NON-CONVENTIONAL ENERGY SOURCES & STORAGE DEVICES

Energy storage as a natural process is as old as the universe itself - the energy present at the initial creation of the Universe has been stored in s...

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NON-CONVENTIONAL ENERGY SOURCES & STORAGE DEVICES Nuclear energy-fission and fusion reactions and light water nuclear reactor for power generation (block diagram only) – breeder reactor – solar energy conversion – solar cells – wind energy – fuel cells – hydrogenoxygen fuel cell – batteries – alkaline batteries – lead-acid, nickel-cadmium and lithium batteries.

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NON-CONVENTIONAL ENERGY SOURCES & STORAGE DEVICES INTRODUCTION: Nuclear reactions, usually, involve energy changes over a million times greater than those involved in chemical reactions. The present fossil fuels like coal and petroleum will not supply the demand of electricity after 50-100 years. Therefore, the discovery of the fission of uranium was of great importance, which can supply the energy for the production of electric power. Non – Conventional sources of energy are those which are being continuously produced in nature and non exhaustible. For example, solar energy, tidal energy, geothermal energy, wind energy, water energy, ocean energy, biogas energy, etc. Energy storage: It is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation. A device that stores energy is sometimes called an accumulator. All forms of energy are either potential energy (eg. chemical, gravitational or electrical energy) or kinetic energy (eg. thermal energy). A wind up clock stores potential energy (in the mechanical-spring tension), a battery stores readily convertible chemical energy to keep a clock chip in a computer running (electrically) even when the computer is turned off, and a hydroelectric dam stores power in a reservoir as gravitational potential energy and also food is a form of energy storage Energy storage as a natural process is as old as the universe itself - the energy present at the initial creation of the Universe has been stored in stars such as the Sun, and is now being used by humans directly (e.g. through solar heating), or indirectly (e.g. by growing crops or conversion into electricity in solar cells). Energy storage systems in commercial use today can be broadly categorized as mechanical, electrical, chemical, biological, thermal and nuclear. Nuclear Energy: It is the energy due to the splitting (fission) or merging together (fusion) of the nuclei of atom(s). The conversion of nuclear mass to energy is consistent with the mass-energy equivalence formula = ², in which = energy release, = mass defect, and c = the speed of light in a vacuum (a physical constant). Nuclear energy was first discovered by French physicist Henri Becquerel in 1896, when he found that photographic plates stored in the dark near uranium were blackened like X-ray plates, which had been just recently discovered at the time 1895. Nuclear energy used as a form of alchemy to turn lead into gold or change any atom to any other atom (albeit through many steps). Radionuclide (radioisotope) production often involves irradiation of another isotope (or more precisely a nuclide), with alpha particles, beta particles, or gamma rays. Iron has the highest binding energy per nucleon of any atom. If an atom of lower average binding energy is changed into an atom of higher average binding energy, energy is given off. The chart shows that fusion of hydrogen, the combination to form heavier atoms, releases energy, as does fission of uranium, the breaking up of a larger nucleus into smaller parts. Stability varies between isotopes: the isotope U-235 is much less stable than the more common U-238. Nuclear energy is released by three exoenergetic (or exothermic) processes: Radioactive decay, where a neutron or proton in the radioactive nucleus decays spontaneously by emitting either particles, electromagnetic radiation (gamma rays), neutrinos (or all of them)  Fusion, two atomic nuclei fuse together to form a heavier nucleus  Fission, the breaking of a heavy nucleus into two (or more rarely three) lighter nuclei Nuclear Reactions (varies from chemical reactions) 

During chemical reactions, electrons in the outermost orbits get involved and interchanged, but there is no change in the nucleus. But nuclear reactions produce change in the nucleus, due to this, an atomic charge occurs. The element loses its identity and becomes another element. This is called transmutation. The energy involved in 2

a nuclear reaction is million times greater than that in chemical reaction. When the nuclear change occurs spontaneously, the element is said to undergo natural radioactivity. When the nucleus of one element is bombarded with another nucleus, the element may become radioactive, and changes to another element. In this case it is called artificial radioactivity. If the new element produced is not stable and undergoes further disintegration it is called induced radioactivity. Nuclear reactions are broadly classified into two categories: 1. Nuclear Fission 2. Nuclear Fusion Nuclear Fission It is a process of splitting of a heavy nucleus into two smaller nuclei with liberation of a huge amount of energy. When is bombarded by slow moving thermal neutron, unstable product is obtained. Then it undergoes spontaneous integration, two approximate equal nuclei with release of neutrons and huge amount of energy.

