Yash
Tamil Nadu is a sun-rich southernmost state of India after Kerala.
Understanding the geography and climate for the right solar power system is essential.
The Geography of Tamil Nadu
The Indian Ocean surrounds it to the east and the south.
In its west, we see Kerala.
Andhra Pradesh to its North.
And Karnataka in the North-west.
Tamil Nadu has flat land in the east and we see hilly regions in the north and the west.
Anai Peak (2695 meters) in Anaimalai Hills is the highest mountain peak in Indian Peninsula.
The main rivers are Kaveri, Thamirabarani, Vaigai, and Palar flow eastward into the ocean.
Its rich alluvial soil is suitable for coconut, cashew nut, tea, and coffee plantation.
- Capital: Chennai
- Coordinates: 11.1271° N, 78.6569° E
- Area: over 1,30,000 km²
The climate of Tamil Nadu
This state has a tropical type of climate.
May and June are usually the hottest months with a maximum daily temperature of 38 degrees.
It lies in the thermal equator.
This means that this state does not have much temperature variation and insolation is similar throughout the year.
The insolation difference between the highest and the lowest level is 1.78 (6.85 – 5.07).
This difference is small when compared to the other states that are farther from Tamil Nadu such as Delhi.
The difference between the highest and the lowest Insolation level is 3.1 PSH (7.03 – 3.93).
Cyclones in Tamil Nadu
The coastline of Tamil Nadu is often hit by tropical cyclones.
The low-pressure region built over the Bay of Bengal is the main reason for cyclones and rainfall in Tamil Nadu.
Let me list a few cyclones that hit the coastline in the past:
- Jal in 2010: Max speed 110 km/hr
- Laila in 2010: Max. wind speed 100 km/hr
- Thane in 2011: Max. speed 140 km/hr
- Nilam in 2012: 85 km/hr
- Madi in 2013: 120 km/hr
- Vardah in 2016: Max. speed 120 km/hr
- Mandous in 2022: wind speed 75 km/hr
Orientation and Tilt of solar panels in Tamil Nadu
Tamil Nadu state lies in the Northern Hemisphere. Therefore, the solar panels are kept in the south direction to get the maximum solar energy.
Its latitude is 11.1271° N which tells that the solar panels should be lifted 11.1271° above the ground to get the maximum sunlight.
Read: How to find the right solar tilt for maximum sunlight?
Peak Sun Hours in Tamil Nadu
We already have got an introduction about this in the above section.
The Peak Sun Hours are the total sunlight intensity received by any location in a day.
This total sunlight is found by adding the sunlight intensities from sunrise to sunset on any given day in a particular location.
However, its value is not constant.
It varies, due to the rotation of the earth around its axis and the revolution around the sun. When I take sunlight on a clear sunny day from sunrise to sunset, it looks something like shown below:
When we add all the sunlight intensity values (represented by dots in the above figure).
We get the total value of the sunlight intensity on that day.
And
- 1 PSH = 1000 W/m²
For example, the total sunlight intensity on any day in a given place is 5880 W/m².
We can find its Peak Sun Hours by using the above relation.
5350 W/m² = 5.88 PSH
More PSH indicates good sunlight. And any value that is > 5 is considered very good for solar PV.
Tamil Nadu receives an average daily PSH of 5.88.
An excellent value for making solar power systems financially attractive.
Sizing of solar panels for Tamil Nadu
After knowing that solar is very attractive in Tamil Nadu.
Let us size the solar panels.
The first step for sizing solar panels is to know the energy requirements.
The Energy Chart
Let us make an energy consumption chart:
This assumed energy chart will help us in sizing the solar panels.
The yellow highlighted value (20,444 W-Hr) is the total energy consumed and I want it to be generated from the solar panels.
For this, we need to appropriately size the solar panels that can meet my energy needs.
Solar Panel size in ideal conditions
When I consider the ideal conditions, the formula for sizing the solar panels is:
(By ideal conditions I mean a clear sunny day all the time and there are no other losses in the system).
Solar Panel Size (Watts) = Energy Needs/Average daily Peak Sun Hours
In the above case, the energy needs are 20,444 W-Hr and the average daily PSH in Tamil Nadu is 5.88.
Therefore, the solar panel size is = 20,444/5.88
= 3480 watts.
I need 3480 watts of solar panels that will produce 20,444 W-hr energy in a day in ideal conditions.
Wait!
Solar Panel size in real world
This is not the right sizing for the real world.
Any solar power system undergoes different types of losses while producing electricity from sunlight.
Let me list a few of them such as:
- Conversion losses
- Transfer losses
- Shading losses
- Heat losses
- Age-related losses
And more…
When I add all these losses, they eat near to 30% of the solar electricity produced by the solar panels.
Therefore, I need to re-size the solar panels so that they provide me requisite energy even after the losses.
I need a multiplier that is 1/(1-30%)
= 1/70%
Or
= 1/0.7
Or
= 1.42
I will multiply this value by the solar panel size that we found above (3480 watts).
The right size of the solar panels after compensating for the losses would be:
1.42 x 3480 watts
= 4941 watts
Or
Round it to 5000 watts
Therefore, I will look for 5000 watts of solar panels which will provide 20,444 W-hr daily in Tamil Nadu.
20,444 W-hr can be written as 20.444 kW-hr
Or
20.444 units. 1 unit = 1 kW-hr
Best Solar Panels for Tamil Nadu Climate
We can find the best solar panels for Tamil Nadu if we know its climate and weather patterns.
The Indian Ocean in the East surrounds it.
Which is responsible for cyclones and humid climates.
It is situated in the tropical zone and thermal equator, making it have fewer temperature variations.
