Cambridge Energy Storage Project

Executive Overview

The Cambridge Energy Storage Project is the world's first commercial deployment of iron-air battery technology — a 1.5 MW / 150 MWh system at Great River Energy's Cambridge peaking plant in Cambridge, Minnesota. Developed by Form Energy in partnership with Great River Energy, the system achieved commercial operation in Q4 2025, when Form Energy's CEO confirmed that batteries had been shipped from the Weirton, West Virginia factory, installed at the Cambridge site, and brought into operation. The project is designed to deliver its rated 1.5 MW output continuously for 100 hours, addressing multi-day periods of low renewable generation rather than the four-to-eight hour duration typical of lithium-ion grid storage. Great River Energy serves as the utility offtaker and has initiated a multi-year performance study of the technology.

How It Works & Differentiation

The Cambridge system uses Form Energy's iron-air electrochemistry: iron pellets oxidise during discharge (absorbing oxygen from the air) and de-oxidise during charging (releasing oxygen) in a reversible electrochemical reaction using iron, water, and air — low-cost, domestically abundant materials. The 100-hour discharge duration addresses multi-day weather events such as polar vortexes, heat domes, and dunkelflaute periods that overwhelm lithium-ion batteries' capacity limits. Form Energy sources iron domestically; ArcelorMittal, which operates iron ore mining facilities in northern Minnesota, is a materials partner — giving the project an unusual regional supply chain dimension for grid storage. The battery modules are manufactured at Form Factory 1 in Weirton, West Virginia.

Commercialization & Traction

As the first commercial deployment of Form Energy's technology, Cambridge provides the first real-world operational data on iron-air performance, durability, and grid integration. The deployment validates Form Energy's manufacturing readiness ahead of much larger planned systems: the 10 MW/1 GWh Sherco system in Minnesota (under construction), the 15 MW/1.5 GWh Georgia Power project (under construction), the 10 MW/1 GWh Commanche project in Colorado (in service Q3 2026), and the 300 MW/30 GWh Pine Island system for Google (construction target 2028). Cambridge's performance during Great River Energy's multi-year evaluation will directly inform the risk assessments underpinning all subsequent iron-air deployments globally.

Scalability & Strategic Context

The Cambridge project's role is primarily as a technology validation platform. The operational data generated here — on charge/discharge cycles, round-trip efficiency (approximately 40%), system degradation, and dispatch behaviour — provides the empirical baseline that Form Energy's entire commercial pipeline depends on. The project also demonstrates that 100-hour storage can be sited at existing utility infrastructure without major facility modifications. Form Energy has raised over $1.4 billion in total funding and has a DOE grant of up to $150 million supporting its Weirton manufacturing scale-up to 500 MW per year of annual production capacity by approximately 2028.