(or)

U235 + 0n1 → 92U236 →

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55

92

Xe144 + 38Sr90 + 2 0n1 + E

Cs144 + 37Rb90 +2 0n1 + E

The large energy is released during nuclear fission, because of a loss in mass. The fission products are radioactive. They decay, by emitting β particles or neutrons and γ radiations and become stable nuclei. This fission of Uranium is carried out by relatively low energy neutrons. The points to remember about this fission reaction are: i. Specific fission fragments are not formed. ii. iii. iv. v. vi.

No unique products are formed. Several modes of fission for are possible. Two groups of elements, one with masses from 130 – 160 U and the other lighter group with 80 – 110 U are produced. The energy released from one fission is different form the energy released from another fission The number of neutrons released from fission varies from 1 to 4. Average energy is released is 200 MeV.

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Nuclear Fusion It is a process in which the combination of light - weight nuclei takes place with the simultaneous release of large amount of energy. For example, fusion reaction in sun may be:

DIFFERENCES BETWEEN NUCLEAR FISSION & FUSION S.No 1. 2. 3. 4. 5.

NUCLEAR FISSION Heavy nucleus breaks up to form lighter nuclei It is a chain reaction It is carried out by bombarding the heavy nuclei with neutrons. It is a controllable process. Energy produced from this process is comparably low.

NUCLEAR FUSION Two lighter nuclei fuse together to form a heavy nucleus. It is not a chain reaction It is carried out by heating the lighter nuclei at very high temperatures. It is a non-controllable process Energy produced from this process is comparablyhigh.

Nuclear Chain Reactions: In nuclear fission reactions, three neutrons are emitted from the fission of 92U235. These three neutrons causing nine subsequent reactions. The neutrons in turn, further give rise to twenty seven reactions. For every set of reactions, a large amount of energy is released. But the amount of energy released will be less than that of the expected one because, some of the neutrons escape to the surroundings or absorbed. This is called as mass defect. A fission reaction, where the neutrons from the previous step continue to propagate and repeat the reaction is called as chain reaction. Example: Nuclear Fission reaction. In some cases, the energy released during the fission is very less due to loss in mass. The loss in mass is converted into energy according to Einstein equations. E = mc2 where, E=Energy, M=Loss in mass and C=Velocity of light. Problems: 1) Calculate the energy released in the fission reaction 92U235 + 0n1 Given that the mass of

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Mo95 + 57La139 + 20n1

U235 =235.125 amu 42Mo95 =94.945 amu, 57La139 =138.945 amu and 0n1 =1.0099 amu

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Solution: From the above data, mass of the reactants M(reactants) = 235.125 + 1.0099 = 236.1349 amu Mass of the products M(products) = 94.945 + 138.945 + 2(1.0099) =235.9098 amu Mass defect = M(reactants)-M(products)=236.1349 – 235.998 = 0.2251 amu 4

We know that 1 amu = 931.5 Mev The energy released by 0.2251 amu of 92U235 = 931.5 x 0.2251 = 209.7 Mev.

Nuclear Reactors: Nuclear reactors are ones in which nuclear fission is carried out in a controlled way. Two types of reactors are in use. (i) Thermal reactors (ii) Fast breeder reactors Thermal reactors In a thermal reactor, 235 U fission is carried out and the neutrons released are moderated by bombarding them against the nuclei or heavy water. The oxide of 235 U is used as nuclear fuel, in the form of aluminum plated rods. To reduce the rate of fission, if it becomes high, Cd rods are inserted. The heat generated is removed by circulating a liquid coolant, which is an alloy of sodium and potassium. The coolant carrying pipes from the reactor pass through water in a heat exchanger. Water takes up the heat and the steam produced is used for running the turbines.

