La nuova app di Alison è ora disponibile su iOS e Android! Scarica ora

Module 1: Hydro, Geothermal e Tidal Energy

    Study Reminders

    Hi friends, now we will discuss on the topic hydroenergy.Hydro means water, so hydro energy is the energy which is generated from the water.So in case of wind energy, we have discussed that the flow of air has some kinetic energyand that can be converted to electrical energy by using turbine and generator.So here also the when the water will be in flow, then the kinetic energy of that flowingwater can be converted to mechanical energy in turbine which is followed by conversionin electrical energy in the generator.So in this case, we need the flow of water and this can be ensured by making dam or byusing some river flow or canal flow, etc.So now in this class we will discuss on hydrologic cycle as a renewable energy source, then mechanismof hydro energy production, components of hydro power plants and their role, classificationof hydro power, hydropower schemes, advantages and disadvantages of hydropower, and hydropowerin India and world.As we discussed that flow of water is required for hydro energy production and availabilityof water is also necessary for it and this is gifted by nature.So in terms of hydrologic cycle, you see here the water which is evaporated from the oceanit is converted to cloud and again precipitates.We know it very well that the water cycle and then when it precipitates on the landor in the water, then from the land the water is flooded and it comes to the river stream,in the mountain, it comes to the dam and dam to river stream and the water gets velocityin this river and in this dam.So the velocity of the water will be used to rotate a turbine, in fact the kinetic energyof this flowing water will be used to rotate a turbine blade, a turbine rotor, and thatwill be connected to a generator for electricity production.So you see this figure shows us that for the production of electricity, hydroelectricitywe need the flow of water that can be done by dams, that can be river flow, water flow,tidal barrage, or water wave power.So these different sources which can be used to ensure the velocity of the water or theflow of the water and that the water flow will come to the water turbine and then turbinerotor will be there and blades will be attached to this rotor and it will be rotating andthe shaft will get some circular movement here, which is coupled with the generatorand then AC power we will get.The water which is coming to the turbine that will lose its velocity and it will go to orin terms of the kinetic energy, the kinetic energy will be lost here of this water streamand that will go as tailrace.This is the mechanism of hydroenergy and now what will be the power we can achieve throughthis hydro turbine, that will depend upon some factors that what is the flow of head,what is the difference in the head from dam to turbine or so that we have to determineand the power determination can be done by using this formula that power in watt thatis equal to ρgQH into efficiency of the system.The overall efficiency including turbine, gearbox and generator and H is here head waterhead in meters, Q is discharge in meter cube per second, and ρ is the density of waterin kg per meter cube.Now if we know as the density of water is equal to one 100 kg per meter cube and ifwe use this one 100 kg per meter cube for water then this watt in terms of kilowattwill be converted to 9.81 which is for g and Q into H into efficiency and this 1000 hereso that will be converted in kilowatt.So in kilowatt 9.81 x efficiency x Q x H that is the formula which can be used to determinethe power productions in the hydropower plant, if we know the head and if we know the flow.Then annual production can be calculated by the formula that power x the time, so whatis the power we have 9.81 x efficiency x Q x H and then we can multiply it to the time,if it is time it is in hour, then that will be in kilowatt hour, so that unit of electricitycan be produced from the thermal power plant and we can calculate in any hydropower plantwhat will be the energy generated in a year or during any span of time.Now we will see one problem statement, say a mountain stream flows over a terrain wheremicro-hydro power plant is possible where an effective head of 50 meter be built anda flow rate of 0.6 meter cube per second can be maintained.How much power can the hydro plant generate, this is the question.So assume plant efficiency is 83%.So in this case, we have the formula that is equal to P = 9.81 x Ƞ efficiency x Q xH, here H is given that is equal to 50 meter, Q is given that is equal to 0.6 meter cubeper second, and efficiency is given 0.83.So we can calculate the value of P in kilowatt hour that is equal to 9.81 x 0.83 x 0.6 x50, so it is coming to 244 kilowatt, so in terms of megawatt that will be 0.244 megawatt.So then, how much energy will be produced in each year that will be say this power 0.244megawatt x 24 hours per day x 365 days per year, so that will be that total 2137 megawatt.Then if we want to know what is the number of population that can be supported by thisenergy, then that can also be calculated