HOW IT WORKS
The word photovoltaic comes from photo = light and voltaic = by (Alessandro Volta, inventor of the battery) .
A photovoltaic plant is an electrical system whose modules (solar panels) use solar energy to produce electricity via the photovoltaic effect.
The photovoltaic modules transform sunlight into electricity: they are made of cells, semiconductor materials for the photovoltaic effect. The mainly used semiconductor material is silicon. A physical feature developed in the ’50s creating the first solar cell in human history.
The solar plants can be installed on different surfaces, on ground, on rooftops, on car park or as parts of building structures. In all these cases, they also can be of two types:
On Grid (connected to the grid)
In this case, the electricity produced by the solar plants is put into the distribution network and taken in the evening and night, when solar plants have to cover energy needs. Usually, when the Net Metering agreement is available , the meter of the solar PV plants records both incoming and outgoing electricity. When the solar system produces surplus electricity, the utility company gives credits for all outgoing (un-used) electricity.
Off grid (not connected to the grid)
This is the system used where energy supplied by the modules, when not immediately consumed, is used to charge batteries. The accumulators will return the energy when required, that is when the need exceeds the delivery capacity of the modules or when, as during nightime , modules do not operate
A solar plant consists of different elements:
This consists of photovoltaic modules vary in number according to the size of the plant. The modules are electrically connected together in strings and each of them produces energy according to the level of solar radiation and the tilt of the module itself.
This consists of control equipment, protection and isolation. It harvests the strings of the solar field and performs the parallel strings. Through its cables the photovoltaic field is connected with the inverter.
An inverter or static converter, is the apparatus that converts the direct current of the modules into alternating current. It is equipped with control systems to verify that the energy introduced into the network is of the quality required to meet safety requirements.
A transformer is a static electric equipment (because it contains no moving parts) and reversible, used to vary the parameters of the electrical power inputs (voltage and current) compared to those in exit, in order to adapt the electrical parameters of the plant to those of the distribution network
This allows the inverter to be connected to the grid. It is situated near the bi-directional electric meter installed by the grid operator to record the output of energy. Remote control system The remote control system is designed to monitor the electrical parameters of the plant, the voltage and current to the grid supply. It can quickly locate problems which can cause absence of energy.
ACCUMULATOR (for off grid solar plants)
Accumulators are rechargeable batteries which store unused electricity produced by the solar plant. When electricity is later needed ,or when the need exceeds the supply capacity of the modules or when modules do not operate during night time, it is returned to the system.