Renewable energy refers to the sources of energy which are
replaced or renewed by natural processes. The sun, our chief
source of energy, is a giant nuclear machine. Almost all
renewable energy sources are derived in one form or another from
the sun. The potential of energy from the sun for the
replacement of energy required by today’s rapidly growing world
is very high. The solar energy striking the earth's surface can
be as high as approximately 600 - 1500W/sq meter. However, due
to various climatic and geographic conditions, this radiation is
not uniform in different parts of the world. When the sun is
positioned directly overhead or 90° from the horizon, the
incoming radiation strikes the surface of the earth at a right
angle and is the most intense. If the sun is at an angle above
the horizon, the incoming radiation strikes the earth's surface
at an angle causing the rays to be spread out over a larger
surface area and reducing the intensity of the radiation. Apart
from the angle of incidence and dust pa