Boston-based technology company Form Energy, Inc. has risen to the challenge of climate change by developing a new category of multi-day, cost-effective energy storage systems. It recently revealed the battery chemistry of its first commercial product while announcing a $200 million Series D financing round led by innovation fund ArcelorMittal’s XCarb™.
Greg Ludkovsky, the Global Head of Research and Development at ArcelorMittal, said:
Form Energy is at the leading edge of developments in the long-duration, grid-scale battery storage space. The multi-day energy storage technology they have developed holds exciting potential to overcome intermittent supply issues of renewable energy. They are exactly the kind of ambitious and innovative company we are seeking to invest in through our XCarb™ innovation fund.
This could be an excellent option for managing the multi-day variable of renewable energy without sacrificing energy reliability or affordability. Because wind and solar have become the lowest marginal cost sources of electricity in most places, but there’s still the issue of reliability – sometimes the wind isn’t blowing, or the sun isn’t shining enough to meet electricity demands, and sometimes it’s too much.
Form Energy is building a commercial-scale pilot of its new grid-scale battery. The remarkable yet simple iron-air batteries store as many as 100 hours of energy at one-tenth the cost of a lithium battery farm. If this project proves successful, systems like it could help us transition away from heavily polluting energy sources like coal. They would serve as the buffer facilities to store and release renewable energy as required cheaply.
Rechargeable iron-air batteries can be mass deployed at a meager cost, and they’re made of widespread materials (no rare-earth metals). Iron is one of the safest and most abundant minerals on Earth, so it’s cheap. Plus, the battery can be used over a multi-day period continuously, ensuring a secure, reliable, and fully renewable electric grid year-round.
Mateo Jaramillo, Form Energy’s Co-founder and CEO, said:
We conducted a broad review of available technologies and have reinvented the iron-air battery to optimize it for multi-day energy storage for the electric grid. 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.

Iron-air batteries work by initiating and reversing the rusting process. During the discharge cycle, metallic iron combines with oxygen to release energy and rust. The power is stored during the charge cycle, turning rust back into metallic iron by releasing its oxygen.
The company recommends using iron-air batteries alongside big lithium batteries because they offer a slower-acting energy solution. In contrast, lithium batteries are better for fast discharge events such as load spike smoothing.
Another big selling point of Form Energy’s system is its recyclability – when it comes to the end of its life cycle, the materials are highly recyclable.