The Public Service Commission of Wisconsin (PSC) has granted final approval for Alliant Energy’s Columbia Energy Storage Project, marking a significant milestone in the deployment of long-duration energy storage (LDES) in the United States. The project, developed in collaboration with Energy Dome, WEC Energy Group’s Wisconsin Public Service Corporation, and Madison Gas and Electric, will feature a first-of-its-kind CO₂-based battery system designed to enhance grid reliability and support the state’s clean energy goals.
Set to be constructed near the existing Columbia Energy Center in the town of Pacific, just south of Portage, Wisconsin, the project will be the first utility-scale CO₂ battery system in the U.S. It promises to deliver up to 200 megawatt-hours (MWh) of electricity storage—enough to power approximately 18,000 homes for 10 hours on a single charge.
“This is a transformational step toward a more resilient and flexible energy future,” said Raja Sundararajan, Executive Vice President of Strategy and Customer Solutions at Alliant Energy. “With PSC’s support, we’re advancing a project that not only addresses future energy needs, but does so in a cost-effective and innovative manner.”
The Columbia Energy Storage Project will utilize Energy Dome’s closed-loop CO₂ battery system, a novel technology that stores electricity by compressing carbon dioxide gas into a liquid. When electricity is needed, the system reverses the process—expanding the liquid CO₂ back into a gas to drive a turbine and generate power. This cycle offers a safe, efficient, and long-duration alternative to traditional lithium-ion storage systems.
This cutting-edge approach supports Alliant Energy’s broader Energy Blueprint strategy, which focuses on creating a balanced mix of generation resources—including renewables and storage—to deliver reliable and affordable energy to customers.
Construction on the Columbia Energy Storage Project is scheduled to begin in 2026, with completion expected by the end of 2027. Once operational, it will represent a significant leap forward in the integration of flexible storage into the grid, offering a scalable solution to bridge intermittent renewable generation with demand.
The project builds on Alliant Energy’s growing portfolio of battery energy storage initiatives and reinforces Wisconsin’s position as a national leader in utility-driven clean energy innovation.
