Module-I-AEE-Energy scenario & Power Plants.pptx

All the wind turbines work on two physical principles (or combination of these two) in blade designs by which energy is extracted from the wind. These principles are either (i) drag principle or (ii) lift principle. Blade designs operate on either the principle of drag or lift.

1. ME 403 Advanced Energy Engineering Module-I Rajesh Kumar R Associate Professor, Dept. of Mechanical Engg ., SNGCE, Kadayiruppu .

2. Power Power is the rate of doing work, which equals energy per time. The units of power are watts , joules per second , and horsepower . 1 Watt = 1 Joule per second   1 Kilowatt = 1000 Watts   1 Megawatt = 1000 kilowatts = 1341.02 horsepower Prime mover is a machine that transforms energy from thermal or pressure form to mechanical form; typically an engine or turbine. A power station (also referred to as a generating station , power plant , powerhouse , or generating plant ) is an industrial facility for the generation of electric power.

3. Sources of power Renewable power sources – Renewable energy is obtained from sources that are essentially inexhaustible. Non-renewable power sources – Non-renewable energy is obtained mostly from fossil fuels such as coal , oil and gas which are likely to deplete with time.

4. Comparing renewable and non-renewable power sources Renewable resources Non-renewable resources Present in the atmosphere of the earth. Found in the underground of the earth. Are replaced by nature itself in a very short period. Not replaced The renewable energy resources are abundant in nature. The non-renewable resources are scarce resources and not in abundant in nature. The renewable resources are obtained free of cost. Are very costly and not easily available. The renewable resources do not affect the environment. Seriously affect the environment.

5. Sources of power in Kerala Sl.No Name of Station Installed Capacity (MW)of station 1 Idukki 6 x 130 780 2 Sabarigiri 4 x 55 + 2x 60 340 3 Idamalayar 2 x 37.5 75 4 Sholayar 3x18 54 5 Pallivasal 3 x 5+ 3x7.5 37.5 6 Kuttiyadi 3x25 75 7 Kuttiyadi Extension 1x50 50 8 Kuttiyadi Additional Extension Scheme 2x50 100 9 Panniar 2 x 16.2 32.4 10 Neriamangalam 3 x17.55 52.65 11 NES 1x25 25 12 Lower Periyar 3 x 60 180 13 Poringalkuthu 4x9 36 14 PLBE 1x16 16 15 Sengulam 4 x 12.8 51.2 16 Kakkad 2x25 50   Sub Total (HEP) 49 Nos 1954.75 Hydel power plants in Kerala

6. Sources of power in Kerala Small hydel power plants in Kerala Sl.No Name of Station Installed Capacity (MW)of station Nos MW 1 Kallada 2x7.5 15 2 Peppara 1x3 3 3 Malankara 3x3.5 10.5 4 Madupatty 1x2 2 5 Malampuzha 1x2.5 2.5 6 Lower Meenmutty (1x0.5 + 2x1.5) 3.5 7 Chembukadavu - 1 3x0.9 2.7 8 Chembukadavu - 2 3x1.25 3.75 9 Urumi -1 3x1.25 3.75 10 Urumi -2 3x0.8 2.4 11 KTR 3x1.25 3.75 12 Poozhithode 3 x 1.6 4.8 13 Ranni-Perinadu 2x2 4 14 Peechi 1x1.25 1.25 15 Vilangad 3x2.5 7.5 16 Chimmony 1x2.5 2.5 17 Adyanpara 2x1.5 +0.5 3.5 Sub Total (SHEP) 31Nos 76.4 Total (Hydel) 80 Nos 2031.15

7. Sources of power in Kerala Thermal power plants in Kerala SL. No. Name of Station Installed Capacity (MW)of station   Nos MW   1 BDPP ( Brahmapuram Diesel Power Plant) 3x21.32 63.96 2 KDPP (Kozhikode Diesel Power Project) 6x16 96   Sub Total (Thermal) 13 nos. 159.96   Wnid / Solar     1 Kanjikode Wind Farm 9x0.225 2.025 2 Kanjikode Solar plant   1   TOTAL (KSEB) 102 Nos 2194.135

