Solar PV system generates electric power by converting solar radiation into Electrical energy. This consists of solar panels installed on roof top made out of crystalline silicon. When sun hits the panels, radiation gets converted to direct current electricity. An inverter

that is connected to the panels converts the direct current electricity into alternate current. The electric power generated is fed into the conventional or public grid. There is a simple meter accounting which directly meters the energy generated through the system before flowing into the grid. (Schematic Diagram ) solar PV roof top is relatively simple to install, operate and maintain and it is most popular and globally accepted configuration.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Schematic Diagram
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Working of Solar rooftop ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Top

PHOTOVOLTAICS is the direct method of converting sunlight into electricity.  This direct conversion of sunlight into electricity is done through devices known as ‘Solar Cells’ which are packed (encapsulated) in a ‘Photovoltaic Module’ (also generally known as a ‘Solar Module’).

                               
Photovoltaics is the ‘solar electric’ technology.  The other type of solar technology is the ‘solar thermal’ technology, which maximizes the utilization of heat from sunlight.  Examples of solar thermal equipment are solar water heaters and solar cookers.

                               
The Gandhinagar Photovoltaic Rooftop Programme is focusing only on the photovoltaic technology for installations on rooftops and terraces.

A photovoltaic system can be physically divided into two parts:

• Photovoltaic Array, which consists of arrays of photovoltaic modules placed on the rooftop or terrace to capture sunlight, and

• Balance of system, which consists of electronics and other hardware such as inverters, meters, junction boxes, wiring, switches/MCBs, mountings, etc. which may be connected to the photovoltaic array and placed indoors very near to the conventional energy meter.

Figure: (a) Photovoltaic Array on a rooftop, and (b) Balance of System (BoS) including an inverter, an energy meter, junction boxes, wiring, etc. mounted on a wall.

The photovoltaic systems for the Gandhinagar Photovoltaic Rooftop Programme will not use any batteries because storage of electricity is not intended here.  The electricity generated by the system will directly be injected into the electricity grid.

• Photovoltaic Modules, which directly convert sunlight into DC electricity.  Many photovoltaic modules are connected in series and parallel combinations to achieve the desired capacity of the system in kilowatts.
  
  
  
  

  Figure: Different types of Photovoltaic Modules.

  
  
  
• Module Mounting Structures, which are used to mount the photovoltaic modules on the rooftops or terraces.

Figure: Photovoltaic Modules mounted on a Module Mounting Structure.

• Inverter, which converts the DC electricity coming from the photovoltaic modules AC electricity.  In the Gandhinagar Photovoltaic Rooftop Programme, a special type of inverter known as ‘Grid-Interactive’ inverter will be used; such grid-interactive inverters can feed the AC electricity directly into the electricity grid.
  
      
  
  Figure: Different types of grid-interactive inverters.
  
  
• Energy (Electricity) Meter, which is the same as a conventional electricity meter, to measure the solar energy (electricity) injected into the grid.

 

• Wires, junction boxes, switches/MCBs, surge arrestors, etc., to make electrical connections, and ensure safety and protection.

A typical 1 kilowatt photovoltaic system would require about 15 square meters (i.e. 150 square feet) of open space.  Larger photovoltaic systems would require proportionally more space to absorb more sunlight.  Hence, for example, a 5 kilowatt system would require 75 square meters.

A typical 1 kilowatt photovoltaic system would generate an average of 4.5-5 units (i.e. kilowatt-hours, kWh) per day in Gandhinagar.  Larger photovoltaic systems would generate proportionally more energy.  Hence, for example, a 5 kilowatt system would generate around 22.5-25 units per day.

• Photovoltaic systems offer one of the cleanest, most practical and scalable methods of generating clean energy.

 

• The fuel, which is sunlight in this case, is free.  Moreover, the earth receives enough sunlight in one hour to provide the world’s energy needs for an entire year.




• Photovoltaic systems are very easy to install, operate and maintain; further they are very easy to understand.  The main activity in maintenance of such systems involves cleaning of the photovoltaic modules with water.




• Photovoltaic modules, which are the main cost of the photovoltaic system are very robust and, now come with a 25 (twenty five) year warranty.
• There are no moving parts in typical rooftop or terrace photovoltaic systems.  This further makes the maintenance very easy and ensures a long life of the system.
Top