Iron-Air Multi-Day Battery

Overview

A grid storage system built from modules the size of a washing machine, each filled with iron electrodes and a water-based alkaline electrolyte. Discharging oxidises the iron with oxygen drawn from the air; charging reverses the reaction and turns the rust back into metallic iron. Because the active materials are iron, water and air, the cost per kilowatt-hour is a small fraction of lithium-ion's, which is what makes 100-hour duration economic. Systems are assembled into multi-acre installations sized from megawatts to hundreds of megawatts.

In production at Form Factory 1; first commercial system being delivered to Great River Energy in Minnesota, with the 75+ GWh order book delivering from 2027