During your class trip to NYC you will probably notice some smoke rising from the sewer or manholes- it’s actually steam and not smoke. It is a distinct feature of New York and other older cities.
What is the steam used for? It is a power source not unlike electricity. It is generated and then pushed along a network of pipes under the city streets. There are over 105 miles of pipes running from the southern tip of the Island to 96th st to the North. You can see one of the thousands of manholes covers with the initials NYSC – New York Steam Company. Today it is the Con Edison company that runs the system.
Here is a diagram of what’s below the ground: Con Ed Steam Pipes
This is also a very cool graphic from National Geographic: NYC underground
Cogenerations plants are around the island and some in Brooklyn and Queens (you can see some of the stacks quite well from the East River). Once generated this vaporized water traveling at 350F circulates to various buildings and also the subway system. It can then to be used as a heat source when needed or the energy is converted to air conditioned air when and where it is needed via ‘absorption chillers’. Have you ever noticed how it is warm behind your refrigerator or A/C unit? Think of it as the reverse process of taking heat to generate cold air.
Some well known older buildings like the Empire State, UN and newer ones like the Time Warner building at Columbus circle use steam as an energy source.
This type of system makes sense for very densely populated places like Manhattan. When you see the steam, it is most likely the result of some rainwater falling on the pipes, construction or repairs or in some cases small fissures or leaks in the pipes or valves. To avoid having the very hot steam injure anyone walking by, these ‘steam stacks’ are placed over the steam source to let it evaporate safely above street level.
So on your next school trip to NYC, you will definitely know the source of this underground ‘smoke’.