This multi-day storage battery can help us decarbonize

One of the challenges in totally decarbonizing our economy is that solar and wind energy is variable. Wind farms produce electricity when it’s breezy; solar panels generate energy during the day, but most electricity generation relies on coal and natural gas as backup when the wind isn’t blowing and the sun isn’t shining. Because lithium-ion batteries are too expensive to solve these problems, the recent unveiling of an aqueous air battery system that uses safe, cheap and abundant materials is a huge breakthrough.

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It won’t replace lithium batteries in your smartphone, and it’s not intended to. Instead,  the rechargeable Iron-Air batteries are a “cost-effective, multi-day energy storage system that will enable a reliable and fully-renewable electric grid year-round”, moving us much closer to being able to fully decarbonize the electricity grid by using renewable sources.

Boston startup Form Energy describes the battery as “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. Made from iron, one of the safest, cheapest, and most abundant minerals on Earth, this front-of-the-meter battery can be used continuously over a multi-day period and will enable a reliable, secure, and fully renewable electric grid year-round.”

Mateo Jaramillo, the CEO and co-founder of Form Energy, went to work at Tesla when it had only 300 employees (now it has over 30,000). After leaving Tesla, he created Form in 2017 and set out to create a battery that was much cheaper than lithium ion and offered long term storage – a question not many people were thinking about then, because they thought it wouldn’t be necessary for a long time. But as renewable resources supply ever-greater portions of energy on the electric grid, long-term storage is becoming vitally important.

Over a quiet four-year period, the team studied sulphur and iron – and iron turned out to be the best solution. An existing technology that dates back to the 1970s or so, it was just waiting to be brought into the modern age and applied to energy. Since it was founded in 2017 by merging two companies working on the same goal, Form Energy has raised more than $50 million in funding from investors including MIT and Bill Gates’s Breakthrough Energy Ventures.

“A few years later, a lot of hard work, some fantastic breaks going our way in the lab, but also the market moving very, very quickly to decarbonize the electricity sector– and we find ourselves today with a solution that has a very clear path to get into the market,” says Jaramillo. “This is a kind of battery that would complement the kinds of energy storage that are being deployed today on the grid, like lithium ion. And it’s a combination of those two things– the lithium ion that’s out there today, plus a lot more of that, and the kind of multiday storage that we’re developing that will deliver a low-cost, reliable, renewable electric system.”

Form Energy is working jointly with ArcelorMittal, the world’s largest steelmaker, which says that Form’s multi-day energy storage technology ‘holds exciting potential to overcome the issue of intermittent supply of renewable energy.” Says Greg Ludkovsky, its global head of research and development: “They are exactly the kind of ambitious and innovative company we are seeking to invest in through our XCarb™ innovation fund.”

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Form Energy’s first commercial project is with Great River Energy, a not-for-profit wholesale electric power cooperative that provides electricity to 28 member-owner distribution cooperatives and serves 700,000 families, farms and businesses in Minnesota.

In announcing the pilot project at the end of June 2020, Great River Energy said that “commercially viable long-duration storage could increase reliability by ensuring that the power generated by renewable energy is available at all hours to serve our membership.” This long-duration storage would be particularly important during extreme weather conditions lasting several days, said Jon Brekke, vice president and chief power supply officer at Great River Energy. It also provides an excellent hedge against volatile energy prices.

Great River Energy plans to eliminate coal from its power supply portfolio and add 1,100 megawatts (MWs) of wind energy by 2023. Working with Form Energy, Great River Energy is developing a long-duration energy storage pilot project on a one-acre site adjacent to its natural gas peaking plant in Cambridge, Minnesota. “The Cambridge Energy Storage Project will be a 1 MW, grid-connected storage system capable of delivering its rated power continuously for 150 hours, far longer than the four-hour usage period available from utility-scale lithium-ion batteries today. The battery is expected to be complete by the end of 2023.”

The long-duration storage will help maintain reliability during extreme conditions, such as a heat wave or polar vortex, says Great River Energy . Low-cost, flexible energy storage solutions can also provide more capability to fill gaps in wind and solar energy production that would otherwise require starting a power plant.

This fascinating video explains how the battery system works.

One of the challenges in selling the idea of long-term battery storage has been convincing utilities that these solutions are useful now rather than waiting till a larger percentage of our power is being generated renewably. Form Energy has developed a grid-modelling toolkit to help utilities plan for long-term investment decisions such as decarbonizing grids.

Form’s grid modeling toolkit, Formware™, can “optimize the investments and operations of any portfolio of technologies over multi-year, hourly resolution data sets to capture real-world weather variability, resulting in more reliable and cost effective designs for renewables-driven power systems.”


New Iron-Air Battery outperforms best Lithium Ion tech. Cheap. Abundant. Non-toxic & Carbon Free. Just Have A Think, Aug. 1, 2021

Multi-day iron-air batteries reach commercialization. P-V Magazine, Aug. 5, 2021

Announces Series D with Leading Strategic Partner, Accelerating Pathway to Commercialization of First Energy Storage Product. Form Energy press release, Jul 22, 2021

Long-duration battery project in the works. Great River Energy, Jun. 17, 2020


Long-lasting grid battery. MIT Technology Review, Feb. 23, 2022.

These plastic batteries could help store renewable energy on the grid. MIT Technology Review, Apr. 13, 2022

Form Energy wins $450M to rust iron for multiday energy storage. Canary Media, Oct. 4, 2022.

West Virginia Governor Jim Justice announces Form Energy will site first American battery manufacturing plant in Weirton, creating hundreds of jobs. Dec. 22, 2022.

What’s next for batteries. MIT Technology Review, Jan. 4, 2023.