Photovoltaic or photoelectric panels allow the synthesis of solar energy into electricity.
For this, they use photovoltaic cells made of semiconductor materials, which can release their electrons under the action of an energy (here the light energy). It is the release of these electrons which under the action of photons, allow the production of an electric current. The current, which is created by the displacement of the electrons, is continuous. It is collected by very thin wires connected to each other and then routed to the next photovoltaic cell. Thus, the current is added by passing from cell to cell until reaching the connection terminals of the panel.
Today we can observe two main types of photovoltaic technologies:
This technology is built from highly pure silicon produced in blocks and cut into ultra-thin discs. Subsequently, this pure silicon will be enriched in doping elements (P, As, Sb or B), in order to be able to transform it into a semiconductor of P or N type. These cells will then be connected in series with each other and coated with anti-reflective coating layers to increase light absorption. Finally, they will be covered by the protective glass module, to avoid premature aging due to environmental effects.
Silicon can exist in three forms (monocrystalline, polycrystalline or ribbon ) which correspond to three crystalline technologies which are differentiated by their yield and their cost.
Today, crystalline technology accounts for around 80% of the photovoltaic market share.
2. Thin film technologies
These technologies are more recent than the previous ones and do not use slices of raw silicon. Indeed, they consist of a substrate (glass, metal, plastic ...) on which is deposited a thin uniform layer, composed of one or more materials which are reduced to powder and which are: copper, indium, gallium, tellurium, germanium and/or selenium. This technique performed under vacuum allows a considerably lower investment in energy and materials for manufacturing. Indeed, while panels of about 250 microns are used in the crystalline technique, the resistors of the absorber in the thin-film technique are only a few micrometers. However, a concern about raw material resources is present. In fact, these new technologies use rare metals such as indium, whose world production is 25 tons per year, and the April 2007 price of $ 1,000 per kilogram; tellurium with world production of 250 tonnes per year; gallium production of 55 tons per year; the germanium of a production of 90 tons a year.
Yet, thin-film panel technology is becoming more prevalent and its market share is growing at an incredible rate, now accounting for about 20%, while in 2005 it was only 5.8%. %.
Solar panels are not a real innovation of Man. Indeed, the capture of energy from the Sun has always been used by plants using photosynthesis. This complex bioenergetic process allows so-called autotrophic organisms to produce organic matter from inorganic materials. Thus, in the presence of visible light, carbon dioxide (CO 2 ) and water (H 2 0) are converted into glucose and oxygen (O 2 ).