8. Sources of power in Kerala IPP(Independent Power Producer)/CPP (Captive Power plants) SL. No. Name of Station Installed Capacity (MW)of station   Nos MW   1 Maniyar 3x4 12 2 Kuthungal 3x7 21 3 Ullunkal 2x3.5 7 4 Iruttukanam 3 x 1.5 4.5 5 Karikkayam   10.5 6 Mankulam   0.11 7 Meenvallom   3 8 Kallar   0.05   Sub Total   58.16

9. Load curves 9 The curve showing the variation of load on the power station with respect to time is known as a load curve . The load on a power station is never constant; it varies from time to time. These load variations during the whole day (i.e., 24 hours ) are recorded half-hourly or hourly and are plotted against time on the graph. The curve thus obtained is known as daily load curve as it shows the variations of load with respect to time during the day.

10. Load curves 10 Important terms and factors used in association with load curve. Connected load – It is the sum of continuous ratings of all the equipments connected to supply system . For instance, if a consumer has connections of five 100-watt lamps and a power point of 500 watts, then connected load of the consumer is 5 100 + 500 = 1000 watts. Maximum demand – It is the largest demand of load on the power station during a given period . Demand factor – It is the ratio of maximum demand on the power station to its connected load. The value of demand factor is usually less than 1.

11. Load curves 11 Average load – The average of loads occurring on the power station in a given period (day or month or year) is known as average load or average demand .

12. Load curves 12 Load factor ( LF ) – The ratio of average load to the maximum demand during a given period is known as load factor , i.e.,     If the plant is in operation for T hours , Load factor is always less than 1 because average load is smaller than the maximum demand. Diversity factor – The ratio of the sum of individual maximum demands to the maximum demand on power station is known as diversity factor , i.e.,

13. Load curves 13 Plant capacity factor – Plant factor or plant capacity factor or capacity factor is the ratio of actual energy produced to the maximum possible energy that could have been produced during a given period , i.e., Thus if the considered period is one year, The plant capacity factor is an indication of the reserve capacity of the plant. A power station is so designed that it has some reserve capacity for meeting the increased load demand in future. Reserve capacity = Plant capacity – Max. demand

14. Load curves 14 Plant use factor – It is ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation , i.e., Suppose a plant having installed capacity of 20 MW produces annual output of 7·35 10 6 kWh and remains in operation for 2190 hours in a year. Then,

15. Load curves 15 Units generated per annum – It is often required to find the kWh generated per annum from maximum demand and load factor. The procedure is as follows.

16. Load duration curve 16 When the load elements of a load curve are arranged in the order of descending magnitudes, the curve thus obtained is called a load duration curve .

17. Types of loads 17 A device which taps electrical energy from the electric power system is called a load on the system . The various types of loads on the power system are as follows. Domestic load – Domestic load consists of lights, fans, refrigerators, heaters, television, small motors for pumping water, etc. Commercial load – Commercial load consists of lighting for shops, fans and electric appliances used in restaurants, etc. Industrial load – Industrial load consists of load demand by industries. Municipal load – Municipal load consists of street lighting, power required for water supply and drainage purposes. Irrigation load – This type of load is the electric power needed for pumps driven by motors to supply water to fields. Traction load – This type of load includes tram cars, trolley buses, railways, etc. This class of load has wide variation.

18. 18 Problems based on loads

19. 19 Problems based on loads

20. 20 Problems based on loads

21. 21 Problems based on loads

22. 22 Problems based on loads

23. Power plants A power plant may be defined as a machine or assembly of equipments that generates electric power. Power plants are of two types. Stationary power plants Mobile power plants . Stationary power plants are further classified as follows. Base load power plants –These systems have more than 5000 full power hours per year (365 days 24 hours = 8760 hours ) and capacity factor of more than 57%. Intermediate load power plants – Power plants that average more than 200 hours but less than 500 full power house hours and a capacity factor between 23% and 57%.

