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Module 1: Leontief's Input/Output Analysis

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Resources Pathways and Net Energy Analysis

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Let us quickly look at option C, which was, where we have the biomass gasifier. So, here what we do is, we have a gasifier, where we fire biomass and then we are getting producer gas. This producer gas goes to a dual fuel diesel engine or dual-fuel engine. It could also go to a dedicated spark-ignition engine so that it could be, but the dual-fuel engine is also consuming a certain amount of diesel and then this is converted over to the pump and this is the energy output. So, we have 3 GJ. Now, for this duel fuel engine, there is usually a certain limit in terms of what is the proportion of the producer gas in this. So, at most what we are looking at is, we are looking at something like 75 % of the input can be provided from the producer gas and 25 % comes through diesel. When we look at this then what we will do is, we will say 3 GJ, which is in the pump, take the pump efficiency and get what is the input which is required here. So, that means 3 divided by 0.75. So, this will be 4 GJ here. Now, from the 4 GJ, let us say by energy terms 75 % will be provided from the biomass gasifier. So, that means 4 into 0.75, it turns out to be 3 GJ as the output of this producer gas, 3 GJ. So, the efficiency of the gasifier is 0.7 so we can do 3 divided by 0.7, is the gasifier input. We can then divide this by the calorific value of the biomass and will get a certain amount of biomass which we get and you can cross-check these numbers. (Refer Slide Time: 02:57) And then so basically, what we get is in this case, we have 75 litres of diesel. Remember we earlier had, 290 litres of diesel and this is 754 kgs of biomass. So, if the biomass price is 2 rupees, per kg then the total cost, operating cost will be, 2 into 754 plus 75 into 50. You can check this, this comes to about 5258. (Refer Slide Time: 03:38) So, let us compare it with the diesel engine pump instead of 14500, we are getting now 5258. So, of course, the operating cost reduces. However, the capital cost increases because now you have the gasifier, there is, also it is more tricky in terms of operation and maintenance. We will see that in terms of CO2 now. The CO2 emissions will reduce because the biomass is considered as carbon neutral and we can then calculate. (Refer Slide Time: 04:13) This is just going to be roughly what we calculated 75 by 290 into 0.9, is what we had calculated, tons. So, the amount of, CO2 reduces significantly in this option and of course, but it is a costly option. There are other things that one can think of and then we have, there is now move to have solar photovoltaic based pumping. (Refer Slide Time: 04:50) So, you can look at this. Now, one of the issues in all of this, is that, the distribution companies because of the agricultural pump sets and the theft which is there, agricultural pump sets many cases have been given, were given free electricity. So, with the result that typically distribution companies have been making significant losses and you can see these are the different years with this Uday scheme, based on the government estimates, reasonably large lost components. (Refer Slide Time: 05:26) So, one of the things that the distribution companies are thinking of is to try and look at supporting agriculture pump sets moving to solar and of course, there is a capital cost involved. So, typically what happens is you will have the solar PV modules and then you will have the pipeline for the, there is a schematic, for a particular company with a solar pumping system. (Refer Slide Time: 05:55) And when we look at this, this is typically how it will look in the field and the advantage also is that in many of these cases if you have some storage, it is possible to then pump whenever you have the solar and then you can use it in the pump, use this in the field if you have the water storage and that may be a. (Refer Slide Time: 06:18) There are many different types of configurations, which we can do and you can see that you have different modules of arrays going from 900-watt p to about 2.7 kilowatts. Different kinds of centrifugal pumps or submersible pumps and their large number of possible configurations. So, this is another option which we can see. (Refer Slide Time: 06:49) And in this, if you look at the efficiency when we talk in terms of this, it is going to be only the pump and then we have some kind of a power electronics and then you have the PV, incoming solar radiation. Power electronics is fairly efficient, will be of the order of, let say 0.95 or even more. The pump we had set, pump efficiency we had set 0.75. Some of these submersible pumps etc. might have slightly lower efficiencies. The PV modules in the field may have efficiencies ranging from 15 to 20 %. So, from an overall efficiency point of view, this is the, you may find that the efficiency is lower than the efficiency which we had from the oil. But please remember efficiency is important provided with the resources constraint. Since this solar insulation i s relatively free. We do not have to pay for it and it is not constrained then the efficiency may not be the criteria when we think in terms of solar. So, with this, we