FAQ

“PV” is short for “photovoltaic,” a word that has been around since the nineteenth century when scientists first started studying light and energy. It combines the Greek word “phos,” meaning light, with “volt,” a unit of electrical measurement. Taken together, the literal translation could be “light-electricity.” It’s an apt descriptor, as photovoltaic processes convert light energy into electricity.

When you see a building with solar panels on the roof, what you’re seeing is one part of a PV system or array. An array actually has several separate components that help it turn sunlight into usable electricity.

A PV system converts light to electricity through a process known as the photoelectric effect. When sunlight hits a PV cell, the solar energy excites electrons inside the cell. This triggers a chain reaction in which the supercharged electron escapes into a conductive contact to become part of an electrical circuit. That new electricity flows across the array’s wiring, through an inverter, and then into your home’s main electrical system for use.

Solar arrays with battery banks follow a very similar process. The only difference is that the raw electricity coming out of the panels runs through a charge controller and into the battery bank for storage before traveling to the inverter.

Photovoltaic systems designed and installed by a professional and kept in good operating condition can last for more than 20 years, though some arrays come with warranties for up to 30 years. Even past that, you’re more likely to request repairs for the wiring and hardware due to wear and tear than to replace the PV panels.

A big selling point for solar power is its positive environmental impact. Solar power is considered a type of green energy, meaning it’s better for the environment than traditional fossil fuels. Because you can use solar power to run nearly any electrical system, including lighting and appliances, it’s an easy and efficient way to reduce your overall carbon footprint.

Another big benefit is that a solar array can help protect you against high electricity bills, as the energy generated by the system can offset reliance on the grid. Some states even allow solar array owners to sell excess solar energy back to the utility through a process called net metering.

Rooftop solar power is much cheaper than power from diesel generators. Solar PV generates power at a cost of about Rs. 4.5-5/KWh while diesel generates power at about Rs. 16/KWh. Whether solar is more expensive than grid power depends on your current tariff. Solar power is not cheaper than grid power for many consumers but in some cases, such as consumers paying a commercial tariff, solar power may be cheaper than grid power.

The area required by a rooftop PV plant depends on the extent of shade-free space available and solar panel efficiency. A solar PV system typically requires 100-130 SF (about 12 m2) of shade free roof area per kW of capacity at current crystalline panel efficiency levels.

The amount of electricity generated by a rooftop solar PV plant depends on the location, orientation of the roof, panel efficiency, and ambient temperature. As a rule of thumb, a 1 kWp plant will generate about 4 kWh (units) of electricity a day on average in a year.

A rooftop solar PV system primarily comprises of Solar PV Modules (panels), Inverters, and Mounting Structures. If battery backup is required Batteries and Charge Controllers would also be integrated with the system.

The capacity of the rooftop solar plant you require to power your facility should be calculated keeping in mind your requirements, your constraints, and the amount of sunlight available. Rooftop space is the most likely constraint that will limit the size of your solar plant. If the size of the plant is not sufficient to power your entire facility, you can choose between powering light loads, powering critical loads, and using a solar-diesel hybrid.

Not all rooftop solar plants generate power during a power failure; only some do. The difference lies in the inverter and the functionality it supports. Grid-interactive and hybrid inverters supply electricity even during a power failure while grid-tied and off-grid inverters don’t.

There are various solar policies that incentivise rooftop solar in India. Central government schemes include 80% accelerated depreciation, capital subsidy of 30% and more based on location, and Renewable Energy Certificates (RECs). Some states have further incentives under their own solar policies. Permissions primarily deal with ensuring the grid isn’t congested by receiving approval from local power distribution authorities.