Nuclear Reactor which consist of the following components namely 1.Reactor Core: In reactor core the controlled fission reaction is made to occur and which comprises the fuel elements, control rods, coolant and moderator. Fuel elements: Nuclear fuel is the fissionable material used in reactors for producing electricity by the fission process. Eg. Uranium metal or alloy, UO2, UC or UC2. Moderator: Moderators are used to reduce the kinetic energy of fast fission neutrons in the reactor. Eg. Heavy water, Beryllium and Graphite 2.

3.Coolants: These are used to reduce the intense heat produced during the fission reaction. Eg. Ordinary and heavy water, liquid metals like Na, Organic liquids like benzene, polyphenyls, gaseous coolants like air, CO2 and He. 5

4.Control rods: The chain reaction is controlled by using control rods which are made up of neutron absorbing materials. Eg. Cd, B, 5.Reflector: Nuclear reflector which surrounds the reactor core and it reflects back the neutrons if they leak from the core. It also increases the average power output from the reactor. Eg. H2O, D2O, Be or Graphite. 6.Pressure-Vessel: It is designed to withstand the pressure up to 200 kg/cm2. It covers the core, reflector and also provides the entrance and exit passage for coolant. 7.Shielding: Shielding has no part to play in the reactor but it is very much important to shield the neutrons, gamma rays coming out from the reactor which are harmful to human. This shielding which weakens the radiations emitted from the reactor. In high power reactors, there are two shields are used. (i)Thermal Shield: It consists of 50-60 cm thick iron or steel covering and is located around the core and capable of shielding the gamma rays and it can be cooled by the circulation of water. (ii)Biological shield: It consists of several feet thick layer of concrete and surrounds the reactor core, reflector, and the thermal shield. It is capable of absorbing any gamma rays and neutrons coming out from the reactor. 8.Heat Exchanger: Heat exchangers which transfer the heat liberated from the reactor core to boil water and get steam at about 400 kg/cm2. 9.Turbine: In heat exchanger, the steam at high pressure is generated which is used to operate a steam turbine. Due to the rotation of the steam turbine electricity is produced which is stored through the electric generator or dynamo fixed to the shaft of the turbine. BREEDER REACTOR Breeder reactor is the reactor where the conversion of non-fissionable fuels likes

(primary fuel) are

converted into the fissionable fuels like (secondary fuel or man-made fuel) and that has conversion factor above unity. The conversion factor can be defined as “the ratio of the number of secondary fuel atoms produced to the number of primary fuel atoms consumed”.

Breeder reactors are of great significance and commercial importance due to this reason worldwide research is going on about the reactor. If India develops breeder reactor, that can utilize its vast 232 Th.

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BATTERIES: A battery is a device that stores chemical energy for later release as electricity. A battery can be defined as a electrochemical cell (combination of several electrochemical cells) can be used as a direct source of electric current at a constant voltage. Cell: A cell is a device in which a small amount of electricity is generated by using a single anode and cathode in the presence of electrolyte. Types of Batteries: (i)

Primary battery or primary cell: In these cells, the electrodes and the electrode reactions cannot be revered by passing an external electric energy. The cell reactions occur only once. Primary batteries have to be discarded after the exhaustion of their reactants. They are not rechargeable. Examples: Dry cell, mercury cell.

(ii)

Secondary battery or secondary cell: In these cells, the electrode reactions can be reversed by passing an external electrical energy. Hence, they can be recharged by passing electric current and used again and again. These are called storage cells or accumulators. Examples: Pb-Acid storage cell, Nickel cadmium cell.

(iii)

Flow battery or fuel cell: In these cells the reactants, products, electrolytes are continuously passes through the cell, which is like a electrochemical cell that converts chemical energy to electrical energy. Example: H2-O2 fuel cell.

Characteristics of Battery: (i)

Voltage: Voltage of the battery depends on the emf of the cells which can be obtained by Nernst equation. E0 cell = ( E0 cathode – E0 anode ) – (2.303 RT/ n F ) log Q = E0 cell – (0.0592 V/n) log [Products/Reactants]

(ii)

Standard Electrode potential (E0 cell): If Ecell is more, the Ecell becomes higher and vice versa.

