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Module 1: Energy Economics and Renewable Energy Sources

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The Overall Annual Fluxes of Bioenergy

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(Refer Slide Time: 14:56) When we talked about renewables, I also told you that we have to start from a small base, but we have been growing at very fast rates and you can see that with the kind of 74% and 30%, 74% for the solar PV and 35%, 20% starting from a small base, but very high growth rates. Of course, these will sort of. they will taper off and they will come to some reasonable numbers in the future. But as of now, they account for a reasonable high. (Refer Slide Time: 15:21) If we look at the overall annual fluxes. When we look at bioenergy, solar energy, geothermal, hydropower, ocean energy, wind energy and we take the fluxes, you can see that these fluxes aresignificantly higher than what is the energy use in the primary energy use in the world in a particular year. So, if we look at the ratio of the annual energy flux by the 2008 primary energy supply we cansee that solar is almost 8000 times that amount. So, it means we are not constrained by the amount of solar energy we have a sufficient amount of solar energy. Geothermal is also about 2 times, bioenergy about 3 times, wind energy 12 times, ocean energy 15 times. So, in many of these cases on a global basis. If we look at the total energy fluxes they are orders of magnitude higher than our requirement. However, these fluxes are not concentrated, they are dilute and they are distributed around the world and we will look at. So, when there are issues in terms of costs, there are also quite variable and hence there is a need for storage and that also adds to the costs. (Refer Slide Time: 16:42) So, we will look at, this in terms of we will try to answer the following questions first is how do we estimate the potential for particular renewable energy? We already said that we are talking of flows and fluxes, not stocks. Unlike in the case of coal or oil or natural gas, in each of these cases, there could be a technical potential and an economic potential. There be a spatial distribution of the resource. There will be a daily and a seasonal variation and there will be uncertainty. So, unlike in the earlier case where we had a certain amount once you mine it you know how much coal is there and then you can use it whenever you want. In the case of solar at a particular time of day depending on whether there is cloud depending on the kind of insulation, you will have a particular generation, it is more or less predictable, but there are uncertainties and we will need to be able to tackle those variabilities. These energy sources and these energy resources will have a different way of operation and we need to understand that and we need to design a system a little differently from how we design fossil fuel-based systems. (Refer Slide Time: 17:59) So, if we look at this what are the options that are there? The renewable can be direct solar that means solar which you use to heat water or working fluid or heat transfer oil this is called solar thermal. Or we can look at the solar conversion of solar into electricity through a photovoltaic cell and this is solar photovoltaics. When most of the electricity that we generate is from solar photovoltaics. and solar thermal is used can be used for electricity generation, but that is currently a little costly. It is being used mainly for solar thermal applications, which is for heating and cooling. Wind one of the earliest electricity sources and now also the largest chunk currently of electricity generation. Wind, again, is caused by indirect solar because of the differential heating of the earth surface. You have high pressure and low-pressure regions and then you have wind going from the high pressure to the low pressure and depending on the kind of wind there is a local factor. We can see what are the wind rates. And there is a power which is available in the wind. We can put a turbine within that power and extract that power connected to a generator and then use that electricity. Ocean thermal, we will talk about ocean thermal wave energy and tidal are all associated with the course. They are localised and we will see what another kind of possibilities in this. We talked about large hydro already. Small hydro does not have the disadvantages of large hydro. They and there is quite a significant amount of potential. The problem is that many of these are in remote areas and not so accessible. There may be a capacity factor, and so even though there may seem cost-effective they have not been growing at a very at the same rate as the wind and solar PV. Biomass is can happen in terms of, there are many different sources of biomass including waste and crop residues, agricultural residues, and we will look at their different modes in which we can use for conversion. Geothermal is happening is an energy source, which is happening because of the Earth's crust being, Earth's core being much hotter than the Earth's surface and then there are hot spots and when the water comes in contact with e hot spots we get steam which comes out and that can be used for power generation for energy. So, we will look at each of these in detail in terms of seeing what are the resources. What is the potential? What is the current status? So, we start with the wind which is one of the earliest commercial renewable energy use. (Refer Slide Time: 21:19) Pw=12 ρV 3 ¿12 ×1.2×(7)3 ¿205.8W/m2 12 ρCp AV 3 When we talk about wind in the wind if you see the depending on the velocity of the wind. The power in the wind is half rho v cube. So, if you just take let us say rho is 1.2 kg per meter cube and if we look at them, let us say, wind velocity of 7 m/s. If you calculate this, you will