Here I am talking about the True South or the True North direction of the panels, not the Magnetic South or the Magnetic North as pointed by the magnetic compass needle. Read: How to determine the angle and the orientation of the solar panels?
What is the magnetic declination?
â€‹Your magnetic compass needle will not always point towards the True North or the True South. There is a difference between the True North or South (the axis around which the earth rotates, pointing to the geographical North Pole) and the Magnetic North or the South (the direction at which the needle will point) is called the magnetic declination. In order to get the optimum amount of the sunshine your solar panels should face towards the True south (If you are living in the Northern hemisphere) or towards the True North (If you are living in the Southern Hemisphere)
Why there is the difference?
The reason lies inside the earth; the core of the earth is made up of hot and molten metal which creates a magnetic field around the earth. This magnetic field is not static; due to the continuous rotation of the earth, the position of the hot molten metal inside the core of the earth is changing every moment, resulting in the change in the magnetic field. The north and the south poles of this changing magnetic field may or may not align with the True North or the True south pole of the earth (the imaginary line passing through the north pole is the true north of the earth) is the reason behind the difference between the compass, results in the difference in its magnetic North and the true North.
How to find the True South or the True North?
Now it is clear that in order to get the maximum sunshine, the solar panels should align towards True south if you are in the Northern Hemisphere like India and towards True North if you are living in the Southern Hemisphere like Australia.
The magnetic declination is either added or subtracted to your magnetic south of the compass needle to get the True South. If you know the coordinates of your location like latitude and the longitude, you can easily find the declination at your location or you can simply find it on the internet just by typing the Declination of your location
Letâ€™s see the True south of some of the locations in the following table:
So, we come to know that we should always face our panels to the True South (when you are living in the northern hemisphere) instead of the magnetic south shown by the needle of the compass. The positive values mean the eastern declination and the negative values refer to the western declination. For example, if I live in an area with magnetic declination \(-15^0\), then it means that the true south is \(15^0\) west of the magnetic south i.e. \(180^0 + 15^0 = 195^0\). Conversely, if my magnetic declination is \(+15^0\), then it means the true south is \(15^0\) east of the magnetic south i.e. \(180^0 - 15^0 = 165^0\).