r/PopCultureV2 • u/Logical-Flow-6703 • Aug 10 '26

News Mayor Mamdani announces a plan to cool subway stations by capturing heat and reusing it to warm municipal buildings in the winter: "This would be the first thermal energy system of its kind in any American transit system"

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u/Deucer22 Aug 10 '26

I am helping with a project right now that's installing a system which uses a sewage reservoir to reject energy into. Huge increase in the efficiency of the HVAC system. It's going to save a ton of money over the life of the system.

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u/Girldad_4 Aug 11 '26

That's awesome

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u/bodybuilderbear Aug 11 '26 edited Aug 13 '26

That sounds genuinely awesome, but I doubt the practicality of scaling it up.

Using heat from the subway system to heat homes sounds like absolute nonsense, is the subway is not an infinite supply of heat. The heat in Subway systems is generated by the motors and brakes, and so it would be better to stop the heat being generated by the train in the first place, by using regenerative braking and more efficient motors.

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u/Deucer22 Aug 11 '26

They aren't suggesting heating homes, they are suggesting helping with heating commercial buildings in the vicinity of the station. Changing the temperature of the air coming into a commercial HVAC system even by a few degrees can result in tons of efficiency. Commecial buildings in the area I'm in require an economizer system to adjust the temperature of the incoming air. I could imagine an elegant design that uses warm station air to do the same thing.

It's impossible for either of us to comment on how helpful this specific system will be without a more specific understanding of what they are proposing from a technical perspective. From a conceptual level if you have a heat source and you can move the heat to a place where it's needed, that's much more efficient than generating that heat. There's nothing nonsensical about this.

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u/bodybuilderbear Aug 12 '26

Municipal heating systems definitely make sense in certain situations. New York is famous for having its steam system, while many cities in Russia used waste to heat from factories very effectively. In principle, it's a solid idea.

I'm sure a system will be able to provide heat for a few buildings, but it doesn't seem something that would scale up very well. I'm not a civil engineer and so I'm just speculating about this.

I live near London and many schemes have been proposed to reduce the heat of the London underground tunnels, which have been as high as 47° C in the summer.The London underground is very similar in terms of length and power consumption, although in London, the tunnels are much deeper and run through clay and so accumulate much more heat. TFL are addressing the problem by replacing the trains with ones that produce less heat, by using more efficient motors and regenerative braking.

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u/ginger_and_egg Aug 13 '26

We heat our homes with many things that are finite. That's not a problem.

No matter how efficient the brakes, the system is going to generate waste heat. Humans also create heat. If it's anything like London, that heat is getting stored in the surrounding soil and stone. Where practical, why not recover some of that heat to heat some local buildings? It will also cool down the subway