Renewable Sources of Energy

good morning welcome back to the course sustainability through green manufacturing systems and applied approach wherein we are trying to study the green manufacturing systems and certain sustainability aspects so in this lecture i would like to cover renewable sources of energy so what are renewable sources renewable sources are the sources that do not deplete while using so this lecture would have a flow like this first of all we will see what is need of renewable source see this i would like to discuss in detail i would use a video by a professor al bartlett to explain that we are living in finite world then we will discuss various green technologies solar wind fuel cell geothermal and biomass then renewable energy status in india would be seen first of all we are living in a finite world the ecosphere we have or the biosphere we have that is being depleted first of all let us see the population growth ah i started from fourteen hundred to two thousand maybe ten a d so it is growing like this so this is fourteen hundred this is sixteen hundred eighteen hundred and two thousand and two thousand ten so when i say total population in millions here today the total population in millions is about seven thousand millions that is seven billion people are there so this is population so you here in year fourteen hundred it was about two hundred millions only so we can see that in last two hundred years the population growth is rising so after that about this point the population growth is going like this so what is this curve if you see it carefully this is exponential growth so what do you think what is this rate of population growth is it fifty percent population growth or is it four to forty percent population growth per year no this rate of population growth is about seven percent here so how is it showing the exponential growth here how is it going on this nobody can explain better than professor al bartlett he is his full name is professor albert allen bartlett who did a great research in this he was actually professor ah of physics in university of colorado at boulder us university of colorado boulder us so actually professor al bartlett passed away he died in year two thousand thirteen to professor

bartlett did a great research on human population growth he is one of the video named arithmetic population and energy is widely watch is widely seen on youtube and this was a talk he gave on human over population so he was the one who highlighted that the this is one of the greatest challenge of the mankind and how the resources which are being live depleted the rate of this depletion is growing like this in exponential way so let us move to the video well its a real pleasure to be here and to have a chance just to meet with you and talk about some of the problems that we are facing now some of these problems are local some are national some are global but they are all tied together they are tied together with arithmetic and the arithmetic isnt very difficult and what i hope to do is i hope to be able to convince you that the greatest shortcoming of the human race is our inability to understand the exponential function so you say well whats the exponential function this is a mathematical function that you would write down if you are going to describe the size of anything which growing steadily if you had something growing five percent per year you would write the exponential function to show how large that growing quantity was year after year and so we are talking about a situation where the time that is required for the growing quantity to increase by a fixed fraction as a constant five percent per year the five percent is a fixed fraction the per years of fixed length of time now thats what we want to talk about its ordinary steady growth well if it takes a fixed length of time to grow five percent it follows it takes a longer fixed length of time to grow a hundred percent now that longer times called a doubling time we need to know how you calculate the doubling time and its easy you just take the number seventy divided by the percent growth per unit time and that gives you the doubling time for example of five percent per year you divide the five and seventy you find that growing quantity will double in size every fourteen years well you might ask where do the seventy come from the answer is its approximately one hundred multiplied by the natural logarithm of two if you wanted the time to triple you would use the natural logarithm of three so its all very logical but you dont have to remember where it came from if you will just remember seventy now i wish we could get every person to make this mental calculation every time we see a percent growth rate of anything in a news story for example if you saw a story that said things have been growing seven percent per year for several recent years you wouldnt bat an eyelash but when you see a headline that says crime has doubled in a decade you say my heavens whats happening what is happening seven percent growth per year divide the seven into seventy the doubling time is ten years but notice if you are going to write a headline you never write crime growing seven percent per year because most people wouldnt know what it really means now do you know what seven percent really means lets take another example from colorado the cost of an all day lift ticket to ski area has been growing about seven percent per year ever since vail first opened in nineteen sixty three and at that time you paid five dollars for an all day lift ticket now whats the doubling time for seven percent growth ten years so what was the cost ten years later in nineteen seventy three ten years later in nineteen eighty three ten years later in nineteen ninety three and what do we have to look forward to now this is what seven percent means most people dont have a clue well lets look at a generic graph or something thats growing steadily after one doubling time the growing quantities up to