(iii)

Temperature: An increase in temperature decreases the value of E cell and vice versa.

(iv)

The current is the rate at which the battery discharging. A battery can deliver high current only if the transfer of the electron is fast.

(v)

The capacity of the battery depends on the size of the battery which is given by Faraday’s relation; C capacity = w nF/M where w= mass of the active material, M= molar mass of active material.

ALKALINE BATTERIES: This is an improved form of the dry cell. It uses a zinc anode and MnO2 cathode. In alkaline batteries KOH is used as the electrolyte (hence, it is of alkaline battery) and Zn in powdered form is mixed with KOH to get a gel. Graphite rod is surrounded by a paste containing MnO2 and the outside body is made up of Zn. Reaction at Anode:

Zn (s) + 2 OH – (aq)

Zn(OH)2 (s) + 2 e7

Reaction at Cathode:

2 MnO2 (s) + H2O (l) + 2 e-

Mn2O3 (s) + 2 OH- (aq)

___________________________________________________________________________________________

Net Reaction:

Zn (s) + 2 MnO2 (s) + H2O (l)

Zn(OH)2 (s) + Mn2O3 (s)

___________________________________________________________________________________________

The emf of the cell is 1.5 V. The zinc anode used in this cell is made porous to provide a large electrode area. This leads to the delivery of more current. The alkaline battery is called a heavy duty battery because it sustains heavy use and has a longer shelf life. It performs better in cold weather than the other types of batters. Advantages of Alkaline Battery: (i) (ii) (iii)

Zn does not dissolve in basic medium It maintains better voltage as the current drawn from it and The life of the alkaline battery is longer than dry cell, since there is no corrosion of Zn.

Uses:

Alkaline batteries are used in camera exposure controls, calculators, watches etc.

LEAD ACID BATTERY (LEAD ACID ACCUMULATOR) OR ACID STORAGE CELL These batteries were developed sometimes back and are now used very widely. The design does not change drastically. Modification and improved versions have flooded the market. Once it was thought that these batteries using an electrolyte solution cannot be sealed airtight. But recently sealed lead acid batteries have been developed. A storage cell is the one which can operate both as a voltaic cell and an electrolytic cell. When it acts as a voltaic cell, it supplies electrical energy and becomes run down. When it is recharged, the cell operates as an electrolytic cell. Construction Lead grids are coated with a paste consisting of lead monoxide (PbO) and dilute sulphuric acid (22%). One set of grids is connected together to a common terminal; similarly another set is connected to another terminal. The two set are arranged such that plates of one set are adjacent to the plates of the other set. Porous PVC diaphragm sheets are placed intermittently, separating one plate from the other eclectically. The assembly is housed in an ebonite or PVC container. The container is then filled with dilute sulphuric acid. The container is closed by a lid which is provided with holes for filling up of acid.

First Charge The terminal of one set of plates is connected to the positive and other set to the negative terminals of a DC rectifier. A suitable current under a suitable voltage is passed for the required time. During this charge , lead 8

monoxide coating on the set of plates connected to the terminal of the rectifier is oxidized to porous, spongy, and electro active lead dioxide. The lead dioxide coating present on the other set of plates connected to the negative terminal is reduced to porous, spongy, and elctroactive lead. Now the battery is ready for use that is discharge. (+) Oxidation PbO2 PbO Pb (-) Reduction Reactions during discharging: At anode (oxidation of Pb) Lead is oxidized to Pb2+ ions, which further combines with SO42- forms insoluble PbSO4 Pb Pb2+ + 2e2+ 2Pb + SO4 PbSO4 + 2ePb + SO42PbSO4 + 2eAt cathode (reduction of PbO2) PbO2 is reduced to Pb2+ ions, which further combines with SO42- forms insoluble PbSO4 PbO2 + 4H+ + 2ePb2+ + 2H2O Pb2+ SO42PbSO4 + 2PbO2 + 4H + SO4 +2e PbSO4 +2H2O The overall reaction during charging is, Pb + PbO2 + 2H2SO4

