1. SOURCES OF ENERGY Namshad.kp Asst Professor,Dept of Polymer chemistry. NAM College,Kallikkandy.

2. What are sources of energy? The source from which we get energy are called sources of energy.For example. Wind enegyFossil fuelSolar enegy

3. Characteristics of a good source of fuel :- i) It should have a high energy output per unit mass or volume. ii) It should be easily available. iii) It should be easy to store and transport. iv) It should be economical. Sources of energy :- There are two main sources of energy. They are conventional 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 solar energy, wind energy, biomass energy, ocean energy (tidal energy, wave energy, ocean thermal energy), geothermal energy, 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.

5. a) Fossil fuels :- are fuels formed inside the earth from the remains of plants and animals after millions of years. The fossil fuels are coal, petroleum and natural gas. Fossil fuels are non renewable sources of energy so they should be conserved and used judiciously. Disadvantages of fossil fuels :- i) Burning of fossil fuels release gases and harmful particles which causes air pollution. ii) Burning of fossil fuels release acidic oxides of sulphur and nitrogen which causes acid rain which is harmful for living organisms, affects soil and water, causes damage to buildings, corrosion of metals etc. iii) Burning of fossil fuels release a large amount of carbon dioxide gas which increases the temperature of the atmosphere and causes global warming (green house effect).

7. b) Thermal Energy :- In thermal power plants the heat energy produced by burning fossil fuels like coal, petroleum or natural gas is used to heat water and change it into steam which rotates the turbines of generators to produce electricity. c) Hydro power plants :- In hydro power plants water from rivers are stored by constructing dams. The water from the dam flows down through pipes and rotates the turbines of generators 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 and for irrigation. Disadvantages :- i) The initial cost is high. ii) Large areas of land gets submerged and the decomposition of vegetation produces methane gas which is a green house gas. iii) It causes displacement of people from large areas of land.

8. THERMAL POWER PLANT

10. d) Biomass energy :- The waste materials and dead parts of living things are called biomass. Eg :- wood, animal dung, vegetable waste, agricultural waste, sewage etc. Biomass is decomposed by anaerobic microorganisms to produce biogas. Biogas is a mixture of gases containing methane, carbon dioxide, hydrogen and hydrogen sulphide.

11. Disadvantages 1. Inefficient (only 30% efficiency). 2. Releases harmful solid carbon particles into the atmosphere Advantages Produces less pollution than fossil fuels. Does not cause acid rain. Can be found locally. It is renewable

12. e) Wind energy :- Wind energy is used in wind mills which converts the kinetic energy of the wind into mechanical or electrical energy. The kinetic energy of wind can be used to do mechanical work like lifting water from wells or grinding grains in flour mills. It can also be used to rotate the turbines of generators to produce electricity. A single wind mill produces only a small amount of electricity. So a large number of wind mills in a large area are coupled together to produce more electricity in wind energy farms. 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.

13. WIND MILL WIND ENERGY FARM

15. a) Solar energy :- Solar energy is the energy obtained from the sun in the form of heat and light. The heat energy is used in solar heating devices like solar cooker, solar water heater, solar furnaces etc. The light energy is used in solar cells. i) Solar cooker :- The box type solar cooker has an insulated box painted black inside. It is covered by a glass plate which allows heat to enter inside but does not allow heat to escape out. It has a mirror to reflect more sunlight into the box. The food to be cooked is kept in containers inside the box It can produce a temperature of 100° to 140°. ii) Solar water heater :- A solar water heater has an insulated box painted black inside with a system of copper tubes. It is covered with a glass plate which allows heat to enter inside but does not allow heat to escape out. When water flows through the copper tube it absorbs heat and becomes hot.

16. iii) Solar cells :- Solar cell is a device which converts solar energy into electrical energy. Solar cells are made from semi conductors like silicon, germanium, gallium etc. A single solar cell produces a voltage of about 0.5 to 1 V and produces about 0.7 W electricity. So several solar cells are arranged in a solar panel to produce more electricity. Advantages :- i) It uses renewable source of energy. ii) It produces electricity which does not cause pollution. iii) It can be used in remote areas where there is no power supply. Disadvantages :- i) It uses a special grade of silicon which is expensive. ii) Since silver is used for connecting the cells together it is more expensive. iii) The current produced is DC and to convert it to AC increases the cost.

17. BOX TYPE SOLAR COOKER SOLAR WATER HEATER

18. SOLAR CELL

19. SOLAR PANELS SOLAR LAMP

20. b) Energy from the sea :- Energy from the sea is obtained in three different forms. They are Tidal energy, Sea wave energy and Ocean thermal energy. Tidal energy :- The periodic rise and fall of sea level due to gravitational attraction of the moon causes tides. A dam is constructed at a narrow opening between the land and sea. The movement of water during high tide and low tide can be used to rotate the turbines of generators to produce electricity.