24. Power plants Peak load power plants – These power plants are operated only to meet the power demands at a time of maximum demand. usually these units have, less than 2000 hours of full power hours and have a capacity factor less than 23%. Central power plants – Generate electric power or general sale to all consumers (public, business and industry, etc.). These plants are set up by state electricity boards, state and public governments, public sector organizations, etc. Captive power plants – These power plants are setup and operated by manufacturing companies for their own use.

25. Power plants-Module-I Steam power plant Hydel power plant Nuclear power plant Gas turbine power plant Diesel power plant

26. Steam power plant A steam power plant using steam as working substance works basically on Rankine cycle . A steam power plant converts the chemical energy of the fossil fuels (coal, oil, gas) into mechanical/electrical energy.

27. Steam power plant

28. Components of steam power plant Boiler – Boiler is an equipment to produce steam. Steam turbine – High pressure super heated steam is fed to the steam turbine which causes turbine blades to rotate. Energy in the steam is converted into mechanical energy in the steam turbine which acts as the prime mover. Generator – It is coupled with the turbine rotor and converts the mechanical energy of the turbine to the electrical energy. Condenser – Condenser is a heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from turbine enters the condenser where it is cooled and converted to condensate (water). The use of condensers improves the efficiency of the power plant by decreasing the exhaust pressure of the steam below the atmospheric pressure. The deposition of the salt in the boiler is prevented with the use of condensate instead of using feed water from outer source which may contain salt. The use of condensers reduces the capacity of the feed water cleaning system. Water circulating through the condenser may be taken from the various sources such as river, or lake. If sufficient quantity of water is not available the hot water coming out of the condenser may be cooled in cooling towers and circulated again through the condenser. Economizers – Economizers are devices fitted to a boiler which saves energy by using the heat energy of exhaust gases from the boiler to preheat the feed water thereby improving the boiler's efficiency.

29. Components of steam power plant Super-heater – Super-heater is a device that heats the steam generated by the boiler again increasing its thermal energy. It converts wet steam into superheated steam (high temperature dry steam). Precipitator – Precipitator is a device (dust collector) that removes particles from the flowing gas. Air pre-heater or air heater – Air pre-heater is used to recover the heat from the boiler exhaust gases which increases the thermal efficiency of the boiler by reducing the useful heat lost in the exhaust gases. Deaerator – It is a device used for the removal of air and other dissolved gases from the feed water to steam generating boilers. A steam generating boiler requires that the boiler feed water should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of the metal. Forced and induced draught fans – The small pressure difference which causes a flow of gas to take place is termed as a draught . In a forced draught draught system , the draught is produced by a fan or a blower installed at the base of the boiler forces the air through the furnace, flues, air pre-heater, economizer, etc. It is a positive pressure draught. In induced draught system , a fan or blower is located at or near the base of the chimney creating a partial vacuum so that the products of combustion pass up the chimney.

30. Various circuits in a steam power plant Coal and ash circuit – The coal from the storage is fed to the boiler through coal handling equipments such as belt conveyors. Heat produced by the burning of coal is utilized in converting water contained in boiler drum into steam at suitable pressure and temperature. Ash resulting from combustion of coal is removed to the ash storage yard through ash handling equipment. Air and gas circuit – Air taken in from atmosphere through the action of a forced draught (air forced to flow in by the use of blower) or induced draught (air flowing in due to decreased pressure) fan first passes through the air pre-heater, where it is heated by flue gases. The hot air then passes through the furnace. The flue gases after passing over boiler and super-heater tubes, flow through the dust collector and then through economizer (economizer capture the waste heat from flue gas and transfer it to the boiler feed-water), air pre - heater and finally they are exhausted to the atmosphere through the chimney . Feed water and steam circuit – The steam generated in the boiler is supplied to the turbine to develop mechanical power. The steam coming out of turbine is condensed in the condenser and fed back to the boiler using feed pump. Some of the steam and water is lost by passing through the different components. Therefore it is necessary to supply 4 to 5 % of total feed water from external source to compensate the loss. Cooling water circuit – Abundant quantity of water is required for condensation of steam. This is mostly taken from river. If adequate quantity of water is not available at the plant site, a cooling tower is used.

