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 Each day more solar energy falls to the Earth than the total amount of energy the planet's 6 billion inhabitants would consume in 27 years. Currently we harness about 1% of this energy
Photovoltaics are one of the fastest growing solar energy technologies. Photovoltaic devices, commonly called solar cells or modules, use semiconductor material to directly convert sunlight into electricity. Solar cells have no moving parts-power is produced when sunlight strikes the semiconductor material and creates an electric current.
PV modules have no moving parts, are virtually maintenance-free, and have a working life of 20 - 30 years.
The PHOTOVOLTAIC (PV) effect was discovered by a French natural scientist Alexandre Edmond Becquerel in 1839 when he discovered that electric current can be generated when certain structures are exposed to light (he dipped platinum plates into liquid electrolytes). The Americans Adams and Day in 1876 using a selenium crystal have done the demonstration of the effect. The efficiency in this case was only slightly above 1%. In 1905 Albert Einstein formulated an explanation of the PV effect (the photon hypothesis). In 1949 the Americans Shockley, Bardeen and Brattain discovered the transistor and clarified the physics of the p and n junctions in doped semiconductors materials. The first solar cell with an efficiency of about 6% was developed and later in 1956 a silicon solar cell was made with an efficiency of 10%.
The rapid development of space exploration opened up excellent opportunities for solar cell application. In 1958, 108 solar cells were sent into space for trials for the first time. Serial production begun soon afterwards, albeit in small numbers. In 1970, annual production of solar cells for space applications totalled 500 m2. Earth-bound use of solar cells was given a boost during the 73/74 oil crisis, and this has since led to the launch of numerous research and development projects. The most important aim here has been to reduce the cost of PV plants.
Solar cells and photovoltaic plants have since become a common part of everyday life. Their application spectrum is broadening all the time and ranges from small - scale applications in pocket calculators and watches to large electricity - generating plants with outputs in the kW and MW ranges.
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