Collectors

The solar collector is the part of the solar installation which takes up the light and the warmth of the sun. For its performance it is vital that it takes up a big part of the sunlight in warmth (absorption), delivers at the same time only a little of it again as a heat radiation (issue).
Instead, the absorbed warmth should be transferred as far as possible lossless to the so-called solar liquid in the solar circulation.

The most important constructional differentiation with collectors is between

• The flat-plate collectors which are protected with customary isolation materials against the warm losses. They have been road-preparing for the efficient solar use. They have according to experience a very long life span; some manufacturers give a functional guarantee for more than 10 years.
• Vacuum tubes collectors; these work after the thermos flask principle: Around the internal absorber tube containing the transport medium the second, external (glass) tube is put and from the space between the air has been taken away (vacuum) for an optimised isolation.
  They are more efficient, above all, with high temperature differences between outside air and absorber than other construction types. Hence, they are also used in the industrial area where process warmth with consistently over 80 ° Celsius is required.

Because flat-plate collectors are clearly inexpensive and with it as a rule more economic, this construction type is used in the house technology redominantly. Vacuum collectors have against it a clearly higher yield per square metre of absorber surface; they are often recommended if only a little for the installation of collectors suitable surface exists. Indeed, the difference strongly melts away by the conversion on the gross surface of the whole collector instead of the pure absorber surface, because with flat-plate collectors the absorber takes a clearly bigger part of the surface required all together for the installation.

Theoretically vacuum tubes collectors should deliver bigger yields in wintertime, if at strong minus temperatures the better isolation is more effective.
Then, however, in practice the collectors are often snowy and ice-covered, and just by the better isolation snow and ice defrost more slowly of vacuum tubes collectors whereby the actual benefit duration sinks.

A hybrid form are so-called vacuum flat-plate collectors. These show an attempt to use the better insulating qualities of the vacuum also in flat-plate collectors. However, design-partly these incline to leakage, so that penetrating air steps at place of the vacuum and this must be restored regularly with the help of a vacuum pump.