Local heating

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The four generations of heating systems and their heat sources

As local heat transferring is heat between buildings paraphrased for heating when compared to the district heating occurs only over relatively short distances. The transition to district heating with larger amounts of heat and pipe lengths is fluid.

Technical implementation

Local heat distributor in the basement of an apartment building with heat meters for individual consumers

Conventional systems

Local heating is supplied via local heating networks. A branched network of pipes pumps water into the heating circuit as a heat storage and transport medium . The water is heated by the heat energy released by one or more heat generators via heat exchangers , the heat is transported with the water to the consumer (flow) and there also transferred to the consumer's heating circuit via heat exchangers. The cooled water flows back via the return line. Flexible composite pipes are usually installed for heat distribution because they are easy to lay , and plastic jacket composite pipes are also used.

In contrast to district heating, local heating is implemented in smaller units in a decentralized manner; typical thermal outputs for local heating networks are between 50 kilowatts and a few megawatts . In addition, the heat can be transferred at relatively low temperatures. Therefore, in addition to the thermal energy generated in heating plants and block -type thermal power stations, the heat generated at lower temperatures from solar collector systems or low-temperature geothermal systems can also be used by local heating.

Local heating networks serve several buildings, a residential or commercial area or a community. The power range required for the supply of local heating networks corresponds to the order of magnitude of the power output of decentralized energy generation systems, as they are mainly used when using bioenergy . Therefore, local heating networks are often created together with biogas plants and biomass heating plants .

Solar energy systems

Solar district heating: open space solar thermal system from the Marstal heating network

With the integration of seasonal storage as long-term storage, solar thermal coverage of even more than 100 percent can be achieved with energy generated by solar thermal , so it would be a plus-energy house , with surpluses being passed on to other buildings. In this way, the share of regenerative energy can be increased significantly, and now at competitive costs per kilowatt hour .

Cold local heating

In addition to conventional systems, there are so-called cold local heating systems , e.g. Sometimes also referred to as Low-Ex or anergy networks , which work with transmission temperatures below 30 ° C. A frost-resistant brine is used for heat transfer , which transports the heat energy from house to house and absorbs ambient heat during operation through the non-insulated pipes. In the individual connected households, the temperature is then raised to the required heating temperature using monovalent heat pump heating. In this way, cold local heating networks have no heat losses in the pipes (particularly important in new buildings with only a low heating energy requirement), but achieve additional energy gains through environmental heat. As heat sources z. B. groundwater wells or solar thermal collectors , heat energy from rainwater are used or waste heat from industrial or commercial areas can be used, which, in contrast to conventional systems, can also be present on a low temperature basis due to the low operating temperatures of the lines. Further possible sources of heat are so-called agrothermal systems for generating thermal energy from agricultural soils. By using environmental heat in connection with electricity from renewable energies for the heat pumps, cold local heating systems enable a completely renewable heat supply .

The first such systems were set up in Switzerland. B. in Oberwald VS , where a cold heating network was set up in 1991, which is fed by the drainage water from the Furka base tunnel and supplies almost 180 apartments and a sports facility. In Germany there are plants in Wüstenrot , Aurich , Troisdorf and Hamburg , among others , which are powered by various heat sources such as B. geothermal energy, groundwater and waste heat from a dairy are fed.

Political objectives

Local heating networks are promoted by politics because they offer the possibility of transporting decentrally generated heat energy to the user. This enables an energy generation system with overall high energy efficiency with high added value in the regions. In addition, as explained above in the Technical Implementation section, local heating networks are a component of the politically desired expansion of the use of renewable energy sources .

advancement

In Germany, the establishment of local heating networks is funded under certain conditions. If the heat energy is generated in cogeneration , investment grants from the Federal Office of Economics and Export Control are possible; if the heat is generated with renewable energy sources, public subsidies can be claimed from KfW Mittelstandsbank .

Legal

There is no legal distinction between local and district heating. The Federal Court of Justice defines district heating regardless of the distance via the supply relationship:

“If heat is produced independently by a third party and supplied to others from a business point of view, then it is district heating. The proximity of the system to the buildings to be supplied or the existence of a larger pipeline network does not matter. "

The operating temperature is also not a legal criterion for a distinction.

literature

  • Chapter 3.1.5 Local solar heating . In: Ursula Eicker: Solar technologies for buildings: Fundamentals and practical examples , 2nd completely revised edition, Wiesbaden 2012, ISBN 978-3-8348-1281-0 , pp. 89–93
  • Chapter 6.8 Local solar heating. In: Solarthermische Anlagen , German Society for Solar Energy, 9th edition, ISBN 978-3-9805738-0-1
  • J. Krimmling: Energy-efficient local heating systems , Fraunhofer IRB , Stuttgart 2011, ISBN 978-3-8167-8342-8
  • M. Schmidt: On the way to the zero emission building , Springer-Vieweg, Wiesbaden 2013, ISBN 978-3-8348-1746-4
    • Chapter 4.5.2.2 Options for local heating supply , pp. 128–129
    • Chapter 4.7.7 Local solar heating supply , pp. 192–194
  • local solar heating. In: H. Weik: Expert Praxislexikon: Solar energy and solar technologies , 2nd revised edition from 2006, expert Verlag, ISBN 978-3-8169-2538-5 , pp. 274–275

Web links

Individual evidence

  1. ↑ Ashreeta Prasanna et al .: Optimization of a district energy system with a low temperature network . In: Energy . tape 137 , 2017, p. 632-648 , doi : 10.1016 / j.energy.2017.03.137 .
  2. ↑ a b "Cold" local heating network saves 40,000 kg of CO2 per year . Energy Agency NRW. Retrieved March 13, 2017.
  3. ↑ Cold local heating network supplies the new building area . In: Sonne Wind & Wärme , March 2, 2017. Accessed March 13, 2017.
  4. ^ "Cold local heating" for the new houses . In: Augsburger Allgemeine , December 1, 2016. Retrieved March 13, 2017.
  5. ↑ Cold local heating: agrothermal heat supply for a plus-energy settlement . Bauma 2013. Accessed March 13, 2017.
  6. ↑ Marco Pellegrini, Augusto Bianchini: The Innovative Concept of Cold District Heating Networks: A Literature Review . In: Energies . tape 11 , 2018, p. 236 , doi : 10.3390 / en11010236 .
  7. ↑ BAFA: Electricity payment / heating networks , accessed on February 24, 2010
  8. ↑ KfW Mittelstandsbank: KfW Renewable Energies Program, Premium Funding Conditions , accessed on February 24, 2010
  9. ^ BGH, judgment of October 25, 1989 , Az. VIII ZR 229/88; Guiding principle, BGHZ 109, 118 = NJW 1990, 1181.