Xcel Energy has received a federal grant of up to $70 million for a novel grid battery project.

Xcel is partnering with Massachusetts-based Form Energy to install an industrial-sized battery in Becker that would store electricity for far longer periods than current grid batteries. Xcel plans to put a Form battery on its electric grid in Colorado, too.

The grant from the U.S. Department of Energy (DOE) will split between the two projects, which are in Xcel's largest markets.

The grant "provides crucial financial support for projects that will provide reliable, low-cost renewable energy to the communities we serve," Xcel CEO Bob Frenzel said in a statement.

Minneapolis-based Xcel, Minnesota's largest electricity provider, received a $20 million grant commitment for the Form battery project in April from Breakthrough Energy Catalyst, a platform Bill Gates founded that funds sustainable energy projects.

Xcel's Form batteries will also be eligible for federal tax credits from a landmark clean energy law passed in 2022. The federal grant is subject to negotiation with the DOE.

Xcel has not publicly disclosed the cost of its Form battery project, designating it a "trade secret" under Minnesota law. The Minnesota Public Utilities Commission (PUC) approved the project in July. The PUC rejected the Star Tribune's challenge to disclose the price tag.

Because of the variability of renewable energy, batteries of all kinds — but particularly those with long-duration storage — are critical to building a carbon-free electrical grid. Batteries can store power and discharge it later to even out electricity flows.

The electrochemistry of Form's battery is based on iron. It would store electricity for 100 hours, compared with the four-hour standard of most lithium-ion grid batteries. Xcel's project is one of Form's first, along with a smaller pilot for Maple Grove-based electricity producer Great River Energy.

The 10-megawatt Form battery at Becker would discharge 1,000 megawatt hours of electricity and should come online by the end of 2025. A $1.1 billion Xcel solar project — which the company will build in three phases — should also come online in Becker at about the same time.

Xcel plans to close three large coal-fired generators in Becker by 2030, with the first one scheduled for shutdown at the end of 2023.