31. Advantages of steam power plant Less initial cost as compared to other generating plants. The capital cost is low compared to hydel plant. Construction time is low. Power generation does not depend on nature’s climatic condition. Power plant can be located near industrial areas. The fuel used is quite cheap. It can be installed at any place irrespective of the existence of coal. It requires less space as compared to Hydro power plants. Cost of generation is less than that of diesel power plants. Steam power plants are most economical if sited near coal mines and by the side of river or canal. Disadvantages of steam power plant Source of fuel i.e., coal reserve all over the world is considered to be fixed and therefore coal mines are being exhausted. Hence, there is a limit in source of power. Power generation cost is considerably high compared to hydal plant. Operating cost is more compared to diesel and nuclear power plant. Maintenance cost is high as compared with that of hydro and diesel power plants. Fuel transportation and handling are difficult.

32. 32 Hydro power plant

33. 33 Hydraulic power The electrical energy produced in kWh is expressed as follows ; where, t is the operating time in hours (8760 h / year ) and is the efficiency of the turbine-generator assembly.

34. 34 Components of hydel power plant Catchment area – Whole area behind the dam, draining into a stream or river across which the dam has been built. Reservoir –The purpose of the storing of water in the reservoir is to get a uniform power output throughout the year. A reservoir can be either natural or artificial. Dam – A dam is any barrier that holds water; the water stored behind the dam is used to drive turbines that are connected to electrical generators. It acts as an artificial reservoir.   Based on structure and design, dams are classified as gravity dams , arch dams and buttress dams .

35. 35 Types of dams Components of hydel power plant Gravity dams –Gravity dams rely on their own weight to hold back large volumes of water. Arch dams – An arch dam is curved in plan, with its convexity towards the upstream side. eg . Idukki dam. Buttress dam – A buttress dam is a dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports.

36. 36 Components of hydel power plant Penstock – It is pipe carrying water from the surge tank to the turbine. This is made of steel or concrete. Spillway – The function of spillway is to release surplus water from the reservoir in order to prevent the possible failure of the dam. Trash rack – The function of trash rack is to prevent the flow of debris, sand and fishes to the turbine. Surge tank – It is a storage reservoir used to absorb the sudden rises of water pressure, as well as to provide extra water during a drop in water pressure.

37. 37 Components of hydel power plant Turbine – The function of turbine is to act as a prime mover to convert the potential energy of water in to mechanical energy. It is explained in a later section in detail. Runner – The runner is a circular wheel on which a series of curved vanes are mounted. Vanes are so designed that water enters and leaves the runner without shock. Power house – The powerhouse accommodates prime mover, generator (generate electrical power using mechanical power obtained from the turbine), accessories and control room sometimes transformer also. Water after passing through the turbine is discharged into a downstream called as tailrace , which carries it into the river.

38. 38 Classification hydro electric power plants Classification with respect to quantity of water available Run-off river plants – Run-of-the-river hydroelectric harvest the energy from flowing water to generate electricity in the absence of a large dam and reservoir. Reservoir plants – A reservoir plant is that which has a reservoir of such size as to allow carrying over storage from wet season to the next dry season. Classification according to availability of water head High-head hydro-electric plants (head more than 250 m ) Medium-head hydro-electric plants (head ranges from 60 m – 250 m ) Low-head hydro-electric plants (head ranges from 60 m – 250 m ) Classification according to nature of load Peak load plants – The peak load plants are used to supply power at the peak demand phase. Base load plants – A base load power plant is one that provides a steady flow of power regardless of total power demand.

39. 39 Selection of site for a hydro power plant Water available – The most important aspect of hydro-electric plant is the availability of water at the site since all other designs are based on it. Therefore the run-off data at the proposed site must be available. Water-storage – The output of a hydropower plant is not uniform due to wide variations of rain fall. To have a uniform power output, water storage is needed so that excess flow at certain times may be stored to make it available at the times of low flow. To select the site of the dam ; careful study should be made of the geology and topography of the catchment area to see if the natural foundations could be found and put to the best use.   Head of water – In order to generate a requisite quantity of power it is necessary that a large quantity of water at a sufficient head should be available. The level of water in the reservoir for a proposed plant should always be within limits throughout the year.   Distance from load center – Most of the time the electric power generated in a hydro-electric power plant has to be used some considerable distance from the site of plant. For this reason, to be economical on transmission of electric power, the routes and the distances should be carefully considered since the cost of erection of transmission lines and their maintenance will depend upon the route selected. Access to site – It is always a desirable factor to have a good access to the site of the plant. This factor is very important if the electric power generated is to be utilized at or near the plant site. The transport facilities must also be given due consideration.

