Nuclearpower stations are massive and complex structures. They are designedto withstand earthquakes and violent storms. They include manyspecial safety devices and systems that help to protect the plant,the people working in it and the public, even in the event of aserious accident. However, in spite of the preventive measures,accidents have occurred, for instance, at Three Mile Island in theUSA and at Chernobyl in the former USSR. These accidents have raisedquestions in the minds of many people about the use of nuclear energyto produce electricity.

Therefore,some years ago scientists started to consider an alternative sourceof electrical energy----sunlight. Using sunlight as a source ofenergy offers considerable advantages. Light from the sun ispractically inexhaustible; in other words, sunlight cannot be usedup. It is available everywhere. Besides, changing sunlight intoelectrical energy does not demand fuel such as coal or oil. Thesystem of converting solar energy into electrical energy would dovery little damage to the environment.