Solar district heating

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Solar thermal system of the Marstal district heating system

Solar district heating describes the supply of larger residential and industrial areas by means of large collector fields and heating networks with renewable, emission-free solar thermal energy . In order to stabilize the heat supply, solar district heating systems are usually equipped with heat storage tanks, often large earth pit storage tanks that enable seasonal heat storage for the winter half-year. Solar district heating systems are often used with other heat sources such as B. heat pumps , power-to-heat systems, combined heat and power plants , peak load boilers or industrial waste heatcombined; It is also possible to supplement existing district heating networks with solar thermal collectors.

term

In connection with solar district heating, two different terms are used in German-speaking countries: solar district heating and solar local heating . There is no delimitation of the terms. In English the term solar district heating is used.

application

This type of heat generation is widespread in Denmark and Sweden . As of September 2016, solar district heating systems with a collector area of ​​1 million m² were installed in the pioneering country of Denmark. Some pilot plants have been implemented in Germany and Austria. At the end of 2016, a total of 199 solar district heating plants with a nominal thermal output of at least 700 kW were listed in Europe. The most powerful system at that time was in the Danish municipality of Silkeborg and has a thermal output of 110 MW with a collector area of ​​approx. 157,000 m²  . Another large system, the beginnings of which go back to the 1990s, is the Marstal heating network , which has been expanded several times and had a solar thermal output of 23.4 MW in 2012. The market for solar district heating grew by an average of 35% annually between 2013 and 2017. For 2018 it is expected that solar district heating systems will produce more than one terawatt hour of thermal energy for the first time in Europe.

At the end of 2019, there were around 30 solar thermal systems feeding into heating networks in Germany with a total output of around 50 MW.

costs

As a result of further technical development since the beginning in the 1970s, the heat production costs of solar district heating systems, which were initially supported with subsidies, fell. As of 2017, large solar district heating systems in certain countries such as Denmark are economically fully competitive with other types of heat generation without subsidies.

Since the heat production costs decrease with the increasing size of the solar thermal system, the trend is towards larger systems. These can produce heat at prices of three to five cents per kilowatt hour. For Denmark, the heat generation costs are given as 3 to 6 ct / kWh. These low heat production costs can be attributed, among other things, to inexpensive seasonal heat storage. Large underground reservoirs with 75,000 or 200,000 m³ capacity were u. a. built in Marstal and Vojens .

business

While heat storage is an important issue in private solar thermal systems, it can be partially or completely dispensed with in solar district heating systems. Large seasonal storage facilities are sometimes being implemented. This could theoretically achieve coverage of around 50% in Chemnitz by the solar thermal system. Furthermore, due to the high continuous heat consumption in large networks, the systems can usually feed in their heat continuously. If this needs to be stored, the network itself can be used as a storage facility in addition to stationary storage facilities.

The advantage of solar district heating is that it is cheaper than the fuel costs for bioenergy and fossil fuels, and thus energy costs can be saved in solar-assisted heating networks. Usually, the solar thermal system can cover the heat supply in the summer half of the year, so that the district heating boilers do not have to run in the low partial load range and thus also with a low level of efficiency. In addition, the break in operation in summer makes maintenance of the boiler easier and easier to plan.

literature

  • Nicolas Perez ‐ Mora et al .: Solar district heating and cooling: A review . In: International Journal of Energy Research . tape 42 , no. 4 , 2018, p. 1419–1441 , doi : 10.1002 / er.3888 .
  • Viktor Wesselak , Thomas Schabbach , Thomas Link, Joachim Fischer: Handbuch Regenerative Energietechnik , 3rd updated and expanded edition, Berlin / Heidelberg 2017, ISBN 978-3-662-53072-6 .
  • J. Berner: Solar heat from the network: Solar collectors are increasingly feeding heating networks with environmentally friendly energy. With local solar heating, municipalities can achieve their climate goals and the industry is gaining a new sales market. SONNE WIND & WÄRME presents the market and current projects. In: Sonne Wind & Wärme No. 6/2018, pp. 76–79

Individual evidence

  1. ^ Solar District Heating. solar-district-heating.eu, accessed on April 30, 2019 (English, /, German).
  2. ↑ A. Dahash et al .: Advances in seasonal thermal energy storage for solar district heating applications: A critical review on large-scale hot-water tank and pit thermal energy storage systems . In: Applied Energy . tape 239 , 2019, pp. 296-315 , doi : 10.1016 / j.apenergy.2019.01.189 .
  3. ↑ a b c Viktor Wesselak , Thomas Schabbach , Thomas Link, Joachim Fischer: Handbuch Regenerative Energietechnik , Berlin / Heidelberg 2017, p. 419f.
  4. ↑ Database of large-scale solar systems. solar-district-heating.eu, accessed on April 30, 2019 (English).
  5. ↑ Solar heating networks: annual market growth of 35 percent. In: newspaper for local economy. April 12, 2018, accessed April 16, 2018 .
  6. ↑ District heating: sun into the network . In: Süddeutsche Zeitung , July 31, 2020. Accessed August 1, 2020.
  7. ^ Nicolas Perez-Mora et al .: Solar district heating and cooling: A review . In: International Journal of Energy Research . tape 42 , no. 4 , 2018, p. 1419–1441 , doi : 10.1002 / er.3888 .
  8. ↑ a b Solar district heating replaces sales of small systems. In: Renewable Energies. The magazine . November 8, 2016, accessed February 20, 2017 .
  9. ↑ Annelies Vandermeulen et al .: Controlling District Heating and Cooling Networks to Unlock Flexibility: A Review . In: Energy . tape 151 , 2018, p. 103–115 , doi : 10.1016 / j.energy.2018.03.034 .
  10. ↑ Solar thermal villages are becoming popular . In: Renewable Energies. Das Magazin , November 8, 2018. Retrieved November 10, 2018.