page_title: District heating
section_title: Heat distribution
hierarchical_section_title: District heating / Heat distribution
caption_attribution_description: English: district-heating-pipeline made of preinsulated bonded pipe systems under construction before joints are applied; in Tübingen, Germany. Deutsch: Fernwärmeleitung aus Kunststoffmantelverbundrohren in der Bauphase, vor Setzen der Muffen; in Tübingen; Achtung dieses Bild enthält mehrere Punkte auf die hingewiesen werden muss um als Lehrbeispiel dienen zu können: 1. Künette im hinteren Teil eingestürzt, das darf nicht passieren. In der Folge wird sonst durch die Steine der Kunststoffmantel beschädigt. 2. Offensichtlich ist die Künette etwa 150 cm tief und ab 120 cm Tiefe ist unbedingt ein Grabenverbau notwendig, auch wenn diese Tiefe nur einseitig erreicht wird. 3. Der Abstand der Auflagerstellen im Bauzustand ist zu hoch, es müssen mehr Unterstützungen angebracht werden. 4. Die Rohrleitung ist auf der nicht gesetzen Muffe gelagert. Darf nicht sein, es besteht die Gefahr der Muffenbeschädigung bereits bevor diese gesetzt ist. 5. Der Abstand zu den kreuzenden Einbauten ist zu gering. Man erkennt in der Trasse 2 davon und es ist nicht anzunehmen, dass dies nur leere Rohre sind. Es besteht Gefahr! 6. Obwohl die Schweissnaht fertig ist wurde die Überhöhung nicht geleich abgeschliffen, die maximal (10% der Nahtbreite + 1mm) sein darf, aber offensichtlich höher ist. --Ulrichulrich (talk) 20:49, 22 January 2011 (UTC)
context_page_description: District heating is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants. Fifth generation district heat networks do not use combustion on-site and have zero emissions of CO2 and NO2 on-site; they employ heat transfer which uses electricity which may be generated from renewable energy, or from remote fossil fuelled power stations. A combination of CHP and centralized heat pumps are used in the Stockholm multi energy system.
context_section_description: After generation, the heat is distributed to the customer via a network of insulated pipes. District heating systems consist of feed and return lines. Usually the pipes are installed underground but there are also systems with overground pipes. Within the system heat storage units may be installed to even out peak load demands.
  The common medium used for heat distribution is water or pressurized hot water, but steam is also used. The advantage of steam is that in addition to heating purposes it can be used in industrial processes due to its higher temperature. The disadvantage of steam is a higher heat loss due to the high temperature. Also, the thermal efficiency of cogeneration plants is significantly lower if the cooling medium is high-temperature steam, reducing electric power generation. Heat transfer oils are generally not used for district heating, although they have higher heat capacities than water, as they are expensive and have environmental issues.
  At customer level the heat network is usually connected to the central heating system of the dwellings via heat exchangers (heat substations): the working fluids of both networks (generally water or steam) do not mix. However, direct connection is used in the Odense system.
  Typical annual loss of thermal energy through distribution is around 10%, as seen in Norway's district heating network.
caption: District heating pipe in Tübingen, Germany
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