A source of energy is the one which provides adequate amount of energy over a long period of time. A source of energy supplies energy which is needed to do work.
There are various sources of energy available to mankind are categorized as:
Renewable sources of energy
- Renewable source of energy
- Non-renewable source of energy
- It is the energy that exists freely in nature.
- A natural source that provides energy continuously without getting exhausted is known as renewable source of energy.
- It is also known as the non-conventional source of energy.
- This energy does not pollute the environment (air, water or land).
Example: Solar energy, wind energy, hydro (water) energy, bio-energy (or biogas), geothermal energy.
1. Solar energy: The Sun is the main source of energy and the sun’s energy is called the solar energy. The energy that we use comes directly or indirectly from the Sun and it is in the form of heat and light.
Solar cooker and solar water heater are the devices that are used to collect the solar energy.
2. Wind energy: Air in motion is called wind. It is used as a source of energy to produce kinetic energy that is used in windmills.
Windmills convert kinetic energy into electrical energy and it is used:
- A water lifting pump to draw water from a well.
- To run a flour mill and
- To generate electricity.
3. Hydro (or water) energy: The kinetic energy possessed by fast flowing water is called as hydro energy. Hydro energy too comes indirectly from sun. The solar energy is responsible for water cycle in nature. This energy is used to generate electrical energy. The water stored in dams is carried through pipes to the turbine. When the water flows down, its potential energy is converted into kinetic energy. The water falls on large turbine wheels which is connected to the electric generators that produce electricity and is called as hydro electricity.
4. Bio-energy: Biomass is the fuel obtained from dead parts of plants and waste material of animals. It contains carbon compounds and the chemical energy stored in them is called as bio-energy. This energy is also received from the Sun as plants absorb energy from the sun and it is converted into chemical energy by photosynthesis which is then stored in biomass.
Example: cattle dung, wood, crop residence and agricultural wastes.
Biogas is a clean and cheap fuel and is obtained when biomass (i.e. cattle dung, wood, crop residence and agricultural wastes) is decomposed in the absence of oxygen. It is popularly known as gobar-gas.
5. Geothermal energy: The word geothermal comes from the Greek words geo means earth and thermo means heat. It is the place below the Earth’s surface where magma (hot molten lava) comes up through the cracks into the crust.
Non-renewable source of energy: Coal, petrol, kerosene and diesel contain chemical energy. When they are burned the chemical energy is converted into heat, light and sound energy.
1. Coal: It is a useful resource that occurs naturally. It is a hard, combustible black or brownish-black sedimentary rock composed of carbon, hydrogen, oxygen, nitrogen and sulphur. It is found deep in the mines under the earth’s surface and is found in abundance in India. It produces heat when burnt in the presence of oxygen.
Example: Coal was used in railway engines as a fuel in olden days and also used in many industries.
2. Petroleum: It is a liquid fossil fuel that is dark coloured thick oil with an unpleasant odour called as crude oil. It is found by drilling deep below the Earth’s surface using oil rigs. The products obtained after refining the petroleum are fuel, petrol, diesel, kerosene.
3. Natural gas: It is a fossil fuel which is obtained by digging wells deep under the earth’s surface. It burns easily in the form of methane gas which is used as domestic and industrial fuel and also used in thermal power plant for generating electricity. It is used as a fuel for vehicles and as a chemical in the manufacturing of plastics. CNG is widely used in industries and in vehicles as a fuel because no pollution is caused by it.