40. 40 Hydrologic cycle The hydrologic cycle , also known as the water cycle describes the circulation of water in the earth-atmosphere system. Precipitation – It includes all the water that falls from atmosphere to earth surface. Precipitation is of two types, viz., liquid precipitation (rain fall) and solid precipitation ( eg . snow). Run-off – Run-off is the part of water cycle that is flows over the land as surface water instead of being infiltrated into soil or evaporating. Surface runoff is that portion of rainfall which enters the stream immediately after the rainfall. Sub-surface runoff is that part of rainfall, which first reaches into the soil and moves laterally without joining the water - table to the streams, rivers or oceans. Base flow is that part of rainfall which after falling on the ground surface which get infiltrated into the soil and meets the water table (level below the surface of the ground where water can be found) and flow to the streams oceans, etc. Runoff = Surface runoff + Base flow ( Including sub - surface runoff )

41. 41 Hydrologic cycle Evaporation – Transfer of water from liquid to vapour state is called evaporation. Transpiration – The process by which water is released to the atmosphere by the plants is called transpiration. Sublimation – Sublimation results from when pressure and humidity are low. It is not only liquid water that can evaporate to become water vapor, but ice and snow, too. Due to lower air pressure, less energy is required to sublimate the ice into vapour .

42. 42 Hydrologic cycle The hydrological cycle can be briefed by the following equation ( hydrological equation ). I – Q = ∆S ; where, I = Inflow of water to a given area during any given time period, Q = Outflow of water from the area during the selected time period, ΔS = Change in storage of water in the given area during the time period. This equation states that during a given period, the difference between the total inflow of water and out flow of water must equal the change in storage of water

43. 43 Factors affecting run-off Nature of rainfall – Short and hard showers may produce relatively little run-off. Rains lasting longer time results in larger run-off. Topography of catchment area – Steep and impervious areas will produce large percentage of run-off. The water will flow quickly and absorption losses will be small. The size of catchment has a definite effect on the runoff. More the area, more will be the runoff. So also, the shape will have a definite effect on the runoff. In case of a fan-shaped catchment area , the period of the resulting hydrograph will be less and thus more peak flow may be expected. In case of an elongated catchment , the period of the resulting hydrograph (graph showing discharge (runoff) of flowing water with respect to time for a specified time) will be comparatively more and thus more will be the infiltration losses and less will be the runoff.

44. 44 Factors affecting run-off Geology of area – The run-off is very much affected by the types of surfaces soil and sub-oil, types of rocks, etc. Rocky areas will give more run-off while pervious soil and sandy soil will give less run-off. Vegetation –Thick vegetation like forest consumes a portion of rain fall and also acts as a obstruction for run-off. Other climate factors – Other factors such as temperature wind velocity, humidity, annual rainfall etc., affect the water losses from watershed (small streams) area.

45. 45 Advantages of hydro electric power plants Water source is perennially available. No fuel is required to be burnt to generate electricity. It is aptly termed as 'the white coal'. Water passes through turbines to produce work and downstream its utility remains undiminished for irrigation of farms and quenching the thirst of people in the vicinity. The running costs of hydropower installations are very low as compared to thermal or nuclear power stations. In thermal stations, besides the cost of fuel, one has to take into account the transportation cost of the fuel also. The number of operations required is considerably small compared with thermal power plants. There is no problem with regards to the disposal of ash as in a thermal station. The hydraulic turbine can be switched on and off in a very short time. The hydraulic power plant is relatively simple in concept and self-contained in operation. Modern hydropower equipment has a greater life expectancy and can easily last 50 years or more. This can be compared with the effective life of about 30 years of a steam or nuclear station. Modern hydro-generators give high efficiency over a considerable range of load. Hydro-plants provide additional benefits like irrigation, flood control, afforestation , navigation and aqua-culture. Being simple in design and operation, the hydro-plants do not require highly skilled workers. Manpower requirement is also low. The cost of land is not a major problem since the hydro-electric stations are situated away from the developed areas.

