• The chief sources of energy in order of importance are fossil fuels, hydropower and nuclear energy.
• In addition, solar energy, wind energy, tidal energy and geo thermal power also provide energy which are alternative sources of energy.
1. Fossil fuels:
• Fuels formed from the remains of dead plants and animals buried under the earth millions of years ago are called fossil fuels.
• Coal, petroleum and natural gases are fossil fuels which are formed by the decomposition of the remains of plants and animals, which got buried under the earth for millions of year.
a. Coal:
• It is found in deep mines beneath the surface of the earth.
• Coal provides about 27% of all the commercial energy used in the world.
• Peat, lignite (brown coal), bituminous and anthracite (hard coal) are some types of coal based on the percentage of carbon in them.
• It is used for domestic purposes like cooking and heating, in steam engines, thermal power plants and in steam boilers.
• Coal is also an important source of many chemicals used for the manufacture of drugs, dyes, fertilizers, plastics, synthetic fibers and explosives.
b. Mineral oil (petroleum):
• It is a dark brown and viscous crude oil with a characteristic foul smell.
• It is found trapped between rocks beneath the earth which is obtained by drilling a hole in the earth’s crust where it occurs.
• The petroleum thus drilled out from oil wells is a crude oil consisting of mixture of hydrocarbons with salt, water and earth particles.
• This crude oil is purified (refined) by fractional distillation to obtain more useful components like petrol, diesel, kerosene, paraffin and asphalt.
• Asphalt, which is a residue in this process doesn’t burn and hence is not a fuel but is used mainly for blacktopping the roads.
Advantages of fossil fuels:
• Coal and mineral oils are cheap and easily available sources of fuels.
• Mineral oil can be easily transported within and between countries.
• Mineral oils (petrol, diesel) are used to run vehicles like motorcycles, cars, buses, trucks.
• Coal is used in industries where large amount of heat energy is required and also in trains.
• Petroleum oils are easy to store.
2. Hydro-electric power:
• Water is cheap and renewable source of energy.
• Water flowing with high speed or made to flow with high speed possess energy (kinetic energy).
• Hydro-electricity is produced when water stored in reservoir come down and rotates the turbines of huge generators to produce hydro-electricity.
• It is regenerative and helps in the conservation of fossil fuels.
Advantages of hydro-power:
• Although the production is high, it is cheaper on a long term basis.
• It can be transmitted through wire to long distance.
• It doesn’t pollute the environment and is environmental friendly.
• The reservoir or dam can be used as recreational area for fishing, boating and can be a tourist attraction.
Alternative sources of energy:
• Natural sources or fossil fuels such as oil, natural gases will eventually run out.
• The renewable sources of energy used instead of non-renewable sources are called alternative sources of energy.
• They are environment friendly and effectively supply the energy requirement.
• Bio fuel is one important alternative source of energy. Some other alternative sources of energy are:
a. Nuclear energy:
- It is the energy generated either from nuclear fission or from nuclear fusion.
1.Nuclear fission:
- One heavy nucleus splits or disintegrates into two or more lighter nuclei of nearly equal sizes with the large amount of energy.
- In this process, atoms or radioactive elements such as Uranium or Plutonium are bombarded with a slow moving neutron.
- The Uranium nucleus splits into smaller nuclei of Barium, Krypton and three neutrons with the release of large amount of energy.
- The released neutrons can cause disintegration of more Uranium nuclei and produce more neutrons.
- The heat released during fission process is used to produce steam to drive turbine to generate electricity.
2. Nuclear fusion:
- The sun produces energy by nuclear fusion. In nuclear fusion at high temperature and high pressure, lighter nuclei fuse to form a slightly heavier nucleus with the release of enormous amount of energy.
- Deuterium and Tritium, which are isotopes of Hydrogen fuse to form Helium at high temperature and pressure.
- Slight amount of mass is lost during the fission and fusion reactions which is transformed into energy in accordance with Einstein’s mass energy equivalence relation, (E=mc2).
b. Wind energy:
• This is the energy obtained from the fast moving wind which might be used to run wind mills.
• The wind energy is used to propel the blades of wind turbines which produces electrical energy.
• Compared to hydro-power, it is cheap and does not need any complex infrastructure.
• Palpa, Lo manthang, Kagbeni, Khumbu regions of Nepal possess a high potential of wind power generation.
Uses of wind energy:
• It is used for pumping water for agricultural need, powering agricultural works such as grinding corn, wheat and threshing and generating electricity.
c. Tidal energy:
• The energy obtained from the tides on the coastal areas is called tidal energy.
• The energy generated depends on the amount of rise and fall of tides in the sea.
• Power generation is possible only in the locations where the tidal range is high.
• At high tide, sea water rushes into the constructed barrage and gets collected there. As the tide goes out, the trapped water rushes down and drives the turbines thus generating electricity.
d. Geothermal energy:
- It is the heat energy stored deep inside the earth as the interior of the earth is very hot.
- During volcanic eruptions, the hot molten materials within the earth come out to the earth’s crust.
- The temperature of the interior of the earth in volcanic regions increases by 800C for one kilometer depth.
- In other regions, the temperature rises by 300C for one km depth. By boring a hole and allowing cold water to seep down in the hot rock, steam can be produced.
- This hot steam drives the steam engine to turn the turbine of a generator to produce electricity.
Advantages of geothermal energy:
- The use of geothermal energy doesn’t cause any pollution.
- It is commercial to use geothermal energy for generating electricity.
e. Solar energy:
- It is the most reliable renewable source of energy at present.
- It is the energy obtained from the sun in the form of heat and light because of nuclear fusion reaction in the sun.
Advantages of solar energy:
- It is inexhaustible form of energy as it is derived from the sun.
- The use of solar energy doesn’t cause any pollution.
- It is easily available during the day time.