Introduction
1.1 RenewableEnergy
Solar radiation is the result of fusion of atoms inside the sun. Part of the energy from the fusion process heats the chromosphere, the outer layer of the sun that is much cooler than the interior of the sun, and the radiation from the chromosphere becomes the solar radiation incident on the earth. The sun acts as a blackbody with a temperature around 6000 K [1], transports its vast energy to the earth in the form of electromagnetic radiation with a wide spectrum of frequency range that varies from infrared, visible lights to ultra-violet. The amount of solar power perpendicular to the beam outside the Earth’s atmosphere is known as solar constant ( S ), approximately 1367 W/m2 [1] [2] [3].
When the solar radiation enters the earth’s atmosphere as Fig. 1, a part of the incident energy is removed by scattering or absorption by air molecules, clouds and particulate matter usually referred to as aerosols. The radiation that is not reflected or scattered and reaches the surface directly in line from the PV module is called beam radiation. The scattered radiation which reaches the ground is called diffuse radiation. The albedo is a radiation that reaches a receiver after reflection from the ground. The total solar radiation on a horizontal surface of PV module consisting three components is called global irradiance. When the skies are clear and the sun is directly in line from the PV module, the global irradiance is about 1000 W/m2 [2]. Although the global irradiance on the surface of the earth can be as high as 1000 W/m2, the available radiation is usually considerably lower than this maximum value due to the rotation on the