Wish to have a rooftop solar power plant in or around Chennai?
Use this city-specific guide from Solar Mango to get an overview of solar power potential for Chennai, and things to watch out for while installing a rooftop solar power plant in this region.
- Average annual generation in Chennai is 5.35 kWh/m2/day with more than 300 sunny days
- Usable AC power generated by solar plants in Chennai is 4kWh/kW/day or more, on average over a year
- Chennai energy consumers pay grid tariff of Rs. 6 for Industrial and Rs. 7.6 for Commercial consumption, or more. At Rs. 8/kWh or less, solar may be cheaper than grid power for some consumers, and cheaper than diesel power of Rs. 18/kWh for all consumers
Chennai is situated about 13° North of the Equator and has an abundance of sunlight. Combined with unreliable utility power and rising cost of diesel power, it is no surprise that the city is seeing solar panels on an increasing number of rooftops. Industrial and commercial units here can benefit greatly from the advantages of solar power but should also keep in mind several constraints when designing the solar system. We will be discussing both below.
Solar Energy Generation in Chennai
Average annual radiation in Chennai is about 5.35 kWh/m2/day with more than 300 sunny days in a year. This table provides the monthly values.
Radiation Data for Chennai (13.0839° N, 80.2700° E)
|Radiation Incident On An Equator-Pointed Tilted Surface
|Number of non-sunshine days
This radiation is converted into DC power by the solar panels and is then converted into AC by the inverter. Some of the energy is lost in this process. Typically, usable AC generation of 4 kWh per day per kW of solar plant capacity is the average for Chennai over the course of a year i.e., a 100 kW rooftop solar plant will deliver about 400 units of electricity per day on average.
Solar Power Advantages for Chennai
- Energy security – Rooftop solar plants can deliver power during load-shedding, ensuring that critical loads are always running
- Not all solar plant configurations can deliver power during load-shedding. More details here
- Cost-effective – Rooftop solar power has a levelised cost of Rs. 4.5-5/kWh (or less), considerably lower than diesel power at Rs. 18/kWh (or more). Additionally, your energy cost is now fixed for the next 25 years, unlike diesel power which keeps increasing
- Grid power tariff is about Rs. 6 for Industrial and Rs. 7.6 for Commercial consumers in Chennai. If penalties are imposed for excess consumption the effective tariff is even higher. Rooftop solar power may be cheaper than even grid power, but this varies on a case-to-case basis
- Reliable – A solar power plant has no moving parts, ensuring reliable power over 25 years
- Minimal maintenance – A solar plant requires very little maintenance from the energy consumer
- As Chennai has a lot of dust, cleaning the solar panels once in every 2-3 months is recommended to ensure that sunlight is not blocked from reaching the solar cells. More frequent cleaning may be required if your plant is located in a very dusty environment
- Flexible configurations – Solar panels can be installed on different kinds of roofs, including parking lot roofs, as long as the structure/mounting points can bear the weight of the panels. They are also highly scalable, with rooftop plants ranging in capacity from less than 1 kW to more than 1 MW
Constraints for Solar Power in Chennai
- Rooftop space – The capacity of the solar plant that can be installed may be constrained by lack of sufficient shadow-free rooftop space. Roof requirements are discussed in detail here; a rule of thumb is that you will need about 100 SF of shade-free roof area for 1 kW of solar panels. Insufficient roof area will mean that the capacity of the solar plant on your roof may be sufficient to meet only part of your electrical load
- When estimating the available roof area any alternate uses of the roof should be considered. Elevated mounting structures may be used if the alternate use of the roof is to continue
- Infirm power – Solar power is dependent on the sun shining, and output varies depending on meteorological conditions e.g., passing clouds can temporarily reduce the solar plant’s output; monsoon rainfall can also reduce the solar plant’s output. Therefore solar power for critical equipment should be used in conjunction with another source of power
- Cyclones – As Chennai is in a cyclone prone area, the mounting structures for the solar panels should be designed to withstand wind speeds of 120-150 kph
- Salt corrosion – As Chennai is a coastal city, the solar panels chosen should have cleared salt mist corrosion testing (IEC 61701/IS 61701 compliant)
- Daylight power – Solar power is only available when the sun shines. Therefore night time applications will require other sources of power, or power from batteries charged through solar
- Load-shedding timings – If you experience load shedding primarily at night, solar power may not help in reducing your diesel consumption as it is available only during the day
- Inverter weight – The DC power output from the solar panels needs to be converted to AC via an inverter which can be very heavy: a 100 kW inverter will weigh about 1,000 Kgs but occupy only a few square feet of space. If the construction cannot support this weight the inverter may need to be placed on the ground floor, with appropriate cables chosen to compensate for energy loss
Our Recommendation for Rooftop Solar in Chennai
Based on the above discussion, Solar Mango’s recommendation for solar plants in Chennai is
- Multiple power source integration – As the output from a rooftop solar plant varies, it must always work in conjunction with other sources of power, typically utility grid power and diesel power. This is achieved using
- Hybrid inverter – A rooftop solar PV system that utilises a hybrid inverter allows the solar plant to integrate with a diesel generator in addition to the utility grid. The solar plant serves to reduce diesel bills by supporting part of the overall load
- Integrating a rooftop solar plant with a diesel generator involves several challenges (discussed here) that need to be overcome with careful design and sizing of the solar plant
- Corrosion resistant panels – Only panels that areIEC 61701/IS 61701 compliant (salt mist corrosion testing) should be used in coastal cities like Chennai
- Cyclone rated mounting structures – Mounting structures that can withstand 120-150 kph wind speed should be used
Cost of a Rooftop Solar Plant
The cost of a rooftop solar plant is discussed in detail here (including incentives and subsidies) and returns from substituting diesel with solar are discussed here. As a rule of thumb, a 1 kW solar plant that generates 4 kWh of solar power per day (on average) will cost Rs. 1 lakh (without considering subsidies, including installation charges but excluding batteries).
Batteries, if required, can add about 30% or more to the cost of the plant depending on the extent of battery backup required.