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New Haven, Connecticut, has broken ground on an ambitious geothermal energy network that will provide low-emission heating and cooling to the city’s bustling, historic Union Station and a new public housing complex across the street.
The project will play a crucial role in the city’s attempt to decarbonize all municipal buildings and transportation by the end of 2030. As one of Connecticut’s first geothermal energy networks, it will also serve as a case study of how well the technology can both lower energy costs and reduce greenhouse gas emissions as the state considers promoting wider adoption of these systems.
“At the end of the day, you’re going to have the most efficient heating and cooling system available for our historic train station as well as roughly 1,000 units of housing,” said Steven Winter, New Haven’s executive director of climate and sustainability. ​“Anything we can help do to improve health outcomes and reduce climate change–causing emissions is really valuable.”
In climate-conscious states across the country, thermal energy networks are emerging as a promising way to reduce reliance on fossil fuels for heating, lower utility bills, and create a pathway for the gas industry to transition its business model for a cleaner-energy future. These neighborhood-scale systems use ground-source heat pumps and a web of underground pipes to deliver heating and cooling to connected buildings.
The thermal energy for heating can come from a variety of sources, including geothermal systems, industrial waste heat, and surface water. Because no fossil fuels are directly burned to produce heat, the only emissions are those created generating the electricity to run the network. At the same time, the systems insulate customers from volatile and rising natural gas prices.
“There’s a lot of excitement around networked geothermal because it actually offers solutions to a lot of problems,” said Samantha Dynowski, state director of Sierra Club’s Connecticut chapter. ​“It can be a more equitable solution for a whole neighborhood, a whole community — not just a single home.”
The practice of deploying such systems as a neighborhood loop is relatively new, but the component parts are well established: Geothermal heat pumps have been around for more than 100 years, and the pipe networks are very similar to those used for natural gas delivery.
“The backbone technology is the same kind of pipe you use in the gas system,” said Jessica Silber-Byrne, thermal energy networks research and communications manager for the nonprofit Building Decarbonization Coalition. ​“They’re not experimental. This isn’t an immature technology that still needs to be proved out.”
There are a handful of networked geothermal systems around the United States, owned by municipalities, private organizations, and universities. A couple of miles away from the Union Station project, at Yale University, development is underway on a geothermal loop serving several science buildings.
But the idea is catching on among gas utilities, too. The nation’s first utility-owned geothermal network came online in Framingham, Massachusetts, in June 2024, and just received an $8.6 million federal grant that will allow it to double in size. Across the country, 26 utility thermal energy network pilots are underway, and 13 states have passed some form of legislation exploring or supporting the approach, according to the Building Decarbonization Coalition.
In Connecticut, a comprehensive energy bill that passed earlier this year established a grant and loan program to support the development of thermal energy networks. Advocates are now pushing Gov. Ned Lamont, a Democrat, to issue the bonds needed to fund the new initiative.
The New Haven network could provide a concrete example of the opportunities offered by such systems.
The plan began when the federal government was seeking applications for its Climate Pollution Reduction Grant program, an initiative created by President Joe Biden’s 2022 Inflation Reduction Act. Union Station seemed like an excellent property to retrofit because of its age, its size, and its prominent role in the city: Nearly a million travelers pass through the station each year, making it one of Amtrak’s busiest stops and an excellent platform for demonstrating the potential of geothermal networks.
“We thought it would be a powerful message to send for this beautiful landmark building that’s also the gateway to the city,” Winter said.
In July 2024, the federal program awarded the proposal just under $9.5 million; though there were questions earlier in the year about whether the Trump administration would attempt to block the money, the grant program ultimately proceeded. Planners expect federal tax credits and state incentives to cover the remaining $7 million in the project budget.
The network will use as many as 200 geothermal boreholes. Fluid will circulate through pipes in each of these wells, picking up thermal energy stored within the earth; in hotter weather, when cooling is needed, the systems will transfer energy back into the ground.
The city began drilling the first test boreholes in November. The results were promising: One test hole was able to extend down 1,200 feet, significantly farther than the 850 feet projected, Winter said. If more boreholes can be drilled that deep, it could mean fewer holes are needed overall — and thus less materials — making the project more efficient, he said.
Construction of the network is still in the early stages. The test boreholes should be completed this month, and the design of the ground heat exchanger — the underground portion of the system in which the thermal energy is transferred — is about halfway done, Winter said. The city is also preparing to accept proposals for the retrofit of the heating and cooling systems in the station itself.
The goal is to have the system up and running in the latter half of 2028. The apartment units, which are still in the design phase, will be connected to the system as they are built.
Even as the initial plan comes together, New Haven is already considering the possibility of expanding the nascent network to include more buildings, such as other apartment units under development nearby, existing buildings in the neighborhood, and a police station around the corner, Winter said.
“Ideally, we end up with a municipally owned thermal utility that can help decarbonize this corner of the city and provide affordable, clean heating and cooling,” he said.
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