Welcome to the semester long course on Energy Resources, Economics and Environment. My name is Rangan Banerjee and today we will start with looking at the basics of the energy flow diagram. So, let us start with an energy flow diagram. (Refer Slide Time: 00:31) What is an energy flow diagram? When we think in terms of any human activity, any human activity needs energy. So, if you are looking at the screen that you see, the screen has to beilluminated, if you are looking at the comfort conditions when we think in terms of air conditioning or the cooling that also needs energy. So, that energy comes through a whole sequence of steps. We have at the energy that is available in nature is primary energy. This is the energy source is like coal, oil, solar, natural gas, wind. The energy that is available in nature is not directly something that we can use. We take that energy; we convert it in an energy conversion facility. So, we first take the coal, convert it, we mine it, we wash it, we transfer it to a power plant and then we get the secondary energy. So, secondary energy is the electricity that we get from the power plant which is burning coal. That secondary energy itself goes through a whole network, a transmission and distribution system. And then it reaches your house or it reaches the campus, the final energy that we buy from the distribution company and that is then use that electricity then goes and it is used in your air conditioners, in the fans, in the lights to give you useful energy or the end-use activities. So, whenever we think in terms of different energy systems we need to look at all these terms: primary energy, secondary energy, final energy, useful energy. We are interested in the energy services, in order to provide those energy services we need to have primary energy extracted, that primary energy needs to be converted in a conversion facility to give secondary energy. That secondary energy is distributed till it reaches the final end user which is and that is the energy that we buy the electricity, the oil, natural gas that is used in the equipment to give the useful energy. So, when you talk about each of these conversion steps, each conversion step needs a certain amount of energy for the conversion and so when if you need 1 unit of energy useful energy, we would probably need 2 units or 3 units of primary energy. So, whenever we do a comparison and when we do a calculation, we can think about whether we are talking of primary energy, secondary energy, final energy or useful energy.(Refer Slide Time: 03:30) So, let us move on. When we talk about all the end-users that we need, so we think of all the things that you do in your daily life. When we look at cooking the energy service is the food cooked. So, you have the Chullah or you have the stove or the microwave oven that is where energy is being used to give you the processed food. If you talk of lighting the energy service is illumination, you have different kinds of bulbs, you have the traditional incandescent bulbs, then we have the fluorescent, then you have this compact fluorescent, and now you have the LED. When we talk about transport we are looking at travelling, distance travelling. So, passengers being transported or goods being transported and then you have a whole host of cycle, cars, train, motorcycle, bus, aircraft and each one of them is an energy system and has a conversion and an efficiency. In the factories, we have a large number of motors which are being used to create some shaft work and the devices the motors. Cooling we are looking at space cooling, we have fans, ceiling fans and we have air conditioners, we have refrigerators. In the industrial processes, we have heating that is provided that is fluid is being heated so the devices are boilers or geysers and in each of these cases we can look at what is the energyinput, what is the output, what is the energy service and do this kind of analysis. (Refer Slide Time: 05:05) So, just to give you an example let us look at a situation where we are using an agricultural pump, a farmer is using a pump to pump water, the pump output is the useful energy, the useful service energy service that is required. The pump is providing the energy in from the motor drives the pump and the pump is transferring the energy into the water which is thenallowing it go to the storage or to the filed directly. Each of these has a certain efficiency. The farmer buys electricity from the distribution company. That electricity is coming through a transmission and distribution system. That electricity is being generated in a power plant which is using coal. That coal is being mined and transported and then you have primary energy. So, if you look at typical efficiencies of all of these the numbers that we have put, the mining efficiency may be of the order of 90%, the power plant has an efficiency of about 30%, transmission and distribution about 78% efficiency and the motor pump depending on actual operating may be of the order motor may be of the order of 70% pump of the order of 60% the best efficiency is maybe 88%, 75%. So, if you multiply all of these you will see that the overall efficiency that we get from the coal to the final pumping that efficiency is actually relatively low and that gives us an incentive to try and see can we reduce some of these steps. So, whenever we look at different kinds of energy systems it