46. 46 Disadvantages of hydro electric power plants Cost of transmission is high since most of the plants are in remote areas. Hydro-power projects are capital-intensive with a low rate of return. It takes considerable long time for the erection of such plants. Power generation is dependent on the quantity of water available, which may vary from season to season and year to year. If the rainfall is in time and adequate, then only the satisfactory operation of the plant can be expected Such plants are often far away from the load centre and require long transmission lines to deliver power. Thus the cost of transmission lines and losses in them are more. Large hydro-plants disturb the ecology of the area, by way of deforestation, destroying vegetation and uprooting people. The emphasis is now more on small, mini and micro hydel stations.

47. Nuclear power plant In nuclear power plant, heat energy available from nuclear fission is used for the generation of steam. Nuclear fission can be defined as the process, in which a nucleus is split into two divisions, more or less of equal mass releasing energy in the form of electromagnetic radiation and kinetic energy . Fission is caused by neutrons which being electrically neutrally neutral can strike and fission the positively charged nucleus at high, moderate, or low speeds. The heat produced by fission in the nuclear reactor is carried out of the reactor by coolant . This heat is used to generate steam. This heat transfer takes place in a heat exchanger such as boiler. The pressurized steam is then fed to a steam turbine which is connected to a generator .

48. Nuclear power plant

49. Components of Nuclear power plant Nuclear reactor – It is an apparatus in which nuclear fuel is subjected to nuclear fission. Heat exchanger – The coolant gives up heat to the heat exchanger, which utilized for generating steam. After giving up heat, the coolant is fed back to the reactor. Steam turbine – The steam produced in the heat exchanger is fed to turbine for doing useful work. Generator – The steam turbine drives the generator which converts mechanical energy in to electric power.

50. Components of Nuclear reactor

51. Components of Nuclear reactor Nuclear reactor is an apparatus in which nuclear fuel is subjected to nuclear fission. Fuel – Nuclear fuels usually used in the reactors are isotopes (atoms of the same element having the same numbers of protons, but different numbers of neutrons) of Uranium and Plutonium. Isotopes like U-233, U-235 and Pu-239 can be fissioned by neutrons of all energies, whereas isotopes U-238. Th-232 (Thorium) and Pu-240 are fissionable by high energy (14 MeV ) only. Usually pellets of fissionable materials are arranged in tubes to form fuel rods . Moderator – Moderator is used to slow down the kinetic energy of fast moving neutrons. This has to be done as only the slow neutrons maintain the fission chain reaction. The neutrons collide directly with the moderator and thus slowed down. Substances like light water, heavy water, carbon, beryllium are used as moderator. Control rods – Control rods are used to control the nuclear chain reaction. It is an essential part of a reactor and serves the following purposes . For starting the reactor. For maintaining at that level. For shutting the reactor down under normal or emergency conditions. Control rods are usually made up of cadmium and boron. Control rods control the chain reaction by absorbing neutrons.

52. Nuclear power plant Coolant – Purpose of coolant is to extract heat generated by the fission process. The various fluids used as coolant are water (light water /heavy water), gas ( Air, CO 2 , Hydrogen ), and liquid metal cooled reactors etc. Reactor vessel – It is a strong walled container housing the reactor core, shield and the reflector. It is strongly built so as to withstand high pressures developed. Reflector – Reflector is used to reduce the loss of neutrons by reflecting back into the core of the nuclear reactor. Reflector is generally made of the same material as the moderator. Shield – Shield prevents the transfer of radiation to the external world.

53. Nuclear power plant Advantages of nuclear power plant No problem of fuel transportation, storage, etc. Less man power is required. It is more economical compared to thermal plant. Power capacity of plant is very high. Capital cost except for reactor is very less. It does not depend up on the condition of the weather. By this process we can conserve the fuels like oil, coal gases and other by-products. Disadvantages of nuclear power plant Nuclear radiation causes severe environmental problems. Disposal of radioactive nuclear waste is menace. Varying load conditions are not suitable. Capital cost is very high for the reactor.  

