Term Photovoltaic refers to technological systems that convert solar radiation directly into electric energy. This transformation takes place in photovoltaic cells, which is made from silicon.

Photovoltaic effect was observed in 1839 by Edmond Becquerel. The first solar cell was made of crystalline silicon in 1954.
 

The term "photovoltaic" comes from the Greek φῶς (phosphorus), which means "light" and "volt" which is translated, the electric force. The term "Photo-Voltaic"is used in English since 1849

The principle of photovoltaic

A photovoltaic cell is made from silicon (semiconductor: PN connection).
When a cell is exposed to the sun's electromagnetic rays, the photons in light transmit their energy to atoms in the connection. This energy enables electrons to be released from the atoms, thereby generating electrons (N-charge) and holes (P-charge).

Photovoltaic power plan

A collection of greater number of solar panels, inverters, and other construction and supporting elements is called a solar power plant. Solar power plants differ mainly in their output power, otherwise they are usually on the same principle – energy generated by the fall of sunlight on photovoltaic panels is converted in invereters to AC values and then they are distributed to home or distribution mains with frequency of 50/60 Hz.

Photovoltaic modules (panels)

 Photovoltaic Modules are made by wiring many solar cells together. The electricity collected by each cell is concentrated into the electrical output of the panel. Panels can be made to produce more electricity or less electricity by adding or removing solar cells. For applications where more electricity is needed, a series of panels can be connected together to give higher power output. Photovoltaic Modules produce direct current or DC and Inverters are needed to make it alternate current or AC as AC is used in Industrial and Household.

Type of modules:

• Monocrystalline modules (also mono c-Si)
• Polycrystalline modules (also poly or multi-crystalline c-Si)
• Thin Film modules
• Hybrid modules (also a-Si / nc-Si panels)

Inverters

Inverters are used to convert direct current (DC) generated by PV modules into alternating current (AC) consumed by elect­rical appliances. There are 2 types of Inverters String and Central and it comes with and without Transformers.

 Using of inverters with transformers is recommended with certain PV modules technologies such as Thin Film modules or if grounding of photovoltaic systems (negative or positive pole) is required. Inverters with transformers also provide galvanic isolation between DC and AC circuits.

Type of modules:

• String inverters
• Central inverters