Form Energy, the billionaire-backed start-up that claimed to have developed an innovative low-cost 150-hour battery, has finally revealed its battery chemistry after more than a year of high-profile secrecy.

The Boston-based company says its first commercial product is a “rechargeable iron-air battery capable of delivering electricity for 100 hours at system costs competitive with conventional power plants and at less than 1/10th the cost of lithium-ion”.

A cheap, safe battery able to store energy for long periods of time is the holy grail of the renewable energy sector, as it would be capable of removing the issue of wind and solar’s variability at a low cost.

With French financial advisers Lazard putting the levelised cost of storage (LCOS) of large-scale lithium-ion batteries at $132-245/MWh in its industry-standard annual report, Form’s battery — at a tenth of that cost — would be the cheapest type of energy storage available by some distance.

“This battery can be used continuously over a multi-day period and will enable a reliable, secure, and fully renewable electric grid year-round,” said Form Energy.

Or as Greg Lydkovsky, global head of R&D at steel giant ArcelorMittal — Form Energy’s latest investor — put it, the technology “holds exciting potential to overcome the intermittent supply of renewable energy”.

Form Energy president and chief operating officer Ted Wiley said: “We’ve completed the science, what’s left to do is scale up from lab-scale prototypes to grid-scale power plants.

“[At full production], the modules will produce electricity for one-tenth the cost of any technology available today for grid storage.”

The battery is said to work through “reversible oxidation of iron”. In discharge mode, thousands of tiny iron pellets are exposed to the air, which makes them rust (ie, the iron turning to iron oxide). When the system is charged with an electric current, the oxygen in the rust is removed, and it reverts back to iron.

Wiley said that a 300MW “pilot” project for Minnesota-based Great River Energy will be commissioned in 2023.

That project, announced in May last year, was originally due to be a 1MW/150MWh demonstration plant capable of outputting 1MW for 150 hours straight.

The air battery is a fairly recent invention that has been the subject of research for at least the past decade.

Canadian start-up Zinc8, was the first to break cover with a commercial product in 2019, announcing that it would be deploying a zinc-air battery system with the technological capability of providing 100-plus hours of storage.

And Oregon-based ESS, which claims to have a market value of $1.1bn, already sells a flow battery that uses iron as its primary ingredient.

Both ESS and Form Energy are part-owned by Breakthrough Energy Ventures, the venture capital company backed by several high-profile billionaires, including Bill Gates and Jeff Bezos.

Current Form Energy investors also include Italian oil giant Eni and Macquarie Capital, while ArcelorMittal revealed a $25m investment in the company on Thursday.

Form has also announced a Series D financing round that aims to raise $200m.(Copyright)