twice its initial size two doubling times its up to four times its initial size then it goes to eight sixteen thirty two sixty four hundred twenty eight two fifty six five twelve in just ten doubling times its a thousand times larger than when it started and you can see if you tried to make a graph of that on ordinary graph paper the graph will go right through the ceiling now let me give you an example to show the enormous numbers you get with just a modest number of doublings legend has it that the game of chess was invented by a mathematician to work for a king the king was very pleased he said i want to reward you and the mathematician said my needs are modest please take my new chess board and on the first square place one grain of wheat on the next square double the one to make two on the next square double the two to make four just keep doubling till you double for every square that will be an adequate payment well we can guess the king thought this foolish man i was ready to give him a real reward all i asked for is just a few grains of wheat well lets see whats involved in this we note there are eight grains on the fourth square now i can get this number eight by multiplying three twos together its two times two times two its one two less than the number of the square now that follows in each case so on the last square i would find the number of grains by multiplying sixty three twos together now lets look at the way the totals build up when we have one grain on the first square of the total on the board is one we add two grains that makes a total three we put on four grains now the total is seven seven is a grain less than eight its a grain less than three twos multiplied together fifteen is a grain less than four twos multiplied together well that continues in each case so when we are done the total number of grains would be one grain less than the number i get multiplying sixty four twos together my question is how much wheat is there you know would that be a nice pile here in the studio would it filled a building would it cover the county to adapt a two meters how much wheat are we talking about the answer is its roughly four hundred times the nineteen ninety worldwide harvest of wheat now that could be more wheat than humans haveharvested in the entire history of the earth you say how do you get such a big number it was simple we just started with one grain but we let the number grow steadily till it doubled a mere sixty three times there is something else thats very important the growth in any doubling time is greater than the total of all of the preceding growth for example when we put eight grains on the fourth square the eight is larger than the total of seven that already there when we put thirty two grains on the six square the thirty two is larger than the total of thirty one that were already there every time the growing quantity doubles it takes more than all that you used and all of the preceding growth now lets translate that into the energy crisis here is an ad from the year nineteen seventy five and then ask the question could america run out of electricity america depends on electricity our need for electricity actually doubles every ten or twelve years thats an accurate reflection of a very long history of steady growth of the electric industry in this country growth at a rate of around seven percent through year which goes with doubling every ten years now with all that history of growth expected the growth had just go on forever fortunately it stopped not because anyone understood the arithmetic its stopped for other reasons but lets ask what if suppose the growth had continued then we would see here the thing that we just saw in the chessboard in the ten years following the appearance of this ad in that decade the amount of electrical energy that we would have consumed in this country would have been greater than the total of all of the electrical energy we had ever consumed in the entire preceding history of the steady growth of that industry in this country now did you realize that anything is completely acceptable as seven percent growth per year could give such an incredible consequence that in just ten years you would use more than the total of all that have been used in all of preceding history well thats exactly what president carter was referring to in his famous speech on energy one of his statements was this he said and in each of those decades more oil was consumed than in all of mankinds previous history now by itself thats a stunning statement now you can understand it the president was telling us a simple consequence of the arithmetic of seven percent growth each year in world oil consumption and that was the historic figure up until the nineteen seventies now there is another beautiful consequence of

this arithmetic if you take seventy years as a period of time and note that thats roughly one human lifetime then any percent growth continued steadily for seventy years gives you an overall increase by a factor thats very easy to calculate for example four percent per year you find the factor by multiplying four twos together its a factor of sixteen now a few years ago one of the newspapers here in boulder quizzed the nine members of the boulder city council and asked them what rate of growth of boulders population do you think it would be good to have in the coming years now the nine members of the boulder city council gave answers ranging from a low of one percent per year now that happens to match the present rate of growth of the population of the united states we are not at zero population growth right now the number of americans is increasing by more than three million people every year no member of the city council said boulders should grow less rapidly than the united states is growing now the highest answer any council member gave was five percent per year you know i felt compelled i had to write him a letter and say did you know [laughter] that five percent growth for just seventy i can remember when seventy years used to seem like an awful long time it doesnt seem so long now well that mean boulders population would increase by a factor of thirty two that is where today we have one overloaded sewer treatment plant in seventy years we need thirty two overloaded sewer treatment plants now did you realize that anything is completely all american as five percent growth per year could give such an incredible consequence in such a modest period of time our city council people had zero understanding of this very simple arithmetic so it was beautiful he explained it in a very good way a brilliant way that even the seven percent of growth which looked like just ok seven percent small figure so how it is affecting exponentially now the question is when did when do the mankind realize this so what is the status now or in other words where are we in terms of resources available versus the needs of mankind taking into account the population growth for this i would like again professor al bartlett to explain so let us move to the second part of the video in there like he would divide this time into ten years in the ten years what is the population growth going on and where do we stand now so let us move to the second part of the video here is an interesting headline from los angeles that headline probably has something to do with this headline so well how are we doing in colorado the denver post tells us that we are the growth capital of the usa and proud of it the rocky mountain news tells us to expect another million people in the front range in the next twenty years but in the post there was an interesting story someone was quoted as saying colorado has a three percent growth rate thats like a third world country with no birth control we send foreign aid family planning assistance to countries that have smaller population growth rates than colorado has well as you can imagine a growth control is very controversial and i treasure the letter from which these quotations are taken now this letter was written to me by a leading citizen of this community he is a leading

