Man is surrounded by an ocean of energy. Mankind has tapped only a fraction of it. The most colossal dynamo of all is the sun, an unimaginable vast powerhouse which affects everything on earth. From time immemorial man has learnt to harness this energy. In 100 B.C. Romans used coal as a fuel to produce fire. In 650 B.C. windmills were used to help travel from place to place. Steam engines later replaced horses and developed into locomotives as modern means of transport.
The supply of energy to the mankind in the present day world is from many different sources.
Sunlight falling on the earth's surface equals 50,000 times the energy used each year by man. Almost all our energy comes from sun.
A solar heating device is one which allows collection of a large amount of heat from the sunlight in a given region and restrict the loss of heat to the surrounding in the form of radiation.
Here heat is absorbed by a blackened metallic pipe or plate and water circulated through these pipes gain heat.
Solar cells are expensive and are used only when supplying electricity becomes difficult.
It does not cause any environmental pollution like the fossil fuels and nuclear power.
Wind energy is one of the first sources of energy known to man.
A device in which wind is used to rotate the blades of a fan like structure is called a windmill. The windmill works on a very simple principle. When the blowing wind strikes across the blades of a windmill it exerts a force which rotates its blades.
The picture shows a seven storey-high 17m wind turbine producing 60 KW of power from a wind with a velocity of 45 km/h.
Water, being a vital resource for all living beings, is also an important source of energy. Hydropower supplies 6% of the world's energy needs. Moving water is highly energized. A hand held into a fast flowing stream can feel the pressure of water trying to push the hand along.
The tides are formed due to the gravitational force of attraction between the earth, sun and moon. During high tides sea water is trapped in a reservoir, and released later to drive turbines, which in turn produces electricity. The block diagram given below illustrates the transformation of energy.
The electricity produced from flowing water is called Hydroelectric power. The world's first hydroelectric power plant was set up in 1882 in Wisconsin USA. It had a very small output, supplying power only for about 250 light bulbs. But from this small start the production of hydroelectricity has grown steadily, and today 6% of the world's need is met with hydroelectricity.
The demand for electricity varies at different times of a year. One big disadvantage is that the wind, waves and tides do not occur at all time and hence cannot guarantee steady production of electricity. Hydroelectric power stations can solve this problem. When the demand is low, excess power generated from other stations can be used to pump water back up into the high reservoir.
Ever since the earth was formed, huge amount of heat energy has been stored in its molten core. Some of this heat is always flowing towards the surface. This heat is called Geothermal Energy.
The first cavemen took firewood from the forests as fuel. Even today firewood is still the main source of fuel for cooking in many parts of the world.
Animal dung in the form of dried cakes is also burned for domestic purposes. Animal dung contains vital nutrients. If burnt directly they produce a lot of smoke leading to air pollution. Instead animal dung can be converted into biogas which is a clean fuel. The residue which is rich in nutrients can then be used as manure.
Biogas is a clean and efficient fuel. It is a mixture of methane (CH4), carbon dioxide (CO2), hydrogen (H2) and hydrogen sulphide (H2S).
Water hyacinth, (weeds that clog major waterways) restricting boat traffic are held in check in a lagoon by careful harvesting. Biogas plants use these dried plants as raw materials.
The Earth contains many resources which are not being replaced. These resources which are not being replaced are called non-renewable sources. Amongst the most non-renewable resources are the three fossil fuels - coal, petroleum and natural gas.
Coal varies in quality according to the amount of pressure and heat to which it is subjected to during its formation. Coal consists largely of carbon, hydrogen and oxygen and a small amount of sulphur. It comes in 3 forms.
When coal is heated without air, it does not burn but produces many by-products. This process of heating coal in the absence of air is called destructive distillation of coal.
Petroleum is a dark, viscous, foul smelling liquid, a mixture of solid, liquid and gaseous hydrocarbons with traces of salt, rock particles and water.
Separation of petroleum into simpler fractions after the removal of unwanted materials.
The burning of a substance is called combustion. It is an exothermic process (chemical reactions which give out heat to the surroundings are called exothermic reactions).
Nuclear energy is the energy released when certain changes take place in the nucleus of an atom. Nuclear energy is partly renewable and partly non-renewable source of energy.
The process of splitting of a nucleus of a heavy atom into a number of light nuclei with the liberation of large amount of energy and two or three neutrons is called nuclear fission.
The sun is the most enormous and direct, source of energy. Where does this enormous energy that the sun radiates come from? The source of this energy was not known to mankind until the year 1939. It was a German physicist, Hans Bethe, who proposed that the sun contains hydrogen nuclei in its core, moving at large speeds. Whenever these nuclei fuse to form a nucleus of a heavier element, a large amount of energy is liberated. Such a reaction is known a nuclear fusion reaction.
Nuclear reactor is a furnace or an equipment in which the nuclear chain reaction is carried out in a controlled manner and the heat energy so liberated is converted into electricity.
In order to live and enable ourselves to do everyday work we need energy. The prosperity of a country depends upon the availability of energy. Huge amount of electrical energy is used to run the air conditioners, cold storage and other domestic appliances. A large share of energy is needed for transportation. There has been increase in the world's population year after year.
Today most of our energy needs are supplied by the fossil fuels. In one hundred years coal will be the only one left as petroleum products may remain only for 3 to 4 decades. Little of stored energy will be left if we continue to use energy at the same rate.