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'The Bat Cave' deep inside Massachusetts mountain provides critical power resource

"The Bat Cave" deep inside Massachusetts mountain provides critical power resource
"The Bat Cave" deep inside Massachusetts mountain provides critical power resource 03:18

NORTHFIELD – There is a cave hidden in the hills of Northfield Mountain. Inside is a power source that can light up hundreds of thousands of homes in New England in a matter of minutes.

It may look like any normal lake, but this pond is so much more. At one time, the water at Northfield Mountain served as the world's largest battery.

FirstLight Power gave WBZ-TV exclusive access to what they call "The Bat Cave," one of the largest biggest single sources of green energy in the northeast.

The tunnel might remind you of the villain's lair in some James Bond movie and it takes a full minute to descend the half mile into the generator room.

"Essentially we are in the middle of it, yeah," operations manager for Northfield Mountain Slocombe said, referring to Northfield Mountain. "Eight hundred feet below the surface of the power station."

The cavern is so big that from floor to ceiling a five-story building could fit inside.

An illustration of how water provides power inside "The Bat Cave" of Northfield Mountain.  CBS Boston

So why the nickname "The Bat Cave?"

"Well we have had bats down here. But not very often," Slocombe joked.

Northfield Mountain's four turbines can generate up to 292 megawatts each. Each turbine is 90-90 feet tall. The roto alone weighs 400 tons.

The power source for the turbines is water. The upper reservoir is 1,000 feet deep with five billion gallons of usable water.

"Basically how Northfield Mountain works is moving water up and down and generating electricity in between. Water moves down, through the mountain, into four turbines. This is essentially a giant water battery," Alicia Barton, CEO for FirstLight Power said. "This could power half of the smart phones in America with what we can generate here. Another way to think about it is up to one million New England homes on any given day. That's a pretty significant footprint and impact that we can have." 

About 10% of the total grid consumption in New England can be from Northfield Mountain - huge amounts from a single source - and the type of numbers needed for Massachusetts to hit its climate goals of net zero by 2050 and 50% reduction in carbon by 2030.

"That is the most aggressive 2030 target adopted by any state in the country, so we do have a lot of work ahead of us," Barton said. "The state is recognizing we need a lot of tools at our disposal to get to our ultimate goals and the state is working hard to put those pieces in place."

And while Northfield Mountain has been an engineering marvel since its construction in 1972, Barton said the future will be even more exciting.

"The pace of change is happening very fast," Barton said. "I've been working in clean energy and climate for my entire career, and there has never been a more exciting time than today."

Just a couple weeks ago for the first time ever in western Massachusetts, a vehicle to grid charger was installed. Barton said this is yet another small step forward in Massachusetts going carbon net zero.

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