In the beginning steam was used to run the machines. Fire was needed to boil the water to produce steam. Coal and wood were widely used for this work. This was the fuel for big machines.
Coal was the first fuel used to run the machines. It is found in mines below the ground. Some deposits of coal are almost on the surface of the Earth.
With the increase in the demand of coal, man kept digging deeper and deeper. Some coal mines are even three to four kilometres deep. Man realised that it is expensive and difficult to work in deep coal mines. The deposits were also limited. He started a search for other sources of energy.
Mineral Oil :
Mineral oil was discovered in America in 1857. It was found deep under the surface. It was taken out and refined to produce kerosene, petrol and other products. Daimler, a German scientist, developed an engine which could run on petrol. This helped in the making of motor cars. It is also used in aeroplanes.
After some years, another German scientist, Rudolf Diesel developed an engine, which ran on another variety of mineral oil. This variety was called ‘diesel’ oil after him. It was comparatively cheaper and could be used to run heavy trucks, buses, railway engines, pumps and even generators.
Now a large variety of machines, other than transport vehicles, are also run with petrol and diesel. The total reserves of mineral oil are also limited and hence it cannot be used indefinitely. So the search for new sources of energy is still going on.
A new source of energy, i.e., electricity was developed. Most of it is produced with the help of coal, mineral oil and natural gas. Some electricity is also produced with the help of running water. This is called, water or hydel power, or hydroelectricity. Huge dams are built across rivers to store water, which then can be used to produce hydroelectricity. There is a story about the discovery and production of electricity.
Once a man in the Netherlands developed a toy, called the ‘Leyden jar’. It had two wires, one in a glass jar and the other outside the glass jar. A spark could be produced by joining the wires. Sometimes it even gave a mild shock. Benjamin Franklin, an American scientist learnt about this jar. He observed that the sparks produced by the Leyden jar and by the lightning in the sky were similar. He tried to prove it through an experiment.
He flew a kite tied to silken thread on a day, when there were clouds, lightning and thunder in the sky. He attached a piece of wire to at the other end of the thread. He flew the kite close to the clouds and touched the metal piece when there was lightning. He received a shock. This confirmed the idea that the sparks produced by the Leyden jar and by lightning were similar. This led to the discovery of electricity.
Now the scientists wanted to produce it. In 1800, an Italian scientist, Volta developed a battery, which produced a small amount of electricity. Later on, generators were developed to produce electricity. These generators need coal, or mineral oil or running water to run and produce electricity.
Other Sources :
Today we use coal wood, mineral oil, electricity, natural gas as sources of energy. But we do not have an unlimited stock. One day these resources will be exhausted. Thus, man is busy in finding a way to use unconventional sources of energy, such as wind power and solar power. Nuciear power, and gobar gas from cow dung are also used as sources of energy. The use of wind and solar energy will also keep the air free from pollution and our environment clean. Some unconventional sources of energy are described below:
1. Hydro-energy :
Have you seen water flow? It carries along with it stones, sand, uprooted trees, animals, etc. This is because water has tremendous energy. When man realised this, he started using water energy to run machines. The water energy (hydro-energy) is used to run various machines. The hydro-energy can be used for grinding grains in water-mills, transporting timber from one place to another and for generating electricity.
Generation of electricity is the most important use of hydro-energy. Water is collected at a certain height in huge reservoirs. This water (which has a lot of potential energy) is then made to fall on turbines connected to huge generators, which generate electricity. Transmission lines are used to distribute this electricity to the consumers. This electricity produced from flowing water is called hydro-electricity.
Hydro-energy has many advantages. The main advantage is that it does not cause pollution. It is also a renewable form of energy as water is a renewable resource. In the long run it is cheaper too. India has many huge hydroelectric power plants. Important ones are the Bhakra Nangal, Hirakud, Damodar power projects.
2. Solar energy :
Almost all the energy flowing on the earth comes from the sun. It is impossible to have life without sun. Plants use solar energy for photosynthesis. A part of it is used in heating air. This in turn causes wind (as hot air being lighter rises up and the cool air from the surrounding areas rush in to take its place, thereby forming wind) and water cycle. Solar energy is also used in solar heating devices like heater, cooker, solar cells, etc.
Solar energy is an inexhaustible natural source of energy. If we tap solar energy, it can be a good replacement for the present sources of energy, many of which will get exhausted in the near future.
3. Wind energy :
Moving air is called wind. The energy obtained from wind is called wind energy. Any moving object possesses kinetic energy with which it can do work. Thus wind has kinetic energy. This energy is used in sailboats, working windmills and even generating electricity. Man is today making more and more use of wind energy as it is a renewable energy. It causes no pollution. But the use of wind energy is limited to areas having high velocity winds. Netherlands is a country which is successfully tapping wind energy. There are several windmill installations in the coastal area of Tamil Nadu.
4. Bio-energy :
The energy obtained by the decomposition of organic matter (animal dung, waste fruits, vegetable, human excreta, etc.) is called bio-energy. When the organic matter is decomposed along with water, in the absence of air, it produces gases like methane, carbon dioxide, hydrogen and hydrogen sulphide. Biogas is an excellent fuel which can be used for cooking, lighting bulbs, etc. As biogas is made from organic wastes, which are easily available, especially in rural areas, it is being increasingly used.