HOLYOKE — Next to the remnants of a coal-fired power plant, a cleaner source of energy popped up about two years ago: a 22-acre field of solar panels.
On Tuesday, the 5.8-megawatt solar farm unveiled a new battery storage system that will give the project a major boost.
On such an overcast day, though, there wasn’t a lot of sun power to harness.
Therein lies a problem with some forms of clean energy: The wind and sun are not consistent fuel, but no matter the weather, people demand energy. A major hurdle then is figuring out how to store the energy.
The new storage system, slated to start providing service this fall, is operated by Engie Storage for municipally owned utility Holyoke Gas Electric under a 20-year contract. This lessens the upfront cost for the utility company, officials said.
The new battery system is capable of storing three megawatts of energy. According to the Solar Energy Industries Association, one megawatt of solar energy powers, on average in the U.S., 164 homes. Engie said, as far as it knows, the system at Mount Tom is the largest utility-scale battery in the state.
The 146-megawatt Mount Tom Power Station closed in 2014 after running for more than 50 years, for most of which it used coal as its fuel. GDF Suez, Engie’s former name, cited competition with natural gas as a reason for closure and said solar was a possibility for the power plant’s replacement, according to previous Gazette reporting.
Environmental and community activists pushed for solar installation, and won. Lena Entin, Toxics Action Center’s deputy director, was part of that push. She said community involvement from people like Holyoke resident and retired factory worked Carlos Rodriguez was key.
“It’s the activists who put forward the vision of where we can be,” she said.
The 17,208 panels on the solar farm started generating power in January 2017.
It’s the largest community solar project in the state, according to a National Renewable Energy Laboratory database compiled last spring.
Massachusetts has been putting resources into increasing its capacity to store energy with its Energy Storage Initiative.
HGE’s manager, James Lavelle, said state benefits have been effective.
“A lot of the incentives that we’re getting through the state through its various agencies are allowing us to get these projects over the finish line,” he said.
And when it comes to solar specifically, Massachusetts is a leader. There are 86,000 distributed solar projects across the state, according to state Department of Energy Resources Commissioner Judith Judson.
“We’re now seeing solar in all 351 cities and towns across the commonwealth,” she said.
Officials expect the storage system will be helpful in lowering costs. Peak demand, when the most energy is being consumed, makes up a disproportionately large share of electricity costs, Judson said. But energy from the storage system can be deployed when demand peaks to lessen the costs, Engie Storage’s Jonathan Poor said.
Judson said that’s a reason why DOER was interested in the project.
“In addition to integrating renewables, what this project will help demonstrate is how can you use storage to reduce peak demand and therefore lower overall costs,” she said.
DOER awarded the project almost half a million dollars in grant funding to help with installation of the battery and for a University of Massachusetts Amherst study that’s analyzing how the system helps ratepayers save money.
Holyoke Mayor Alex Morse commented, “Holyoke is a great example of how we go from a coal plant — that type of energy — to renewable energy, expanding our renewable energy portfolio here in Holyoke.”
Entin said there are still questions about cleanup of the coal-fired power plant and its coal ash. The Valley Advocate reported in 2016 that the facility had created 21 coal ash ponds on its property near the Connecticut River.
Engie spokeswoman Carol Churchill said that power station cleanup efforts are ongoing.
Still, Entin says she’s thrilled about the battery installation.
“We have a vision of getting to 100 percent renewable and we know that battery storage is essential,” she said.
Mayor Morse expressed similar sentiments.
“We have a vision of being one of the first carbon-neutral communities in the state, throughout Northeast, and throughout the United States,” he said. “And this helps us further accelerate that goal.”
Greta Jochem can be reached at email@example.com