find that this comes out to be 205.8. This is an SI units watts per meter square.So, this is at a wind speed of 7 m/s. If the wind speed is half this amount, what would happen? The power in the wind will become 1/8th is proportional to the cube of the velocity will become 1/ 8th of this amount. So, it is going to be of the order of 22 watts per meters square. So, this is the power which is there in the wind. Now, depending on the turbine, it will have its coefficient of performance. So, the actual power which you get will be half rho Cp into the area into V cube. This Cp is typically you will get something of the order of 0.3 to 0.4 and depending on the machine that we have. So, in general, what will happen is we can measure if you see here. This is a wind anemometer, which will give you the direction and the speed and then there is a wind vane anemometer this is of this type and the windsock is giving you the direction. So, we have usually wind measurement stations located all across the areas where we expect to have high wind and these this data is then monitored. It is then mapped and you have maps which show you the distribution of wind speeds. (Refer Slide Time: 24:00) (V2 V1 )=(Z2 Z1 )α α 0.1−0.4Wind speed varies with the height from the ground, and typically what we have is we have a formula which is. If we measure. So, if we have a wind monitoring station at a particular height and we want to estimate what will be the wind speed at a different height. Because we may put we may have wind speed monitoring at let's say 50 meters, but we will put a turbine at 80 meters or 100 meters. We can use this correction factor, this correction factor. The values of alpha are for different. It goes between point one to point four, and if it is a relatively smooth terrain, we can use point one and then we can use this and get extrapolate what will be the wind speed at a different height and we can use this to get maps of the wind speeds. (Refer Slide Time: 25:04) When we look at this, you will see that this is the kind of map which is available and we talked about the, you know for 7 m/s. We said it is about 200, that means point 2. You can see that in this case, we are looking at you look at these colours you can see some of the largest, highest winds are of course offshore. But we have different kinds of wind regimes which are there. (Refer Slide Time: 25:44) Look at the wind classification again in the GEA Chapter 7 you can see that these are the types of wind classification the wind tower class going from less than 100 and going to the largest one,the highest wind power class wind class 7 greater than 400 and this is the kind of wind speeds at 10 meters above the ground and in the case of 80 meters above the ground, that same class is greater than a 1000 watts per meters square and you can see this is the kind of wind speed which we are talking of. In every wind machine, when you put a turbine, there will be a certain speed, which is the minimum speed at which the turbine must rotate to overcome all the inertia and then start generating and from the minimum to the rated speed to the cut-out’s speeds. There is a maximum speed beyond which the turbine will get damaged so that within that range when you have a wind speed within that range, it will generate. And remember, the wind fluctuates over the day, fluctuate over the season. And because of that when you talk about the power supply, we need to be able to adjust that and match this supply with the demand and I will show you some data about the Indian context before we do that. (Refer Slide Time: 27:15) Let us look at. So, this is giving you some of the fractions in different countries. What are the kind of wind speeds in the and the number of sites extra? In the Indian context. If you see this is a this is the MNRE’s map, the ministry of new renewable energy and you can see that we have some sites in Tamil Nadu and some in Gujarat and the most of the wind is related is typically along the coast. You will also see that we do not have most of the wind speeds that we have are much lower than the high wind speeds which are there in the US and Europe. The other point that we have is that our wind is very, very seasonal. We get the highest wind during the monsoon months, four mont s of the year where you get the maximum amount of generation.(Refer Slide Time: 28:18) A similar kind of map has been drawn. This is at 80 meters and you can see here that we do have some of the generations of the order of you know most of them are still in the lowest Category 1 and 2. The high winds regimes are in wind class 2. We do not have anything at a very high wind regime. However still in many of these cases even with seasonality and with this wind regime we can have wind which is cost-effective and that is why we have quite a several wind machines which have been installed. (Refer Slide Time: 28:58) If you look at the wind potential 80 meters you can see that wind power density going greater than 250 watts per meter square at a height of this, we are looking at a 1400 GW of wind. That is a fairly large potential. And then if we look at something higher, this is we are talking of 800 gigawatts of this. So, total we are looking at something of the order of 2000 gigawatts of total wind potential at 80 meters. If we go to higher heights of course the potential can increase. This is based on a study done by LBNL. (Refer Slide Time: 29:53) We like to take a look at what is the actual renewable generation in our country. And if you see this, this is in 2015-16. This is the picture of the renewable generation for different months. A couple of things emerge from this picture. The first thing is that it is the wind which is the largest chunk, of course, there is a reasonable amount of bagasse base and biomass-based as well as some small hydro and solar also coming up, solar increasing