if we know the consumption of energy per capita.So assuming per capita electricity consumption India as 780 kilowatt hour annually, thenthe number of population that can be served by this energy is this how much energy weare producing divided by 780 kilowatt hour, then we are getting this much equal to 2740people, so this much of people can be served by this hydropower plant.Now we will see the components of hydropower plant and their role.So this figure shows us schematically one thermal power plant, so here we see some civilstructures are there, these are the civil structures.This is our reservoir, water is stored here, and then water is passed through this penstockto this turbine and then turbine casing etc is there and then generator electricity isproduced.So basically if we classify this different parts of it, so 1 is civil work, that is civilworks control of water flow the main role of this, then here the kinetic energy of wateris converted to mechanical energy here, the turbine shaft will be rotating, will givesome rotatory movement and that is done by the flow of water.So that hydro mechanical equipment is important that is the heart of this whole plant andthen conversion of kinetic energy of water stream to mechanical energy that is the mainrole of this part.Then third is electrical equipment, so this mechanical energy in the shaft will be convertedto electrical and then for distribution etc, we need some dedicated system.So then conversion of mechanical to electrical energy it is done by electrical equipmentand power, so that is the different parts of it.Now we will see the civil work contents dam or intake or diversion in some cases, we willdiscuss and we will see some figure which will explain these things.Then power channel, then desilting tank for removing the silts and forebay tank to takecare of small variations in flow, so during that time if variation in the flow, so forebaywater will be stored and it will maintain the continuous flow of the water.Then penstock through which the water will come to the turbine.Then surge tank or chamber in case of dam it is available, power house building so onebuilding is also required, and the tail race that is exit from the power house.So these are the civil work we need.Then hydro mechanical equipment we need turbine, we need gate, we need valve, and we need speedincreaser.Electrical equipment and power evacuations include generator, transformer, controls andprotections, and transmissions and distribution.It is going to grid or it is off-grid, both options may be available.So now we will see how the hydro power plants can be classified.So that can be classified depending upon the capacity; so pico, micro, mini, small, medium,and large.So pico means that is install capacity less than 5 kilowatt, micro 5 kilowatt to 100 kilowatt,mini 100 to 2000 kilowatt, and small 2 megawatt to 25 megawatt, medium 25 to 100 megawatt,and large greater than 100 megawatt.So these are the typical range which is used for the classification.Then on the based of head also that is your ultra low, low, medium, and high head hydropower are classified.So ultra below 3 meter, low 3 to 30 meter, medium 30 to 75 meter, and high 75 and above.Somewhere in some reference, it is given as 75 is given as 300 meter.So classification of hydro power on other basis is also based on purpose whether itis for single purpose, only for electricity production, or it is have some other purposealso, like say Tehri damn, it is irrigation plus power generation plus drinking waterthat way you can classify.Classification based on hydraulic features, so what are the hydraulic features that meansconventional hydro power plants that means only it is the dams or rivers are used toproduce the electricity or pumped storage plants that means recycling of water for supplyingpeak load.So from the bottom tank the water will be sent to the top tank so that way also it ispossible, but normally it is not used in the country, and the tidal power plants is alsoanother type of power plants.Then we may classify on the basis of operation that is your isolated plant or grid connectedplants, that may be the energy produced in the plant can be connected to the grid orit may be used off grid for the permitting the local need.There is Khopoli hydroelectric power for Bombay only.Then we will see the schemes for hydro power.So we have run-of-river, we have canal based, we have storage dam, we have pump storage.So run-of-river we will see in this case normal flow of river is not materially disturbeddue to the construction of the plan.At first we see the figure.Here the river is there, so this river some diversion is there here, so desilting tankfor the silt separation, then it is coming to forebay, the main objective is to ensurethe constant flow of water here through the penstock to the turbine and then in the turbinethe water is coming and electricity is generated and this is your tailrace and again it iscoming to the main river stream.So this is with small diversion of water without affecting the main stream of the river, thishydro power plant can be established and this is called run-of-river power plant.These are the some