is always useful to try and look at it draw, the energy flow diagram and look at it from the context of primary energy to the final energy service. (Refer Slide Time: 06:56) So, let us look at what are the terms that we have studied? We studied the terms primary energy, secondary energy, final energy or the delivered energy, useful energy, energy service. And then we can also classify it into different kinds of end uses. So, end uses will be like, one end-use is lighting, end-use of heating, end-use of cooling, end-use of cooking, end-use of transport and then the sector. When we talk about sector, we are talking of residential, industrial, commercial. Whenever we talk in terms of a, we want to get an idea of an energy system we have to decide what is the level of aggregation and disaggregation. What are aggregation and dis-aggregation? When I put things together that is aggregation when I separate them out that are dis-aggregation. So, we may want to calculate for the city of Mumbai what is the overall energy used, or for the state of Maharashtra what is the overall energy used, for the country for India what is the overall energy used, for the world what is overall? So, that is an aggregate calculation. We want to dis-aggregate it by in each household by each end-user how much is the energy used, so that is the dis-aggregated. So, in any of these cases, we can always calculate and do an energy balance and try to see how the energy is being used and what is the quantification. (Refer Slide Time: 08:21) When we move forward with this in order to do this is quantification we have different kinds of units. So, traditionally we used to use calorie and the British thermal unit and the Quad, now in the SI system we use joules and we use kilo watt-hours. We also need to differentiate between energy and power. When we are talking of power if you are talking of watt or kilowatt or megawatt that is the rate at which the energy is being supplied and that power aggregated over a period of time will give you the energy. So, watt and horsepower these are units of power. When you take 1 watt and you run it for an hour you get 1 watt-hour, or the kilowatt-hour is 1-kilo watt running continuously for an hour. So, we need to be able to convert between different units and for this, you can look at any source on the web or you can look at the energy basics in the global energy assessment which I will put at the end of the references. We also have different prefixes like Kilo 103, Mega 06, Giga 109, Tera 1012, Peta 1015, Exa 1018 and depending on the kind of calculation we are doing. So, if you are doing the calculation for the world, you will be talking in terms of Exa joules, if you are talking of a country may be Exa joule or Peta joules if you are looking at a smaller thing it may be kilojoules or megajoules or Giga joules. There is also these are all in terms of energy units, earlier we could also calculate in physical units. So, we can talk in terms of million tons of coal, a million tons of oil. So, there is an energy unit where all if you talk of coal, oil, natural gas, we convert them all into equivalent oil. So, million tons of oil equivalent and you will see if you look at the BP side or you look at many of these sides the energy balance is are given in terms of Mtoe. Which is million tons of oil equivalent, the coal is also converted into oil equivalent and million tons of coal equivalent kilo tons of coal equivalent. So, these you should be familiar with the units and you should be able to make conversions between the units and some in some of the tutorials that we provide you will have some examples where you can do this. (Refer Slide Time: 10:59) So, here is this exercise which will give you an order of magnitude of the different kinds of units and the idea is that you see for different kinds of activities, I want you to think about it and insert in order of decreasing energy with the highest energy being on top and then the lowest. So, the different items that we have put energy use of an average US detached house, burning a candle, the world energy use annually, the Boeing 747 going from Tokyo to Frankfurt and back to Tokyo, 1 litre of gasoline or petrol, energy use of an Indian village typically of 500 people, New York City annual energy is used, solar energy reaching the earth in an hour, a power plant of 700-megawatt annual electricity production and the daily metabolism of an adult. So, take a minute and just put down your sequence the highest energy to the lowest energy, and if you see compare this sequence with the results that we have here. (Refer Slide Time: 12:15) The world energy use annually is about 500 EJ, solar energy reaching the earth is an hour is about 445 EJ. So, that means we have abundant solar energy right, in 1 hour we have enough which is equal to the amount which the world is using annually. New York City annual energy use 0.8 EJ, Power plant 15.5 PJ and 747 Tokyo Frankfurt to 9 TJ a lowest is the burning the candle daily metabolism of an adult is somewhere in between and this just gives you a sense of the relative magnitudes of things. (Refer Slide Time: 12:53) So, you can look at this on this axis this is from the global energy assessment you can see this, this axis talks about different activities and in different units and you have a scale which goes from 10 raise to 1 to 10 raise to 23 and you can see them in terms