Many of the world’s biggest cities have miles of underground pipes built decades ago that provide district energy. District energy systems use a central plant to produce steam, hot water or chilled water that is then piped underground to individual buildings for space heating, domestic hot water heating and air conditioning. As a result, individual buildings served by a district energy system don’t need their own boilers or furnaces, chillers or air conditioners.
The U.S. alone has more than 700 of these subterranean systems, some of which date back to the 1880s. While they were originally attached to coal- or oil-fired power plants, many old systems are getting retrofits to deliver “green steam” generated with cleaner fuels or with recovered waste heat.
In the Boston-Cambridge area, a network of district energy steam pipes now delivers recaptured thermal energy that was previously lost to the environment with the use of advanced co-generation technology. The gas-fired Kendall Station power plant in Cambridge previously dumped its waste heat into the Charles River. Now that heat is funneled into a new 7,000-foot pipeline to Boston. The new green steam system is estimated to reduce greenhouse gas emissions by nearly half a million tons annually.
District energy is becoming an important tool in the global effort to reduce greenhouse gas emissions while sustaining growth. Major cities such as Oslo and Tokyo have used district energy to reduce primary energy use by 30 to 50 percent. In Copenhagen, 97% of the city’s buildings get their heat from an underground network instead from boilers or furnaces.
These venerable energy systems from the past may well become our cities’ key energy systems of the future.
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How Hidden Labyrinths Under Cities Are Becoming Clean Energy Powerhouses
Photo, posted August 20, 2011, courtesy of Paul Sableman via Flickr.
‘Green Steam’ from Earth Wise is a production of WAMC Northeast Public Radio.