Solar Energy

Solar Energy

Life is sustained by the energy from the sun. Without the sun all

plants and animals would die. The sun provides 99.98% of the energy,

which naturally flows through the surface environment of the earth.

Put another way, the sun supplies 5000 times more energy than all

other sources combined. This emphasizes the importance of solar energy

to us.

Solar energy arrives at the earth at 170 thousand million joules every

second!

About 30% of the radiation energy is reflected straight back into

space. The icecaps and particles in the atmosphere form good

reflectors. It is thought that an increase in the area of ice covering

the surface of the earth, or an increase in atmospheric dust might

reflect even more radiation back into space and so cause the earth to

cool towards another ice age.

About 47% of solar radiation is absorbed and converted into heat

energy or internal energy. During the day the earth's surface is

warmed up, and during the night this energy is radiated back into

space as radiant heat energy.

About 23% of solar radiation is absorbed causing evaporation of water

from the oceans and lakes and from the land and plants. The high

latent heat of vaporization of water means that a lot of absorbed

radiant heat energy is used to convert liquid water into the

atmosphere where it forms clouds. Much of this energy then becomes

stored as a potential energy in glaciers and rivers. As the water runs

back to the sea, the potential energy is eventually converted into

heat energy.

A small amount of energy, about 0.2% of the total, drives convection

currents in the oceans and the atmosphere. Some of this energy appears

as wind power and wave power, which are forms of kinetic energy or

mechanical energy.

An even smaller amount of energy, only 0.02% of the total, is absorbed

by growing plants via a chemical process called photosynthesis. This

energy is converted into heat energy when humans and the animals do