Commanche Generating Station Iron Air Battery

Executive Overview

The Comanche Generating Station Iron Air Battery is a 10 MW / 1,000 MWh Form Energy iron-air battery multi-day energy storage project being deployed at the retiring Comanche Generating Station coal plant site in Pueblo, Colorado, by Xcel Energy. It is one of two concurrent Form Energy / Xcel Energy multi-day storage projects announced simultaneously (the other being Sherburne County Generating Station, 10 MW / 1,000 MWh, Becker, Minnesota). Both projects were expected to come online as early as 2025 subject to regulatory approvals. Xcel Energy's stated carbon targets are 80% carbon reduction on its electric system by 2030 and carbon-free electricity by 2050. The Comanche site was selected because deploying storage at retiring coal plant locations repurposes existing grid infrastructure and workforce community assets.

How It Works & Differentiation

Form Energy's iron-air battery stores electricity through the reversible oxidation and reduction of metallic iron in an aqueous electrolyte, with oxygen taken from and returned to the ambient air. During discharge, iron oxidises to iron oxide (rust), releasing electrons; during charging, the process reverses. The system uses iron, water, and air — no lithium, cobalt, vanadium, or other critical minerals — and cannot catch fire or explode. At 1,000 MWh / 10 MW, the Comanche project provides 100 hours of continuous rated discharge — spanning multi-day weather events and grid stress periods that conventional 4-hour lithium-ion BESS cannot address. Extensive modelling using Form Energy's Formware™ tool validated the grid reliability benefit, including performance across severe winter storms and polar vortex events.

Commercialization & Traction

The Comanche and Sherburne County projects are Form Energy's first utility-scale deployments with a major investor-owned utility. Xcel Energy serves approximately 3.7 million electricity customers across eight states; its Minnesota and Colorado operations are among the largest wind-dependent grids in the United States, creating structural demand for multi-day storage to manage multi-day low-wind periods. The brownfield deployment at Comanche reduces permitting complexity, transmission interconnection cost, and community opposition risk compared to greenfield alternatives.

Scalability & Strategic Context

The Comanche project, alongside Sherburne (Minnesota) and the Lincoln iron-air battery (85 MW / 8,500 MWh, Maine), establishes Form Energy's commercial operating track record across three geographically and meteorologically distinct U.S. grid regions. The 100-hour duration at 1,000 MWh per site gives Xcel Energy a storage asset that operates over timeframes relevant to seasonal grid reliability — a function no commercially deployed battery technology could previously provide. The coal plant repurposing model is directly replicable at Xcel's other retiring coal assets and at retiring coal plants throughout the Midwest.