Automatic solar tracking system

Figure 3.1: Earth Rotation 
Revolution
, that is the motion of the earth around the sun is responsible for the different seasons 
in the year. The earth takes 365 days to revolve around the sun. Earth revolves around the sun in 
an elliptical orbit and the plane covered by the earth during the revolution is known as an ellipsis. 
The axis of rotation and ellipsis makes an angle of 66.5 degrees between themselves. This is the 
explanation behind the summer/winter solaces and spring autumn equinoxes. Due to these motions 
of the earth, the amount of sunlight received throughout the year varies. 
Sunlight is the electromagnetic radiation from the sun expropriated by the earth. The total power 
given off by the sun into space is much more than that intercepted by the earth. 

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THEORITICAL BACKGROUND OF SOLAR TRACKER 
15
AEIE, RCCIIT 
Figure 3.2: Earth Rotation and Revolution 
Within a given period of time, the emission of solar radiation is somewhat constant and the 
intensity this radiation hitting a unit area of the earth’s crust is also constant, known as solar 
constant. The value of this solar constant can be expressed as: - 
G
SC
= σ. T
4
. (
4πR
4πD
)
2
= 1367 W m
2
⁄
In the above expression, 
σ
is termed as Stefan Boltzmann Constant with a value of 5.67
×
10
-8
W m
2
⁄
. K
4
, R is known as the radius of the Sun, 696·106 m and D is 150 ·109 m, the average 
distance between the Sun and the earth. 
The absorption of solar radiation on the surface of the earth also varies with different parameters. 
Latitude and longitude are one of the prescribed parameters. Latitude the horizontal imaginary 
line, parallel to the equator, is the angle suspended by the arc linearly join a person’s position and 
the equator, at the center of the earth. On the contrary longitudes are the vertical imaginary lines, 
where longitude is the angle suspended by the arc joining the north-pole and south-pole as well as 
passing through the given location, linearly with the Greenwich meridian, at the center of the earth. 
The latitude and longitude express north-south and east-west directions respectively on the earth. 
The sunlight is observed at different angles depending on the place on the earth and the angles of 
the sun. The sun’s angle can be classified into the following: - 
•
Elevation Angle

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THEORITICAL BACKGROUND OF SOLAR TRACKER 
16
AEIE, RCCIIT 
•
Zenith Angle
•
Azimuth Angle