes it through a turbine, which spins, drives a generator, and returns electricity to the grid.
The company uses carbon dioxide because, as a heavy molecule with a low critical temperature, it liquefies at ambient temperatures, making the circular process of turning it from gas to liquid and vice versa “highly efficient.”
Energy Dome’s business model is common among pumped hydro storage users, natural gas users, and lithium-ion storage projects. It is, in Potter’s words, “tried and tested.” And it exemplifies the company’s attitude towards innovation: take something that works already, and put a spin on it.
Energy Dome attributes its speed to market in part on its reliance on immediately available components. That’s what its engineers did to bring its FOAK carbon dioxide battery technology to market as fast as possible.
“We took existing off-the-shelf components from established supply chains — that are readily available, cost-competitive, with performance guarantees, and with which banks are comfortable — and integrated those in a novel way,” Potter said. “We’ve innovated on the process, not on the supply chain and the commercial side. We’re not reinventing the wheel.”
Additionally, Energy Dome standardized the process so that the design, engineering, and set- up of the supply chain only occur once. As a result, every battery plant is built with the same “Lego bricks” and fits into the company’s fixed 20-MW frame.
The standardization also yields another business model option. Aside from offtaking plants through its energy-storage-as-a-service approach, Energy Dome can also sell and deliver entire plants; it is currently in the process of delivering one to the Midwestern utility Alliant Energy, for installation in Wisconsin.