in coming up. We find that there is a significant amount of seasonality in the renewable generation and that is predominantly driven by wind where the wind is mainly during the monsoon months and then tapers other cases. (Refer Slide Time: 30:47) So, let us look at some of these in terms of the actual generation you see that this is from several sights and talks you about the wind speed you can see that the wind speed fluctuates and significantly and in different months you have a different kind of wind regime. (Refer Slide Time: 31:12) So, if we look at this in a little for Tamil Nadu for the particular year 2007 you can see that the generation in a few months was more than average been generation they wind energy generators with a million units in the monsoon months but in the other months is significantly lower. (Refer Slide Time: 31:39) This is a show, you can see also this is the annual and all India region-wise annual wind generation pattern and you can see even here that most of this is happening during the monsoon months and rest of the time it much, much lower. (Refer Slide Time: 31:57) This Tamil Nadu plot shows you the generation over 0 to 24 hours and over different months and you can see that four of the months the generation is very high and, in some months, it is almost negligible. So, what does it mean it means that when we provide the requirement in these months from wind in the months where there is low wind you have to have something else which is meeting that requirement. And that means if it is a thermal power plant that thermal power plants have to be back down or switched off when there is high wind and this will involve additional costs. So, that cost is being met by the thermal power plant. Do we need to look at regimes by which we see what is the value of the energy provided? When it is provided and what kind of wind has to be able to compensate for the non-availability in the other seasons and so this is the situation in terms of wind. Let us know to move ahead and look at solar, so in the case of solar, solar is much more predictable and when we talk about solar Isolation. (Refer Slide Time: 00:30) We are looking at the direct and diffuse, so we have a direct and diffuse, if you looking at direct isolation, this is an instrument which is used to measure the direct beam insolation, this is called the Pyrheliometer, this is the focus so that it is directly depending on the position of the sun, it will be taking the direct normal beam radiation to the sun and you have this is measurement. (Refer Slide Time: 01:02) You also have what is known as a Pyranometer and the Pyranometer can be used for measuring diffuse radiation or total, this is a blocking sheet which can be used to block the direct and then what is measure becomes only the diffuse, if we remove this then we will get the total insolation which is on a horizontal surface and that will be the global horizontal insolation. And so, the direct plus diffuse will give us the horizontal and these are the instruments that can be used to measure. Most of the measurement stations will have these types of instruments. (Refer Slide Time: 01:45) I sc 1361W/m2 DNI And the solar constant Isc which is incident is of the order of 1361 W/m2, that is the total amount of solar isolation available per meter square of the surface. When it comes through the atmosphere some of it gets scattered, some of it comes down and diffuse, some of it gets absorbed. And what we have is what is known as the direct normal irradiance DNI and DNI at any point of time when we talk about the solar photovoltaic we usually have a standard which is based on a thousand watt per meter square and we create the characteristics for that insolation when the insolation is lower the output would be lower. So, DNI is the flux density of the direct unscattered light from the sun measure on a flat plane perpendicular to the sun’s rays. And this DNI that we talk about which is, so this is DNI is perpendicular to the sun’s rays so that it is you have the normal irradiance which is there and this flux varies over the day as the sun rises and the there is a peak and then it goes down in the evening. When we look at the DNI every hour we can measure the DNI and then make a plot, we can take the aggregate amount of the irradiance over the year and that is plotted as the annual DNI, so those are the kind of values which are put. (Refer Slide Time: 03:46) When we look at the spectrum of the solar radiation if you see this, will have the sunlight which is there some of it is observed then it reaches, this is at different wavelengths and some of it is in the visible range and the infrared in the ultra-violet and all of this incident onto the device and depending on the characteristic of the device we have an efficiency which is there and this is used to convert the energy. (Refer Slide Time: 04:15) So if you look at now, this solar irradiance these are from 3 a few of the sites which are there where there are been solar plants and you can see that in some cases you have this pattern but because of cloud cover for some hours there is a drop in the irradiance and this is from a site in Gujrat for a particular day one of the days you have no cloud cover and this can see that the generation megawatts is followed the classic example of what we expect from solar PV plant. On another day there is some cloud cover at this point and then there is a cloudy day in this one is a cloudy day with several cloudy hours and disruptions, so these are the kind of things which I told you in terms of the interruption and the variability which is there in solar. (Refer Slide Time: 05:13) Solar is much more predictable as we said that with the different kinds of you can measure this is with a different unit its kilojoules per hour square meter. Usually, we will put it in terms of watts per meter