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Solar photovoltaic (SPV) is primarily a semi conductor based technology used to convert solar radiation into direct electricity. A PV system basically comprises of PV modules and the balance of systems (BOS). Balance of systems includes support structure, wiring, storage, power electronics etc. When solar radiation strikes the PV module, DC (direct current) electricity is generated. During generation, power can be used in any DC load directly. But the generation exists till sun shines. So, some storage device is needed to run the system at night or in low sunshine hour. Again this power cannot be used to run any AC (alternating current) load. Inverter has to be used to convert DC into AC.

Initially photovoltaic was confined to space application but gradually Success of solar cells in space led to their use in terrestrial applications - starting from consumer goods to telecommunication. Now it has found its multi-dimensional ways in building application.

PV is becoming more popular because of the following points

  • PV technology is one of the well proven renewable technology
  • PV system has successfully been used in different small and large applications
  • PV is a modular technology. Any amount of power, starting from miliwatt to megawatt can be generated. PV system can be added to the existing PV power if load demand increases.
  • PV system has no moving parts, consuming no conventional fuels and creating no pollution.

Types of PV system (PV configuration):

There are two basic configuration of SPV system

  • Stand-alone system
  • Grid interactive system (PV system with a connection to utility grid)

Stand-alone system:

Stand-alone systems are virtually self sufficient and not interacted with grid. Such system may have some backup/storage system to run during the no sun or low sun hour.

  • PV system without storage battery (Direct coupled PV system)
  • DC system with storage battery
  • DC systems powering AC load (with or without storage)

PV system without storage battery (Direct coupled PV system):

This is the simplest and least expensive photovoltaic system designed to be used only during daytime. Here the electricity generated is directly and simultaneously used by the appliances. Through out the day, the insolation level is changing continuously and so the output.

Examples of direct use systems include:

  • Remote water pumping with a storage tank.
  • Stand alone solar powered appliances such as calculators and toys.

DC Systems With Storage Batteries:

Photovoltaic systems must include a means of storing electrical energy if they are to operate loads at night or during cloudy weather. Batteries are used to store the electrical energy generated by the photovoltaic modules. Power can be drawn from the batteries whenever required- during the day or night, continuously or intermittently. In addition, a battery bank has the capacity to supply high surge currents for a short time. This gives the system the flexibility to start large motors or to perform other “high power” tasks. This system’s basic components include a photovoltaic module, a charge controller, storage batteries and appliances that represent the system