“A correct tilt angle improves the performance of the solar plant by 25%”
Basics of Tilt angle
Tilt angle of solar panel is the optimum angle at which solar panel is tilted in south direction to get maximum sunlight throughout year. Solar panel should always face true south for location which falls in Northern hemisphere and true North for the location in southern hemisphere.
Solar irradiance and Insolation
It is the amount of solar irradiance falling on fixed area over a period of time. Hence it is the solar energy a particular location receiving in a day. It is measured in kwh/m2 per day. Solar irradiance of India is 1999W/m2. To capture maximum solar insolation, solar panel should be tilted in south direction at an angle with the horizontal.
Impact of seasonal variation on solar insolation
The angle at which sunlight falls on the earth changes with seasons as distance between Sun and Earth keeps on changing between month to month.
During summer season, Sun is very close to the earth and the sunlight falls almost at 90° on the earth, while in winter season, Sun is furthest away from Earth and its sunrays falls at around 15° to 30° depending upon location.
We get maximum power output from solar panel when sunrays fall at almost 90°. As a thumb rule to achieve this we must arrange solar panels in south facing tilted with angle equivalent to the latitude of the location of solar plant.
Tilt angle calculation
To get more accurate tilt angle used in utility scale project, a formula is used to calculate the tilt angle.
Tilt angle ɵ = 0.87 x latitude, if latitude is < 25°
Tilt angle ɵ = 0.76 x latitude + 3.1°, if latitude is between 25° and 50°
Fixed Tilt angle
For rooftop solar plant, fixed type structure is most suitable. In this type of structure, the mounting frame is fixed. We can not change the angle. The tilt angle is arrived as per above calculation. The tilt angle is dependent on the latitude of the location.
The performance of the solar plant is fixed at 71% (approximate) of the maximum output we can achieve.
| Structure Type | Fixed | Adjustment 4 times a year | Dual axis tracker |
| % Optimization | 71% | 75% | 100% |
Can tilt angle be changed with season?
Yes!! We can improve the output of solar panel by changing the tilt angle in each season. This can be achieved by using movable mounting structure either single axis or dual axis tracker.
To change the tilt angle of solar panel with season, we need single axis or dual axis mounting structure.
Variable Tilt angle
The tilt angle of the panel can be changed by using single axis or dual axis mounting tracker. In single axis tracker, the solar panel can be moved in vertical direction at a desired angle as per the season.
Dual axis tracker is motorized mounting structure which changes the direction of the panel facing the sun throughout the day as well as the tilt angle as per the season.
Month of change of tilt angle 2 times a year
| Season | Month of change |
| Summer | March |
| Autumn | September |
Month of change of tilt angle 4 times a year
| Season | Month of change |
| Summer | April |
| Autumn | August |
| Winter | October |
| Spring | March |
Note that the winter angle is about 5° steeper than what has been commonly recommended. The reason is that in the winter, most of the solar energy comes at midday, so the panel should be pointed almost directly at the sun at noon. The angle is fine-tuned to gather the most total energy throughout the day.
Conclusion
Tilt angle (ɵ) is the major deciding factor for getting maximum output from the solar plant. Hence, the tilt angle of solar panel should be properly chosen.
