Form Energy to back Google data center with giant iron battery

A technician worked with some of Form's products in 2022.David L. Ryan/Globe Staff

Somerville-based Form Energy says it’s found the biggest customer yet for its iron-based battery technology.

Form will build a massive battery system in partnership with electric utility Xcel Energy, to provide power for a new Google data center in Pine Island, Minn. The battery will put out 300 megawatts of power, enough to support about 240,000 homes. But much of its power will be used to operate Google services like online search, Gmail, and YouTube.

The Form battery will work alongside new solar arrays and wind turbines that will provide up to 1,600 megawatts of power. Excess power will be used to charge up the battery, which can release the power at night or when there’s no wind. Xcel Energy said the system will enable Google to open a major data center in Pine Island without driving up electricity costs for existing homes and businesses.

Utilities worldwide are adding giant batteries to their power networks, to provide stable service and to store up renewable energy for future use. But many of these systems rely on lithium-ion batteries like those used in cellphones. These batteries release their energy quickly and can only provide supplemental power for a few hours.

Form Energy uses batteries based on iron pellets which generate an electric current as they rust. Feeding current back into the battery reverses the process. Scientists discovered the process in the 1960s but saw no practical use for it because batteries are mostly used for portable devices and iron is much too heavy.

But weight doesn’t matter when the battery is stationary and wired to the electrical grid.

Iron is much cheaper than lithium and releases energy more slowly. The Pine Island battery will provide power for up to 100 hours, enough to meet the needs of a midsize town for several days.

And the iron-air system offers another major benefit — it’s extremely fire-resistant. By contrast, lithium batteries can burst into flame because of mishandling or manufacturing defects. A California electric utility’s 300-megawatt lithium storage battery burned to the ground last January.

Form Energy, which has raised about $1.4 billion in venture funding, builds its batteries in a factory in Wheeling, W.Va.

The Pine Island battery is a major bet on a company that has yet to fully deploy one of its systems. In 2024, Form Energy began building a pilot plant in Cambridge, Minn., in cooperation with electric utility Green River Energy. That plant will produce just 1.5 megawatts, only enough to sustain about 1,200 households, and is scheduled for completion sometime this year.