Should I align my panels to the Magnetic South or the True South?

Our country India is located in the Northern hemisphere closer to the equator. In order to get maximum sunshine or the solar insolation, the solar panels should be placed southwards. For countries located in the Southern Hemisphere like Australia, the solar panels should face in the north direction in order to get the optimum sunshine.

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?

​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

• If the declination is east of magnetic south then you subtract declination value from the magnetic south to get the True South
• If the declination is west of the magnetic south then you add the declination value to the magnetic south to get the true south

​Let us say you have your solar power system in New York City. After finding it on the internet the magnetic declination \(13^0 and\ 28\ minutes\) east. I am rounding it down to \(13^0\) to ease the calculations (1 degree is equal to 60 minutes; if the minute value is above 30 then I will round or else I will round it down to the nearest integer). It means that the true south is \(13^0\) east of the magnetic south; the value of the true south will be \(180^0-13^0=167^0\)

Conversely, the magnetic declination of Tokyo is \(7^0 and\ 25\ minutes\ west\). In this case, it means that its true south is \(7^0 and\ 25\ minutes\ west\) of the magnetic south. Further rounding it down to \(7^0\), we need to add \(7^0\) to the magnetic south to get the true south, we get \(180^0 + 7^0 = 187^0\). I should align my panels to \(187^0\) to get the true south.

Let’s see the True south of some of the locations in the following table:

S.No	Place	Magnetic Declination (Degrees)	Magnetic South (Degrees)	True South (Degrees)
1	New Delhi	1.16	180	179
2	Beijing	-8.6	180	189
3	Islamabad	2.67	180	177
4	Baghdad	4.57	180	175
5	Ottawa	-13.31	180	193

 

Conclusion

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. \(180^0 - 15^0 = 165^0\).

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