Yash
Yes, the solar panels do work in cloudy day but their performance is reduced significantly.
The solar panels are the main component in any solar power system.
They act as an interface between the sunlight and our energy needs.
They absorb the sunlight and convert it into electricity.
When the solar panels are given proper tilt with the ground and the sunlight falls straight on their surface, they perform to their maximum extent.
However, the sunlight intensity is not constant.
It varies throughout the day from sunrise to sunset.
(It is due to the relative motion between the earth and the sun).
Also, there are seasonal variations in the sunlight intensity.
When the sky is clear and the sun is shining, the solar panels work to their maximum capacity and you get more power.
During the monsoon period, the clouds cover the sky and hence less sunlight reaches the solar panels’ surface.
And they produce less current.
Let us understand more deeply the deterioration in the performance of solar panels when clouds cover the sky.
Cloudy day on September 9, 2023
You can see the dark clouds in the picture.
This place is Sahibabad, Ghaziabad (North India).
The monsoon season in North India extends from July to September.
This picture was taken on September 9, 2023, at 10:45 am.
We are going to find the power produced by our 5-kW solar power system.
Tilt of 5 kW solar
This place Delhi/NCR has coordinates of latitude 28.4° N and longitude 76.83° E.
Theoretically, the solar panels’ tilt should be the location’s latitude which is 28.4°.
But we have made it 20°
Reason: When the sun rises, its sunrays graze over the surface of the solar panels, and when you keep the solar panels slightly at a lower angle than its theoretical angle which is the latitude. Then the sunray will be more direct and help the solar panels to absorb more sunlight.
A similar situation happens during the sunset.
Therefore, making it 20° allows our solar panels to absorb more sunlight during sunrise and sunset.
Effect of clean solar panels: Top view
The solar panels are clean due to the rain in the early morning.
The solar panel performance also degrades due to the presence of dust on its surface.
The dust makes a layer over its surface making it difficult for the solar panels to absorb the sunlight.
Therefore, we must keep them clean to know the deteriorating effects of the cloudy day.
Otherwise, we will not get the fair results.
Also, the technology does play an important role in the power production of the solar panels under these conditions.
The monocrystalline solar panels are more efficient and perform better than the polycrystalline solar panels under these situations.
These are the latest technology solar panels which are half-cut monocrystalline solar panels 10 solar panels of 500 watts each.
The components of the sunlight
In the picture, you can see the dark clouds in the sky.
They obstruct the sunlight from falling directly on the solar panel’s surface.
The sunlight has 2 main components when it enters the Earth’s atmosphere:
Direct and diffused components:
The direct component is that part of the sunlight which falls directly over the solar panel’s surface.
And when part of the sunlight is scattered and reflected by the air molecules and the dust particles, it gets diffused in the atmosphere.
The direct sunlight has more intensity while the diffused component is less intense.
The clouds in the sky make it difficult for direct sunlight to reach the panel’s surface.
Most of it gets diffused in the atmosphere and becomes less intense.
Now the solar panels are left with less intense sunlight which is spread in the atmosphere.
They absorb this less intense sunlight and produce less current.
Yes, the solar panels do work on a cloudy day but their output is reduced significantly.
Total sunlight intensity = Direct sunlight + Diffused sunlight
The Yield of the 5-kW solar on a cloudy day
The solar inverter display shows us the amount of power generated on a real-time basis.
The solar inverter is connected to the solar panels.
It takes in the direct current produced by the solar panels and converts it into the alternating current.
This alternating current runs our electrical appliances such as fridges, fans, lights, etc.
The inverter display is showing 1320 watts of power generated by the 5 kW solar panels at 10:45 a.m. on the cloudy day of September 09, 2023.
We can calculate the yield of the system.
The formula for calculating the yield is:
Yield (%) = Output Power/Installed power of the system
= 1320 Watts/5000 W x 100%= 26.4% at 10:45 am on September 09, 2023.
Units produced by 5 kW solar on a cloudy day
Let us find out how many units the system had made till 10:45 a.m. on September 09, 2023.
Let us assume that sunrise is at 6 a.m. on that day.
From 6 am to 10:45 am is almost 5 hours.
So, the energy produced in those 5 hours on September 09, 2023, is 3.6 units or 4 units.
The following is the full-day energy chart of September 09, 2023.
On that day it produced 11.2 kWh.
How do we know that it has produced less or more?
We need to compare this performance with the one when it was a clear and sunny day.
5 kW solar yield on the sunny days
September 2, 3, and 4 were sunny days of the first week of this month.
Upon closely looking at the energy chart.
The Yield at the same time at 10:45 am on the sunny days were:
70%, 71%, and 69.6% respectively.
Whereas the yield at the same time on the cloudy day of September 9 2023 at 10:45 am was 26%.
This is a 63% reduction in the yield when compared to its yield on sunny days.
Cloudy Day vs Sunny Days: The energy production by 5 kW solar
The comparison on the real time basis may not give you the accurate results.
Assuming the day was cloudy for the whole day except for few minutes when we observed the streak of sunrays.
Again assuming that we measured the yield of the solar when clouds disappeared in those few minutes.
We would get the high yield, giving wrong picture about the whole day which was otherwise cloudy.
Therefore, in order to eliminate this chance of error, we would take the energy produce by the system for the whole cloudy day.
And we will compare it with the energy production by the system on the sunny days.
Similarly, when we compared its energy production on cloudy days vs. sunny days.
We observed a 58% reduction in energy production.
What did we learn?
- On a cloudy day the solar panels do work but their performance reduces drastically.
- The direct sunlight is obstructed by the clouds making solar panels absorb less sunlight and hence produce less current.
- The tilt was lower than the latitude of the location so as to absorb more sunlight during sunrise and sunset.
- The yield was reduced by 63% at 10: 45 a.m. on September 09, 2023, and the energy production was reduced by 58% on a cloudy day.
- Yield (%) = Power produced on a real-time basis/Total power produced
- The energy is measured in kWh and 1 unit = 1 kWh
- Efficient solar panels such as half-cut monocrystalline solar panels are capable of absorbing more diffused sunlight and perform better than polycrystalline solar panels.
- Keep the solar panels clean so your solar panels perform efficiently on cloudy days.
- The whole day’s energy production on a cloudy day gives a better picture than the performance at a particular time of the day.
