Technical manual
SOLAR
in Figure 2, namely direct, reflected and diffuse radiation. The various types of radiation can occur in isolation but in most cases the radiation incident on a solar thermal collec- tor is a combination thereof.
<200 W/m² | strong | |
diffuse | ||
| ||
<600 W/m² |
| |
| diffuse | |
<1000 W/m² |
| |
| direct | |
<1200 W/m² | direct + reflected | |
|
Figure 2 – Forms of incident solar radiation
The solar radiation available outside the earth’s atmosphere, the so called extraterres- trial radiation, has a density of 1367 W/m². Depending on:
-the location of the solar system
-the time of day and year
-the “obstacles” in the atmosphere such as cloud cover and pollution
-and the inclination of the solar system in relation to the sun
this value varies strongly. A map of the United Kingdom and Ireland is shown in Figure 3, indicating average annual solar energy gains on the horizontal surface.
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