Utilization of Solar Energy – Part 1

In the context of global warming caused by large scale use of fossil fuels, solar energy assumes tremendous importance as an alternative source of energy. Realizing the tremendous influence the Sun had on virtually every aspect of existence of all living things on earth, many ancient cultures such as the Egyptians, the Greeks and the Romans feared and revered the Sun.

With the spread of science, we now have a much great appreciation of this gigantic source of energy around which our planet earth orbits. Now we know the enormity of the Sun in relation to earth. The Sun is a ball of burning hydrogen gas and is about 1,500,000 times bigger than the earth. Its surface temperature is about 27,000,000 deg C. Due to this high temperature it emits energy in all directions The Solar radiations cover a very wide range of frequencies. A very small part of the energy is emitted as visible radiation – the light, as we call it. Radiations from the Sun extend from infra-red (lower in frequencies than the lowest visible radiation frequency – red) and well into the ultra-violet (higher in frequencies than the highest visible radiation frequency – violet).

Sun is the centre of our planetary system and the planet earth rotates around the Sun. As the earth rotates around the Sun, solar radiation carrying energy falls on the Earth. About 5% of the radiation coming towards the earth is reflected away from the earth and the atmosphere absorbs about 15%. Thus the maximum solar power we can receive at the equator is about 1000 W/m². Presence of clouds, dust, etc. reduces this further and on an average we receive only about 800 W/m² of solar power at the equator.

Solar energy gives us the light and heat, and plants convert the solar energy by photosynthesis into chemical energy for their growth. The plants and the trees provide fruits, grains and also the fuel – wood, grass, etc. The whole interdependent kingdom of living organisms – plants, birds, fish, animals and humans – draw their sustenance from this life giving source of energy. (Fuels such as oil, gas and coal that we use today were formed from fossilized plants and trees and in a way they represent the solar energy stored by nature). All the energy received from the Sun is not utilized in this manner and the excess energy results in the rise of temperature of the earth and the oceans. This causes infra-red radiation from the earth outward into atmosphere.

Solar energy—power from the sun—is free and inexhaustible. Human civilization has always used the energy of the Sun as far back as they have existed on this planet. However, the amount of this bounty we utilize is insignificant in comparison to what the Sun bestows on us. We receive enough energy from the Sun in barely twenty days of sunshine to make up for all the energy stored in Earth's fossil fuel reserves. We realize that currently we utilize barely 1% of this energy and it has a tremendous potential as an important inexhaustible alternative source of energy.