of the starting from joule to ZT and going up to EJ and you can see the relative magnitudes of some of this you know this gives you an idea of the relative magnitudes of the energy use. So, this is very similar to the exercise at we just now did. so, now let us look at the question of what is the total amount of primary energy used by the world. And let us try and also see what is the trend or variation of this energy used over the years. We will look at the world we will also look at the energy used in India and we will see how to create and make these kinds of energy balances from the data that is available in the public domain. So, let us look at the global energy use. So, we will talk in terms of, when we talk about energy use we are talking about the primary energy use by the world. Remember we talk about the energy that we have available in nature and then that goes into different sources, going to secondary and to the final energy use and giving the energy service. And then we would like to see how this energy use has been changing over the years, what factors affect the change of this energy use. (Refer Slide Time: 01:21) Ok so, there are many different sources and couple of sources that I would I think you can look at is the international energy agency has details statistics for almost every country in the world and the US DOE also has statistics. Many of these companies like the British Petroleum provides a statistical review of all-day energy. For every country, there are also energy statistics, so in India, there is an energy statistics released by the ministry of statistics and program implementation and that is an annual kind of statistic. Each of our suppliers like the ministry of power provides statistics related to electricity, ministry of petroleum, Natural gas and these are compiled and provided in these overall international statistics. (Refer Slide Time: 02:30) So, if we look at what is the history of the world primary energy use, you can see this is a figure which shows you that the, we had a very significant increase in the energy use. You can also see the different colours represent the different sources of energy. So, in the initial period, it was all traditional energy. If you look at 1800 we are looking at biomass, wind, water and slowly then with the steam engine and with the use of coal we had the coal coming in and we had the electricity, we have Edison’s first grid and then we started using the next invention which changed the energy sector is the gasoline engine and the growth in the automobiles and then, of course, we had aircraft and television and nuclear energy, the micro cheap and the internet. And you can see it started off with mostly all renewables then went on to coal and then oil started coming in. You see the red which is the oil and oil became the predominant source of energy, then we had natural gas coming in and now again we are moving back. So, it has gone to a situation where it becomes predominantly fossil, we are now moving back and we want to go with modern renewables. So, that is the transition that we are looking at in the future. (Refer Slide Time: 03:47) When we look at this, this is an example of the total energy use, I think this is for 2010 and you can see of the almost 500 Exa joules that are being used that gets converted to about 350 Exa joules of secondary, 330 Exa joules of final and the useful energy is only 169 Exa joules, out of this and then you have a significant amount of waste and rejected energy. (Refer Slide Time: 04:17) These are the this is the balance, energy balance which is there and it shows you, this diagram is called the Sankey diagram on an energy balance diagram. Each of the blocks which is shown there is proportional to the energy use and it shows you the flows from crude oil, coal, natural gas and to the different sectors. So, if you look at transportation and you have industry, residential and commercial. It also shows you how much is going into the electricity generation sector and this helps you get an overall picture of the energy use pattern in the worlds. Similarly, you, one can actually do the same thing for any country in the world. And one of the things that I would like you to attempt on your own is taking a particular country and use that data and create this kind of a diagram, then see what are the mixes in terms of, so we can do the mixes in terms of either primary if you look at this segment or youcan look at it in terms of the final energy or you can look at the secondary which is in between, and so this is a Sankey diagram or an energy balance diagram for the entire world as a whole. (Refer Slide Time: 05:46) And if you look at 2016 you will find that predominantly we are looking at oil and followed by the natural gas and coal as the major chunks and there is a significant amount of bioenergy and some other renewables and nuclear, and it is expected that in future we are going to the share of renewables is going to increase. This is from the world energy outlook, of course, these are all different scenarios. Whenever we talk of the future, we know that there will be differences in the energy system and we are going to have more renewables in the future. (Refer Slide Time: 06:29) So, the question we need to ask is what does the energy use of a region depend on, wherever it is a country or a state or the city, what will it depend on? And