How America's Greenest Cities Got Green

Chicago produces twice the energy with a third the carbon

A typical fuel-burning power plant is wasteful in two ways: It produces harmful emissions, and it squanders two thirds of the energy it generates. The primary reason? Heat, the natural by-product of fuel combustion, dissipates into the atmosphere unused.

Chicago is among the first cities to confront energy loss head-on. The city government has invested in cogeneration, the simultaneous production of heat and electricity, which is twice as efficient as conventional fuel-burning power production. The strategy is also a potent means of reducing greenhouse-gas emissions. A cogeneration plant produces only one third the CO2 of a coal-fired power plant. In its most recent energy plan, Chicago committed to producing 1.5 billion kilowatt-hours of electricity from cogeneration by 2010—25 percent of the city’s increased energy needs from 2000 to 2010.

Rather than allowing accumulated heat to escape through exhaust vents, a cogeneration facility collects the hot steam exhaust produced by natural gas combustion and channels it into a network of pipes that distributes it throughout the building. “You can take steam and use it directly for heating the building, cooking, and hot water,” says John Kelly of Illinois-based Endurant Energy. “That’s huge.” Chicago’s famed Museum of Science and Industry developed a cogeneration plant in 2003, and in recent years other city institutions, such as the Jesse Brown VA Medical Center, have followed suit. Kelly thinks the cogeneration meme will soon spread. “Manhattan is anticipating a power shortfall of 1,000 megawatts,” he points out. “It’s a perfect candidate.”

HOW IT WORKS
Cogeneration starts when a generator burns natural gas [A] to produce electricity. The hot exhaust from that combustion boils water [B], and that steam powers a turbine [C] connected to a second generator [D], producing another shot of electricity. Any leftover waste steam heats the building.