Iron-air battery technology holds the promise of becoming the lowest cost energy storage – less than one-tenth of that of lithium-ion.
The technology being advanced by the Massachusetts-based startup Form Energy in essence involves the rusting and de-rusting of iron to deliver energy storage in the multi-day range up to about 100 hours.
In the discharge process, iron is rusted when exposed to oxygen from the air. Then with the application of an electrical current in the charging process, the rust is converted back to iron as the oxygen is removed.
The technology has long been known but is yet to be commercialised and its promise is in the abundance and availability of iron, which the Form Energy founders believe can enable it to be cost-competitive with conventional power plants.
“We conducted a broad review of available technologies and have reinvented the iron-air battery to optimise it for multi-day energy storage for the electric grid,” says Mateo Jaramillo, CEO and co-founder of Form Energy, who was previously involved in Tesla’s energy storage business.
“With this technology, we are tackling the biggest barrier to deep decarbonisation: making renewable energy available when and where it’s needed, even during multiple days of extreme weather or grid outages.”
To date, Form Energy has been operating below the radar with the technology but has nevertheless attracted the interest of several high-level investors including the Gates and co Breakthrough Energy Ventures, Energy Impact Partners and Macquarie Capital among others.
The latest $200 million Series D financing round is led by ArcelorMittal’s XCarb innovation fund. Form Energy and ArcelorMittal are collaborating on the development of iron materials which ArcelorMittal would then supply for the battery systems.
Form Energy intends to source the iron domestically and to manufacture the battery systems near where they will be sited.
The first project with a 1MW/250MWh battery is due to pilot in Cambridge, Minnesota with Great River Energy.
The Form Energy battery is about the size of a washing machine and is claimed to be scalable into the hundreds and even thousands in modular megawatt-scale power blocks. For scale, in the least dense configuration, a 1MW system requires about 0.4ha of land, but higher density configurations can achieve over 3MW in the same area.
The multi-day storage opportunity is attracting growing interest with various novel technologies in development and is set to become increasingly important and competitive with their maturity and the greater penetration of renewables.