Sources of Energy-Notes

•  Conditions of the good fuel

      (i) High calorific value

      (ii) Less smoke

      (iii) Less residue left after burning

      (iv) Easy available

      (v) Inexpensive

      (vi) Easy to store and transport

•  Conventional sources of energy

     •  FOSSIL FUELS: Millions of years ago plants and animals tissues got buried under the ground and were subjected to high temperature and pressure. Coal is a fossil fuel which was formed due to subjection of plant tissues under high pressure and temperature. While petroleum is obtained from the remains of animals between sedimentary rocks.

         These are non-renewable sources of energy and lead to pollution on combustion.

     •  THERMAL POWER PLANT: -Thermal power plant use coal, petroleum and natural gas to produce thermal electricity.

          -The steam produced is used to run the turbine to generate electricity.

          - Electricity transmission is more efficient.

      Disadvantages

     •  Fossil fuels are used which is non- renewable source of energy.

     •  Leads to water and air pollution.

•  HYDRO POWER PLANTS

     It is themost conventional renewable source obtained from water falling on from the height

     •  It Is clean non- polluting source of energy

     •  Dams are constructed near rivers. As the water level rises, the kinetic energy of water gets changed to potential energy

     •  The water is released to rotate the turbine and electricity is generated.

          Disadvantages

     •  Highly expensive

     •  Dams can be made at limited areas

     •  Large areas of human habitation and agricultural fields are submerged

     •  Problem of rehabilitation of displaced people

•  NON CONVENTIONAL SOURCES OF ENERGY

•  WIND ENERGY: - It can be converted to mechanical and electrical energy

•  Kinetic energy of wind is used in lifting water from pump, grinding grains etc.

    ADVANTAGES

    •  Eco friendly

    •  Renewable

    DISADVANTAGES

    •  Wind speed is not uniform

    •  Need large areas for wind mills

    •  Need lot of investment

    •  Output is less

    •  SOLAR ENERGY: - Solar radiations can be converted to other forms of energy through photovoltaic cells.

    •  These cells convert solar radiations directly into electricity through silicones solar cells.

    •  Solar cookers are painted black from outside and a have glass plate to trap solar radiations by greenhouse effect.

    ADVANTAGES

    •  Eco friendly

    •  Renewable

    •  Used in rural areas

    DISADVANTAGES

    •  Silicon cells are expensive

    •  Solar radiation are not uniform over earth’s surface

    •  Can’t be used at night or on cloudy day.

    •  Maximum temperature achieved by solar cooker is 100° C

    •  GEOTHERMAL ENERGY

        Utilization of heat in the interior of earth for power generation is called geothermal energy. In places where hot springs or geysers occur steam trapped in rocks is brought in turbine through pipes to generate electricity.

    ADVANTAGES

    •  Renewable

    •  Inexpensive

    DISADVANTAGES

    •  Only available in few sites

    •  NUCLEAR ENERGY

        Radioactive elements generate large amount of energy e.g. 1 ton of U-235 provide as much as energy as 3 million ton of coal.

        It is sued for heat generation and as fuel for marine vessels.

    ADVANTAGES

    •  Alternative source due to depletion of fossil fuels

    •  From small amount of fuel large amount of energy is obtained

    DISADVANTAGES

    •  Risk of nuclear wastage

    •  High cost

    •  Pollution

    •  Tidal energy: depends upon the harnessing of rise and fall of the sea level due to tidal energy. Dams are constructed across a narrow part of sea and turbine converts tidal energy to electricity

    •  Ocean thermal energy: the difference in temperature of water at surface and the water at the depths is exploited. The warm surface water is used to boil ammonia and turbine is run by the vapours of ammonia.

    •  Waves of sea are used as their kinetic energy is converted into electrical energy

    •  Turbine is used to produce electricity