Columbia Energy Storage Project

Executive Overview

The Columbia Energy Storage Project is a 20 MW / 200 MWh CO₂ battery long-duration energy storage system being developed at the Columbia Energy Center site in the Town of Pacific, Columbia County, Wisconsin — the first utility-scale CO₂ battery deployment in the United States, and the first full-scale Energy Dome CO₂ battery outside Europe. Alliant Energy is the lead developer; co-owners include Wisconsin Public Service Corporation (WEC Energy Group subsidiary), Madison Gas and Electric, and Electric Power Research Institute. Additional partners include Shell Global Solutions US, Madison College, and the University of Wisconsin-Madison. Construction is expected to begin Q2 2026; targeted completion is Q3 2027. The 1,023 MW Columbia Energy Center coal plant co-located at the site is scheduled to shut down by mid-2026. DOE awarded up to $30.7 million in cost-share via the Office of Clean Energy Demonstrations (Notice to Proceed Q4 2024; Phase 1 completion November 2025). PSC approval was received June 2025. The system can power approximately 18,000–20,000 Wisconsin homes for 10 hours on a single charge. Alliant Energy serves approximately 1 million electric and 425,000 natural gas customers.

How It Works & Differentiation

The Energy Dome CO₂ battery stores electricity by compressing ambient CO₂ gas into liquid (storing the compression heat in a packed-particle TES system), holding liquid CO₂ in ambient-temperature carbon-steel pressure vessels, then evaporating and expanding the CO₂ through a turbine to regenerate electricity. The Wisconsin plant is rated to discharge 18 MW for at least 10 hours; charging takes 10 hours normally. Round-trip efficiency exceeds 75%. Expected service life is 30-plus years with no capacity or performance degradation. No lithium, rare earth metals, or exotic materials are used — the system is constructed mainly from steel, water, and CO₂, all recyclable at end of life. The site's brownfield status (former coal plant with existing grid connection) reduces transmission infrastructure costs.

Commercialization & Traction

The Columbia project follows Energy Dome's Sardinia demonstration (2.5 MW / 4 MWh, commissioned June 2022) and the Ottana 20 MW / 200 MWh full-scale plant (commissioned Q4 2024 with ENGIE offtake). Columbia's 20 MW / 200 MWh configuration matches the Ottana full-scale plant specification exactly, providing a direct operational reference. The Wisconsin Public Service Commission approval in June 2025 cleared the primary U.S. regulatory hurdle. The coal-to-CO₂-battery site conversion is a directly replicable brownfield model for retiring coal infrastructure across the Midwest.

Scalability & Strategic Context

The Columbia project, if commissioned on schedule in Q3 2027, would be the first CO₂ battery in operation in the United States, validating the technology's supply chain and construction scalability in a new regulatory and logistics environment. At 200 MWh and 10-hour duration, the system fills a niche between 4-hour lithium-ion (too short for multi-period renewable balancing) and pumped storage hydro (too geographically constrained) — precisely where the LCOS competitive advantage of the CO₂ battery is most compelling.