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Sources of Energy

Chapter: Sources of Energy

Energy crisis has been so predominant these days. We learnt that energy during a physical or a chemical process is conserved. Then why are we facing energy crisis? Also we know energy can be neither created nor destroyed. Then we should be able to perform endless activities without worrying about energy crisis.
Energy is basically defined as the ability of a body to do work. The unit of energy is joule A source of energy is that which is capable of providing enough useful energy at a steady rate for a long period of time.

What is a Good Source of Energy?

 A good source of energy should be
       • Safe to use. For example, nuclear energy should be used by trained engineers and in highly restricted area.
       • Convenient to use.
       • Easy to store. For storage of oil, petro, huge tanks are used.
       • Easy to transport.

Characteristics of an ideal or a good fuel:

       • It should have a high calorific or a heat value, so that it can produce maximum energy by low fuel       consumption.
       • It should have an optimum ignition temperature, so that it can burn easily.
       • It should not produce any harmful gases during combustion which may harm the ecological balance. .
       • It should be cheaper and easily available in abundanc.
       • It should be convenient to handle, store and transport from one place to another.
       • It should burn smoothly and much residue should not be left after its combustion.

There are two types of sources of energy:
      1. Conventional sources of energy
      2. Non conventional sources of energy
Let us discuss each of the above in detailed.

Conventional Sources of Energy

1. Fossil Fuels

Fossil fuels are actually the remains of prehistoric plans and animals which were buried deep inside millions of years ago because of some natural processes. Coal, petroleum and natural gas are some of the fossil fuels.

How do fossil fuels form?

An organism or its parts gets buried in sand or mud. They gradually decay and decompose totally and leave no signs of their existence. The harder parts of organisms after their death settle down and are covered by sediments and they are subjected to extreme pressure and temperature of the earth and thus converts them into fossil fuels, This process is called fossilization.

Disadvantages of Fossil Fuels:

1. The fossil fuels are non-renewable sources of energy and once used cannot be renewed.
2. Air pollution is caused by the burning of fossil fuels.
3. The fossil fuel reserves in the earth are limited and may get exhausted soon.

Thermal Power Plant

Thermal power plant is a plant where fuel is burnt and heat energy is produced and this is converted into electrical energy. In a power plant, large amounts of fossil fuels are burnt daily which heats up water and converts into steam. This steam is used to run a turbine and generate electricity. Many power plants are setup near coal deposit fields or oil fields to minimize transport costs.

Hydro Power Plants

This is another traditional source of energy. In this the kinetic energy of flowing water or potential energy of water at some height is used to generate energy. For example waterfalls come under this scope. Hydro power plants convert this potential energy into electricity. But there are very few waterfalls hence dams serve the purpose. A large number of dams are constructed worldwide and it is found that in India one quarter of our energy requirement is generated by hydro power plants.


Water flowing in a river is stored in a dam and is allowed to fall down from the top of the dam. The water flows with a high velocity and this force is used to drive a large turbine. Electric generators are connected to the turbine and hence electricity is produced. The electricity generated in this process is termed as hydro electricity or hydel power. In fact the process involves transfer of potential energy of the water into kinetic energy and then into electric energy.

Advantages of hydro electricity

  1. Water is available readily and abundantly everywhere.
  2. Water is available free of cost
  3. Water is eco-friendly. It does not disturb ecological balance and does not produce any sort of environmental pollution
  4. It is cheap source of energy
  5. Water is renewable and inexhaustible resource


Biomass is defined as living matter or its residue and is a renewable source of energy. The biomass includes

  1. All the plants
  2. Agricultural and forest residues like saw dust, tree barks, roots, etc
  3. Carbonaceous wastes (like sewage, garbage, night-soil, etc.)
  4. Biodegradable organic affluent from industries.

Biogas is a mixture of gases produced by anaerobic degradation of biomass in the absence of oxygen and presence of water. Biogas is mainly composed methane (up to 75%), CO2 (25%) and little traces of other gases such as nitrogen and hydrogen. Whereas methane is a high value calorific fuel, carbon dioxide is an inert gas.

Advantages of Biogas:

  1. Bio gas is a clean fuel that burns with smoke and leaves no ash.
  2. Bio gas plant is simple in construction and can be easily setup in rural areas.
  3. The slurry is rich in nitrogen and phosphorus and this serves as  a good manure
  4. Deforestation is reduced by the use of bio gas.

Wind Energy

When large volumes of air move from one place to another it is referred to as wind. In this process kinetic energy gets associated with it which is referred to as wind energy.

Principle of utilization of wind energy: -

Wind mill is a device which converts wind energy into electrical energy. A wind mill consists of large fan having big blades. They rotate by the force exerted by the moving wind  and it is connected to generator. Thus electricity is generated.

