# Great River Energy Builds Cambridge Iron-Air Battery

Great River Energy and Form Energy are developing the 1.5 MW/150 MWh Cambridge Energy Storage Project in Minnesota, an iron-air battery pilot designed to discharge for up to 100 hours. Construction began in August 2024, and commercial operation is targeted by the end of 2026. The project has no stated contract value or solicitation, but it provides a concrete market-validation reference for utilities and public-sector buyers assessing long-duration energy storage procurements.

- The project’s 100-hour discharge capability offers procurement teams a benchmark for comparing multi-day storage against shorter-duration battery systems.
- Utilities, agencies, and contractors working on grid resilience can assess whether iron-air storage fits their long-duration capacity needs; the signal does not identify an open procurement opportunity or published pricing.
- The end-of-2026 operating target makes the Cambridge project a near-term demonstration point for evaluating this technology, rather than evidence of a completed deployment.

**Jurisdictions:** sled
**Industries:** Energy & Utilities
**Topics:** Physical Infrastructure
**Published:** October 28, 2026

### Vendors
- Form Energy (Iron-air battery technology developer)
- Great River Energy (Utility developing the Cambridge Energy Storage Project)

### Sources
- [A Minnesota battery pack is being built to run nonstop for 100 hours on rusting iron, and that is roughly ten times longer than the lithium batteries that dominate the grid today](https://gcn.com/minnesota-battery-pack-being-built-run/22820) - gcn.com