2PbSO4 + 2H2O + Energy

Lead sulphate is precipitated at both the electrodes. When 21.4% H2SO4 is used as an electrolyte at 250C, the voltage is about 2.0 V. Lead cell is commonly used in automobiles (combination six cells in series to form a battery with an emf of 12 V. Reactions during Charging: When an external emf greater than 2 V from generator is passed to the battery,(the positive pole of the generator is attached to the positive pole of the battery) the cell reaction get reversed. Reaction at the anode:

PbSO4 + 2H2O + 2e-

PbO2 + 4 H+ +SO42-

Reaction at the Cathode: PbSO4 + 2 eNet chemical reaction:

Pb + SO42Pb + PbO2 + 4 H+ +SO42-

2PbSO4 + 2 H2O + Energy

During charging process the concentration of the sulphuric acid increase, while during discharging process, the concentration of sulphuric acid decreases. Uses: Lead acid storage battery used in gas engine ignition, mines, laboratories, hospitals, broadcasting stations, automobiles, power stations etc. Lead acid battery is used to supply current mainly in automobiles such as cars, buses etc. NICKEL –CADMIUM (nicad) BATTERIES: Ni-Cd battery is the recently developed one and it is a portable, rechargeable and it has voltage about 1.4 V. This type of battery consists of a Cd anode and cathode is NiO2 and an alkaline KOH electrolyte. It can be represented as Cd/Cd(OH)2//KOH(aq) NiO2/Ni). The cell reactions are 9

At Anode:

Cd (s) + 2 OH- (aq)

Cd (OH)2 (s) + 2 e-

At Cathode: NiO2 (s) + 2 H2O (l) + 2 e-

Ni(OH)2 (s) + 2 OH- (aq)

Net reaction: NiO2 (s) + Cd (s) + 2 H2O (l) Cd (OH)2 (s) + Ni(OH)2 (s) The reaction can be readily reversed, because the reaction products, Ni(OH)2 (s) and Cd (OH)2 (s) , adhere to the electrode surfaces. From the reactions, it is clear that, there is no formation of gaseous products. Like lead acid battery, this battery can also be recharged by sending current in the opposition direction. The electrode reactions are reversed, as a result, cadmium gets deposited on anode and NiO2 on the cathode. Advantages:

1) It gives a constant voltage of 1.4 V. 2) It has a longer life than a lead acid battery. 3) It is smaller and lighter. 4) Like a dry cell, it can be packed in a sealed container.

The only disadvantage is more expensive than lead storage batter. Uses: Nicad batteries are used in electronic calculators, electronic flash units, cordless electronic shavers, transistors and other battery powered small tools. LITHIUM BATTERY: It is a solid state and rechargeable battery with high voltage around 3.0 V, which consists of a lithium anode and titanium sulphide (TiS2) as a cathode. A solid polymer is used as the electrolyte backed in between the two electrodes. The solid polymer (electrolyte) allows the passage of ions through two electrodes but not electrons.

Reactions during discharging: When the anode and cathode are connected through an electrolyte (solid polymer), Li+ ions move from anode to cathode and electrons generated at anode. The cathode receives Li+ ions and electrons through external circuit. Reaction at anode: Li (s) Li + + eReaction at cathode:

TiS2 (s) + e-

Net Reaction:

Li (s) + TiS2 (s)

TiS2 – Li + + TiS2 – (LiTiS2)

Reactions during recharging: When an external current is passed to the battery, the Li+ ions are converted into Li. The net reaction is Li + + TiS2 –

LiTiS2 10

Advantages of Li battery: The lithium battery is considered to be the cell of the future because 1) Its cell voltage is high, 3.0 V. 2) Lithium being a light metal, only 7 g (1 mole) material is just sufficient to produce 1 mole of electrons. 3) Li has the most negative E0 value and hence, generates higher voltage than other types of cells. 4) All the constituents of the battery are solids and hence, there is no risk of leakage from the battery. 5) This battery can be made in a variety of sizes and shapes. Uses: Li battery is used in calculators, electronic flash units, transistors, headphones and cordless appliances.