Considering all these factors, the best solar panels for Tamil Nadu’s climate are those:
- Which are corrosion and mist resistant
- Having a high wind load rating to withstand the high wind pressure
- Performs well in high temperatures and less heat-related losses.
- Which are highly efficient. Due to moisture in the air, less sunlight reaches the solar panel surface.
Financial Feasibility of a 5-kW solar power system in Tamil Nadu
We need to consider various factors before finding the return offered by the 5-kW solar power system in Tamil Nadu.
Let us discuss a few important ones:
Price of 5-kW solar power system in Tamil Nadu
The price of a 5-kW solar power system in Tamil Nadu depends on many factors such as:
a) Type of system:
We see three main types of solar power systems namely: On-grid, Off-grid, or Hybrid
The systems with battery backup such as the Off-grid system are costlier than the other types with similar power ratings.
(The batteries are costly which increases the overall cost of the system).
In case, you choose Off-grid solar power system over On-grid or Hybrid (it also has battery backup but less compared to the Off-grid system).
Then you need to invest more money.
b) Quality of Equipment
Equipment such as solar panels, batteries, solar inverters, and more are used in the system.
The price of the system is proportional to its quality.
High-quality branded solar panels are costlier than low-quality ones.
With the advancement in solar PV technology, we see different types of highly efficient solar panels such as:
These solar panels produce more power in limited space, perform great even in high temperatures, have low heat losses, and high structural strength, are immune to PID and LID losses, and more…
But
All these features come at some extra cost.
I prefer using high-quality branded solar panels to cheaper ones.
Because solar panels are the main component in any system.
A good quality durable one lasts for over 25 years that can save you a lot of money.
c) Installation cost
The installation cost is the cost of erecting the solar panels on the roof and making the system work effectively.
The installation cost varies due to the type of roof.
The team of highly efficient professional solar installers may charge you more but they make your system efficient enough that you enjoy smooth electricity for decades.
Also, the installation cost depends on the type of roof, and the shade-free area available for installation.
I would advise my readers to go for high-quality solar panels and look for experienced solar installers nearby to do the work.
So, after considering all the parameters discussed above the average cost of 5-kW:
- The on-grid system is Rs. 3,10,000
- Off-grid with 2 days battery backup: Rs. 4,75,000
- Hybrid with 1-day backup is Rs. 4,20,00
Grid Price and its Escalation in Tamil Nadu
- 101 – 400 units: Rs. 4.5 per unit
- 401-500 units: Rs. 6 per unit
- 501-600 units: Rs. 8 per unit
- 601-800 units: Rs. 9 per unit
- 801-1000 units: Rs. 10 per unit
- And >1000 units: Rs. 11 per unit
Our 5-kW solar power system in Tamil Nadu produces 20.44 units in a day.
Or
I am rounding off it to 20 units per day.
Therefore, in 30 days it will produce 600 units (20 units x 30 days).
I can say that by using solar electricity, I am saving money on 600 units.
The cost of 600 units if I take them from the grid would be:
- Rs. 4.5 per units x for first 400 units = Rs. 1800
- Rs. 6 per unit x for next 100 units = Rs. 600
- Rs. 8 per unit x for last 100 units = Rs. 800
In total, I am saving Rs. 3200 (1800 + 600 + 800) per month when I am using 5-kW (which produces 600 units per month) solar power system in Tamil Nadu.
The average price is Rs.3200/600 units = Rs. 5.33 per unit
And
This saving per unit will increase year-on-year.
Because the grid price will increase.
How much will the grid price increase?
When I look at the national average, the yearly escalation in grid price is 8%.
Wait!
As time passes, the output from the solar power system reduces, and its maintenance cost increases.
These factors have a negative impact on our overall savings.
Still, our savings will increase because:
the grid rate > the maintenance cost and units lost by the system.
Well, not going much into the technical. After considering all the factors, the 5-kW.
Payback Period
Although, the payback Period does not consider the time value of money.
But I am mentioning it to give you an idea about how much time your investment would be paid off under different configurations.
Its formula is simple:
Payback Period = Cost of the system/Annual savings
For 5- kW On-grid system:
Payback period = Rs. 3,10,000/38,400
= 8 years
I can summarize all three Payback periods in a tabular form:
IRR and NPV
It is good to know the Payback period of the system.
But knowing the IRR and NPV of the system gives you a more realistic view.
How I will differentiate between Payback and IRR in one word?
Payback gives you a static view while IRR or NPV shows us the dynamic picture considering the maintenance cost, reduction in power output, and escalation in grid price.
After considering all the above factors.
A 5-kW solar power system in Tamil Nadu will produce 1,64,600 units in 25 years.
The IRR and NPV values are different for the different types of solar power systems.
(If you want to know how to find the
Being the highest for the On-grid system and the lowest for the Off-grid solar power system. It can be shown below in tabular form:
And
I have not considered the incentives offered by the state government on Solar PV.
Conclusion
Tamil Nadu is a sun-rich state with average Peak Sun Hours of 5.88.
Its location makes it have solar insolation values with little difference between the max. and min values.
The temperature variation is small throughout the year.
With hottest months are May and June.
The average price of a 5-kW solar power system in Tamil Nadu is:
- Rs. 3,10,000 On-grid
- Rs. 4,20,000 Hybrid with 1-day backup
- Rs. 4,75,000 Off-grid system with 2-day backup.
Solar PV technology is financially attractive with an IRR spread over from 8% to 16% for the various types of solar power systems.
Yash has over a decade of experience in Solar PV technology and is the founder of Solar with Yash.
Check out his Youtube Channel Solar Design and Payback with Yash
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