21. c) Geothermal energy :- The deeper regions of the earth’s crust is very hot. This heat melts rocks and forms magma. The magma moves up and collects below at some places called Hot spots. The underground water in contact with hot spot gets heated into steam at high pressure. By drilling holes into hot spots the steam coming out can be used to rotate turbines of generators to produce electricity.

22. Disadvantages 1.There are not many places where we can build geothermal power stations. 2.Harmful gases and minerals may occasionally come up from the ground below.These can be difficult to control. Advantages 1.Geothermal energy does not produce greenhouse gases. 2.The energy source is free and will not run out

23. d) Nuclear energy :- Nuclear energy is the energy is the energy released during nuclear reactions. During nuclear reactions some mass is converted into energy and so a very large amount of energy is produced during nuclear reactions. Nuclear reactions are of two types. They are Nuclear fission and nuclear fusion. i) Nuclear fission :- is a nuclear reaction in which the nucleus of a heavy atom like uranium, plutonium, etc. splits into smaller nuclei with the release of a large amount of energy. It is used to make atom bombs and to produce electricity. In a nuclear power plant the heat energy produced by a controlled nuclear fission chain reaction is used to produce steam which rotates the turbines of generators to produce electricity. ii) Nuclear fusion :- is a nuclear reaction in which small nuclei fuse together to form a heavier nucleus with the release of a very large amount of energy. The energy of sun is produced by the fusion of hydrogen nuclei to form helium nucleus. It is also used to make the hydrogen bomb. Advantages of nuclear energy :- i) It produces a very large amount of energy per unit mass than any other source of energy. ii) If safety measures are taken, it is more environment friendly than fossil fuels. Disadvantages of nuclear energy :- i) The cost of a nuclear reactor is very high. ii) The availability of nuclear fuel is limited. iii) Nuclear reactors produce harmful nuclear wastes which is difficult to dispose.

24. NUCLEAR FISSION

25. NUCLEAR FISSION CHAIN REACTION

26. NUCLEAR FUSION

28. Although solar is most often used to make hot water for washing, solar thermal technology can also be used to keep the building warm (space heating). The most common way to implement this is to use a heat store. A heat store differs from a conventional hot water cylinder in that the water in the store is not the water that will come out of the tap. Instead the store is filled with a mixture of water and inhibitors (additives to prevent corrosion) that remain there indefinitely. Heat store for solar space heating

29. Solar energy is added to the heat store via an indirect coil at its base which can heat the whole height of the store by convection. Backup heat for lower solar energy days is provided by a conventional boiler. The fluid from the heat store is circulated to the boiler, where it is heated to be returned at a higher temperature. The tapping point where the fluid leaves the heat store is some way up the store, to leave a solar dedicated volume at the bottom that the boiler cannot heat. Domestic hot water is heated on demand by running the cold water through a heat exchanger and pumping hot liquid from the thermal store through the heat exchanger in the opposite direction. As the two liquids flow past one another, the cold water on its way to the hot outlet is warmed up, and the fluid from the heat store is cooled down. The cooled fluid is returned to the heat store in the solar dedicated volume. Space heating is provided by pumping heat store fluid from a tapping high up the heat store around the heating circuit, and returning to a tapping near the bottom. Low temperature heating systems such as underfloor heating will give the best results, because their low return temperatures mean that the solar panel is more often operating at lower temperatures and therefore higher efficiencies.

30.  Solar power is arguably the cleanest  most reliable form of renewable energy available, and it can be used in several forms to help power your home or business.  Solar-poweredphotovoltaic (PV) panels convert the sun's rays into electricity by exciting electrons in silicon cells using the photons of light from the sun.  This electricity can then be used to supply renewable energy to your home or business.

32.  The photoelectric effect relies on the principle that whenever light strikes the surface of certain metals electrons are released .In the p-n junction the n-type wafer treated with phosphorus has extra electrons which flow into the holes in the p-type layer that has been treated with boron. Connected by an external circuit electrons flow from the n-side to create electricity and end up in the p-side.

33. The solar pond works on a very simple principle. It is well-known that water or air is heated they become lighter and rise upward. Similarly, in an ordinary pond, the sun’s rays heat the water and the heated water from within the pond rises and reaches the top but loses the heat into the atmosphere. The net result is that the pond water remains at the atmospheric temperature. The solar pond restricts this tendency by dissolving salt in the bottom layer of the pond making it too heavy to rise

34. Solar ponds can be effectively used as replacements in industries that use fossil fuel to generate thermal energy. Solar ponds can be used for process heating, refrigeration, water desalination, production of magnesium chloride, bromine recovery from bittern, enhancement of salt yield in salt farms. It will be the future energy source