FLOW TYPE BATTERY (FUEL CELLS): A Fuel cell is the device which is capable of converting the chemical energy in to electricity directly. The essential process in a fuel cell is Fuel + Oxygen

Oxidation Products + Electricity

The most successful fuel cell is hydrogen-oxygen fuel cell. It consists of an electrolytic solution such as 25% KOH solution, and two inert porous electrodes. H2 and O2 gases are bubbled through the anode and cathode compartment respectively, where the following chemical reactions take place, Anode: 2H2(g) + 4 OH- (aq)

4 H2O (l) + 4 e-

Cathode: O2 (g) + 2H2O (l) + 4 e4 OH – (aq) --------------------------------------------------------------------------------------Net : 2H2 (g) + O2 (g) 2 H2O (l) The standard emf of the cell Eo = Eo ox + Eo red = 0.83 V + 0.40 V = 1.23 V In practice, the emf of the cell is 0.8 to1.0 V. It may be noted that the only product discharged by the cell is water. The large number of these fuel cells is stacked together in series to make a fuel cell battery or fuel battery. Requirements of electrodes: Electrodes should be very good conductors, good source or sink of electrons, they should not be affected by the electrolytes, heat or electrode reactions. In H2-O2 are used as the fuels, the electrodes are made of either graphite impregnated with finely divided Pt, or a 75/25 alloy of Pd and Ag, or Ni. The most common electrolytes are KOH or H2SO4 or ion exchange resin saturated with water. For low temperature operating fuel battery (-540C to 720C), potassium thiocyanate dissolved in liquid NH3 is employed. Advantages of Fuel Cells: 1) The energy conversion (from chemical to electrical) is highly efficient. 2) H2-O2 fuel cell produces drinking water. 3) Noise and thermal pollution are low. 4) They are modular and have low maintenance costs. 11

5) H2-O2 fuel cell is used as auxiliary energy source in space vehicles, submarines and other military vehicles. 6) H2-O2 fuel cells are preferred in space crafts due to their lightness and product water is a valuable source of fresh water for the astronauts. Disadvantages: 1) Their initial cost is high. 2) Life times of fuel cells are not known accurately. 3) There is lack of infrastructure for the distribution of hydrogen. 4) Pure hydrogen is also costly. Ie., liquefaction of hydrogen requires 30% of the stored energy.

SOLAR ENERGY: The most abundant solar energy can be converted into very useful electrical energy by means of solar cells. Solar Cell: Solar cell is a photovoltaic cell which is capable of converting the solar energy (energy received from sun) in to electrical energy. When a large number of photogalvanic cells are interconnected, solar cell is formed. Principle: In a photovoltaic cell, two types of semiconductors namely n-type( Si doped with P) and p-type semiconductors (Si doped with B) are arranged in close contact with each other. Due to the close contact, a limited extent of electrons (from the n-type semiconductor) and positive holes (from the p-type semiconductor) can cross the boundary or junction between the two types of semiconductors. Working: 12

When solar energy (solar rays) falls on the surface(outer layer) of the p-type semiconductor, the electron form the valence band moves (get promoted) to the conduction band by absorbing the solar energy. Since the conduction electrons can easily crosses the p-n junction into the n-type semiconductor, thereby a potential difference takes place between the two layers. This potential difference is the reason for the migration (flow) of electrons between the layers (electrical energy). The potential difference and hence current increases as more solar energy falls on the surface of the outer layer and excites more electrons. Thus, when terminals attached to the p and n layers are connected to an external circuit, electrons flow from n-layer to the p-layer, thereby electric current is generated. This type of device which convert directly the solar energy to electrical energy is called photovoltaic cell and the arrangement of large cells are called as solar battery.

A large number of solar cells are joined together in a definite pattern to get solar cell panel, which is capable of providing sufficient electric power to lift water from deep well or light in a house or to operate radio and TV etc.,

Advantages of Solar cells: 1) 2) 3) 4)

Solar cells can produce about 0.7 W of electricity on exposure to the sun. It does not need any focusing device because it has no moving parts and requires little maintenance. It provides a pollution free environment. These can be used in places where the transmission of power lines may be quite expensive.

