New York City plans to capture subway waste heat to warm nearby buildings
The project would use a geothermal network to store heat from stations and transfer it to buildings like City Hall.
NEW YORK — New York City is launching an effort to capture and recycle waste heat from its subway system to warm nearby buildings.
Mayor Zohran Mamdani announced the project, to be known as the Thermal Energy Network, earlier this year. It aims to store heat from subway tunnels and stations in deep boreholes fitted with circulating pumps and pipes to upcycle the energy.
Anyone who has stood on a subway platform in August knows that our stations do not just get hot; they turn into underground saunas. And if you, like me, do not know what a summer suit is and choose instead to commute in a wool one, let me tell you, it is far from a therapeutic experience.
Mamdani said at a press conference on a sultry summer day. The project will be jointly funded by the state government, which owns the Metropolitan Transportation Authority.
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Eric Wilson, the MTA's senior vice president of climate and land-use strategy, said the waste heat comes from a range of sources, including modern subway cars whose air-conditioning equipment radiates warmth, especially in terminal stations.
Our subway system was designed in the 1910s to passively evacuate heat from the system using the piston effect, where we have a ventilation system and the movement of trains pushing and pulling fresh air in and out. But it’s not a sufficient way of moving large amounts of heat that tend to accumulate onto the subway platform.
The project begins with a feasibility study and has a dual objective.
We are looking to expand tools to mitigate extreme heat and potentially put that heat to a beneficial use [in] adjacent buildings or to other kinds of off-takers that we could ultimately work with.
Wilson said the MTA is exploring the use of a "cassette system", networks of pipes and coils affixed to the interior of stations that contain water or a refrigerant. These would absorb warmth from the air, which is then shunted into a geothermal network below to create a "thermal battery."
This concept has been deployed in many places, particularly in residential buildings around the world.
Wilson said, adding that New York will "be hopefully the first transit system in North America to really deploy this."
The initial target is the subway station next to City Hall. If successful, Wilson said the system could be scaled up as a network linking multiple stations and nearby structures.
We think that there’s a lot of opportunity for us to work with hospitals and university systems and [will] be able to offtake some of the heat that we collect from subway infrastructure.
Such a system would displace some gas-fired power. The project dovetails with a city law requiring large landlords to reduce emissions, creating potential partners in adjacent buildings that need to comply.
A similar system in Toronto traps and upgrades waste heat from a major downtown sewer main to help warm a nearby hospital.
A 2022 study by Swedish researchers observed that urban heat sources from infrastructure and buildings could meet approximately 10% of European building heating demand, but noted limited information on how to use them.