features, neither have a large reservoir nor do they have a diversionsof the water away from the main channel.Power house is located along the main course of the river and do not substantially alterthe regime of the river, small pools of reservoirs to provide the necessary pondage in orderto balance day to day fluctuations, generally medium and high head installations, and thenquite popular in Europe and hilly regions of India.So these are some features of this run-of-river.Then canal based plants are also available.So here these are the main stream here, so here we are getting powerhouse, so this isour powerhouse, water is coming through, this is the diversion canal, so this is your canaland this is diversion canal, so this water is coming here electricity is produced andagain it is going and meeting there.This is one example of say canal fall based system that is Ganga canal, 10,500 cusec capacity,then Pathri powerhouse 3 x 6.8 megawatt capacity, and Mohammadpur 3 x 3.1 megawatt, so 3 unitsare there for 3.1 megawatt capacity.Then storage dam based hydropower scheme, so this is also very important one and widelyused like the Tehri dam.So storage dams, so this is our dam here, so water will come from this penstock andthis is our powerhouse, and then water is going at the tailrace it is meeting the mainstreamof the water here, what do we do, that dam is a dominant feature of this in case of storagedam based, so dam is necessary and power house is at the toe of the dam and that no diversionof water away from the main river is involved.So this is the basic features of this type of hydropower plant like say Bhakra, Hoover,and Tehri are of this type.So here it is coming the penstock and it is turbines, just I have mentioned in this casethis is one.(Refer Slide time: 16:35)So this is the photograph of Tehri hydel project at a generation capacity 1000 megawatt.Then surface of impoundment on 52 kilometer square, water storage 4 meter cube, irrigationpotential 270,000 hectare and drinking water 1.2 x 10 to the power 6 meter cube per day.Then pump storage power plant.This power plant as you have mentioned that the water will be sent from lower head toupper head at the high elevation to ensure the flow of water to meet the peak load, andin this case it is the indirect way of storing electrical energy and 2 reservoirs with thehigh difference in water levels between the two is very essential.These 2 reservoirs may be both the reservoirs on the same river, may be on 2 different readerrivers.Higher reservoir and artificially constructed pool and lower reservoir on a natural riverthat can be possible, but the lower reservoir is a natural lake while the higher reservoiris artificial.So that way different types of options can be produced.Now we will see the advantage and disadvantage of this hydropower production.So it has obviously more advantages because it does not create any pollution, emissionfree with virtually no carbon dioxide, no SOx, and no NOx.Renewable resource with high conversion efficiency, the conversion efficiency is very high inthis case, it is greater than 80% efficiency, but whatever other thermal conversion methodswe have discussed in case of combustion or gasification base or IGCC all are having lowerefficiency than this.Then dispatchable with storage capacity, usable for base load peaking and pumped storage applications,scalable from 10 kilowatt to 20,000 megawatt, low operating and maintenance cost, and longlifetimes.These are the advantages of the system of this power plant, but it has some these advantagealso like frequently involves impoundment of large amounts of water with loss of habitatdue to land inundation, variable output dependable on rainfall and snowfall, so rainfall andsnowfall affects the availability of water and disturbs the continuous flow of it.Impacts on river flows and aquatic ecology including fish migrations and oxygen depletion,then social impacts of displacing indigenous people that is also one major issue, healthimpacts in developing countries, high initial capital cost, and long lead time in constructionsof large projects.So these are the disadvantage of this hydel power plant and there is many times we seethe debate whether such and such state should go for hydel power or not.These are some examples of world’s largest dams and hydropower generation.So we see hydro power is used in different countries like China, Brazil, Venezuela, UnitedStates, Russia, Canada, and Romania/Serbia.Some examples are given here.Out of these, the Three Gorges that is 2009 it is established, it has 18,200 megawattthe largest capacity in the world.In India, we have many hydel power like say Bhakra, Dehar, Kalinadi stage I, Sharavathy,Koyna, Nagarjuna Sagar, Idduki stage I, Srisailam, Salal, Ranjit Sagar and Chamera I, II, III.So these are different projects and these are the rivers on which these power plantshave been installed and these are our installed capacity.So these are the overall discussion and informations on the hydel power plant, and we will discussin the next class on different mechanical equipment and electrical equipments used forthe production of electricity.Thank you very much for your patience.