3.2 TECHNICAL PRINCIPLES

3.2.1 Solar Collectors

The collection of solar radiation is based on the "greenhouse effect". The solar collector is mounted on or near the house, facing south (in the northern hemisphere). A large proportion of the sun's radiation can pass through the glass or plastic glazing and strikes a light-absorbing material. The material converts the sunlight into heat, which is prevented from escaping by the glazing because most of the resulting infra-red waves are reflected. A car parked in the sun with its windows closed illustrates this greenhouse principle. The sunlight passing through the windows or glazing strikes the upholstery and is converted into heat energy. This heat is prevented from escaping by the closed windows and the inside of the car becomes extremely hot. A proper solar collector can easily achieve 95oC.

3.2.1.1 Types

Source CRES-TRASOL CD-Rom
Figure 3.2 - Typical layout of a flat plate collector

 

Flat plate collectors (figure 3.2) are the most economical choice for applications requiring energy delivery at moderate temperatures, up to perhaps 100°C. They capture both beam and diffuse solar radiation, do not need to track the sun, and require little maintenance. The major applications of these units are in solar water heating, building space heating, air conditioning and industrial process heat.