1) Characteristics of a good source of fuel :-i) It should have a high energyoutput per unit mass or volume.ii) It should be easily available.iii) It should be easy to store andtransport.iv) It should be economical.v)It should not leave any residue orash after burning.
Sources of energyThere are two main sources of energy. They areconventional and non conventional sources of energy.i) Conventional sources of energy :- are wood,flowing water and fossil fuels (coal, petroleum, natural gas).ii) Non conventional sources of energy :- are solarenergy, wind energy, biomass energy, ocean energy (tidalenergy, wave energy, ocean thermal energy), geothermalenergy, nuclear energy etc.Some sources of energy are renewable like sun, wind,flowing water, ocean, wood, biomass etc.Some sources of energy are non renewable like coal,petroleum and natural gas.
3. Conventional sources of energy :-a) Fossil fuels :- are fuels formed inside the earth from theremains of plants and animals after millions of years. Thefossil fuels are coal, petroleum and natural gas. Fossilfuels are non renewable sources of energy so theyshould be conserved and used judiciously.Disadvantages of fossil fuels :-i) Burning of fossil fuels release gases and harmfulparticles which causes air pollution.ii) Burning of fossil fuels release acidic oxides of sulphurand nitrogen which causes acid rain which is harmful forliving organisms, affects soil and water, causes damageto buildings, corrosion of metals etc.iii) Burning of fossil fuels release a large amount of carbondioxide gas which increases the temperature of theatmosphere and causes global warming (green houseeffect).
Hydro power plantsIn hydro power plants water from rivers are stored by constructing dams. Thewater from the dam flows down through pipes and rotates the turbines ofgenerators to produce electricity.Advantages :-• i) Flowing water is a renewable source of energy.• ii) The electricity produced does not cause pollution.• iii) The water stored in dams can also be used to control floods andfor irrigation.Disadvantages :-• i) The initial cost is high.• ii) Large areas of land gets submerged and the decomposition ofvegetation produces methane gas which is a green house gas.• iii) It causes displacement of people from large areas of land.• Iv) It disturbs the ecosystem of adjoining areas.
d) Biomass energy :-The waste materials and dead parts of livingthings are called biomass. Eg :- wood, animaldung, vegetable waste, agricultural waste,sewage etc. Biomass is decomposed byanaerobic microorganisms to produce biogas.Biogas is a mixture of gases containingmethane, carbon dioxide, hydrogen andhydrogen sulphide.Biogas plant :-The biogas plant has a large undergroundtank made of bricks andcement. The lower part is the digester and the
BIO-GAS-IDEAL FUELBio-gas is considered an ideal fuel because* It burns without any smoke and so does not cause pollution.*It produces large amount of heat per unit massand thus highcalorific value.*It does not leave any residue on burning and is thus a cleanfuel.*It does not cause any storage problem. It can be continuouslysupplied by pipes directly from the gas plant.*The production of biogas does not involve any running cost andis cheaper than most common fuels.
ComparisonBiomass• It produces too muchsmoke.• Its calorific value is low.• Ash is left as residue.• Organic matter getsdestroyedBiogas• It does not produce any gas• Its calorific value is high.• It does not leave anyresidue.• Organic matter is securedand is available for use asmanure.
e) Wind energy :-Wind energy is used in wind mills which converts the kineticenergy of the wind into mechanical or electrical energy. Thekinetic energy of wind can be used to do mechanical work likelifting water from wells or grinding grains in flour mills. It canalso be used to rotate the turbines of generators to produceelectricity.A single wind mill produces only a small amount ofelectricity. So a large number of wind mills in a large area arecoupled together to produce more electricity in wind energyfarms.Advantages :-i) It is a renewable source of energy.ii) It does not cause pollution.iii) The recurring cost is less.Disadvantages :-i) Wind is not available at all times.ii) It requires a large area of land.iii) A minimum wind speed of 15 km/h is required.
ALTERNATE OR NON-CONVENTIONAL SOURCES OFENERGY
Energy from the seaEnergy from the sea is obtained in three different forms. They are Tidalenergy, Sea wave energy and Ocean thermal energy.i) Tidal energy :-The periodic rise and fall of sea level due to gravitational attraction ofthe moon causes tides. A dam is constructed at a narrow openingbetween the land and sea. The movement of water during high tide andlow tide can be used to rotate the turbines of generators to produceelectricity.ii) Sea wave energy :-When strong wind blows over the sea it produces huge waves. Thekinetic energy of the moving waves can be used to rotate the turbinesof generators to produce electricity.iii) Ocean thermal energy :-There is a temperature difference between the warm surface waterand the cold water at the bottom of the oceans. This difference is about20°C. The warm surface water is used to boil liquid ammonia and thevapour is used to rotate the turbines of generators to produceelectricity. The cold water from the bottom is then pumped up to coolthe vapour back to liquid.
ENVIRONMENTAL CONSEQUENCESThe factors that should be counted for choosingsource of energy are*Ease of extracting energy from the source andits transportation.*The economics of extracting energy from thesource .*The efficiency of technology available.*The environmental damage caused by usingthat source.
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