| Abstract: |
Strictly speaking all forms of energy on the earth are derived from the sun. There are four primary sources of ene-rgy such as petroleum,natural gas and natural-gas-liquids,coal and wood. Excepting wood,all these common sources havefinite supplies. The life-time is estimated to range from 15years for natural gas to nearly 300 years for coal. Therefore, just these non-renewable sources are consumed, the human being must look for longer-term, permanent type for energy sources.The two most significant sources are nuclear and solar wind and water head energy. Nuclear eneigy requires advancedtechnology and costly means for its afe and reliable utilization and may have undesirable side effects.solar energy on the other hand, seems to promise of becoming a de-pendable energy source without new requirements of highly technicaland specialized nature for its wide-spread utilization.In addition, it has no significant polluting effects from its use.All countries in the world receive some solar energy.This amount varies from a few hundred hours per year as in the northern countries to thousands hours per year as in the case of Egypt.
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