Uses of wind energy: -

The important uses of wind energy are;

1. It is used to drive windmills, water lifting pumps and flour mills etc.

2. It is used to propel sail boats.

3. It is used to fly aero planes (engine less) or gliders in the air.

4. It is used to generate electricity which is used for various purposes like lightening, heating etc.

Advantages of wind energy

The advantages are as follows:

  1. It is a cheap source of energy
  2. It is abundantly available
  3. It is eco friendly and does not produce any environmental pollution
  4. Wind is renewable and inexhaustible resource

Non-Conventional Sources of Energy

Non-conventional sources of energy are not used as extensively as the conventional ones. They meet our energy requirement only on a limited scale. Solar energy, ocean energy (tidal energy, wave energy, ocean thermal energy, OTE), Geothermal energy and nuclear energy come under non conventional sources of energy. They are also called alternative sources of energy.

Solar Energy

The energy produced by the sun in the form of heat and light is called solar energy. Solar cell is a device which converts solar energy into electrical energy. It is made of semi-conducting material like silicon, germanium, selenium or gallium. A modern solar cell is made from wafers of semi conducting materials containing impurities in such a way that when light falls on them, a potential difference gets generated.

A number of solar cells are arranged together in a definite pattern in a solar panel to generate a large amount of current. The electrical energy generated in a solar panel is stored in a battery connected to it and thus can be used for various purposes.

Solar cells are used to produce electricity which is used for lighting houses and streets, to run electrical appliances like TV, radio, calculators etc, off-shore drilling platforms, artificial satellites, space vehicles and rockets.

Advantages of solar cell:

  1. It has no moving parts
  2. It required little maintenance
  3. It works without the use of any focusing device
  4. They can be set up even in remote and inaccessible areas.

Energy from the Sea

Water bodies occupy almost 71% of the surface of the earth and the huge amount of water collects solar energy and stores a due to its specific heat. Thus sea and ocean water can be used as a renewable resource of energy. The main forms of sea energy are as follows:

  1. Tidal energy
  2. Wave energy
  3. Ocean thermal energy

 Let us explain each of the above in detail

1. Tidal energy

Tide is the rise or fall of water due to the attraction of moon. The rise of water is called high tide and the fall is called low tide. This movement of water produces a large amount of energy which is called tidal energy. This tidal energy can be used by constructing a dam.          

2. Wave energy

Wave energy is the energy obtained from high speed of waves in sea. These waves have a lot of kinetic energy which can be converted into electrical energy using dynamos.

3. Ocean thermal energy

The water at surface of the sea gets heated due to the sun. Hence it is hotter than the water present deep inside the sea. This temperature difference is used to obtain energy.

Hence ocean thermal energy can be defined as the energy available due to the temperature difference between surface of an ocean and the deeper portions of ocean.

Geothermal Energy

Geothermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations. Geothermal energy does not come directly or indirectly from the solar energy.

The underground hot water which is in contact with hot spots changes into steam.  Steam gets compressed to high pressure as it gets trapped between rocks. At some places, hot water and steam forcibly comes out from the Earth’s surface after making their way through large cracks between the rocks and form natural geysers. Geothermal energy carried by natural geysers is utilized for generating electricity.

Advantages geothermal Energy:

  1. Geothermal energy is the most versatile source of energy which produces less pollution.
  2. It can be harnessed for 24 hours throughout the year.
  3. It is relatively cheaper.
  4. The power generation level of geothermal energy is higher compared to solar energy and wind energy.
  5. It can be used for power generation as well as direct heating.
  6. In USA, water is pumped from underground hot water deposits and is used to heat houses.

Limitations of Geothermal Energy:

  1. Geothermal hot spots are scattered and usually some distance away from the areas that need energy.
  2. The overall power production has a lower efficiency (about 15%) as compared to that of fossil fuels which is 35% to 40%.
  3. As a whole, geothermal energy by ore has a limited life span of about 10 years.
  4. It leads to little noise pollution as it includes drilling at sites.

Nuclear Energy

Nuclear energy is produced by a reaction in which the nucleus of an atom undergoes a change, forms a new atom and releases an enormous amount of energy. There are two ways of obtaining nuclear energy.

1) Nuclear fission

The nucleus of a heavy atom bombards with low energy neutron and splits apart. In this process it produces tremendous amount of energy. This released energy is used to produce steam and thus electricity can be generated.

2) Nuclear fusion

Lighter nuclei are joined to make heavier nucleus and during this process huge amounts of energy is released and is used to generate electricity.

Difference between Nuclear fission and fusion


Nuclear Fission

Nuclear Fusion

1. It involves splitting of heavy nucleus into lighter nuclei

1. It involves joining of two nuclei

2. It occurs due to the bombardment of heavy nucleus with neutron

2. It occurs due to extreme heating

3. It is a chain reaction

3. It is not a chain reaction

4. It is a controlled process

4. It is an uncontrolled process

5. It produces tremendous amount of energy

5. It produces more energy than fission

6. Fission products are hazardous

6. Fusion does not cause pollution


Environmental Consequences

The following points are the environmental consequences of the increasing demand of energy:

  1. The combustion for fossil fuels is producing acid rain and damaging plants/crops, soil and aquatic life.
  2. The combustion of fossil fuels is increasing the amount of greenhouse gas carbon dioxide in the atmosphere.
  3. Deforestation for obtaining fire-wood is causing soil erosion and leading to the destruction of wild life.
  4. The construction of hydro-power plants is disturbing ecological balance.
  5. Nuclear power plants are increasing radioactivity in the environment.