square and then we can take watt-hour per meter square multiplied by the number of hours and then over the year you will get something like a kilowatt-hour per meter square, per year. (Refer Slide Time: 05:39) And this is the global solar irradiance and you can see this is the direct normal DNI which is there and you can see the yellow region these regions are the ones with high DNI. In the Indian context, we have reasonably good DNI across most parts of the country. (Refer Slide Time: 06:10) And there is a variation, of course, see this is the kind of average global irradiance and you can see this is in watts average in watts per meter square over December, Jan, Feb and this is June, July, August this is again both of these are from the global energy assessment. (Refer Slide Time: 06:34) In the case of India, you find that most large parts of the country have, most of the country has DNI greater than 1900 kilowatt-hour per meter square and some of these regions for instance this is more than 2200 and so this is quite a good DNI. (Refer Slide Time: 06:59) Now in oto calculate if we look at the total amount of electricity that we require we can take that electricity to divide it by the DNI that we have, take the efficiency of the cell and then calculate what is the area that is required and if for instance if you are talking of 500 billion kilowatt-hours we can see that this can be met by installing about 2500 square kilometres of 50 into 50 km or 4 smaller squares of 25 km x 25 km. And so really speaking this location which has been selected is a location which has the highest insolation in terms of DNI it is also a location which is a desert and relatively low population density. However, still, you know getting 50 km into 50 km is difficult creating the transmission and distribution line, creating the storage in actual practice when we try to get land, the land is always difficult to acquire. And the requirement for land, the requirement for water in terms of the cleaning the panels and in the case of solar thermal even as a working fluid, these are some of the problems in terms of the solar penetration. (Refer Slide Time: 08:35) As I told you for you can see this is the global horizontal insolation watts per square meter for a particular location of a PV module in the IIT campus and you can see that the generation follows the insolation data. (Refer Slide Time: 08:59) We can also look at the DNI variation over the year and you can over this is for a particular site at Noida and you can see that every day the DNI goes up and down but there is a variation in theseasons and there is a fluctuation and so this is one of the issues when it comes to solar but when we look at solar there are large tracks in the Indian context we have a significant amount of solarradiation, most parts of the country are good solar radiation. Most of the solar is happening though in mostly in the west and the south, east and north-east relatively have less solar radiation, so we have this situation where when we talk about fossil fuels, it was mostly in the east and little bit in the centre most of the solar and the wind ishappening more in the west and the south, so there is a sort of regional disparity in terms of the kind of available resources. Let us now look at some of the other sources of energy, if we look at tidal, tidal is the renewable energy source where it is not dependent on the sun but it is the moon, so the gravitational effect of the moon on the earth causes the high tide and the low tide and the principle typically in a tidal situation, of course, you can have tidal turbines which are in the stream just like the wind turbines but in the other case, we allow the water to come in at the high tide and then we block it and then we release the water at the low tide. This difference between the high tide and the low tide that is called the tidal range that gives us the head for running the turbines which give us the power generation, so the power generation happens only at a fraction of the time when we are releasing the water during the low tide and it will, of course, be in. (Refer Slide Time: 11:14) So, in the case of this kind of data, we will need to have what is the tidal you know there will be a daily tide or a semi-diurnal tide, there will be a tidal range between the high tide and low tide and this has to be mapped. This has been for all locations of the course there are ranges of tides which are provided and this is the tidal range map which is given in the, you can see of course that we are looking at a tidal range of 10 to 30m would be, could be cost-effective again depending on the location and the kind of things one can think in terms of. In India, we have not yet built there is a plan to build and I am not sure what is the status of that of the coast of in the Bay of Bengal of the coast of Sundarbans. (Refer Slide Time: 12:17) There is a plan to build a tidal plant, there is also a plan at the Gulf of Kutch, the largest tidal plant is the one in France which is a 240 MW La Rance plant which has been operational for decades and it is also a tourists attraction, there is a recent one which is being built in Korea in the Sihwa lake somewhat 254 MW. So, tidal as of now there is a potential it is not yet a commercial technology there are a few projects, they are demonstration projects, they can be near cost-effective but we do not expect them to have a very major role in the future unless there are technology breakthroughs. In addition to tidal, there is also something called the ocean OTEC, or the Ocean Thermal Energy Conversion. (Refer Slide Time: 13:26) And this is using the principle that the surface of the ocean is much warmer than the water which is there at the depth. And because of this, it is possible to have a normal ranking cycle where we use the temperature this temperature difference to