In just one second, the Sun gives off 13 million times the energy that is generated by all the electricity consumed in one year in the United States. Only one millionth of the Sun's energy reaches Earth, but this scant amount would be more than sufficient to meet the energy requirements of our entire planet. The relative difficulty in extracting energy from the Sun, when compared to systems that derive energy from fossil fuels or nuclear power, has hindered its development as a widespread source of energy. On a smaller scale and in many experimental projects, however, solar energy has proven highly effective in producing both electricity and heat.
Solar energy was first explored for electrical purposes in the 1950s, when the need for continuous electric power generation