Battery Company Claims Astonishingly Cheap Long-Term Storage Capacity


Stephen Luntz

Freelance Writer

clockJul 29 2021, 11:25 UTC
form energy

Schematic of a proposed Form energy iron-air battery complex to back up wind and solar farms. The technology requires a lot of space, and can only release its electricity slowly, but claims to offer long-term storage at an astonishingly cheap cost. Image Credit: Form Energy.

Battery technology start-up Form Energy has claimed they have solved the technical problems involved in producing an iron-air battery and can do it at a price far below anything else on the market. Battery development is a field that seems to be particularly prone to over-hyped, and just outright false, claims and the basis of Form's confidence remains to be independently verified. However, they've reached an agreement to demonstrate their product at scale within two years, and have shown enough to potential investors to announce $200 million in new funding


Iron-air batteries are remarkably simple compared to the complex chemistry other batteries use. They rely on the oxidation of iron, a process so familiar we call it rust, and its reversal. Extracting electricity from the process in an efficient manner is much more challenging, but few alternative technologies use such cheap ingredients – iron, water, and air. Electricity is released as iron pellets oxidize, then the input of energy reverses the reaction.

Form Energy claim on their website their technology can store a megawatt-hour of electricity for a price a tenth that of the cheapest lithium-ion batteries. Recently, Tesla made the prices for its large-scale storage systems public for the first time. Depending on the size and location of the system these are around $300-400/kWh capacity. Renewable energy advocates have long used $100/KWh as an approximate benchmark for the point where storage will beat fossil fuels on price, so if Form's claim is true, they're smashing that target.

The technology has some limitations, however. Rust is slow, so iron-air batteries can't charge or discharge anything like as fast as those currently on the market, and therefore can't compete with existing technologies for many purposes. However, at the claimed price they could do something different – offer multi-day storage to keep things running when several cloudy/windless days in a row deplete most other options.

“With this technology, we are tackling the biggest barrier to deep decarbonization: making renewable energy available when and where it’s needed, even during multiple days of extreme weather or grid outages,” said Form Energy CEO Mateo Jaramillo in a statement.


Iron-air showed enough promise that from the start Form Energy attracted investments from Bill Gates and Jeff Bezos. Now, that has been supplemented with $25 million from steel manufacturer ArcelorMittal’s XCarb™ innovation fund, as part of a $200 million financing round.

Besides cost, Form also promote their batteries' safety, since they contain no toxic elements and the electrolyte isn't flammable. Their energy density is low, and likely to stay that way, so there's no chance this will become the favored battery technology for transport uses. In fact, Form Energy's batteries require so much room for even a modest amount of energy storage they will probably never be competitive with lithium-ion batteries to back up residential solar panels. The technology may also struggle to establish itself in places where land is so scarce floating solar cells are becoming dominant

However, if Form's claims stand up they will fill one of the major gaps in the mix of storage types required to run a 100 percent renewable electricity grid.

 This Week in IFLScience

Receive our biggest science stories to your inbox weekly!

  • energy,

  • batteries,

  • Renewable Energy,

  • iron-air battery