too, what are the parameters affecting energy use. (Refer Slide Time: 06:52) You see whenever we look at the population of a country that is one of the important parameters which will affect the energy use. So, if I have more people there will be a demand for more energy, the level of effluents or the level of the industry, the level activity, level of services also will matter. When we talk about a population by its very nature the rate of change of population or dP by t will be proportional to P and to the existing population. (Refer Slide Time: 07:42) So, that there will be an overall exponential growth rate so that we call this is as a, we can call this as a compound annual growth rate and we can write, we can essentially write that If you take it in the P zero is in the initial years and this is the compound annual growth rate.between this years. Now, we can compare this growth rates and we can see so this is like an exponential growth and when we talk about energy we can look at what is the energy used per person and then multiply that by the population and then you get the total energy use. (Refer Slide Time: 08:22) So, when you look at some of the trends, what would you think when we look at the trends of energy and population growth what do you think, think about it trend of world population versus time for the last 2000 year which show significant crest and troughs corresponding to period of global stability and recession, monotonic linear growth, monotonic exponential growth, monotonic growth of the form PT is equal to A plus BT plus CT square, none of the above. (Refer Slide Time: 08:53) And you will that in general this has been monotonic exponential growth, and that is been the way in which this happen and you can see this, this is population statistics are all available inthe public domain. You can take the data and plot it and you can see that this has been growing exponentially. And following this many of the things which are used by humans will also follow these kinds of exponential growth patterns. (Refer Slide Time: 09:20) So, this is from the global energy assessment and you can see there are different things that we have project shown here. This is the population, this is the total real GDP which means this is the total sum of all the output of the world, and then you have the foreign direct investment, damming of rivers, water use, fertilizer consumption, urban population, paper consumption, even Macdonald restaurants, you can see exponential growth patterns, transport motor vehicles, telephones, international tourism. So, all of this follows the exponential growth of population and what does this mean is this something that is sustainable, this is basically unbounded growth, so if you look at now, take the area under the curve you will find that this going to be infinite. So, if we are talking of a finite resource and we will be talking about energy resources in another lecture. You will see that if you are going for exponential growth the resource will get depleted, resource will get depleted, so it is not obvious that an exponential growth can be sustainedindefinitely in to the future and that is point to keep in mind. (Refer Slide Time: 10:44) And now let us think about we talked about the population growth we also talked about world energy growth. So, the world energy trend for the last 2000 years would show: do you think it will show an exponential growth similar to the population growth, exponential growth with a growth rate less than the population growth, monotonic growth that initially follows thepopulation growth but a reversal of growth seen after seventies, exponential growth with the growth rate higher than the population growth, or none of the above. And the answer to this is actually 4 which is exponential growth with a growth rate higher than the population growth. The energy use per person has been increasing over time and this is because we have use more and more of appliances to make our lives more comfortable and so the history of human development is characterised by an increasing use energy per person, this of course may not be sustainable into the future and so there would plateauing out over all. But as of now this the kind of trend that you can see. (Refer Slide Time: 11:53) So, just to give you an idea. This is a paper from Grubler in 2004. He compares the north, the developed courtiers with the south which is the developing countries and you can see that the population share of the south is the developing countries is significant in the total, but the primary energy, if you look at this with south has 78 percent of the world’s population but has only 34 percent of the modern energy used. So, obviously there is a disparity in terms of the energy use. (Refer Slide Time: 12:31) And this disparity is plotted by Grubler in the, there are two curves you can see this is the industrialised curve the per capita energy used for the industrialised nation, you can see how it is been growing and you can see for the developing nations this there are two completely different kinds of slopes or two different kinds of growth rate and this is how the average isgoing. And so with the result that if everyone aspires to have the life of the industrialised countries, the energy demand of the world will grow at much much faster rates then our currently sustainable.
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