James Merrihue takes me through a pair of gray double doors from the sleek halls of New York University’s Stern School of Business, and immediately it’s warmer. Most students probably walk by these doors every day without considering what’s behind them. But when I follow Merrihue through a series of doors and hallways and down a flight of stairs, we reach a cavernous, steaming hot room, the length of a city block, where a system of turbines, generators, heat exchangers, and chillers provides electricity, heat, and hot and cold water for dozens of campus buildings.
This system lives just below ground, a block off Washington Square Park,underneath a pleasant walkway spotted with local grasses and benches. If you sit and listen quietly, you can hear the noise of the turbines spinning at 13,000 revolutions per minute below. Once, the university created energy in this spot by burning oil. In that plant, you could smell the diesel exhaust fumes, Merrihue, the plant manager, tells me. But this new plant, which opened in 2011, starts by burning natural gas, which produces less air pollution and fewer greenhouse gas emissions. After that fuel produces electricity, the plant takes the leftover energy and uses it over and over again. “That’s what gets us the efficiency”—almost 90 percent, says Merrihue. The hot exhaust from two gas-fired turbines fuels a steam turbine, which produces additional electricity. The leftover steam travels to a hot water heat exchanger and then to a chiller, where the last bit of energy is used to cool a 2400-gallon tank of water down to 45 degrees.
Power plants like this one, which eke every drop of work they can out of their fuel, are called cogeneration or combined heat-and-power plants. The technology isn’t new: Thomas Edison first used it commercially in 1882, at the Pearl Station, where heat from electricity generation went to warm nearby buildings. But it has been underused. In 2008, the Department of Energy called cogeneration “one of the most promising options in the US energy efficiency portfolio” and estimated [PDF] that if these plants accounted for 20 percent of the country’s electricity capacity, they would keep as much carbon dioxide out of the atmosphere as taking 154 million cars off the road would.