District Heating

District heating is a system for distributing heat generated at a centralized location through a network of insulated supply and return pipes to residential and commercial buildings, where heat exchangers typically connect each building to the network without mixing its own water directly with the district system. The heat source can be a combined heat-and-power cogeneration plant, geothermal energy, large heat pumps, or waste heat recovered from industrial processes. The earliest known system, drawing on geothermal energy, has operated in Chaudes-Aigues, France since the 14th century, but the first commercially successful modern system was built in Lockport, New York, in 1877 by engineer Birdsill Holly. District heating is widespread today across Europe and parts of Asia, most extensively in Iceland, where 93 percent of housing is connected to a district heating network, and modern combined heat-and-power systems can reach total energy efficiencies approaching 80 percent; Project Drawdown ranks district heating 27th among its 100 solutions to global warming.