A solar photovoltaic (PV) system mounted on a rooftop of a building is a minipower plant that converts solar energy into electricity to meet the property’s

power requirements or feed into the grid. Although anyone can install a solar rooftop system, the size of the installation varies significantly depending on availability of space, amount of electricity consumed by the property, and the ability or willingness of the owner to invest the capital required.

TYPICAL LAYOUT OF A SOLAR ROOFTOP SYSTEM
The basic components of a solar rooftop PV system include PV modules, inverters, and mounting structures. Other components like string boxes, transformers, meters, charge controllers, batteries, and generators can also be incorporated into the system, depending on its size.

1. Solar panels

2. Charge controller

3 Battery bank

4. Interactive inverter

5. Main switch box

6 Consumer load

7.Power meter

8 Utility service

EFFICIENCY
It is important to choose the right components for the most effective use of solar PV systems. A PV module can generate 10–300 W output. The size of a solar PV module or panel required will depend not only on the output (requirement of the system) but also on the efficiency of the system. Expressed in percentage, the efficiency of the solar panel quantifies its ability to convert sunlight into electricity. Therefore, more the efficiency, more will be the electricity generated by a panel for a given area of exposure to sunlight. A majority of the panels available in the market today are around 14–16 per cent efficient, with a lifespan of 25 years. Solar modules do not require a lot of maintenance but it is good to clean the system of dust and bird droppings regularly to maintain the efficiency of the system.

TYPES OF BATTERIES –

Two types of batteries are commonly used in solar systems—lead-acid batteries and lithium-ion batteries. Lead-acid batteries are cheaper and more reliable. Most household inverters rely on the dependable technology of lead-acid batteries. But these batteries are bulkier and have a lower lifespan of five–ten years. They are 80 per cent efficient (four-fifths of the energy stored in them can be reclaimed). Lithium-ion batteries are used in phones and laptops. They possess a greater depth
of discharge (reusable capacity) and, therefore, have a longer lifespan of 13–18 years. However, they are 50 per cent costlier than lead-acid batteries, and are less commonly used in rooftop systems.
LIFE OF A SOLAR MODULE
Generally, modules come with a warranty of 20–25 years. The output of a panel falls down every year (degradation) by around 0.8 per cent, which means a panel will produce around 80 per cent of its rated power after 25 years of use. Most solar panels used in India are made in China. The longest operating PV plant in the world is in Spain. Installed in 1994, it supplies electricity to the national grid. Small-scale solar PV systems began to be installed in India in the 1980s. The longest operating large-scale PV plant in the country was established in 20