In order to receive the maximum solar energy, the PV modules should be faced in the right direction and should be aligned at the proper angle with respect to the horizontal surface of the earth.
In this post, we'll try to find the best placement of the solar panels so that you get smooth electricity from your solar panels.
You're not going to get one answer (angle) for this.
Because the relative position of earth with respect to the sun is changing every moment.
so does our best placement angle.
it is not practical to change the position of the solar panels every-time.
We'll try to find the optimum static angle on which solar panels are aligned, absorbing most of the solar energy.
The tilt of the solar panels depends on:
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Let's understand each one of them one by one.
Which Hemisphere you live in?
If you live in northern hemisphere then face your solar panels towards true south, or true north if your location is southern hemisphere.
True north is not same as magnetic north.
True north or south are the points from where the earth's axis of rotation is passing.
Magnetic north or south are the points where your magnetic compass needle points.
Read: Should I align my panels to magnetic south or true south?
If you're living in equator then your panels should placed directly overhead facing the sun.
By what angle you should align the solar panels depends on the location (latitude) on earth.
Your location on earth can be exactly determined by the co-ordinate system: Latitudes and Longitudes.
Latitude is a metrics that describes your position (in degrees and minutes) north or south of the equator.
The greatest possible values of latitude are 90° North or 90° South of the equator.
Longitude is a measurement of your location east or west of the prime meridian.
(*We'll restrict our discussion to latitude only as it is used to determine the tilt of the solar panels)
The position point 'A' with latitude 20° North means, it is subtending an angle of 20° at the center of the Earth.
If you live 20° north (latitude) then you should face your panels towards south making an angle of 20° with earth's surface.
A person living in 30° south should face the solar panels towards north, making an angle of 30° with the horizontal surface.
The above calculation would be right if the earth's axis of rotation is not tilted.
The earth's axis of rotation is tilted
It's axis of rotation is not upright, it is tilted 23.5 degrees.
The gravitational pull of Moon gives stability to this tilt.
This tilt is responsible for seasons on Earth.
The earth's axis of rotation always points in one direction when it circles around the sun.
While circling around the sun, each hemisphere receives varying amount of sunlight.
For some time, the Northern hemisphere leans towards the sun.
It is the time when we see long day hours, temperature increases and we have summers.
When Earth moves to the other side of the sun, the Northern hemisphere leans away from the sun.
The days become short, temperature drops and the winter season arrives.
The places near equator see less variation in the sunlight but when we move towards poles, this variation becomes more pronounced.
The Declination Angle
The angle which the sun rays make with the equatorial plane of the Earth is called the declination angle.
This angle varies between -23.5° to +23.5° while circling around the sun.
The complete scenario can be shown as below:
The declination angle can be calculated using the following formula:
where N is the day of the year ( 1 to 365 or 366 in case of a leap year).
We take Jan 01 as the first day of the year.
The declination angle on the 150th day would be 21.8°
you can find the declination angle on any day of the year.
We should combine both latitude and declination to know the right tilt of the solar panels.
Finding the tilt of the panels
In summer solstice, the northern hemisphere is leaning towards the sun and its equatorial plane is making 23.5 degrees with the sun rays.
At this time, the latitude of 23.5° N is just aligned with the sun rays.
It means, the sun rays are falling straight on this location.
Therefore, you should place your solar panels directly overhead (making 0° with the surface of the earth) and facing south to capture the maximum sunlight.
The right formula for calculating the tilt is:
The value of Latitude of any place is constant but the declination angle is changing every moment with the movement of the earth.
Similarly, the tilt angle keeps on changing.
The solar panel tilt angle on 150th day on location 23.5° N is:
Tilt angle = 23.5° N - 21.8°(as calculated above under heading declination angle)
Tilt angle = 1.7° from the horizontal surface and should be facing south direction
you can find the tilt angle of any day for location 23.5 degrees North, using the following formula by putting the value of declination in equation (i):
If I find the tilt angles from 23.5°N from day 1 to day 365 then the chart will look something like shown below:
But I can not change the solar panel tilt everyday as it is not feasible.
Therefore, I should find the optimum tilt angle that can work most of the time.
If you are going for fixed tilt for your solar panels round the year then it is generally find by reducing the latitude by 15% or multiplying the latitude by 0.85.
a place with latitude 30° will have solar panels inclined at:
= 0.85 x 30°
= 25.5° with the surface of the earth.
The fixed angle is convenient but the disadvantage is that you are going to capture around 75% of sunlight than what you get when you keep changing the position.
(*These calculations are acceptable up to 50° latitudes)
If panels are not placed at optimum angle
The simple answer is the efficiency will reduce.
Your solar panels will produce less current.
The optimum angle for a place is 45° (with the surface of the earth)
But it is placed horizontally to the surface.
The situation is depicted below:
The solar panel if placed at 45° with the horizontal surface would receive maximum sunlight, say 'x'.
when placed horizontally, the component of light that is perpendicular to the panel is xsin 45° or 0.71x (sin 45° = 0.707)
The output will reduced by almost 30% in this case.
It shows the importance of right tilt of the solar panels.
It is most convenient to mount your solar panels at fixed tilt and just leave them.
But, the sun is high in summers and lower in winters, one can adjust the tilt twice year to capture most of the sunlight.
This way, you can have more current from your panels than you were getting from the panels at fixed tilt.
Let me share you the tilt angles when you are adjusting them twice a year.
If you go adjusting your solar panels 4-times in a year then the increase in the efficiency would be less when compared with the increase in the cost.
In the last, we can say that right tilt helps us in increasing the output of the panels and improves the financial feasibility of the solar power system.