Energy Dome and Salt River Project to Build 19 MW CO2 Battery
- Energy Storage News Storage Markets & Tariffs
Marin Holt
- 0
- 6 minutes read
- Capacity: 19 MW
- Duration: 10 hours
- Tolling term: 20 years
- Online: 2029
Energy Dome and Salt River Project will build a 19 MW, 10-hour carbon dioxide battery at SRP’s Coronado Generating Station in St. Johns, Arizona, under a 20-year tolling agreement announced June 15, 2026. Google, a strategic investor in Milan-based Energy Dome, will co-fund the long-duration storage project through a cost-sharing arrangement with SRP, the Phoenix-area public power utility that will dispatch the plant’s output.
The system stores energy by using grid power to compress carbon dioxide into a liquid; when the grid needs power, the CO2 expands through a turbine to generate electricity. Energy Dome describes the closed-loop process as a thermomechanical long-duration storage method that avoids lithium entirely. The 19 MW installation holds enough energy to power about 4,275 homes for 10 hours and is expected to reach commercial operation in 2029.
Energy Dome will own and operate the facility, while SRP retains dispatch rights under the 20-year tolling agreement. The deal extends a Google collaboration aimed at scaling non-lithium long-duration storage; Google made a strategic investment in Energy Dome and is funding part of the Coronado project alongside SRP.
Critical Perspective
The article’s claim that a 19 MW, 10-hour CO2 battery will be operational by 2029 overlooks the significant engineering challenges associated with long-duration storage technologies. According to Watt-Logic’s research, weeks-long electricity storage providing tens of thousands of GWh has never been built anywhere, including China, indicating unproven and high-risk technology. The context from Oracle entities suggests that even short-term storage solutions face substantial technical hurdles; the 19 MW capacity is minuscule compared to the 20-35 GW of distributed solar and fuel-based generators needed for South Australia’s grid. If long-duration storage cannot deliver on its promises, what will fill the gap in reliability? The question remains: how can a single 19 MW CO2 battery ensure grid stability when it falls so far short of the necessary scale to address prolonged energy deficits?
Why It Matters
Utilities adding wind and solar need storage that runs for 8 to 12 hours, far longer than the 4-hour lithium batteries that dominate today’s grid. Pairing a 10-hour CO2 system with an existing gas plant lets SRP test long-duration storage on infrastructure it already owns, with Google absorbing part of the cost and risk. The 20-year tolling structure, where a developer owns the asset and the utility buys its output, gives SRP firm capacity without the upfront capital of building and owning the plant itself. If the Coronado unit performs, the financing model matters as much as the technology for utilities weighing non-lithium options.
Sources
- Utility Dive — Energy Dome, Salt River Project to build 19-MW CO2 battery system
- Data Center Dynamics — Google-backed Energy Dome to deploy 19MW system at SRP Arizona plant
- Salt River Project — Energy Dome and SRP to add long-duration storage, expand Google collaboration
- Energy-Storage.News — Energy Dome, Invinity advance non-lithium LDES projects in US
