Inside a large but nondescript building near the Longfellow Bridge on the Cambridge side of the Charles River is what’s essentially a jet engine.
“If you look up, you’ll get a sense of the size,” said Kevin Hagerty, president and CEO of Vicinity Energy, as he pointed up at his company’s technology, towering several stories high.
This is a natural gas fueled power plant and the process of generating electricity also produces a lot of heat. So, instead of letting that heat go to waste, they capture it.
“We turn it into steam. And that’s the steam that we pump underground to heat Boston and Cambridge.”
Underneath the cities’ streets are 26 miles of steam pipes. The first steam pipes were installed under Boston over 130 years ago. It’s called a district energy system, and it now heats about 70 million square feet of building space in Boston and Cambridge, including all of the major medical complexes in the area.
Still, the underlying process that creates that steam is powered by natural gas – a fossil fuel. As climate change makes reducing those carbon emissions a more urgent priority and regulations about emissions become more stringent, more and more buildings are looking to decarbonize. That’s why Vicinity plans to launch a new technology.
“We’re making room for a state-of-the-art high-pressure, high-temperature heat pump complex,” Hagerty said.
In this heat pump technology, the energy source is the temperature of the water in the Charles River.
Vicinity will use a complicated process to exploit the energy that’s in that water temperature.
First, they’ll use what’s called a heat exchanger, which holds a refrigerant under high pressure surrounded by river water that they’ve pumped into the plant. That refrigerant is forced to turn from a liquid to a gas — a process that draws in heat from its surroundings.
“That energy didn’t just disappear,” Hagerty explained. “It came out of the river water and it went into the refrigerant.”
The plant will return the water back into the Charles at a cooler temperature.
And a few steps later, the energy in the refrigerant will be used to create steam that will be pumped through those existing underground pipes to heat buildings in Boston and Cambridge.
Vicinity anticipates that the new heat pump will create about 110,000 pounds of steam per hour.
“That’s enough steam to supply enough heat at peak of winter to about three buildings the size of the Prudential center,” Hagerty said.
And after they install this first heat pump, they’re planning on putting in two more, until the whole steam system is eventually powered by the temperature of the Charles. It’s a technology that’s currently being used in Europe.
“I wish we could take credit for this, but we’re more than happy to copy a good idea,” Hagerty said.
Morten Jordt Duedahl is with an industry association called the Danish Board of District Heating.
“Recently, meaning the last ten years or so, heat pumps have popped up everywhere because that is our next step in making our district heating system truly renewable,” Duedahl said.
These kinds of heat systems are a much bigger deal in Denmark, and not just in big buildings like in Boston. They heat two thirds of households in the country.
But, Jordt Duedahl pointed out, the systems in Denmark don’t use steam. They use hot water.
“Copenhagen got rid of the last, very last, old steam system, say, five years ago or something,” Duedahl said. “And now it’s all hot water. And the reason why we use hot water is it’s more efficient.”
But converting Boston to a more efficient hot water system would be a large, expensive project of installing all new pipes.
Christopher Reinhart is a professor of building technology in MIT’s department of architecture. He said using renewable heat pumps along with the old, existing steam infrastructure is a good option for Boston and other cities around the country that have district energy systems.
“I think you would see a lot of those, especially with the overall push towards decarbonization,” Reinhart said.
In New York City, for example, Con Edison is currently looking into putting a similar system in both the East and Hudson Rivers.
Here in Cambridge, Hagerty said Vicinity plans to have their first heat pump in operation by 2028.
“We will be the first. That’s something that we’re very proud of,” he said. “A lot of folks are watching us, seeing how we’re doing it.”
Once their system is in place, he said, others are going to follow.
Produced with assistance from the Public Media Journalists Association Editor Corps funded by the Corporation for Public Broadcasting, a private corporation funded by the American people.
