Massachusetts-based energy storage innovator Form Energy is set to construct an 85 MW/8.5 GWh iron-air battery system at a former paper mill in rural Maine. This cutting-edge project, which will be the largest long-duration battery storage plant globally by capacity upon completion, promises to deliver power for up to 100 hours—far surpassing the typical four-hour duration of conventional lithium-ion batteries.
Form Energy’s new facility will be a significant departure from other major U.S. projects, such as California’s Edwards & Sanborn with its 875 MW solar and 3.2 GWh battery storage, and Nevada’s Gemini project, featuring 690 MW of solar combined with a 380 MW, 1.4 GWh battery system. Unlike these short-duration systems, Form Energy’s iron-air battery utilizes a unique technology capable of extended energy storage.
Innovative Iron-Air Technology
The iron-air battery operates on a reversible rusting process. During charging, an electric current transforms rust into metallic iron, while discharging involves the battery absorbing oxygen from the air and reverting the iron back to rust. This process relies on iron, one of the planet’s most abundant metals, rather than the rare materials like lithium or cobalt used in conventional batteries.
Each unit comprises a stack of 50 three-foot-tall cells with a water-based electrolyte and iron-air electrodes. These modules are housed in protective enclosures, organized into scalable MW power blocks.
Expanding Capabilities and Production
Form Energy is also advancing its commercial footprint with a 1.5 MW/150 MWh system under development in Minnesota and a collaboration with utility Xcel Energy on a DOE-funded initiative to deploy 10 MW storage systems at retiring coal plants in Minnesota and Colorado. To meet high demand, Form Energy is constructing a high-volume manufacturing facility in West Virginia, with an annual production capacity of 500 MW.
Addressing New England’s Energy Storage Needs
The Maine project is part of a larger strategy to enhance electric reliability across New England’s six-state network. The Power Up New England initiative, led by Massachusetts and involving partners such as National Grid and Eversource, has recently secured $2.2 billion in funding from the Bipartisan Infrastructure Law. This effort aims to address the growing need for reliable energy storage as the region transitions away from fossil fuels.
Historically, New England has depended on two large-scale pumped-hydro storage plants for about 2 GW of on-demand capacity. As renewable energy sources like wind and solar become more prevalent, additional dispatchable storage solutions are required to manage grid volatility. Currently, energy storage projects make up nearly half of the interconnection requests in ISO New England’s queue.
The region’s solar PV capacity exceeds 7 GW and is expected to reach 13.4 GW by 2033, with significant offshore wind development also anticipated. Massachusetts aims to acquire 5.6 GW of offshore wind by 2027, Connecticut plans for 2 GW by 2030, and Maine targets 3 GW by 2040.
Form Energy’s research suggests that 23 GW of multi-day storage could mitigate the need for 149 GW of new solar and short-duration resources by 2050. To ensure winter reliability, the region will need 4.5 GW/300 GWh of storage reserves by 2030. A recent whitepaper from Form Energy highlights that a combination of 2.9 GW of multi-day storage and 1.6 GW of short-duration storage represents the most cost-effective solution for maintaining winter reliability.
The Maine installation benefits from a $389 million DOE grant awarded to the Power Up New England initiative, which supports new transmission and storage infrastructure across Massachusetts, Maine, New Hampshire, Connecticut, Rhode Island, and Vermont.