Applications of Solar cells: Solar Cells can be used in the followings (i) Electric street light, 13

(ii) (iii) (iv) (v) (vi)

For running pumps In calculators, electronic watches, radios, TV etc. To produce electricity To melt metals, for heating purposes, As a source of electricity in space craft and satellites.

Disadvantages of Solar Cells: It is only capable producing electricity during sunny days but in rainy days an alternate source of electricity is necessary. WIND ENERGY: Wind is essentially a mass of air in motion, which carries with kinetic energy. The amount of energy contained in the wind at any instant is proportional to the wind speed at that instant. A windmill works on the principle of converting kinetic energy of the wind to mechanical energy. The blades of the windmill keep on rotating continuously due to the force of striking wind. The rotational motion of the blades drives a number of machines like water pumps, flour mills and electric generation. A large number of windmills are installed in clusters called wind farms, which feed power to the utility grid and produce a large amount of electricity. These farms are ideally located in coastal regions, open grasslands or hilly regions, particularly mountain places and ridges (crests) where the winds are strong and steady. The minimum wind speed required satisfactory working of a wind generator is 15 km/h. The wind power potential of our country is estimated to be about 20,000 MW, while at present we are generating about 1020 MW. The largest wind farm of our country is near Kanyakumari in Tamil Nadu generating about 380 MW electricity and Tamil Nadu is the first largest producer of wind energy in India.

Limitations of Wind Energy: 1) 2) 3) 4)

Wind flow, the speed of the wind varies with time and seasons, the kinetic energy of the wind can be utilized only at the site. The wind is an unpredictable one and no guarantee to get wind in all seasons and all places. Small units are more reliable but have higher capital cost. Require energy storage batteries which indirectly contributes to environmental pollution.

Advantages of Wind Energy: 1) It is a pollution free resource of energy at free of cost and it is inexhaustible source. 2) It is economically competitive for remote areas. 3) Wind machines can be built “on shore” or “off shore”. 14

References 1. A Textbook of Engineering Chemistry by Shashi Chawla, 3rd Edition, Dhanpat Rai & Co. (Pvt) Ltd., New Delhi. 2. A Textbook of Engineering Chemistry by Jain and Jain, 18th Edition, Dhanpat Rai Publishing Company (Pvt) Ltd., New Delhi. 3. A Textbook of Engineering Chemistry by Jain and Jain, 15th Edition, Dhanpat Rai Publishing Co. (Pvt) Ltd., New Delhi. Model Questions: 1. Define nuclear fission? 2. Write any two examples for nuclear fission reaction? 3. Define nuclear fusion reaction? 4. Write any two examples for nuclear fusion reaction? 5. What is nuclear energy, compare with binding energy? 6. Differentiate nuclear fission from fusion reaction? 7. Discuss about nuclear stability and stability belt? 8. What is nuclear reactor? Describe the components of a light water nuclear power plant with a suitable block diagram. 9. Write in detail about fast breeder test reactor. 10. Define conversion factor. 11. Write the role of coolants in nuclear reactors with few examples. 12. What are solar cells and explain its functions? 13. Give any two applications of solar cells. 14. What is wind energy and how it is converted into electrical energy? 15. What are fuel cells, give examples? 16. Describe about H2-O2 fuel cell. 17. Write advantages and disadvantages of fuel cell. 18. Discuss in detail on non-conventional energy resources and storage devices. 19. Write about various types of batteries. 20. Write about primary battery or primary cell. Give an example. 21. Write about secondary battery or secondary cell. 22. Write any few characteristics of battery. 23. What is reversible battery? Describe the construction and working of lead acid storage battery with reaction occurring during charging and discharging. 24. Give a detail note on alkaline battery. 25. Give a detail note on Ni-Cd battery. 26. Give a detail note on Li battery. 27. Define the fuel cell. 28. Write the role of control rod and moderators in nuclear reactor. 29. Write in brief about chain reaction and nuclear fission reactions.

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