## Types of Solar Radiation –

The sun’s rays falling on the earth’s surface is known as solar radiation. There are three types of solar radiation. They are as follows –

1. Beam Solar Radiation

2. Diffuse Solar Radiation

3. Solar Radiation reflected from the ground and the surroundings.

*BEAM SOLAR RADIATION –*

Beam Solar Radiation is defined as the ratio of the beam radiation flux incident on an inclined surface to that on a horizontal surface. It is denoted by R-b. The beam radiation flux falling on the horizontal surface is given by

I

_{b }= I_{N}Cos Ɵ_{Z}_{ }

The beam radiation flux falling on an inclined surface is ,

I

_{b}^{’ }= I_{N }Cos Ɵ_{i}_{ }

The two thetas are the angles of incidence on the horizontal and inclined surfaces respectively and I is the intensity of the beam radiation. Beam Solar Radiation can be expressed as

R

_{b }= I_{b}^{’}/ I_{b}= Cos Ɵ

_{i }/ Cos Ɵ_{z}*DIFFUSE SOLAR RADIATION –*

Diffuse Solar Radiation is the ratio of diffuse radiation flux inciden on the tilted surface to that on a horizontal surface. This depends on the distribution of the diffuse radiation over the sky and on the portion of the sky seen by the surface. it is expressed as,

R

_{d}= ( 1 + Cosβ ) / 2*REFLECTED SOLAR RADIATION –*

This is the component which comes from the ground and other surrounding objects. If the reflection of the beam and diffuse radiations incident on the ground is assumed as diffuse and isotropic, then the situation is opposite to that of the diffuse radiation. This is expressed as,

Where I

_{T }is the flux falling on the tilted surface.R

_{r}= ( 1 – Cosβ ) / 2The flux falling on the tilted surface at any instant can also be calculated by the following equation –

I

_{T}= I_{b}r_{b}+ I_{d}r_{d}+ ( I_{b}+ I_{d}) r_{r}_{ }