Poojan Thakrar, MJLST Staffer
In coming years, both Great River Energy and Xcel Energy are installing pilot projects of a new iron-air battery technology. Both utilities are working with Boston-based company Form Energy. Great River Energy, which is Minnesota’s second-largest energy provider, plans to install a 1.5-megawatt battery next to its natural gas plant in Cambridge, MN. Xcel Energy, the state’s largest energy provider, will deploy a 10-megawatt battery in Becker, MN and Pueblo, CO. The batteries can store energy for up to 100 hours, which the utilities emphasize as crucial due to their ability to provide power during multi-day blizzards. The projects may be online as early as 2025, Form Energy says.
The greater backdrop for these battery projects is Minnesota’s new carbon-free targets. Earlier this year, with new control of both chambers, Minnesota Democrats passed a bill mandating 100 percent carbon-free energy by 2040. Large utility-scale batteries such as the ones proposed by Great River Energy and Xcel can play an important role in that transition by mitigating intermittency concerns often associated with renewables.
This technology may be uniquely suited for a future in which utilities rely more heavily on batteries. While this technology is less energy-dense than traditional lithium-ion batteries, the iron used at the heart of the battery is more abundant than lithium.  This allows utilities to sidestep many of the concerns associated with lithium and other minerals required in traditional batteries. Iron-air batteries also tend to be heavier and larger than lithium-ion batteries that store equivalent energy. For batteries in phones, laptops, and cars, weight and volume are important features to keep in mind. However, this new technology could help accelerate uptake of large utility-scale batteries, where weight and volume are of less concern.
If your high school chemistry is rust-y, take a look at this graphic by Form Energy. When discharging electricity, the battery ‘inhales’ oxygen from the air and converts pure iron into rust. This allows electrons to flow, as seen on the right side of the graphic. As the battery is charged, the rust ‘exhales’ oxygen and converts back to iron. The battery relies on this reversible rust cycle to ultimately store its electricity. Form Energy claims that its battery can store energy at one-tenth the cost of lithium-ion batteries.
Xcel has recently filed a petition with the Minnesota Public Utilities Commission (MPUC), which has jurisdiction over investor-owned utilities such as Xcel. The March 6th petition seeks to recover the cost of the pilot battery project. This request was made pursuant to Minnesota statute 216B.16, subd. 7e, which allows a utility to recover costs associated with energy storage system pilot projects.
In addition, the pilot project qualifies for a standard 30 percent investment tax credit (ITC) as well as a 10 percent bonus under the federal Inflation Reduction Act because Becker, MN is an “energy community.” An “energy community” is an area that formerly had a coal mine or coal-fired power plant that has since closed. Becker is home to the Sherco coal-fired power plant, which has been an important part of that city’s economy for decades. The pilot may also receive an additional 10 percent bonus through the IRA because of the battery’s domestic materials. Any cost recovery through a rider would only be for costs beyond applicable tax grants and potential future grant awards. The MPUC has opened a comment period until April 21st, 2023. The issue at hand is: should the Commission approve the Long Duration Energy Storage System Pilot proposed by Xcel Energy in its March 6, 2023 petition? 
As a member-owned cooperative, Great River Energy does not need approval from the MPUC to recover the price of the battery project through its rates.
Ultimately, this is a bet on an innovative technology by two of the largest electricity providers in the state. If approved by the MPUC, ratepayers will foot the bill for this new technology. However, new technology and large investment projects are crucial for a cleaner and more resilient energy future.
 See Kirsti Marohn, ‘Rusty’ batteries could hold key to Minnesota’s carbon-free power future, MPR News (Feb. 10, 2023), https://www.mprnews.org/story/2023/02/10/rusty-batteries-could-hold-key-to-carbonfree-power-future. See alsoRyan Kennedy, Retired coal sites to host multi-day iron-air batteries, PV Magazine (Jan. 26, 2023) https://pv-magazine-usa.com/2023/01/26/retired-coal-sites-to-host-multi-day-iron-air-batteries/.
 Andy Colthorpe, US utility Xcel to put Form Energy’s 100-hour iron-air battery at retiring coal power plant sites, Energy Storage News (Jan. 27, 2023), https://www.energy-storage.news/us-utility-xcel-to-put-form-energys-100-hour-iron-air-battery-at-retiring-coal-power-plant-sites/.
 Dana Ferguson, Walz signs carbon-free energy bill, prompting threat of lawsuit, MPR News (Feb. 7, 2023), https://www.mprnews.org/story/2023/02/07/walz-signs-carbonfree-energy-bill-prompting-threat-of-lawsuit.
 Form Energy Partners with Xcel Energy on Two Multi-day Energy Storage Projects, BusinessWire (Jan. 26, 2023), https://www.businesswire.com/news/home/20230126005202/en/Form-Energy-Partners-with-Xcel-Energy-on-Two-Multi-day-Energy-Storage-Projects
See Amit Katwala, The Spiralling Environmental Cost of Our Lithium Battery Addiction, Wired UK (May 8, 2018), https://www.wired.co.uk/article/lithium-batteries-environment-impact/. See also The Daily, The Global Race to Mine the Metal of the Future, New York Times (Mar. 18, 2022), https://www.nytimes.com/2022/03/18/podcasts/the-daily/cobalt-climate-change.html
 https://formenergy.com/technology/battery-technology/ (last visited Apr. 6, 2023)
 Petition Long-Duration Energy Storage System Pilot Project at Sherco, page 4, Minnesota PUC (Mar 6, 2023),
 Notice of Comment Period, Minnesota PUC (Mar 21, 2023),