complete the part, on we, the example that we saw. (Refer Slide Time: 08:23) Now, we would like to look at another example and that is for a car. We would like to see, is it possible to think in terms of a fuel cell-based car, and how would that compare with the IC engine based car. So, in this example, we are going to just, I will just show you some of the numbers and you can calculate it yourself. We are not going to, do the detailed calculations as we did in the earlier example so that you have already got that. Now, when we think in terms of hydrogen, there are several, several researchers and several energy professionals believe that hydrogen is going to be the future and hydrogen is in general, it is a secondary fuel. So, when we think in terms of a pathway to have hydrogen, we can have hydrogen from a variety of different sources. We can start with fossil and then we can do cracking and shift reaction and then get hydrogen and that is the largest this steam methane you reforming is the largest chunk of hydrogen production. It is, today it constitutes more than 90 % of the hydrogen produced in the world. We can look at hydrogen from nuclear, we can look at hydrogen from solar, both and when we can look at, photochemical, photobiological, hydrogen from biomass, gasification, fermentation. So, there are a whole set of possible ways in which we can get hydrogen. After we get hydrogen, we can use that hydrogen in a fuel cell, to give us electricity. And this is compact, it has no emissions with it and no moving parts. So, it is, and it is high efficiencies. Unfortunately, it is still very costly and life is relatively low. So, this is why fuel cells and hydrogen has not become as common as one expected it to be. (Refer Slide Time: 10:32) So, we will look at two applications for hydrogen, one is an application where we are looking at distributed power generation. So, we want to generate power and in the case of distributed power generation, we have many different options. Let us look at an option where you have, so here we are looking at not the grid, but it is an isolated system. We can, I have the diesel engine, generator or we can have a gas engine fired by natural gas, gas engine generator and in the third case we can have essentially a hydrogen-based option. So, these are the base cases, we can, I have compared it with a fuel cell hydrogen option. In the second case for the vehicle, the base case can be an IC engine for petrol or diesel and at second base case could be CNG engine. (Refer Slide Time: 11:21) So, if we look at the option for power generation, from diesel we can see the generator, the diesel engine, transport of diesel, oil mining and refining and this is very similar to the system that we saw for the pump. We have put down typical efficiencies, you can multiply it. (Refer Slide Time: 11:42) And the second option is when you look at natural gas, natural gas the same thing generator, you have a gas engine, then natural gas transport, natural gas extraction. Again, you can see the efficiencies are pretty good. (Refer Slide Time: 11:54) In the case of the fuel cell, we now, let us look at natural gas giving us, the natural gas having the extraction then we have natural gas transport and then we are using that natural gas in steam methane reforming to get hydrogen, that hydrogen is used in a PEM fuel cell. Which can have efficiencies from 40 to 50 % and then you get electricity. (Refer Slide Time: 12:20) And we look at this, if you look at the distributed generation you find, that you can do these numbers, now convert it into primary energy. And you find that in the overall case, for the A1, which is based on oil, we are getting point, about 0.25 kgs of crude per kilowatt-hour. Similar kinds of things for natural gas. In the case of fuel cells, the overall efficiency is slightly lower and it is similar to the fuel cell. If you take a higher efficiency of the fuel cell, of 50 % then it goes up to 37 %. So, it is very similar to the natural gas cycle, if we can go up to higher efficiencies. From an efficiency point of view, it is almost similar to a, when we are taking it from natural gas. (Refer Slide Time: 13:18) But the interesting thing is, from a carbon dioxide point of view, this turns out to be better and we can see that in the case of, with an efficiency of, 0.5, we are getting now 0.136 kg of carbon per kilowatt-hour, as compared to 0.187 or 0.211 kgs of carbon, for crude oil or natural gas. So, from there is an incentive to go for, fuel cell hydrogen from a CO2 point of view. And of course, if we get the hydrogen from renewable sources or biomass, that would be an even better incentive. (Refer Slide Time: 14:04) So, this is in terms of the distributed generation option. Now, let us look at the option for, hydro gen vehicles as compared to an IC engine vehicle. So, if we look at the chain that we had, we have the vehicle, you have the petrol filling station, the petrol transport, the refinery, transport and crude oil production and that is the fossil fuel chain. Hydrogen chain will be a vehicle, filling station hydrogen storage and delivery, the pipeline transport, hydrogen production centre and the primary energy source that we have. (Refer Slide Time: 14:36) We will take an example, with a small vehicle, a small size passenger car, Maruti 800. Petrol fuelled 37 bhp – Brake Horse Power, which is