The direct conversion of sunlight into electricity, the photovoltaic effect, was first observed almost two centuries ago by the French scientist, Edmond Becquerel. However, it took the development of quantum theory in the early 20th century before the phenomenon could be explained and practical photovoltaic devices manufactured.
Photovoltaics is a truly unique way of producing electricity on site, directly from the sun, without concern for energy supply or environmental harm. These solid-state devices simply make electricity out of sunlight, silently with no maintenance, no pollution and no depletion of materials. Photovoltaic technology is also exceedingly versatile - the same technology that can pump water, grind grain and provide communications and village electrification in the developing world, can produce electricity for the buildings and distribution grids of the industrialized countries.
The modular structure of photovoltaic systems makes it possible to convert solar energy into electricity over a wide power range from milliwatts to megawatts directly at the place of use. This environmentally acceptable way of generating electricity offers even more advantages when it is applied to buildings. In that case, the building itself acts as a support structure for the modules, and at the same time, PV modules can be an integral part of the building. For example, as a weatherproof roof or facade element or as a shading device. With these advantages, it can be foreseen that PV will become a common component in newly erected, as well as retrofitted buildings. | 
