The maps of Global horizontal irradiation for various countries and regions are available on this page to download. SolarGIS database is the source of solar data represented on the maps. Global horizontal irradiation is the most important parameter for evaluation of solar energy potential of a particular region and the most basic value for PV simulations.
The word “Solar Radiation” is the electromagnetic radiation or energy emitted by the sun. Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through the Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. One of the main cause of climate change is due to solar radiation. Depending upon the nature of the surface, the radiation will be absorbed, reflected or transmitted through the object. This take place when solar radiation strikes any object. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by the clouds or reflects off other objects, it is experienced as diffused light.
The extraterrestrial radiation is the radiation which is incident outside the earth’s surface.
The extraterrestrial radiation is 1367 watts/m2.
Due to the change in distance between earth and sun, there is a seasonal variation in the extraterrestrial rate.
Terrestrial Solar Radiation:
It is the electromagnetic radiation which originates from earth and its atmosphere.
Terrestrial Radiation is a longer wavelength which is totally infrared.
When the terrestrial solar radiation reaches the earth’s surface,it is broken into two components i.e.,diffuse radiation and beam radiation.
Beam Radiation is the solar radiation which moves through the atmosphere in a straight line without being scattered, reflected or absorbed by particles in the air.
Diffuse Radiation is the solar radiation which is being scattered, reflected or absorbed by the particles while passing through the atmosphere but ultimately reaches the earth’s surface.