proponent of controlled growth now control growth just means growth this man writes i take no exception to your arguments regarding exponential growth i dont believe the exponential argument is valid at the local level so you see arithmetic doesnt hold in boulder [laughter] now i have to admit that man has a degree from the university of colorado its not a degree in mathematics in science or in engineering lets look now at what happens when we have this kind of steady growth in a finite environment bacteria grow by doubling and one bacterium divides to become to the to divide to become four the four become eight sixteen and so on suppose we have bacteria that doubled in number this way every minute suppose we put one of these bacteria in an empty bottle at eleven in the morning and then observe that the bottles fall at twelve noon now there is our case of just ordinary steady growth it has a doubling time of one minute its in the finite environment of one bottle i want to ask you three questions number one at what time was the bottle half full well would you believe eleven fifty nine one minute before twelve because they double in number every minute and the second question if you were an average bacterium in that bottle at what time would you first realize that you were running out of space now think about this this kind of steady growth is the centerpiece of the national economy and of the entire global economy think about it well lets just look at the last minutes in the bottle at twelve noon its full one minute before its half full two minutes before its a quarter full than an eighth and a sixteenth let me ask you at five minutes before twelve when the bottles only three percent full and is ninety seven percent open space just yearning for development how many of you would realize there was a problem now in the ongoing controversy over growth in boulder someone wrote to the newspapers some years ago and said look there isnt any problem with population growth in boulder because the writer said we have fifteen times as much open space as we have already used so let me ask you what time was it in boulder when the open space was fifteen times the amount of space we had already used the answer is it was four minutes before twelve in boulder valley well suppose it at two minutes before twelve some of the bacteria realized that theyre running out of space so they launched a great search for new bottles and they searched offshore on the outer continental shelf and the over thrust belt and in the arctic and they find three new bottles now that is a colossal discovery that discovery is three times the amount of resource they ever knew about before they now have four bottles before the discovery there was only one now surely this will give them a sustainable society would you know what the third question is how long can the growth continue as a result of this magnificent discovery well lets look at the score at twelve noon one bottle is filled there are three to go twelve o one two bottles are filled there two to go in a twelve o two all four are filled and thats the end of the line now you dont need any more arithmetic than this to evaluate the absolutely contradictory statements we have all heard and read from experts who tell us in one breath we can go on increasing our rates of consumption of fossil fuels in the next breath they say but dont worry we will always be able to make the discoveries of new resources that we need to meet the requirements of that growth well some years ago in washington our energy secretary observed that in the energy crisis we have a classic case of exponential growth against a finite source so lets look at some of these finite sources from the work of the late dr m king hubbert we have here his some logarithmic plot of world oil production the lines been approximately straight for over a hundred years clear up here to the year nineteen seventy average growth rate very close to seven percent per year so its logical to ask well how much longer could that seven percent continue well thats answered by the numbers in this table in the top line the numbers tell us that in the year nineteen seventy three world oil production was twenty billion barrels the total production in all of history including that twenty was three hundred billion the remaining reserves seventeen hundred billion now those are data

