HOW A PHOTOVOLTAIC SYSTEM WORKS
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The photovoltaic process converts the sun of the light directly into electric energy. The photovoltaic cell is the basic element in a PV system. It consists of two layers of specially treated silicon; when light strikes the PV panel, at the zone of separation between the two layers (the so-called "p-n junction"), electric charges of opposite sign are generated. These charges are then collected by the upper metal grid (negative electrode) and the lower layer (positive electrode) and an electric current is generated by the connection between the two.

The intensity of the current generated by the PV cells depends on the quantity of light. When no load is connected to the system, voltage is ca 0.5 V, a value too low for practical exploitation. Hence, the photovoltaic cells are connected in series to obtain the desired voltage level and are fitted with a frame ensuring stiffness and protection against the atmospheric agents. This is the photovoltaic module, the minimum unit of a photovoltaic system that is able to generate electric energy at a usable voltage.

By connecting in series and/or in parallel several PV modules we get a system that can generate the power required at the desired voltage. At this point, however, the energy is in the form of direct current. Accordingly, it is necessary to have a conversion section that will transform it into alternate current for delivery to the energy distribution network.

This section of the system is made up of a series inverters, i.e., devices whose function consists precisely of transforming the instantaneous power generated by the PV modules into electric energy in the form specified by the distribution network.
As a rule, the equipment is fitted with ad hoc protection and interface devices and must comply with the regulations and directives of the Network Manager to which the system is connected. Inverter technology makes it possible to maximise the overall efficiency of the conversion process, both at full load (rated power) and with a partial load, through an automatic control system which optimises the utilisation of the devices themselves and hence their service life. Ad hoc communication interfaces are provided to record and transmit the operating data, keep an error log and permit continuous monitoring, whether on-site or in remote mode.

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