Energy Dome’s 10-hour Wisconsin battery approved
The project will utilise Energy Dome’s CO2 Battery, which stores energy via the adiabatic compression of carbon dioxide.
Energy Dome and Alliant Energy have won approval from Wisconsin regulators to build a 20 MW/200 MWh long-duration energy storage system (colloquially known as a “CO₂ battery”) near Portage, Wisconsin. The Columbia Energy Storage Project will use compressed carbon dioxide to store energy over a full 10‑hour discharge period—enough to power around 18,000 homes in that time.
The technology relies on a closed-loop system: excess electricity compresses and liquefies CO₂, which is stored under pressure. When the energy is needed, the liquid CO₂ is warmed, vaporises, and drives a turbine to generate electricity. This adiabatic cycle delivers around 75 per cent round-trip efficiency according to the company’s Italian demonstrator, and can be built using readily available industrial equipment without relying on lithium or rare-earth minerals.
Plans include beginning construction in 2026 and commissioning by late 2027. The initiative falls under the U.S. Department of Energy’s long-duration energy storage programme, which awarded the project US$30 million from a US$325 million demonstration fund. Energy Dome has also attracted international support: the European Investment Bank and Breakthrough Energy Ventures backed its Sardinian project with €60 million, conditional on milestones being achieved.
Energy Dome first deployed a smaller-scale plant in Sardinia in 2022—a 2.5 MW/4 MWh system that continues to provide real-world data and validate the standardised design now planned for Wisconsin. Lessons learned in Italy are being transferred to the U.S. project to accelerate delivery.
Alliant Energy, together with WEC Energy Group and Madison Gas & Electric, lead the project. The goal is to enhance grid resilience and flexibility while reducing reliance on fossil fuel generation, especially near Alliant’s existing coal-fired Columbia Energy Centre.
With an estimated cost of around US$90 million, the project represents a major step toward diversifying storage technologies beyond lithium, offering longer-duration discharge at competitive cost. Energy Dome highlights that CO₂ batteries do not degrade like traditional lithium-ion systems, meaning less performance loss over time and no need for repowering.
This initiative marks the first deployment of its kind in North America and forms part of Alliant Energy’s broader plan to develop a balanced energy mix for reliable, affordable service. If successful, it may become a model for further installations across the U.S. and internationally, including a planned deployment in Karnataka, India.
Source: Energy Storage News
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