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New Iron-Air Battery Could Speed the Shift to Renewable Grid, Deep Decarbonization

A new chemistry for an iron-air-exchange battery that promises “multi-day storage” for electricity could be the breakthrough that will speed up the shift to an all-renewable grid, according to the battery’s developer, Somerville, Massachusetts-based Form Energy.

Form CEO Mateo Jaramillo said the “capacity of the Form battery to dispatch energy for 100 hours ‘puts it in a different category’ than the broad definition of long-duration storage, generally defined as systems with at least 10 hours of duration,” reports Utility Dive.

The new iron-air-exchange battery operates through a process called “reversible rusting”. As the battery discharges, it “breathes in” oxygen and converts metallic iron pellets to rust. When electricity is applied to the battery during charging, the current converts the rust back to iron as the battery “breathes out” oxygen, Form explains.

The company kept the details of its debut product under wraps until its latest announcement last month. But now, the start-up says the battery is a “first step to tackling the biggest barrier to deep decarbonization: making renewable energy available when and where it’s needed, even during multiple days of extreme weather, grid outages, or periods of low renewable generation.”

Currently, renewable energy meets a small portion of U.S. power demand, mostly because existing energy storage capacity prevents round-the-clock power supply, the Washington Post explains. If it can successfully store electricity for 100-plus hours, the iron-air-exchange battery can upend this dynamic and allow renewable energy to surge forward.

In their current design, the Form battery modules are about the size of a washing machine. “Each of these modules is filled with a water-based, non-flammable electrolyte, similar to the electrolyte used in AA batteries,” the company writes. Immersed in the solution are stacks of 10 to 20 cells with iron and air electrodes to enable charging and discharging. Modules are grouped by the thousands to create megawatt-scale power blocks housed in environmentally protected enclosures. 

Depending on the density of the modules, a one-acre-sized power block can yield roughly 1 to 3 MW and store energy at a rate of $20 per kilowatt hour, says Form—less than one-tenth the cost of the lithium-ion batteries that currently dominate the market. 

Form’s breakthrough is a critical advance toward a renewable energy “grid of the future,” veteran climate journalist David Roberts writes in his Volts newsletter. “In terms of its function on the grid, the best way to think of Form’s battery is not as storage, but as the equivalent of a carbon-free natural gas plant,” he says. “Rather than methane, it runs on renewable energy as fuel, but from the grid’s perspective, it provides basically the same service, which is reliable, dispatchable generation that can run for 100 hours or more when needed.”

But Form still needs to carve out a market within the grid. Natural gas is still considered an affordable electricity source, and will continue to be cheap until policy intervenes. For now, Jaramillo’s optimism for long-duration storage markets depends on regional variations in the carbon transition.

“There’s no time at which the country will uniformly be at 80% renewables,” he said.

For now, the increasing favourability for renewables among investors may play to Form’s advantage. Utilities, as well, are becoming wary of traditional energy supplies and may be inclined to pursue renewables as they get cheaper. Pressure for decarbonization in some states could also tip the scales away from gas.

“They don’t want to build a natural gas plant with a 30-year rated lifespan only to face a carbon price or a clean electricity standard (CES) forcing its retirement in 10 or 20 [years],” writes Roberts. 

Form does not plan to fully enter the market until 2025, but has in the meantime secured $200 million in new funding from steelmaker ArcelorMittal, Canary Media reports. The company is set to install its first project for Minnesota Utility Great River Energy in 2023.