Columbia Energy Storage Project

Advancing our clean energy future

The Columbia Energy Storage Project is the first long-duration energy storage project of its kind to be developed in the United States. The system’s unique features will boost grid stability and deliver enough electricity to power approximately 18,000 Wisconsin homes for 10 hours on a single charge.

Development of the Columbia Energy Storage Project is led by Alliant Energy in partnership with WEC Energy Group, Madison Gas and Electric, Shell Global Solutions US, Electric Power Research Institute, the University of Wisconsin–Madison and Madison College. Pending approval, the project will be built south of Portage, Wisconsin, in the town of Pacific, near the current Columbia Energy Center. Construction is expected to begin in 2026 and be completed by the end of 2027.

How does a CO2-based energy storage system work?  

Utilizing a system design by Energy Dome, this innovative and efficient approach to long-duration energy storage is both simple and sustainable. The Columbia Energy Storage Project will take energy from the grid and store it by converting CO2 gas into a compressed liquid form. When energy is needed, the system converts the liquid CO2 back to a gas, which powers a turbine to create electricity.

CO2-based energy storage is a proven technology that delivers exceptional efficiency compared to many other long-duration energy storage systems. Using mainly steel, and an initial supply of water and CO2 to construct the system, it is highly sustainable and easily recycled at the end of life.

Energy dome illustration

System illustration for conceptual reference. Diagram not to scale.

Energy storage

As the electric grid continues to evolve, Alliant Energy is leading the way with new and innovative solutions. We are working to integrate emerging technologies and optimize energy resources such as wind and solar power, battery storage and traditional generation systems. These efforts will benefit our customers with improved energy reliability and efficiency.

The expansion of energy storage infrastructure is key to accelerating the transition to cleaner, more sustainable renewable energy. With major transformations underway, we’re working rapidly to balance energy demands, reduce the need for traditional power grid updates and increase security in the event of an outage or severe weather. Additional information about our deployment of energy storage solutions can be found on our Energy Storage page.

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