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History. The Earth receives an incredible supply of solar energyThe Earth receives an incredible supply of solar energy. The sun, an average star, is a fusion reactor that has been burning over 4 billion years. It provides enough energy in one minute to supply the world's energy needs for one year. In one day, it provides more energy than our current population would consume in 27 years.
Producing electricity from solar energy was the second discovery. In 1839 a French physicist named Edmund Becquerel realized that the sun's energy could produce a "photovoltaic effect" (photo = light, voltaic = electrical potential). In the 1880s, selenium photovoltaic (PV) cells were developed that could convert light into electricity with 1-2% efficiency (the efficiency of a solar cell is the percentage of available sunlight converted by the photovoltaic cell into electricity), but how the conversion happened was not understood. Albert Einstein proposed an explanation for the "photoelectric effect" in the early 1900s, for which he won a Nobel Prize. "Solar technology advanced to roughly its present design in 1908 when William J. Bailey of the Carnegie Steel Company invented a collector with an insulated box and copper coils." By the mid-1950s Bell Telephone Labs had achieved 4% efficiency, and later 11% efficiency, with silicon PV cells. From then on, interest in solar power intensified. During the late 1950s and 1960s, the space program took an active role in the development of photovoltaics. Unfortunately, the cells were not practical for use on earth due to the high cost of making them efficient and lightweight, so further research was necessary.
Considering that "the first practical solar cells were made less than 30 years ago," we have come a long way. The biggest jumps in efficiency came "with the advent of the transistor and semiconductor technology." The production cost has fallen to nearly 1/300 of what it was during the space program of the mid-century and the purchase cost has gone from $200 per watt in the 1950s to a mere $5 per watt today. The efficiency has increased dramatically to 18.8% (February 1999).
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