generate electricity and the advantage that we have is that we have a large volume of water and even though the temperature difference s are relatively small in the sense that we are looking at temperature differences of 18 - 20o even though they are relatively small because there are large volumes we can get, we can generate a reasonable amount of energy. We had the largest plant being planned of the cost of Tamil Nadu it was a 1 MW power plant and the problem was that most of the components were tested however when it was out in the field the pipeline the HDP pipeline 1.1 km pipeline kept getting ruptured and because that was not able to establish that was the project was abandoned. There is a number of them this is the mostdifficult challenge in the sense that it has to be put in the ocean which is the most the, most adverse and harsh environment. However, there is a significant potential to do this, in the case of wind also in many of the countries in Europe the land for wind is not available and the plan is now to move offshore. In the case of offshore, can have, essentially, we will have much higher wind speeds and we can have large wind farms and that is the way this is going offshore is costlier again there are technological challenges but this has been the way we going. In the case of wind also we have gone for larger and larger plants and now we have a single turbine which can be generated of the order of 10 megawatts. So, this is in terms of we have looked at tidal and we have looked at ocean thermal. (Refer Slide Time: 16:10) Then there is also we can also look at these ocean currents and it is possible to use some of these ocean currents in terms of energy generation. (Refer Slide Time: 16:21) The other possibility related to the course is to have the energy which is available in waves and to harness that and to do that what happens is that see on the surface of the water because of the wind we have the waves and the waves have the crest and troughs and we have several different devices which can be used you have the oscillating water column and you have the Edinboro duct and you have the Pelamis different kinds of devices which bob up and down and that movement reciprocating air is converted into electricity. This has the largest number of patents which are available for wave power. The problem is that this is all distributed you need to have a wave for taking out that power, we need to have a wave for taking that power and converting it into electricity and then evacuating that electricity and connecting it to the shore. So, this is again something, where we do not that, is a reasonable amount of potential. (Refer Slide Time: 17:40) And this is that you can see in different regions you can see that the total terawatt hour which we are looking at exajoules it is about 106 EJ it is very large potential but cost-effective extraction isan issue, there could be breakthroughs and this could provide reasonable amounts of requirement especially for islands and coastal regions. So, we looked at tidal, we have looked at OTEC, we have looked at the wave and the other source of energy as we talked about is the geothermal energy. (Refer Slide Time: 18:12) And in the case of geothermal as we said there is that the at the depth the temperatures are much higher and then you may look at the water coming in contact with this, we have essentially hot water or steam coming out, there are many natural hot springs where these come out and these are usually tourists attractions. Here there are many different technologies where we can have an injection well and an extraction well where you inject water inside and or a working fluid inside and then you can have an organic ranking cycle and have power generation. If you have a lower temperature, we can also directly use it for heating or we can use the vapour absorption refrigeration system using for cooling there are also geothermal heat pumps and geothermal, so you can have ground. From the ground if you take things the temperatures are 5o, 6o lower and you can run, you can save energy when you are trying to heat or cool a space, so that is again another application there are many different countries where this is a commercial technology cost-effective but it needs I will be in areas where there is already the falls and you have the steam emerging at high temperatures. (Refer Slide Time: 19:48) So, this is, this gives you an idea of some of the different countries and the kind of geothermal installed capacity and you can see Indonesia, Island, Philippines several different countries where there is a geothermal capacity. (Refer Slide Time: 20:09) And this is a map showing the geothermal falls. Before we look at that in the case of India these are the geothermal provinces and if you see the in the Indian context the around the fault areas these are the areas where you have the geothermal but the temperatures in most of the case the temperatures are relatively low. In some cases, in the Puga valley, we are getting temperatures of 200 centigrade. So, this kind can be used for power generation a pilot is being planned at Puga valley, many of these are the places you can use it for cooking, you can use it for heating and in we do not expect geothermally to have a very major role in the Indian context but locally this can provide some of this requirement. (Refer Slide Time: 20:56) The supply curve for we talked about supply curve, the supply curve for geothermal with current technology you can see that we can get of the order of 200 EJ or 300 EJ at different kinds of prices and with the new technology, of course, the prices will go down, that is what the supply for geothermal electricity. And this is for supply for geothermal heat, so similar kinds of supply curves are available for many of these and this is available in the global energy assessment resource chapter.