the rest of this table has just calculated out assume that the historic seven percent growth continued steadily each year following nineteen seventy three exactly as it had been for the preceding one hundred years now in fact the growth stopped not because of the arithmetic it stopped because opec raised their oil prices so we are asking what if suppose the growth had continued lets go back to the year nineteen eighty one by ninety eighty one on the seven percent curve the total usage in all of history would add up to five hundred billion barrels the remaining reserves fifteen hundred billion the reserves at that point are three times the total of all that have been used in all of history thats an enormous reserve but what time is it when the remaining reserve is three times a total of all you have used in all of history and the answer is two minutes before twelve well we know for seven percent growth the doubling time is ten years we go from nineteen eighty one to nineteen ninety one by nineteen ninety one on the seven percent curve the total usage in all of history would add up to a thousand billion barrels thatd be a thousand billion left at that point the remaining oil would be equal in quantity to the total of all that we had used in something like a hundred and thirty years of the oil industry on this earth by most measures you would say that is an enormous remaining reserve but what time is when the remaining reserve is equal to all that you have used in all of history and the answer is its one minute before twelve so we go one more decade to the turn of the century thats like right now thats one seven percent would finish using up the oil reserves of the earth now lets look at this in a very nice graphical way suppose the area of this tiny rectangle represents all the oil we used on this earth before nineteen forty then in the decade of the forties we use this months thats equal to the total of all that have been used in all of history in the decade of the fifties we use this much thats equal to the total of all that have been used in all of history in the decade of the sixties we use this much and again thats equal to the total of all the preceding usage now here we see graphically what president carter told us now if that seven percent had continued through the seventies eighties and nineties there is what we need but thats all the oil there is now there is a widely held belief that if you throw enough money at holds in the ground oil is sure to come up well there will be discoveries in new oil there may be major discoveries but look we have to discover this much new oil if we would have that seven percent growth continue ten more years well ask yourself what do you think is the chance that oil discovered after the close of our class today will be in an amount equal to the total of all that we have known about in all of history and then realize if all that new oil could be found that would be sufficient to let the historic seven percent growth continue ten more years so i think this very well explains why do we need renewable sources of energy so besides ah saving the non-renewable or finite resources of energy renewable sources also helps us to give clean energy that is emissions though there are emissions and cost that is associated with installation and maintenance of the equipments i would say maybe maintenance of the equipments or plants here by plant i am trying to say is this solar or wind energy plants or solar energy parks or in the further terms infrastructure however other missions which are due to the use of non renewable resources are less for

example coal petroleum those are all non renewable resources and here we have the clean sources of energy so what are these clean sources solar energy wind energy then i have geothermal energy then we have fuel cells these fuel cells may be hydrogen fuel cells or may be natural gas fuel cells then also we have biomass these are clean energy technologies so we will see how does these technologies work and what is the status in the present time what is solar energy question is what is solar energy how is it exploited what are the requirements to use solar energy so the answer to the first question is solar energy is the energy that is provided by sunlight the amount of sun that hits our country that hits india is enormous we live in south asia and the amount of sun hits here is very good ah in the countries in maybe in north america and some places the sunlight doesnt come very openly so here we have a great opportunity to exploit to use to harness this solar energy for a positive cause so how is it exploited we need to have pv cells photovoltaic cells what are these cells i will just discussed what are the requirements we need to have a set up a set up to convert this solar energy into electric energy tend to use it wherever it is required so solar photovoltaic cells or the short name it is known as pv pv cells better i would call it pv systems pv systems ah are the most popular solar technology that is employed in power generations there are power generation plants that employ that employ pv systems in iit kanpur also we have a fifty megawatt solar plant of capacity fifty megawatt now the major component of pv systems are so how is it exploited i am talking about the second question here major components of a solar system we need to have a solar module what is a solar module it is a number of cells those are connected in series number of cells connected in series so ah the solar photovoltaic power system produces negligible emissions the emissions here are negligible so in comparison to the other fossil fuels for example fossil fuels

