In order to receive the maximum solar energy, the PV modules should be faced at the right direction, aligned at the proper angle with respect to the horizontal surface of the earth and the right orientation. The sun's position with respect to the reference point on the earth is determined by the two parameters which are (i) sun altitude and (ii) the azimuth angle.
Angle of Incidence
Let us first understand the altitude angle or the elevation angle or the angle of incidence.
The relative change in earth’s axis with respect to the sun causes the height of the sun to vary in the sky. The angle at which the sun rays are coming to the earth’s surface with respect to the horizontal surface of the earth is called the angle of incidence.
The total angular variation in the height of the sun for any location on the earth is (23.5 X 2) degrees i.e. 47 degrees.
We can calculate the altitude or the angle of the incidence for the various latitudes by using the following formula:
The important parameter in setting the direction of the solar panels is the maximum angle of altitude.The maximum solar angle occurs at the solar noon and it depends on the latitude of the location and the declination angle at a particular point.
Let us understand the altitude at the various positions:
Let us look at the max. altitude angle of few cities as on Jan 06,2015:
We can see that as the angle of the altitude decreases the tilt angle of the solar panel increases. It is the angle from the ground to make the panel perpendicular to the rays of sun so as to receive the maximum energy
While the azimuth angle is the horizontal rotation angle from North (in the Southern hemisphere) or from South (in the Northern Hemisphere). It is the angular measure of the sun as it moves in the sky from east to the west. It is calculated from the south. At the solar noon the azimuth angle is zero.
For the northern hemisphere, this angle is 180 degree and the facing of the panels should be towards south and for the southern hemisphere, it is zero degree and the facing of the panels should be towards north.
Generally the solar panels mounted are fixed,then it is advisable to take tilt of the solar panels as the latitude of that particular location.
We can now understand that how important is the orientation and positioning of the solar panels.