RENEWABLE ENERGY TECHNOLOGIES

RENEWABLE ENERGY TECHNOLOGIES

The sun is the only star of our solar system located at its center. The earth and

other planets orbit the sun. Energy from the sun in the form of solar radiation supports almost all life on earth via photosynthesis and drives the earth’s

climate and weather.

About 74% of the sun’s mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements. The sun has a surface temperature of approximately 5500 K, giving it a white color, which, because of atmospheric scattering, appears yellow. The sun generates its energy by nuclear fusion

of hydrogen nuclei to helium. Sunlight is the main source of energy to the surface

of the earth that can be harnessed via a variety of natural and synthetic processes.

The most important is photosynthesis, used by plants to capture the energy of

solar radiation and convert it to chemical form. Generally, photosynthesis is the

synthesis of glucose from sunlight, carbon dioxide, and water, with oxygen as a waste product. It is arguably the most important known biochemical pathway, and nearly all life on earth depends on it.

Basicallyall the forms of energy in the world as we know it are solar in origin. Oil, coal, natural gas, and wood were originally produced by photosynthetic processes, followed by complex chemical reactions in which decaying vegetation was subjected to very high temperatures and pressures over a long period of time. Even the energy of the wind and tide has a solar origin, since they are caused by differences in temperature in various regions of the earth.

Sinceprehistory, the sun has dried and preserved humankind’s food. It has

also evaporated sea water to yield salt. Since humans began to reason, they have

recognized the sun as a motive power behind every natural phenomenon. This

is why many of the prehistoric tribes considered the sun a god. Many scripts

of ancient Egypt say that the Great Pyramid, one of humankind’s greatest

engineering achievements, was built as a stairway to the sun ( Anderson, 1977 ).

 

Fromprehistoric times, people realized that a good use of solar energy is benefi cial. The Greek historian Xenophon in his “ memorabilia ” records some of the teachings of the Greek philosopher Socrates (470 – 399 BC) regarding the
correct orientation of dwellings to have houses that were cool in summer and
warm in winter. Thegreatest advantage of solar energy as compared with other forms of energy is that it is clean and can be supplied without environmental pollution.
Over the past century, fossil fuels provided most of our energy, because these were
much cheaper and more convenient than energy from alternative energy sources,
and until recently, environmental pollution has been of little concern.
Twelve autumn days of 1973, after the Egyptian army stormed across the Suez
Canal on October 12, changed the economic relation of fuel and energy as, for the first time, an international crisis was created over the threat of the “ oil weapon ” being used as part of Arab strategy. Both the price and the political weapon issues quickly materialized when the six Gulf members of the Organization of Petroleum Exporting Countries (OPEC) met in Kuwait and abandoned the idea of holding any more price consultations with the oil companies, announcing at the same time that they were raising the price of their crude oil by 70%.Therapid increase in oil demand occurred mainly because increasing quantities of oil, produced at very low cost, became available during the 1950s and 1960s from the Middle East and North Africa. For the consuming countries, imported oil was cheap compared with indigenously produced energy from solid fuels.