The startup Form Energy is banking on iron rather than lithium for grid-scale storage. It has devoted years to building a battery that employs rust as its active substance, and it is now shipping product on a large scale. The company’s iron-air batteries with a 100-hour duration are moving toward commercial use, while a $2 billion funding round is supporting the expansion.
The stated aim of the company is a straightforward one: reach $20 per kilowatt-hour, a level that would put its systems on par with natural gas peaker plants in cost terms. The question of whether it reaches that target still hangs in the balance, yet the initial indications of progress are promising.
The Rust Battery
The fundamental technology behind Form relies on a straightforward chemical reaction. As the battery discharges, oxygen from the surrounding air reacts with iron, converting it to rust and producing electrons. Charging works in reverse: an electric current reverts the rust back into iron. The company refers to this as “reversible rusting.”
The result is a battery that can store energy for 100 hours. That is far beyond the four to six hours typical of lithium-ion systems, which dominate the market today. Lithium-ion batteries are fast-charging, energy-dense, and portable, but they rely on expensive metals and are costly to scale.
Form’s iron-air approach skips the rare earths entirely. Iron is abundant, cheap, and widely available. The tradeoff is a larger physical footprint — Form’s batteries stack together in enclosures the size of shipping containers, requiring an acre for every two to three megawatts.
First Commercial Deployment
Over the past two years, Form has been making batteries at its West Virginia factory. The first actual use of these batteries is a 150 megawatt-hour system built for Minnesota electricity provider Great River Energy, which is expected to start working in 2027.
Several additional agreements with power suppliers have been concluded. Among these, the most significant involves Minnesota-based utility Xcel Energy. The arrangement pairs wind and solar generation with 30 gigawatt-hours of Form’s energy storage, which will supply a new Google data center. The project is scheduled to begin operating in stages from 2028 through 2031.
Once finished, the project would hold an energy storage capacity of 30 gigawatt-hours, which could make it the largest battery system in the world measured by how much electricity it can store.
Why Long Duration Matters
What’s being offered is simple: fresh solar and wind installations now produce power at a lower cost than fossil fuels in most locations. However, the amount they generate changes depending on the season, the hour of the day, and the weather. That’s where storage comes in, smoothing out those fluctuations for utilities.
The most rapidly expanding form of stored power is the lithium-ion battery, yet its capacity for continuous output is confined to four to six hours. This duration suffices for smoothing demand peaks and maintaining grid frequency, but it fails to remedy supply and consumption mismatches that span multiple days. Such gaps arise when temperatures soar, when cold snaps strike, or when prolonged periods bring scant sunshine or wind.
The batteries from Form are built to bridge stretches of several days. They hold their charge through long periods of inactivity without losing capacity, a trait that suits seasonal storage needs well. The firm aims to bring prices down to $20 per kilowatt-hour, matching what natural gas costs.
The firm refused to disclose how much its battery systems currently cost. The $20 goal has not been confirmed independently, yet it stands as the declared aim.
The Data Center Angle
The Xcel-Google partnership joins wind and solar power with cloud computing. Data centers rank among the largest users of electricity, and their demand for it has risen as artificial intelligence tasks swell. Wind and solar generation paired with long-duration storage is intended to demonstrate that renewables can handle heavy loads without leaning on natural gas peakers.
Cheap energy storage could help renewables meet more of this AI-driven growth in electricity demand. A data center powered by wind and solar, backed by Form’s batteries, would be a showcase for that idea. The project is expected to come online in phases between 2028 and 2031.
Scaling the Factory
To address its production backlog, Form is adding new equipment to its factory to increase manufacturing capacity. The company disclosed fresh funding in August, which, combined with West Virginia state and US federal grants, has pushed its total money raised to over $2 billion.
A major investment signals faith in the enterprise, yet the firm must show it can meet its commitments. Right now, its output stands at 2 gigawatt-hours of storage annually, a modest share of the 80 gigawatt-hours secured through commercial arrangements.
Whether the effort succeeds or fails will depend on whether the factory can scale up. The company must prove that it can take its prototype and turn it into a working line capable of producing large volumes while keeping both quality and reliability intact.
The Physical Footprint
The batteries used by Form are far from modest in size. Each enclosure measures the size of a shipping container, and the company’s own estimate puts the space requirement at an acre for every two to three megawatts. This suggests that its installation for Google would cover the equivalent of at least 75 football fields.
The size of the space involved is considerable. For those building power lines and data centers, the sheer scale of the project demands serious thought. Yet the people pushing this technology insist the cost is justified — iron costs less, and the battery life spans exceed what lithium-ion systems can offer.
Competitors and Challenges
While the market for storing power over long periods remains young, Form’s iron-air system competes against a host of other methods. Those include pumped hydropower, compressed gas, fuel cells, gravitational systems, and flow batteries that hold energy within liquids.
Long periods of inactivity are common for multiday battery systems because their large upfront costs mean they are rarely used. That difficulty in making the business case work has been a persistent issue. Form’s 100-hour runtime does help address it, though it does not solve the problem entirely.
Money from data center builders might give the company a big push forward. The arrangement with Google proves that hyperscalers are ready to back fresh storage methods. What remains uncertain is whether the firm can actually deliver those technologies on a large enough scale to matter.
The Path Forward
The path forward for Form is straightforward: it must complete its first commercial project, increase factory production, and begin working through the backlog. Money has been secured, and the agreements have been made.
The coming years will put the technology’s scalability to the test. The 30 gigawatt-hour Google project stands as the real trial. Should it come online on time and deliver as promised, Form will have a solid argument for wider acceptance.
Founded in 2017, the company calls Somerville, Massachusetts home and has drawn in excess of $2 billion in funding, with state and federal grants among its sources.
Key Facts Box
- Company: Form Energy
- Founded: 2017
- Headquarters: Somerville, Massachusetts, US
- Battery technology: Iron-air, reversible rusting
- Run time: 100 hours
- First commercial deployment: 150 megawatt-hours for Great River Energy, online 2027
- Largest project: 30 gigawatt-hours for Xcel Energy/Google, online 2028–2031
- Current production: 2 gigawatt-hours per year
- Backlog: 80 gigawatt-hours committed
- Funding raised: More than $2 billion
- Goal: Reach $20 per kilowatt-hour
A genuine iron battery system already exists, operates successfully, and is currently being put into service. Whether it can expand its production enough to alter the economics of the power grid is still unknown. The early indications, however, are encouraging, and the firm possesses the funds, the contracts, and the drive to attempt the expansion.
So far, the narrative tracks a steady advance. Design work has traveled from laboratory benches to manufacturing plants, from initial models to actual use, and from experimental demonstration to genuine market presence. The following section will reveal if the technology can match what it has promised.
Source material: “Form Energy and its iron batteries,” MIT Technology Review.
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