coming out to 27 kilowatts. This was the largest chunk of Indian passenger market in 2005, 2006. Today, that share would be lower because you have the other models. But just to give you for the example, this is an example, we had done some time back, you can make this as a basis. (Refer Slide Time: 15:06) Now, when we calculate this, we have to calculate all on the same common basis. So, what we have to do is, we have to see how what is the weight that we put on the vehicle because based on the weight that is there on the vehicle the power requirement will change and hence the fuel requirement will also change. So, the, we take the weight of the empty vehicle, the body excluding the engine and the tank and that for the 800 Maruti, 800 was five 550 kgs. Assume a certain number of weight of the passengers, that is 350 so that this becomes 900. We have the coefficient of drag and the coefficient of rolling resistance, the frontal area and then we have to presume a certain amount of travel. We have done this calculation for 100 kilometres of travel per day. Now, look at based on the amount of range or the amount of time that you have to, you can use before you refuel, we can decide what is the capacity of the tank. And I will give you a, I will upload a paper where you can see the details. So, the petrol tank is, least in terms of weight because of the, it is 40 kg, CNG tank is 140 kgs and fuel cell turns out to be 130 kgs. And the engine 60 kg, 60 kgs and then this is 15, for the motors and 15, so that is 30. So, total if you see this is 160 kgs and CNG is about 200, here it is 100. So, that is the difference in weight. (Refer Slide Time: 16:50) That difference in weight. So, what we do is, if you look at, different kinds of drive cycle and you can look at there is the automobile research association of India, which does work on different kinds of automobiles. Drive cycle shows you the speed versus time trace typically. And then there is, there are different drive cycles for highways and urban. In the case of urban driving, mainly it is the road conditions and the traffic that limits and then so you have certain amounts of acceleration, deceleration. So, if you see as compared to the European drive cycle, Indian urban drive cycle has a lower average speed. Rapid accelerations as compared to 23.4 kilometres per hour, instead of 62.4. (Refer Slide Time: 17:47) So, with this drive cycle, we then calculate. You can look at there is a freely downloadable software called advisor. You can put in the values over there, to choose your vehicle, vehicle characteristic and then we can, you can also just calculate it upfront. By calculating the power required to overcome the drag, the frictional resistance and the inertial force and then this gives you the total and then you have the power at the wheel. (Refer Slide Time: 18:18) And then these are the data that we use for the base case and we can, you can take a look at all of this. (Refer Slide Time: 18:24) And then with we said, we have a driving range and then we got a cost in terms of rupees per kilometre. (Refer Slide Time: 18:35) So, essentially with this what we can do also is we have to have not just the vehicle but we also look at the hydrogen fuel chain, then the production, production can be from different sources as we said PV electrolysis, wind electrolysis, biomass gasification, steam methane reforming. And then you have a transport which is pipeline transport. Storage could be compressed hydrogen, liquid hydrogen, metal hydride and there is, this is an area of research and then the utilization which we are talking of is in the PEM fuel cell. (Refer Slide Time: 19:08) So, in the steam methane reforming, what we are looking at is, CH4 plus a 2H2O, giving you 4H2 plus CO2 and then you can get a price of hydrogen, based on the price of coal. (Refer Slide Time: 19:18) So, if we look at now the efficiencies, you can find them for the petrol engine, this is the transmission, the IC engine, transport of petrol and oil mining. (Refer Slide Time: 19:33) If we look at the gas engine, slightly different but almost similar order of magnitude. (Refer Slide Time: 19:40) In the case of the fuel cell. We look at the, in here, it is the fuel cell efficiency which is the determining factor. The motor and the transmission are highly efficient and overall this is the kind of efficiency. (Refer Slide Time: 19:55) So, based on this you can multiply the numbers and cross-check. You would find that the overall efficiency of the fuel cell is higher than this, that in both the cases. In the gas, gas engine, CNG it is almost similar and the interesting thing is there is an incentive in terms of efficiency. There is also an incentive in terms of the CO2. I have not shown you these numbers, but you can cross-check and you will see that the CO2 emissions per 100 kilometres of travel, is lower and you can calculate this from the first principles. We have in India, like in most parts of the world, we are looking at a transition, to electric vehicles and there is a policy where we would like to have much more of electric vehicles in our mix. Currently, of course, electric vehicles are a very, very small almost negligible percentage of our mix. Now, when we talk about an electric vehicle and comparison of electric vehicles with the IC engine vehicle, whether it will result in a saving in CO2 or not, will