54. Nuclear power plant Advantages of nuclear power plant No problem of fuel transportation, storage, etc. Less man power is required. It is more economical compared to thermal plant. Power capacity of plant is very high. Capital cost except for reactor is very less. It does not depend up on the condition of the weather. By this process we can conserve the fuels like oil, coal gases and other by-products. Disadvantages of nuclear power plant Nuclear radiation causes severe environmental problems. Disposal of radioactive nuclear waste is menace. Varying load conditions are not suitable. Capital cost is very high for the reactor.  

55. Nuclear power plant Types of reactors Light water-cooled and moderated reactors ( LWR ) using slightly enriched uranium fuel are the type most commonly used for power production. These reactors are further divided into :- Pressurized water reactor ( PWR ) and Boiling water reactor ( BWR ).

56. Pressurized Water Reactor (PWR)

57. 57 Pressurized Water Reactor (PWR)

58. Pressurized Water Reactor Pressurized Water Reactor ( PWR ) make use of two loops viz., primary and secondary loops to convert the heat generated by the fuel into electric power. In the primary loop, the pressurizer maintains a high pressure in the water in the range of 150 bar . The pressurized water (coolant) is circulated in the reactor. Due to the high pressure of the water, the water does not boil. The coolant gets heated in the reactor and the hot water enters the boiler and transfers heat to the feed water in the boiler in the secondary loop. The transfer of heat is accomplished without mixing the two fluids, which is desirable since the primary coolant might become radioactive. Feed water evaporates and runs the turbine.

59. Pressurized Water Reactor Advantages of PWR   Because the water used in the high-pressure water loop is isolated from water in the steam loop, no radioactive material is contained in the steam. PWR has high power density and has compact size.   Disadvantages of PWR   Capital cost is high as high primary circuit requires strong pressure vessel. In the secondary circuit, the thermodynamic efficiency of the plant is quite low.

60. Boiling Water Reactor (BWR)

61. 61 Boiling Water Reactor (BWR)

62. Boiling Water Reactor (BWR) In Boiling Water Reactor ( BWR ), the coolant (water) used in the reactor absorbs heat produced during the fission reaction in the reactor. The fuel used is enriched uranium oxide . Water evaporates and steam is generated in the reactor itself. In this type of reactor, there is no need of separate boiler. In BWR, the coolant is in direct contact with turbines, so if a fuel rod had a leak, radioactive material could be placed on the turbine.

63. Boiling Water Reactor (BWR) Advantages of BWR   A major advantage of the BWR is that the overall thermal efficiency is greater than that of a pressurized water reactor because there is no separate heat exchanger. The pressure inside the pressure vessel is not high so, a thicker vessel is not required.   Disadvantages of BWR   Possibility of radioactive contamination in the turbine mechanism.

64. Gas turbine power plant In steam turbine plants, the products of combustion do not form the working medium. These are utilised to produce the intermediate fluid, i.e., the steam which is expanded in the turbine. If this intermediate step of converting water to steam by means of gases is eliminated, the arrangement would be far simpler and less wasteful. This principle is used in gas turbine power plants where the gases are directly expanded through the several ring of fixed and moving blades .

65. Gas turbine power plant In principle, a gas turbine plant consists of a compressor in which the working medium is raised to a high pressure. So, generally, a centrifugal or an axial compressor is employed. The turbine drives the compressor and so it is coupled to the turbine shaft. From the compressor, the working medium is taken to a combustor where its temperature is raised. This high pressure and high temperature working medium is then expanded in a gas turbine . In the turbine blading , the expansion of the working gas takes place and the heat energy is converted first into the kinetic energy and then into the work of the turbine shaft rotation.

