Google-backed Energy Dome and Salt River Project announced Monday that they have struck an agreement to add a 19-MW, 10-hour carbon dioxide-based battery system to the grid, co-located at SRP’s Coronado Generating Station in St. Johns, Arizona.
The project will be developed under a 20-year tolling agreement, “with Energy Dome owning and operating the facility and SRP dispatching its output,” SRP said in a release. It is expected to come online in 2029, and store enough energy to power around 4,275 homes for 10 hours.
Coronado Generating Station is a coal generation site that is undergoing a conversion to natural gas generation. The natural gas conversion is set to be completed by 2029, SRP said in 2025, with all coal generation set to cease by 2032.
Energy Dome is a Milan-based company, which Google made a “strategic investment” in last year. The project is “also part of Google and SRP’s innovative collaboration to accelerate deployment of non-lithium-ion long-duration energy storage technologies,” SRP said, and Google will fund “a portion of the project through a cost-sharing agreement with SRP.”
“The system will utilize Energy Dome’s CO2 Battery and proprietary thermomechanical long-duration energy storage process,” said the release. “The technology works by using power from the grid to compress and store CO2, then, when power is needed, expanding the CO2 through a turbine to generate energy to send back to the grid.”
In a July release, Google said it believes this particular technology “has the potential to commercialize much faster than some of the other advanced clean energy technologies in our portfolio.”
“This means we can use it in the near term to help the electricity system grow more flexibly and reliably, alongside other tools we’re developing, such as data center demand response,” Google said.
SRP said it is working to “at least double the number of generating resources on its power system by 2035 to meet increasing energy demand in the Phoenix metropolitan area,” and that energy storage is key to that goal. The project was selected through a request for proposals that SRP issued in 2024.
“This project will enable SRP to test the real-world performance of Energy Dome's technology in the Arizona climate,” Chico Hunter, SRP manager of innovation and development, said in the release.
