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How it works

Solar Heating

Rayotec has been active in the solar energy business since 1987, specialising in both domestic and commercial installations. Through our knowledge and extensive experience of completing over 6000 solar installations, we offer the Rayotec CPC 6 INOX evacuated solar collector with its high build quality, reliability and performance.

The Rayotec CPC 6 INOX evacuated tube collector consists of 3 main components, which come completely pre-assembled:

  1. Evacuated tubes
  2. CPC mirrors
  3. Manifold with heat transfer unit


The Evacuated Tube


Each Rayotec vacuum tube is composed of two Borosilicate 3.3 glass tubes, one slightly smaller than the other, fused together at the top to make a single tube. The air in the void between the two tubes is then pumped out, creating a vacuum thermal insulation layer.

To convert the daylight into useful solar heat, the internal glass tube is coated with an environmentally friendly, highly "selective" light absorber (Aluminium Nitrite). The absorber converts both direct and diffused light from a large spectrum of wavelengths into heat. The heat produced by the absorber is protected from the atmosphere by the vacuum layer, thereby eliminating thermal-loss. This significantly increases the performance of the solar collector.


How is it controlled?

The whole system is controlled by a differential temperature control unit. The controller has three temperature sensors: Collector, Cylinder and Return. When the temperature of the collector is 8°C hotter than the bottom of the hot water cylinder, the control unit will turn on the pump starting the solar thermal transfer process. The controller ensures the pump is only running when positive solar gain is available.

The control unit also has various safety features, as well as useful solar gain information.

The CPC Mirror

In order to increase the output of the evacuated tubes, a highly reflecting, weather-proof CPC mirror (Compound Parabolic Concentrator) is placed behind the evacuated tubes. The special mirror geometry ensures that direct and diffuse light, travelling from all orientations, falls onto the absorber. This substantially improves the energy yield of a solar collector in unfavourable conditions, such as Easterly early morning and Westerly late afternoon light. It is also beneficial when it is not possible to install the panels in the ideal south-facing orientation.

Manifold and "U" Tube

Within each glass tube there is a stainless steel "U" tube collection pipe, with a circular metal heat absorber plate. All the "U" tubes are connected to a well insulated manifold, which is designed to allow a direct flow of the heat transfer fluid through the system. The heat transfer fluid collects the heat from the absorber inside the glass tube and transports it to the cylinder. The manifold has a special design which ensures all the tubes exhibit the same hydraulic resistance. The heat transfer fluid collects the heat from the absorber in the glass tube and carries it down to a twin coil cylinder where it heats the bottom part of the cylinder, being the coolest part. The second, upper coil within the cylinder, is connected to the boiler.

A typical installation


How is it controlled?

The whole system is controlled by a differential temperature control unit. The controller has three temperature sensors: Collector, Cylinder and Return. When the temperature of the collector is 8°C hotter than the bottom of the hot water cylinder, the control unit will turn on the pump starting the solar thermal transfer process. The controller ensures the pump is only running when positive solar gain is available.

The control unit also has various safety features, as well as useful solar gain information.