Sherco Iron Air Battery Project

Executive Overview

The Sherco Iron Air Battery Project is a 10 MW / 1,000 MWh iron-air battery storage system being deployed by Form Energy at Xcel Energy's Sherburne County Generating Station (Sherco) site in Becker, Minnesota, under a 10-year agreement with Xcel's Minnesota utility, Northern States Power (NSP). The system is capable of delivering rated power continuously for 100 hours, and is co-located with up to 710 MW of solar capacity being developed on the same retiring coal plant site. Minnesota regulators approved the project, and construction commenced in Q3 2024 with operations expected by end of 2025. The project is eligible for a 30% investment tax credit, a 10% bonus credit for siting in an energy community, and potential DOE grant support.

How It Works & Differentiation

Form Energy's iron-air battery uses a reversible rusting process: iron anodes react with oxygen from air during discharge and are electrochemically restored during charging, using a water-based, non-flammable aqueous electrolyte with no rare earth metals. At 100 hours of discharge duration, the system is designed to cover multi-day periods of low renewable generation — polar vortexes, heat domes, or extended cloudy and calm weather — that fall well outside the operating range of the four-hour lithium-ion systems currently dominant in the market. The system is engineered to operate in Minnesota's extreme temperature range, and Form Energy manufactures at its Weirton, West Virginia facility, which is expected to reach 500 MW of annual production capacity in 2028.

Commercialization & Traction

The Minnesota Public Utilities Commission imposed a cost cap on the project as a condition of approval, providing ratepayer protection while enabling the technology demonstration. The project is part of Xcel's broader transition of the 1,879 MW Sherco coal site, which is retiring in phases through 2030 and being replaced with solar and storage. Xcel is simultaneously developing a similar Form Energy system at its Comanche coal plant in Pueblo, Colorado, indicating internal confidence in the technology following Sherco's approval. The project is also referenced in Xcel's regulatory filings as a direct precedent supporting the much larger 300 MW / 30 GWh Pine Island system announced in early 2026.

Scalability & Strategic Context

The Sherco project is the second Form Energy commercial deployment after the 1.5 MW Cambridge pilot, and the first at 10 MW scale with a major investor-owned utility. Its 10-year operational term will generate the performance, cost, and dispatch data needed to inform NSP's and other utilities' subsequent long-duration storage procurement decisions. The co-location with 460–710 MW of solar directly tests the operational pairing of multi-day storage with large-scale variable generation, a configuration relevant to virtually every state pursuing high renewable penetration. U.S. DOE modelling cited during the regulatory process projects a national need for 225 to 460 GW of long-duration storage by 2060, representing $330 billion in capital spending — underscoring the significance of early deployments like Sherco as commercial proof points.