Solar energy is clean and renewable. Fortunately, we don't need to worry about running out of sunlight, whereas the present world faces an energy crisis owing to the coming shortage of the fossil fuels, such as oil and coal etc., which were accumulated in the earth's crust originated by the solar energy many years ago. Ralph Nader stated that "the use of solar energy has not been opened up because the oil industry does not own the sun".

The typical solar cell consists of at least two semiconductors which can produce the electric charges, electron and hole, when irradiated with light. The flow direction of the electric charges produced by light irradiation can be regulated using the appropriate combination of semiconductors. Thus, the electric power to operate the electric loads such as a light bulb or a motor can be produced by the solar cells. The phenomenon of producing the electric power, both of voltage and electric current, in this way is known as the photovoltaic effect.

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A non-renewable resource is a natural resource which cannot be produced, grown, generated, or used on a scale which can sustain its consumption rate, once depleted there is no more available for future needs.

15 Jan., 2012