Drain-back system

from Wikipedia, the free encyclopedia

A drain-back system ( English drainback solar water-heating system ) is a specific type of a solar thermal system . With this type of construction there is no conventional stagnation state of the solar system . The English term drain-back means something like backflow , in this case an automatic emptying of the collectors when the pump is idle is effected by gravity .

As soon as the collector circuit's circulation pump comes to a standstill, the liquid drains by itself and flows into a collecting container inside the building. This is achieved, among other things, because the connecting lines of these systems have a certain gradient. In some of these systems, the collection volume for the reflux is included in the heat accumulator.

advantages
  • In this case, the liquid in the solar collectors cannot evaporate, because when the storage tank is fully charged with heat, the circulation pump first switches off and then the liquid flows back from the collectors by itself before evaporation due to heat could occur.
  • Rather higher operational reliability, since there cannot be any higher pressure states, as with conventional stagnation.
  • In winter, the liquid in the collector cannot freeze because the solar collectors are only filled if a certain minimum temperature is reached through sunshine. Therefore, distilled water without frost protection can be used in the collector circuit instead of solar fluid .
  • Less maintenance, as the liquid in the collector circuit does not have to be checked for aging.
disadvantage
  • More installation work because the lines must have a certain minimum angle of inclination. This is a considerable additional effort, especially in very large systems with many collectors.
  • A more powerful pump is required in the collector circuit.
  • Previous training of the fitters may be required for this type of system.

literature

  • Chapter 3.7.1. In: Peuser, Remmers, Schnauss: long-term experience of solar thermal energy , Solarpraxis, Berlin 2001, ISBN 3-934595-07-3 , pp. 61–62
  • Chapter 4.2.6. In: T. Delzer u. a .: Solar heat for domestic use , 2nd completely revised edition, Solarpraxis, Berlin 2009, ISBN 978-3-934595-90-3 , pp. 84–85
  • Chapter 4.5.4. In: Solar systems: Handbook of thermal solar energy use , 11th edition from 2011, Staufen near Freiburg, ISBN 978-3-936896-40-4 , pp. 146–147
  • Chapter 6.4.4.1. In: R. Stieglitz, V. Heinzel: Thermal solar energy: Fundamentals, technology, applications , Springer-Vieweg, Berlin / Heidelberg 2012, ISBN 978-3-642-29474-7 , pp. 456–459
  • Chapter 7.2.3. Drainback technology. In: Werner Weiss (Ed.): Solar Heating Systems for Houses: Design Handbook for Solar Combisystems , Routledge, ISBN 1-902916-46-8 , pp. 182-189
  • H. Weik: Expert Praxislexikon: Solar energy and solar technologies , 2nd revised edition from 2006, expert Verlag, ISBN 978-3-8169-2538-5 , pp. 64–65
  • Joachim Berner: Safe from too much sun. Drainback systems. In: Sonne Wind & Wärme , Vol. 34, No. 1, 2010, pp. 76–81. ISSN  1861-938X

Web links

Individual evidence

  1. ↑ Goran Mijic: Solar Energy and Technology , Volume 2, De Gruyter, 2018, ISBN 978-3-11-047577-7 , p. 190
  2. ↑ Solar systems: Manual of thermal solar energy use , 11th edition of 2011, ISBN 978-3-936896-40-4 , p. 146