66. Closed and open cycle plants In this turbine, the air from the atmosphere is drawn into the compressor. After compression, it is passed into a combustion chamber. The hot gas is then made to flow over the turbine blades. The gas, while flowing over the blades, gets expanded and finally exhausted into atmosphere. losses in the drive. In this turbine, the working fluid ( eg . helium) is compressed. The compressed gas is heated (by burning fuel or by nuclear reactor) through a heat exchanger . It is then made to flow over the turbine blades and gets expanded. From the turbine, the gas is passed to the cooling chamber. The working fluid is then made to flow into the compressor.

67. Components of a gas turbine power plant Gas turbine – There are two basic types of gas turbines viz., radial flow and axial flow turbines. Air-compressor – There are mainly two types of air-compressors used in gas turbine power plants viz., centrifugal compressor and axial flow compressor . Combustion chamber

68. 68 Axial flow compressor of gas turbine power plant

69. 69 Combustion chamber of gas turbine power plant

70. Gas turbine power plant Advantages of gas turbine power plant The mechanical efficiency of a gas turbine (95%) is quite high as compared with I.C. engine (85%) since the I.C. engine has many sliding parts. The work developed by a gas turbine per kg of air is more as compared to an I.C. engine. Gas turbine power plants are compact in design and can generate high power. They require less space than steam turbines or IC engines. Compared with steam plants, they have lower initial cost per unit output. Gas turbine power plants have bigger power weight ratio, so it is very useful for marine power plants. The machine is simple to operate and is smooth running. It requires little or no water for cooling. They have relatively low maintenance costs. Disadvantages of gas turbine power plant The thermal efficiency of a simple turbine cycle is low (15 to 20%) as compared with I.C. engines (25 to 30%). Its overall efficiency is very low since a large proportion of the power developed, about three fourth, is required to drive the compressor and also by the temperatures safely attainable. The noise of operation is a source of extreme annoyance unless the plant design includes sound control features.

71. Diesel power plant

72. Components of diesel power plant Engine – For electric power generation, four-stroke engines are predominately used. Horizontal engines are used for comparatively smaller outputs, while vertical engines with multi-cylinder construction are used for larger outputs. It is generally directly coupled to the generator. Air supply system – Air from atmosphere after filtering is admitted to the engine. In large plants supercharger (uses an air compressor that increases the pressure of air supplied to the engine so that more fuel is burned and do more work) /turbocharger (uses an air compressor driven by the exhaust gases to compress the air supplied to the engine increasing the amount of fuel and air fed into the engine and hence more efficient) is used to increase the output power. Exhaust system – Exhaust system is used to discharge the engine exhaust to the atmosphere outside the building. A silencer is incorporated to reduce the noise level. Fuel system – Fuel is stored in the storage tank is pumped to a smaller service tank at daily or short intervals. Fuel stored in the service tank is fed to fuel filter and is finally injected in to the engine.

73. Components of diesel power plant Cooling system – Hot water from the engine is carried to the surge tank. From the surge tank, hot water is fed through the heat exchanger. In the heat exchanger, cold water from the cooling towers is circulated which takes away the heat of the water from the engine. Cold water is then pumped back to the engine. Lubricating system – It includes the oil pumps, oil tanks, filters, coolers and pipe lines. Lubricating system provides lubricating oil to moving parts of the system to reduce the friction and wear and tear of the engine parts. Starting system – This is an arrangement to start the engine initially, until firing starts and the unit runs with its own power. There are mainly three types (1) petrol driven auxiliary engine (2) use of electric motors (3) use of compressed air from an air compressor. Governing system – The function is to maintain the speed of the engine constant respective of load on the plant.

74. Diesel power plant Advantages of diesel thermal power plant   Design layout of diesel power plant is simple and cheap. Part load efficiency diesel power plant is very high. Diesel power plant can be started quickly. Maintenance of diesel power plant is easy. Thermal efficiency of diesel is quite higher than of steam power plant. It can also be designed for portable use. Diesel plants can be located very near to the load centers.   Disadvantages of diesel thermal power plant   The cost of diesel is very high compared to coal. Hence, the running cost of this plant is higher compared to steam and hydro power plants. There is a limitation for size of a diesel engine. Life is less. Noise pollution is very high. High maintenance and lubrication cost. Capacity of diesel plants is limited.