6.6 KWp On-Grid Domestic Rooftop Solar PV Power Plant: First Domestic project under CESC

Location: Kolkata
Capacity: 6.6 kWp
Department: Residency
Purpose: Reducing Electricity Bill

Overview – 6.6 kWp Solar Rooftop Power Plant

Dr. Rajen Kumar Pandey, a renowned doctor and renewable energy enthusiast was the first to introduce a domestic net metering system for his residential solar rooftop power plant under CESC.

Net metering is a billing mechanism that credits solar energy system owners for the electricity they add to the grid. If a home is net-metered, the electricity meter will run backward to provide a credit against what electricity is consumed at night or other periods when the home’s electricity use exceeds the system’s output. In other words, consumers are only billed for their “net” energy use. To maximize the return on investment, it is very crucial to have a robust structural design. Since the solar panels are mounted on rooftops, it is susceptible to corrosion and environmental degradation. Hence mounting structures made of galvanized iron or anodized aluminum should be used to ensure the plant’s protection and extend its life up to 25 years.

It is often noticed that most system integrators neglect to install an AJP-ACDB. AJP or power distribution box is essential to control and supply electricity to the various power outlets. These boxes are vital for the safe consumption of electricity because they act as circuit breakers when there is uncontrolled energy or an increased power surge flowing through the electric cables and the distribution board. Similarly, ACDB is a crucial Surge Protection component when high voltage is experienced in the distribution box that offers alternate current to home appliances. The system has circuit breakers, fuses, current, and voltage meters; when the power surge is more, the circuit breakers fuse and prevent devices using electricity from getting damaged.

Proper earthing systems are also ignored. This can prove hazardous as earthing protects against lightning, switching surges, static, contact with high voltage system, and line to ground fault. An earthing method comprises a network of conductors (strips, wires, cables, etc.) and earthing electrodes that connect all equipment to the grounding pits. The network configuration and the specifications (size, material, etc.) of conductors and electrodes are determined with an earthing calculation/study. A good earthing system will be able to ground any surges during fault conditions.

Similarly, LA installations are also disregarded sometimes as an attempt at cost-cutting. But this practice should not be entertained since any of the equipment is directly struck by lightning; the electric discharge may result in an explosion, burn, or destruction. Indirect lighting can also cause transient voltage and current surges, which may travel for many kilometers, hence posing a potential threat to the equipment’s safety. The presence of a lightning arrestor or LA offers the least resistance path for lightning to pass into the ground and can provide the necessary protection to equipment and personnel.


Technical Details

The 6.6 kWp solar rooftop power plant is equipped with a grid-connected system with net metering. A total of 20 solar PV modules were used with 72 cells, each made of 330Wp Polycrystalline Solar Panels. The inverter is of SMA-Zuver variety, having a power of 6kW with a DC switch present. To ensure the safety of the solar plant’s consumers and reliability, Sunshell has equipped the structure with AJB ( SPD type II, 1000V 40 kA) on a PV string fuse of 1000V 15A. Simultaneously ACDB with AC side SPD, LED indication light, and suitable MCB have also been fitted into the structure to protect it against high voltage. Further safe termination system on the LT side 415V and lightning arrestor with dedicated earthing is also present in the structure. Proper earthing protection measures are ensured by SunShell Power in compliance with IB and BIS rulebooks.



After successfully installing and executing the 6.6 kWp solar rooftop power plant, due to the elevated nature of the structure, the roof’s total space remains accessible to the residents, and the solar panels double as an indirect shed. Due to SunShell’s uncompromising nature and promise of providing the absolute best materials, the super-strong frame of galvanized iron can withstand the wind capacity of 180KMPH. When Bengal was devastated during the Amphan phenomenon, the solar plant stood tall despite the area being heavily affected.

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