District heating
A network of insulated pipes distributing hot water or steam from central heat sources to many buildings for space heating and hot water.
District heating (DH) supplies heat from centralised or distributed sources through buried pre-insulated pipes. Sources include CHP plants, waste incineration, industrial waste heat, large heat pumps, biomass and gas boilers, geothermal wells, solar thermal fields and electric boilers using surplus power.
Network design has evolved through generations:
- 1st: steam (pre-1930s), large losses
- 2nd: pressurised hot water above 100 °C
- 3rd: 70–100 °C, prefabricated pipes, Scandinavian standard
- 4th: 50–70 °C supply, integrating heat pumps and low-grade waste heat
- 5th ("ambient"): 10–25 °C loops with decentralised heat pumps in each building
Distribution losses: typically 10–20% of heat delivered in modern networks, up to 30%+ in old ones
DH supplies about half or more of building heat in Denmark, Finland, Sweden and the Baltic states, and is widespread in Russia, China, Poland and Romania. Iceland's capital is supplied almost entirely by geothermal district heating. Globally it meets roughly 9% of final heat demand in buildings (IEA). Large-scale thermal storage lets DH networks absorb cheap renewable electricity via heat pumps and electric boilers, providing valuable flexibility to power grids.
Related terms
All terms →- CHP (Combined Heat and Power)
Simultaneous generation of electricity and useful heat from one fuel input, reaching total efficiencies of 75–90% versus about 35–60% for power-only plants.
- Thermal energy storage
Storing energy as heat or cold, in sensible, latent (phase-change) or thermochemical form, for later use as heat or for power generation.
- Heat pump
A device that uses a refrigeration cycle to move heat from a cooler source (air, ground, water) to a warmer sink, delivering 2–5 units of heat per unit of electricity.
- Geothermal gradient
The rate at which temperature increases with depth in the Earth's crust, averaging about 25 to 30 °C per kilometre away from tectonic plate boundaries.
- Solar thermal collector
A device that absorbs sunlight and transfers the heat to a fluid, mainly for domestic hot water, space heating, district heating and industrial process heat.