The site of the former Lincoln Paper and Tissue mill, seen in 2005, is slated to be redeveloped into a massive energy storage system. Maine’s congressional delegation says the 85-megawatt battery would discharge energy for up to 100 hours over four days and would have the most energy capacity of any battery system yet announced. Shawn Patrick Ouellette/Staff Photographer

A onetime paper mill in Lincoln will be redeveloped to become the world’s largest long-duration energy storage system, Gov. Janet Mills announced Tuesday, providing Maine with a key tool to capture solar and wind power and release it to the grid at night and on windless days.

The 85-megawatt battery system would discharge energy for up to 100 hours over four days and would have the most energy capacity of any battery system announced yet, said Mateo Jaramillo, CEO and co-founder of Form Energy, the project’s partner. Approximately 85 MW of electricity could serve between 64,000 and 85,000 homes, according to ISO-New England, the region’s grid operator.

The Somerville, Massachusetts, energy storage and manufacturing startup uses iron-air technology that develops batteries to store large amounts of energy at low cost with inexpensive and abundant iron and freely available oxygen.

Energy storage is increasingly important as wind and solar power projects replace fossil fuel sources of energy, such as natural gas. Wind and solar are intermittent energy sources that require storage so the electricity can be sent to the grid on windless days and at night. The Lincoln battery project will help Maine reach its goal of 400 MW of energy storage installed by the end of 2030, the governor’s office said in announcing the project Tuesday.

Patrick Woodcock, president and CEO of the Maine State Chamber of Commerce, said storing power for days – known as long-duration energy storage – will address seasonal changes. Long-duration storage ranges from eight hours to days, weeks or seasons, according to the Long Duration Energy Storage Council.

“It’s incredibly important for New England,” said Woodcock, who was formerly the director of Maine’s Energy Office and Massachusetts’ commissioner of energy. “We go through our load profile changes dramatically from summer to fall and winter. Winter is the biggest issue.”

Winter demand for heating and electricity is significantly greater than in the summer months, and long-duration energy storage will help meet electricity demand and help us “be confident we have a reliable electric system,” he said.

The project, supported by a $147 million grant from the U.S. Department of Energy, will be subject to contract negotiations and other steps, the Governor’s Energy Office said. It’s part of a $389 million regional grant to New England states funded through the federal Bipartisan Infrastructure Law to strengthen the regional electric grid and advance the deployment of clean energy.

A regional proposal, Power Up New England, was selected through the Department of Energy’s Grid Innovation Program. Power Up features upgrades to points of grid connections in Massachusetts and Connecticut to prepare the onshore transmission system for up to 4,800 MW of additional offshore wind energy.

MILL VACANT FOR 14 YEARS

Lincoln Town Manager Richard Bronson said the former Lincoln Pulp and Tissue Mill has been vacant for 14 years and was one of nine paper mills, now closed, that once operated on the Penobscot River. Form Energy will build the storage project at the Lincoln Technology Park, a 387-acre site at the former mill.

Steven Levesque, economic development adviser to the town of Lincoln, said the number of jobs at the battery energy project will be small and not comparable to large-scale employment created by manufacturing.

The town owns the site, and the parties have not yet negotiated a lease or purchase agreement, Bronson said.

The announcement did not include information on when the storage center will begin operations, but Woodcock said it will be “multiple years.”

As of March, Maine had 63 MW in energy storage capacity connected and operating in six projects, according to the state Public Utilities Commission. The largest battery sites are in Millinocket and Yarmouth.

State law established a goal of deploying at least 300 MW of energy storage by the end of 2025 and at least 400 MW by the end of 2030, but it does not specify the uses, benefits or configurations of energy storage systems required to meet those goals, the PUC said.

Regulators, citing ISO-New England, said four battery projects with about 215 MW are planned for development in Maine. Nineteen “co-located” storage and generation projects of about 799 MW in Maine are waiting for ISO approval, the PUC said. For the co-located projects, it is unclear how the megawatts are apportioned between the battery and generator, making it difficult to estimate how many megawatts will be apportioned to projects’ energy storage portions.