Photovoltaic (PV) technology
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Photovoltaic involves the direct generation of electricity from light by using a semi-conductor material which can be adapted to release electrons.
The most important parts of a PV system are the cells which form the basic building blocks, the modules, which bring together large numbers of cells into a unit, and, in some situations, the inverters used to convert the electricity generated into a form suitable for everyday use.
All PV cells have at least two layers of semi-conductors, one positively charged and one negatively charged. When light shines on the semi-conductor, the electric field across the junction between these two layers causes electricity to flow, generating DC current. The greater the intensity of the light, the greater the flow of electricity.
The most common semi-conductor material used in photovoltaic cells is crystalline silicon but PV cells can also be made from thin film, deposited in thin layers on a low cost backing. The majority of module production (89% in 2003) has so far involved the former, while future plans will also have a strong focus on the latter. Thin film technology based on silicon and other materials is expected to gain a by far larger share of the PV market in the future. This technology offers several advantages such as low material consumption, low weight and a smooth visual appearance.
A photovoltaic system does not need bright sunlight in order to operate. It also generates electricity on cloudy days, with its energy output proportionate to the density of the clouds.
Example: Comparison PV-Diesel
