Alliant Energy plans energy storage facility near Portage

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With approval from state regulators secured, a Madison-based utility is readying a 200-megawatt-hour carbon dioxide-based energy storage project in Columbia County.

Alliant Energy on Friday announced plans for the Columbia Energy Storage Project are advancing after approval from the Public Service Commission of Wisconsin. Using components by vendor Energy Dome, the project will use carbon dioxide to release and store energy when needed by the grid. It’s the first of its kind in the United States and construction is expected to begin in 2026, utility officials said.

When everything is finalized with a contractor and engineer, Alliant will build its storage system south of Portage in the town of Pacific, Wis. The energy storage system will be tied to the Columbia Energy Center, which is currently a coal-fired plant. In 2024, the utility said it will explore converting at least one of its units to natural gas before the end of 2029.

The utility is still finalizing plans and expects to invest around $90 million in the project, a spokesperson for Alliant Energy said. Project cost will depend on factors including grant funding, site options and system design alternatives, they added.

Alliant expects to put out a “balance of plant” bid request later this year, the spokesperson said. Most of the project components will be provided by Energy Dome, they added.

Based off a system developed in Italy, the project will feature a closed-loop system which will take excess energy from the grid and convert carbon dioxide gas into compressed liquid for long term storage, officials said. When stored energy is needed for the grid, the system converts liquid CO2 back to gas which powers a turbine to create electricity, officials added.

The system will deliver enough electricity to power around 18,000 homes for 10 hours on a single charge, officials noted.

“We appreciate the PSC’s approval of this innovative solution as we continue to build a strong and resilient energy future,” said Raja Sundararajan, executive vice president of strategy and customer solutions at Alliant Energy, in a statement. “The Columbia Energy Storage Project positions us to meet the growing energy needs of our customers and the communities we serve. It’s also a key part of our balanced energy mix, our roadmap for delivering the reliable, cost-effective energy customers count on,” he added.

The facility will be built on the site of the current Columbia Energy Center, a spokesperson said. Construction is expected to begin in 2026 and the project is expected to be completed by the end of 2027, they added.

Storage project development is led by Alliant Energy in partnership with the Wisconsin Public Service Corporation, an affiliate of WEC Energy Group and Madison Gas and Electric.