What is Photovoltaic?
PV Stands for Photovoltaic, which means electricity from light. A Photovoltaic system converts
daylight into electricity and it mostly consists of a natural material, silicon. In 1839, it was first discovered
that some materials produce a small current when light is made available to the material, but it was not really understood why.
Photovoltaics was first used in around 1890, but not developed until 1954 in the USA by Bell Laboratories.
In 1954, scientists at Bell Laboratories depended on the Czochralski process to develop the first crystalline
silicon photovoltaic cell, which had an efficiency of 4%
The efficiencies now are much higher, generally between 14 and 18% depending of the type of PV cell used. The main material that makes up a solar cell today is silicon, and by adding materials to the silicon its ability to produce electricity from light is improved. A solar cell on its own produces quite a small amount of electricity, but a cell is linked to other cells which make up a photovoltaic panel. A panel can produce any amount of power depending on how many cells are linked, with a typical panel being 100 Watts - 200 Watts.
PV panels are generally referred to as solar panels, and also are confused with solar thermal panels (the type that heat hot water).
The type that heat hot water are totally different as water runs through the panel, and indirectly heats water in a hot water storage
cylinder. Solar thermal also uses direct heat from the sun, whereas PV uses daylight. PV can use either direct or indirect (diffuse)
sunlight, which is daylight. PV does not need direct sun to work, and the panels work better if they are kept cool!.
PV output DC voltage, which in some cases such as boats and caravans this can be used straight from the panel to power 12V equipment.
PV can also be used for producing power in homes, office blocks, power plants etc. by linking the required number of panels together.
A system with panels linked together is called a PV array.
For example, to produce a good amount of electricity for use in the home, 24 x 125 Watt panels could be installed on the roof. The power output when all these panels are linked together in a circuit is 3000 Watts, which is 3kW. The size of the system output in Photovoltaic systems is referred to as kWp, which is kiloWatt peak. This is the peak output that the system can produce when sufficient light conditions are present. The system will still work if there is not the full amount of light available, just producing slightly less power.
When it is daytime, the PV array produces electricity in DC. This needs to be converted to AC to work in a power system of a building. The power is converted with a piece of equipment called an inverter. This is linked to the power supply of the building (normally with a kWh meter installed so power production can be viewed) and if the power produced by the PV system is needed by appliances being used in the building, then that is where the power from the PV will go first. If you do not need some or all of the power being produced by the PV system at the time, then the power is sent out to the national grid where it will be used by others. PV systems can be installed where there is no mains powers available. These systems involve special solar batteries that will store the power until it is needed in the building.
The power that is sent out to the national grid is not just given away, there are various suppliers that will pay/credit you for electricity that is sent out to the grid from a PV system.