Form Energy launches new battery technology that relies on iron rust

A field of shipping container–sized modules are set to be installed in coming months next to a Mendocino County electrical substation as part of a demonstration of a new type of battery technology intended to supply power to the grid over days — not hours — and with less chance of fires.

Form Energy’s system being installed next to the Pacific Gas & Electric Co. substation on East Road in Redwood Valley is designed to produce 1.5 megawatts hourly (enough for up to 1,500 homes) for up to 100 hours, or 150 megawatt-hours, a measure of battery capacity. The company received a $30 million grant from the California Energy Commission in 2023 to build a 5 megawatt battery there.

The smaller size of the system was chosen based on the charging capacity of the substation, spokesperson Sarah Bray said

Standard battery energy storage systems (BESS) currently on the California grid now are based on lithium-ion technology and commonly provide power for four hours. Form Energy’s battery uses iron-air technology and can discharge over four days.

“The battery operates on the principle of reversible rusting: when discharging, metallic iron in our battery reacts with oxygen from the air and water from the electrolyte to form iron hydroxide — essentially, rust,” Bray said. The process is also called reversible rusting.

Meaning, when iron rusts, the chemical reaction releases energy.

“When charging, excess electricity from the electric grid flows back into the battery, reversing that reaction: oxygen and water separate from the iron, and the iron returns to its original metallic state. The reversible rusting process can be repeated over and over, delivering electricity to the grid when and where it is needed most.”

The battery modules are being made at Form Energy’s 550,000-square-foot factory on the site of a now-shuttered West Virginia steel mill. The Mendocino County system is set to be operational next year.

The project is part of a broader strategy to diversify California’s energy storage portfolio beyond lithium-ion batteries to meet goals of grid reliability and carbon-free electricity by 2045, according to Michael Gravely, a senior electrical engineer and leader of a team integrating new energy technologies at the commission.

The state currently has 16 gigawatts of battery power installed, with 99% of that being lithium-ion technology. However, Gravely emphasized the need to explore alternative technologies that offer longer lifespans, discharge power for more hours and potentially lower costs.

Other projects the commission is supporting in its Long-Duration Storage Program, each with different technologies, are a 70 megawatt-hour system for the Viejas Tribe of Kumeyaay Indians land in San Diego County, 15 megawatt-hour system to support the Paskenta Band of the Nomlaki Indians in Corning, 3.6 megawatt-hour iron-flow battery for Sacramento Municipal Utility District and a 48 megawatt-hour installation at the Pendleton Marine Corps Station.

“We believe some of these long-duration storage will be able to provide eight to 12 hours of storage at a price that’s substantially cheaper than lithium ion,” he said.

The commission aims to have 50,000 megawatts (50 gigawatts) of storage installed by 2045, with at least 10% expected to be long-duration systems. These technologies offer promising advantages, including the ability to operate for 30 years with little degradation and potentially eliminate the need for natural gas power plants to make up for daily or seasonal times when solar and wind power output drops.

The target cost per kilowatt-hour for alternative storage technologies is $20 to $40 per kilowatt-hour, compared with $200 to $250 for current lithium-ion systems and $300 to $500 now for long-duration systems that are still being developed, Gravely said. But in the past three to four years, the cost of alternative systems have come down 20% to 40%.

The iron-air batteries tend to have lower efficiency in discharging as much electricity as was put in during the charging process — in the 40%–50% range at production scale in the next decade, compared with upwards of 90% initially for lithium ion — but the iron-air technology’s longer discharge, less degradation and low potential for fires from overheating (called thermal runaway) are pluses, he said.

“They are showing the fact that they can produce something at a more competitive price,” Gravely said. “Given time and as they get smarter, they can manufacture them cheaper, automate it, reduce the price and be competitive or cheaper than lithium ion.”

Jeff Quackenbush covers wine, construction and real estate. Reach him at [email protected] or 707-521-4256.