Long-Duration Energy Storage: Iron-Air Batteries Enter Commercial Deployment

Form Energy has begun commercial deployment of its iron-air battery technology, marking a pivotal moment for long-duration energy storage. The company's 100-hour storage systems use iron, water, and air — some of the most abundant and inexpensive materials on Earth — to store electricity at a fraction of the cost of lithium-ion batteries for multi-day storage applications.

The first commercial installation, a 10 MW / 1,000 MWh system in Minnesota, was commissioned by Great River Energy to provide multi-day backup during extended periods of low wind and solar generation. The system can discharge at full power for 100 hours, compared to the typical 4-hour duration of lithium-ion installations.

Form Energy reports that its iron-air technology achieves a cost below $20 per kilowatt-hour of storage capacity for long-duration applications, compared to $200+ per kWh for lithium-ion at similar durations. This dramatic cost advantage makes multi-day storage economically viable for the first time.

The implications for grid planning are significant. Utilities can now consider storage as a viable alternative to natural gas peaker plants for reliability during extended weather events. Several utilities including Xcel Energy, Georgia Power, and Southern California Edison have signed agreements with Form Energy for future installations.

The technology does have limitations. Iron-air batteries have lower round-trip efficiency (approximately 45%) compared to lithium-ion (85-90%), making them less suitable for short-duration applications where multiple daily cycles are needed. However, for seasonal storage and multi-day resilience, the cost advantage is compelling.