We've been obsessed with Con Edison's NYC steam system ever since we discovered that National Geographic diagram last month and Evan sent in that informative email. We decided to do some more research, and stumbled across this great article on steam power from the Gotham Gazette:

If steam is an easier concept to grasp than, say, fiber optics, producing it on this scale is nowhere as simple as turning on a giant teakettle. Some of the steam comes from the Con Edison steam generating plant on 14th Street and the East River. Inside, two massive boilers -- one 95 feet high -- burn natural gas or fuel oil and air. The resulting heat sends the temperature of water inside the boiler's pipes to a blistering 1,000 degrees Fahrenheit, converting it to steam. Workers wear ear protectors to keep out some of the roar of millions of gallons of flowing water and the sound of spinning turbine blades. Little, though, can shield them from the warmth radiating from pipes filled with superheated vapor.

"When we used to bring people into the plant for tours, their first impression, when we have them look inside of the furnace, is that it's huge. People are taken back by the sheer size of it - eight stories high," says Wilton Cedeno, former manager of Con Edison's Hudson Avenue steam plant. "There are intricate control systems -- systems for treating the water, electrical systems, pressure systems. It's all very complex."

On average, the plant converts a gallon of water into eight pounds of steam -- every hour, approximately 125,000 gallons of water are turned into more than one million pounds of steam. "We use city water, but the water has to be processed and cleaned," says Cedeno. "If it's not pure, you get build up on pipes and can damage the turbine blades."

The East River plant is one of seven Con Edison plants -- five in Manhattan and one each in Queens and Brooklyn. Three of these plants, including the one on the East Side, produce both steam and electricity through a process called co-generation. In these plants, the steam leaves the boiler and then goes through pipes into a turbine generator. The resulting spinning of the turbine blades produces electricity. The remaining steam then goes into the steam system.

From the plants, the steam goes into Con Edison's underground pipes. On a cold winter day, nearly 10 million pounds of steam at 350 degrees Fahrenheit flow each hour through 105 miles of underground mains. The pipes coming out of the plant can be several feet in diameter, but the steam travels through progressively smaller pipes, ending at ones that may be only a couple of inches wide.

Con Edison fills in some more facts:

The New York Steam Company began providing service in lower Manhattan in 1882. Today, Con Edison operates the largest steam system in the world. The system contains 105 miles of mains and service pipes and 3,000 steam manholes. Steam is provided from seven Con Edison steam-generating plants, five in Manhattan, one in Queens, and one in Brooklyn, along with receiving steam under contract from a steam plant at the Brooklyn Navy Yard.

Con Edison's steam system provides service to more than 1,800 customers and serves more than 100,000 commercial and residential establishments in Manhattan from the Battery to 96th Street.

Our commercial and residential customers use steam for heating, hot water, and air conditioning.

The winter peak sendout is nearly 10 million pounds per hour.

Steam sales account for about 7 percent of total Con Edison revenues.

Steam traveling through Con Edison's system is used to heat and cool some of New York's most famous addresses – the United Nations complex, the Empire State Building, and the Metropolitan Museum of Art are just a few.

Interesting! Can someone explain how steam power can be used for air-conditioning? That's hugely counter-intuitive! And good news for you who value clean air: despite the fuel burned to create the steam, it sounds like the NYC steam system actually produces less pollution than some of the other power sources.