depend on what is the mix of our is electricity. (Refer Slide Time: 21:19) So, there is this interesting graph, which is from the world energy outlook of 2019, which talks about the gram CO2 per kilometre of travel and it shows different countries. And this is the value which you can see for India and you can see currently this value is, the IC engine is of the order of 150. And when we look at an electric vehicle, we are looking at something which is today it is higher than that and it depends on the, of course, how you do the calculation. As the mix changes with this, this is going to be, so the hybrid vehicle may be higher, the existing, this is the kind of difference that we can get. As the mix changes with the sustainable scenario, the electric vehicle can be significantly lower. And so that is the kind of thinking but basically what happens is you can calculate that the relative carbon footprint of IC engine versus the cars will strongly depend on the power sector mix. And so, because of that the trade-off that we are talking of, this is the IC engine, which will go through if we looking at the hybrid, this is the kind of thing that we are looking at, and. So, depending on the calculations and depending on the type of mix, if our mix is completely going to be more coal. In some states, that it may actually, there may not be significant CO2 savings. However, of course, local emission savings would be there and as our mix gets reduced, we can, the share of CO2 in our electricity mix gets reduced. We can move towards something like this, much lower value and that is the kind of target that we are thinking of. So, just to summarize what we have looked at in this module is, how do we calculate and compare different routes from the primary energy viewpoint and we start by drawing the energy flow diagram, put down efficiencies and then compare them with primary energy. There are different, sometimes the two different sources are compared. So, then we are comparing coal versus oil and then can also calculate the total CO2 emissions over the chain. We can compare not just based on the energy, but then we can see, what is the relative scarcity and from an energy security point of view what is the trade-off between these fuels. We will take this forward in the next module, where we will now go to the next step, where we talk about net energy analysis. And we will look at everything from an energy viewpoint. Thank you. In the earlier module, we have looked at primary energy analysis. Where we looked at different options from how much primary energy they are using. We, now extend this and move forward to look at a new technique, the life cycle analyses and within life cycle analysis we are going to focus on net energy analysis. So, we will look at some applications of these techniques, different criteria and how this can be used to help in decision making. We have seen earlier the decision making based on economic analysis and at sometimes it is we want to look at the different options from how much energy it takes over its life cycle. So, the whole field of life cycle analysis or LCA as it is known started in the early 1960s 1970s. In the initial phase, this was, there were multiple methodologies and in the 1990s there were two different societies the SATAC and the ISO which tries to standardize and provide a set of methodology for carrying out life cycle analysis. So, let us look at what is life cycle analysis. (Refer Slide Time: 2:06) You may want to look at the International Standard ISO 4040, which sets out the methodology for life cycle analysis and you look at this. It is available in the public domain. (Refer Slide Time: 2:09) There are some additional values, this one is 1997 edition and this provides a framework for carrying out environmental management or life cycle assessment and the principles and the framework. This initially LCA was used to compare different products and most products for packaging. So, we looked the entire life cycle from the point at which it was manufactured right from raw materials, to use and to the disposal. So, all of this constitutes the life cycle analysis. So, in life cycle analysis the basic steps involved are first we compile an inventory of relevant inputs and outputs. The different inputs, which are coming into the process and the outputs for the process. And then for each of this, we evolved the potential environmental impacts associated with these inputs and outputs and then we interpret the results. (Refer Slide Time: 3:22) Now, there are two approaches here, we can do what is known as cradle to gate or cradle to grave. And this typically means that we start with the initiation, the actual manufacture and then the to the gate where it is the produce and use. Cradle to grave means we also look at disposal the phase so the full cycle, if you want to take it, will be a cradle to grave analysis, in some cases we just analyze till we get the end-use and that the cradle to gate. (Refer Slide Time: 4:17) So, if we look at the different the mythology for life cycle analysis. The first step in the life cycle analysis is to identify the goal and the scope, define the scope and the goal. Once we define the goal and the scope. We can then look at, what is inventory what are the inputs and outputs doing into the system boundary that we have. And of course, there is some iteration both