New England’s Largest Battery Is Hidden Inside A Mass. Mountain
It was Boston-born Ben Franklin who first used the term “battery” to describe an electric storage device. Now, nearly three centuries later, Massachusetts is hoping to jump-start the development of new kinds of batteries to power the future.
The state has launched a $10 million Energy Storage Initiative. The 10-year goal: Save electric ratepayers hundreds of million dollars, make the electrical grid more reliable and resilient, and reduce greenhouse gas emissions.
Today’s batteries come in all shapes and sizes. The largest in New England — and once the world — was built 45 years ago and is still working.
But it’s hidden, on top and deep inside a mountain in north-central Massachusetts.
Northfield Mountain is a naturalist’s wonderland. But if you look around, you’ll see an unnatural site: a 5-billion-gallon battery.
“So what you’re looking at right here is the upper reservoir, and I consider this to be the battery for the station,” says Gus Bakas, director of Massachusetts hydro operations for FirstLight Power Resources.
The company owns and operates the Northfield Mountain pumped storage hydroelectric station. The generators are powered by this manmade mountaintop lake.
“So this is our supply, our stored energy, similar to a battery,” Bakas continues. “So when we need that battery to turn on, we would take this water and we would run it into the facility to produce power.”
The hydroelectric generating facility is located hundreds of feet below the reservoir, hidden deep inside the hollowed-out Northfield Mountain. But you’d never know it, except for an occasional hint.
“There are people that have been coming here for 30 years,” Bakas says, “and somebody will ask, ‘What are those wires?’ And somebody will explain, ‘Well, there’s a power plant underground.’ ”
Typically public tours aren’t allowed, in part due to security concerns.
We go past a security fence, under the watchful eyes of surveillance cameras. We come to a hole in the mountain, chiseled out of gray granite. It’s wider than Boston’s Sumner Tunnel.
“Right now we’re going to drive through a portal door that gives us access to the underground project,” Bakas says.
It’s enormous, and looks like the Batcave.
“That’s funny, that’s what we call it sometimes,” Bakas says. “It’s like James Bond, or ‘Get Smart’ — remember ‘Get Smart’ from the ’60s?”
The Northfield pumped hydro plant was built in the late 1960s. The tunnel leads to the giant generating station inside.
“When this facility was built, it was actually the largest pumped storage facility in the world,” Bakas says. “This facility here is capable of just under 1,200 megawatts, so we’re good for well over a million homes.”
Water from the reservoir, now high overhead, flows through four 18-foot-diameter conduits drilled into the rock. Gravity and powerful pumps force the water down to the hydro plant carved into Northfield Mountain. The water spins the electric-generating turbines.
To recharge the battery and get water back up to the mountaintop reservoir, the pumps work in reverse.
When Northfield was constructed, the electricity for the pumps came from the then-just-built Yankee nuclear power plant located a few miles up the Connecticut River.
“Vermont Yankee being a nuclear power plant generates power 24/7, or what they call base load,” Bakas says. “So as a result of that at night they had all this excess power on the grid. So somebody needed to take it. So this plant was conceived and built to take that off-peak power and utilize it through pumping water during off-peak periods.”