are the other fossil fuels are coal fossil fuels like coal natural gas oil etcetera they contain number of chemical elements chemical elements including these elements are may be carbon phosphorus sulfur so burning fossil fuels in electricity production leads to a generation of emissions so these emissions are not good for environment so these they pro have pollutants such as carbon dioxide ah methane sulfur nitrogen oxides and so on so these pollutants are here in case of folio fossil fuels and these emission are released into environment which are which have damaging effects on global warming so the bad effects here are global warming ah then hm acidification of the environment then eutrophication that that call so be there the level of severity of environment impact depends upon the amount of emissions that is these emissions have chemical and physical properties these pollutants have chemical and physical properties i would use a word chemico physical properties chemico physical properties here so these effect so in case of our solar energy or in case of clean energy these all are not there these emissions are not there so the emissions are negligible in case of solar cells in case of solar energy so this is one of these solar energy setup so in this case what is happening we have pv modules over here the sunlight is falling on these pv modules and the energy is being generated and stored in the inverters here so these inverters are charged and keep the energy so there are there is a battery to store energy here so this energy can be used in various ways so maybe feed in meter consumption meter is there that is telling ah what is the energy so this energy is ah going to our power grid also here so this is power the consumer is using and even ah commercially also this can be used so this is taken from a reference here so in domestic use the solar energy can be used to fulfill the needs but in case of industrial use the solar energy cannot the infrastructure is not this much available that it can ah fulfill the whole needs of the industry in the present time so there is a study by allwood in in this regard ah it was conducted in two thousand five he says that there are five options for sustainability five options for sustainability number one he said use less material and energy number two he says substitute substitute the input materials substitute the input i would say that is he says go from toxic to non toxic

go from non renewable to renewable that is some part some portion of energy i would say also the other thing he suggested we had been discussing those were ah reduced unwanted outputs convert outputs to inputs and change structures of ownership and production that is change the structure of supply chain product service system ownership and production so i would suggest to read this study so how the power output from ah solar for voltaic cells is calculated so ah the power is ac i would put air output power that is proportional to the average annual solar insolation i would say i average i will put the details here then it is also proportional to the area of one pv module area of pv module here and module efficiency and i would say here a factor that is from dc to ac conversion efficiency so ah this is it is total ac output that is power consumed is proportional to this one so this is for one pv module so if i put here my number of pv modules here so i could put an is equal to sign here so in this case this is my actual power output that is in maybe if i say kilowatt hours then this is number of pv modules i is my average annual solar insolation that is per year this can be in kilowatt hour per meter cube per year then a is my surface area of module so this surface area would be in meter square em is my module efficiency and this one is the conversion efficiency that is conversion insufficiency from dc to ac so this relation was given by zhai and others zhai et al in two thousand eleven so they developed this relation and helped us

to calculate the output power for a solar plant so with this i would come to my next energy that is wind energy so this is one kind of wind energy park in rajasthan india it is taken from a reference so what is wind energy wind is another soft source of energy only it is actually the form of solar energy only so because it is a kind of i would say it is a form of solar energy how because the wind is generated by uneven heating of the earth surface and sea shores the uneven heating would let the wind to pass from the higher pressures to lower pressures so because of the heating the pressure rises and the wind flow so that is why the wind flows its if again the sun is playing its role in producing wind so wind energy sources are geographically dependent on the local resources measurement of wind energy resources can be made by using wind energy density so the terms here wind energy or wind power what does these represent these describe the processes by which the wind energy or the flow of the wind can be used to generate mechanical power or electricity to generate this is the purpose here so for this what is required we need to have wind turbines wind turbines are like ah the aircraft propeller blades so this is our turbine here so these are the blades i can show this schematic here so this is these are my blades they are just like aircraft propeller and ah they turn in the moving air the when air is coming these keep on turning these key starts rotating here and ah an electric generator is connected to this one this is my generator so this is actually the speed is not very fast so that is why a gearbox is here sorry the gear ratio here is such that the speed of the motor is much larger than the rotation speed of the turbines and these turbines this fins are ah of large size and this turbines rotate our generator and electricity is produced and controller is there and this electricity can be further stored into a cell so we have a break here as well in case of in case we need to stop the job motor is there to ah like maybe if we need to convert it into mechanical energy then we have tower blades so this is it has given very clearly this is a low speed shaft and this is gearbox head so this becomes our high speed shaft this portion this becomes our high speed shaft so anemometer and wind when vane are there to control this rotation of our turbine that is along this axis along this axis so they could even tell the direction of the wind so this is how our wind turbine setup is there so wind turbine types may be horizontal or vertical these are types of types of wind turbines then it also depends upon the local conditions that what kind of turbine can be installed so in general the most large modern wind turbines are horizontal axis turbines only so this is a kind of horizontal axis turbine this also is a horizontal axis turbine these are all horizontal axis turbines here

