Rust-powered battery to deliver 100-hour backup in California

Form Energy is set to deploy a novel iron-air battery system near a Pacific Gas & Electric substation in Mendocino County, California, by early 2026. Backed by a $30 million grant from the California Energy Commission, this 1.5-megawatt, 150 megawatt-hour battery can power approximately 1,500 homes for four days, offering a significant leap in long-duration energy storage. Unlike conventional lithium-ion batteries that rely on ion movement, this system generates electricity through a reversible rusting process, oxidizing iron to produce power and then reversing the reaction during charging. Although iron-air batteries have a lower round-trip efficiency (~60%) compared to lithium-ion (>90%), they provide advantages such as reduced fire risk, less degradation, and the ability to deliver continuous power for up to 100 hours—over 20 times longer than typical lithium-ion systems. California currently depends heavily on lithium-ion batteries for its 16 gigawatts of storage capacity, but