ways between the goal and the inventory analysis. Based on this we can then assess the different impacts again and then in all of this we would interpret the results. So, there is scope for interpretation we have these values which will there and there will be multiple different criteria. And then this will also. So, this essentially represents the framework for LCA. Now, what you need to do is need to take some examples so that you know how to do this type kind of calculation and it will be useful in a whole variety of examples. And we take we will take some examples from literature this entire framework will then go for the this will give us the direct applications. And there are different types of application we can look at it for improving the current mechanism so that we can reduce the environmental impact. The second is we can look at it for decision for product development, we can look at if choices, we can look at it for strategies for companies, we look at it for policy analysis. (Refer Slide Time: 6:46) So, what we had just seen this is let me just put the pointer. This is what we have now just seen this was the LCA framework this from the ISO manual and this give you finally the direct application that we are talking of. (Refer Slide Time: 7:06) So, as we moving forward when we look at the products system we may want to decide in the system. The different kinds of flows, which are there in the systems. So, when we are creating a product, we may build in some materials which come in, raw materials and then there will be flows into that system. These raw materials will be converted and there is the production phase. There is a use phase, there is the recycling and reused and then the waste and the waste treatment, there is some energy supply and transport and finally, there is this product flow which we are taking of. So, this could be an example of a product system based on which we can do the life cycle analysis. (Refer Slide Time: 7:56) The, when we talk about the goal, it is important for us to understand who, what is going to be the application of the LCA. And depending on the application you may modify the mythology, decide the system boundary. So, what is the intended application what is the reason for the study? Who is the audience who is the person, who are the people who are going to use this LCA? Maybe it is being used for some comparative assessment so this goal and then based on the goal identify the scope what is the product system, what is the functions. What kind of we may want to define a functional unit. This is very important in most of the LCA that we carry out that we define clearly a functional unit. Use it as a basis for comparing between different things, identify the system boundary also in the many of these cases allocation procedures because in your process we may have multiple products and to allocate the energy flows or the material flows to one of the products. We will have to have a basis by which we make this allocation. (Refer Slide Time: 9:14) There is a large number of different life cycle analysis, which have been done. Which are available in the public domain, in the papers and reports and books. And depending on your application, you can always find something which is similar, which have been done but then you want you to do that for your local context. Because globally or nationally or locally the, there are differences in the way, in the electricity mixes, in the kind of procurement of the raw materials, in the environmental impacts and so the LCA, an LCA which has done for Europe may throw up different results from the LCA which has been done for an Indian context. So, as I told you with the functional unit is a very important point in your starting point for the LCA. We must define a functional unit, which is related to the purpose of the processor system. So, and it should be consistent across the options being assessed. So, for instance, if you are looking at a power plant we may say you want to generate 1-megawatt hour of electricity, per megawatt-hour of electricity. How much is the energy input? How much are the emissions? And then we can compare coal-based plants, photovoltaic based plants or wind-based plants or biomass-based gasification. And then the quantified performance of a product system which is for use as the definition of a functional unit is the quantified performance of a product system for use as a reference unit. So, initially, once we start the study and we identify what is the use we can then define a functional unit then compare all the options based on that functional unit. So, let us take one of the interesting studies, which is there in the literature. Several papers on it are when we look at them, we know when you have tea or coffee there as many different options by which you can have your tea coffee in. So, you can look at a paper cup, you can look at a cup which is a polystyrene cup which is made, which is basically plastic and one can also think in terms of the ceramic cup which can be washed and reused. One can think in terms of a glass cup. Which made of glass again can be washed and reused. And you can also think in term of in rural India and even in some of our towns we still have those coolers. Which are fired clay and then you can have tea in that and it is disposal cup but it gets, it can the broken cups are again fired and reused.