Minnesota's biggest solar project will help replace a huge coal plant
One of the largest solar projects in the country is moving closer to completion, and it’s not in a famously sunny state like California, Texas, or even Florida. It’s in Minnesota, on former potato farms near the site of a retiring coal plant.
The Sherco solar and energy-storage facility will be the largest solar project in the Upper Midwest, and the fifth-largest in the U.S. by the time it’s fully completed in 2026. The first phase of the project should begin sending emissions-free electricity to the grid this fall, heralding the start of a new era in a state whose largest solar project until now has been just 100 megawatts. This new project will have a capacity of 710 megawatts. It’s being built by utility Xcel Energy, which will also operate the facility once it’s online.
The project is poised to deliver on the many promises of renewable energy: It will partially replace the nearby coal plant set to retire over the coming years, address the variability of solar power by pairing it with long-duration storage, and provide good-paying union jobs in a community that’s losing a key employer in the coal facility.
The mammoth solar installation, which will cover about 4,500 acres across three sites, will be one of the first large-scale projects to use a long-duration iron-air battery from Form Energy.
The solar project and Form battery will make use of the coal plant's existing grid interconnection. One unit of the retiring coal plant will also house a synchronous condenser to help provide stable and strong electricity from renewable energy.
The sheer size of this project — and its transformation of a coal-burning power plant into a clean, emissions-free facility — puts the town of Becker and the Sherco site solidly at the center of Minnesota’s energy transition. Xcel, which led the way among utilities by pledging in 2018 to cut its emissions 80 percent by 2030, plans to retire its entire coal generator fleet by the end of the decade. It also plans to triple solar power capacity on its Upper Midwest grid by 2028.
Minnesota Senator Tina Smith (D) credits the Inflation Reduction Act with laying the groundwork for the solar project. It’s “the perfect example of how this historic legislation is paving the way to a clean energy future. It’s providing targeted funding to repurpose existing energy infrastructure, like Sherco’s old coal plant, with clean energy,” she said last year when Xcel broke ground.
The project comes as the state looks to cut its emissions 50 percent by 2030, compared to 2005 levels — and as it seeks to eliminate power-sector emissions altogether by 2040, in line with a law passed last year.
From coal to clean
The Sherco coal generator complex has been the largest power plant in Minnesota, with a total capacity of 2,238 megawatts. It’s one of the largest employers and sources of tax revenue in Sherburne County. It’s also by far the biggest single source of greenhouse gas emissions in the state.
On New Year’s Eve 2023, Xcel shut down a 680-megawatt unit at the plant. It plans to retire Sherco’s remaining two coal-fired units in 2026 and 2030 — they’ll be the last of its Upper Midwest coal plants to close. Xcel expects to transition the coal plant without laying off any of its hundreds of employees; some will be reassigned to other facilities.
This technological and cultural change is not coming about by accident. The Sherco solar project leverages incentives in the Inflation Reduction Act for the use of union labor and for siting renewable energy projects in so-called energy communities.
Last year, the U.S. government also provided support for the storage portion of the Sherco project with an award of up to $35 million from the U.S. Department of Energy. Bill Gates’ Breakthrough Energy Catalyst fund chipped in another $20 million.
The remainder of the approximately $1 billion in project costs will be paid for by Xcel’s electricity customers. The Minnesota Public Utilities Commission approved Xcel’s proposal to recover costs through a renewable energy fee on customers' bills.
Those customers will begin to reap the benefits of clean electricity as soon as October of this year, when phase one of the project is set to go online.
Form Energy’s part of the facility, a pilot project, is on track for late 2025 operation, according to the storage startup. Permitting and interconnection work is underway, and construction is set to start late this year.
Xcel will be trying out a new class of energy storage in Form’s iron-air battery — one capable of storing 10 megawatts of power for up to 100 hours. That’s enough backup for the grid to ride out a plant shutdown from a weather event such as a polar vortex, and far more than the 4-hour duration of the lithium-ion batteries that now predominate grid storage.
Form’s iron-air batteries for this project will be manufactured at its factory in Weirton, West Virginia, which is currently installing manufacturing equipment, trialing new manufacturing lines, and ramping up its manufacturing workforce.
This massive solar-plus-storage project is the sort of thing Minnesota will need much more of in order to hit the ambitious climate goals it has set out for itself.