so wind energy is again the free resource of energy also it is clean resource of energy it is renewable so these are the benefits so clean non polluting electricity can be obtained using wind energy but there are certain issues as i discussed the cost of installation is high the initial investment is high high initial investment i would say is high so here approximate eighty percent of cost is machinery so i will discuss the cost benefit analysis after discussing these clean technologies so environmental concerns ah are there so a little light on the environmental concerns so though it is a clean energy and the wind power plants have very little impact only when environment compared to the fossil fuel ah that fossil fuel power plants there are some concerns over the noise that is produced thereby environmental concerns i would say the noise produced by the rotation of blades is noise produced by rotation is high and there are aesthetic or visual impacts that is the birds and bats having been killed by this one ah these rotating blades by like by flying into the rotors so these kind of environmental impacts ah into the habitat also are there so most of these problems have been resolved or greatly reduced through technological development these days by properly sighting the wind plants properly sighting means it is generally sited at remote locations otherwise the noise that is produced by the wind turbines is not acceptable in the domestic or in the living areas so the supply and transport issues are here because the wind plants are only at the remote locations so here come the problem of transportation of energy transportation of energy if cannot be transported then storage of energy how do we store this energy there are problems in this so the major challenge in using wind as a source of power is that it is intermittent the energy is intermittent it is only generated when wind flows the question is wind has to flow this is the major issue only when wind flows the energy can be produced so this does not ah always allow to blow when electricity is needed although wind generated electricity can be but if batteries are used ah but wind cannot be stored and not all winds can be harnessed to meet the timing of electricity demands and ah further because these are located in remote locations that are far from the electric power demand such as cities etcetera ah finally the wind resource development may compete with other uses of the land and those alternative uses may be more highly valued than electricity generation so the wind turbines can also be located on the land that is used for grazing or even farming so at those places it can be used so let us put some light on the wind speed at a specific location so wind energy density is the function of wind speed or ah air density

at a specific location so i would like to put here the wind energy density is proportional to wind speed and is also proportional to air density i would not say proportional i would say it is related to this one or this one is a function of wind speed and air density so wind speed vary with the height above the surface of earth and ah these two parameters jointly determine the wind energy density so wind speed at a given height above the ground can also be calculated using a relation wind speed at a given height above ground can be obtained by a transformation that was given by simiu and scanlan in nineteen ninety six so they say that this wind speed is equal to wind speed that is known at a specific location and that is at specific location z naught and there is a hellmann exponent over here that is k here vz is our wind speed that we need to determine this is wind speed at height that is height we need to determine here is said this height we need to determine it is given height or to know what a given height this we need to determine so wind speed at height z i would say meters now v naught is wind speed at height z naught meters that is known so this is known this is unknown this height is known sorry this speed is unknown here and this speed is known now what is the deciding factor here so if you see the deciding factor that is here is our this exponent here so what is this this k is hellmanns exponent and its value this is a key parameter here i would put here this is a key parameter here that determines this wind speed so this hellmann exponent is a key factor here that is hellmann exponent now it depends upon certain factors what are those factors the location and the shape of the terrain above the ground also the stability of fear

now the typical values of this factor ah for example if it is a stable aware air above open water so source this k value is equal to zero point two seven some typical values so this is stable air above open water surface so the point of interest here is the flat open area for the flat open coast for example if i say flat open coast its value is equal to zero point four zero for ah human inhabited areas its value is zero point three four that is neutral air above human inhabited areas so here we can see how we can calculate the wind speed now to find the wind energy another relation was given by chang et al in two thousand three who said that wind power density wind power density of a location can be calculated using an expression in which we have p by a so this p is simply my air pressures in newton per meter square this is my area in meter square so this can be detailed further as one by two rho times wind speed at that location to the third degree and a gamma function is involved here in which we have lambda plus three over lambda so here this is my wind power density this what is this rho this is my air density this we know is pressure that is air pressure and this is the area now this is again wind speed and this gamma function has a lambda that is a weibull factor it is a weibull function which is dimensionless so this is the key factor here which determines our wind energy so we will not go into details because this goes out of the ambit of this course to discuss the gamma function and this lambda however we have a relation to determine the wind power density so with this i would like to take a break here and we will discuss fuel cells geothermal energy and biomass energy in the connecting session thank you