 Hello everybody once again. So, this is the lecture number 2 that I am talking about solar radiation. I was telling you that I have also uploaded on Moodle this kind of files. Now, this is the word file available to you and you can use it later also. This file actually gives details about the lecture itself. So, it will talk about the contents of the lecture solar radiation. For example, what is the objective of this lecture? So, what are the basics of solar radiation? The sun and earth movement it will talk about. It will give the possible formulas. What is the learning outcome? For example, the idea of this lecture is to understand the basics of solar spectrum, define various terminologies related to solar spectrum, appreciate the sun earth movement and its impact on the earth climate, understanding concept like a declination angle, apparent motion of the sun etc. So, these are the objectives of this lecture. It will also define and there are some problems which you can see. These problems are already solved problems that you can get. For example, this is the problem to calculate the zenith angle for air mass 1.5. So, this will learn actually this is the part of the program and where you can read more about this. So, this you can read more animations are there on the websites, you can read from the book etc. And then the summary of this. So, this is the word file. I have put lot of efforts to prepare for all of the lectures. So, that you when you are going to teach this course, you can actually use this learning objective seeds to actually plan your lecture and deliver as per the plan. So, all the seeds are available. Now, let me go directly to the presentation. So, let us start. I hope everybody is ready all remote centers. So, this lecture is about solar radiation. Because, when we are talking about the solar photovoltaic technology, the fuel to the solar photovoltaic technology is the radiation. And we should know how much is the radiation falling. So, that we can find out how much is the energy that is generated by PV module. So, we should know what is the input to the module. And in order to find out we also should know how the motion between the earth and the sun is happening, how the intensity is changing, why there is a season, why there is a summer, why there is a winter, what should be the ideal inclination angle of a module. So, that you can collect the maximum possible energy from your module. So, these are the basic questions that we want to answer in this particular lecture. Again be ready with your questions at the end. Topics to learn for example, is how much solar radiation we receive from the sun, how does sun moves around the earth apparently actually the earth moves around the sun, but how the sun moves around the earth apparent that is referred as apparent motion. How to install a solar PV module to collect the most solar radiation possible. So, these are the three main question we are looking at. This is the basic information about the sun that it is a very large sphere of diameter transfer of distance, having a distance transfer 11 meter from earth, having a diameter of transfer 9 and it is having a black body temperature of 5150 degree centigrade that is the temperature and the power that is received in the range of petawatt or 10 to 7 watt. The earth is revolving around the sun in a not a circular manner, but a elliptical manner and there are two focal point of ellipse and earth is the sun is actually one of the focal point, but the eccentricity of the ellipse is very small and therefore, you almost feel that that the motion is almost circular, but not exactly circular. So, this is what happens we can quickly go forward. There is a term what is called the solar constant. This is the amount of solar radiation received outside the earth atmosphere and that value is a constant it is about 1367 watt per meter square. That is the power density you can say this is the power density of the solar radiation received outside the earth atmosphere. Now, because the earth is not moving in a circular motion around the sun it is moving in a elliptical motion. So, therefore, the distance between sun and earth is also not constant. So, when earth is here the distance is larger when earth is here distance is smaller. So, because the distance will change and therefore, the intensity of the solar radiation will also change. So, 1367 is a average value of the solar constant, but it actually varies and this variation can be calculated using this formula. Very simple formula ISC is actually 1367 ISC dash is what you want to calculate for any given day. This day is given by here n and come back to that in the solar radiation we need to whenever do the calculation we talk about the day of the year. So, in many formulas this day of the year come it will be represented by a symbol n, n is the day of the year. So, when you take n equal to 1 actually it means January 1, when you take n equal to 2 it means January 2, when n equal to 31 it means January 31 and so on and n equal to 365 should mean December 31st. So, this is what the n represents, n represents the day of the year. So, that is what is shown. So, once you put the value of n you can actually solve this equation and you can find out what is the solar radiation outside the earth atmosphere. Remember I am talking about it is outside the earth atmosphere only it is called the extra terrestrial solar radiation. We may skip this, but basically this is showing that because the sun is a kind of body at very high temperature it radiates the energy in the various wavelength and this wavelength can be estimated the power density at each wavelength can be estimated this by the playing planks black body radiation will not go into the details of that, but we can find out and eventually what happens is the spectrum the electromagnetic spectrum is a very wide spectrum covering large range of frequencies and wavelength. The solar spectrum is particularly concentrated around this band. So, solar spectrum consists of ultraviolet radiation small portion it consists of a visible spectrum small portion and it consists of an infrared radiation. So, the solar spectrum consists of this part. Now, at this point we should now start thinking about the spectrum or the way energy is coming to the earth and this energy comes in the form of photons or the quantum of energy everybody must have heard known about this and the energy of the photon is given in terms of the h and the nu. This parameter is when you put this value of parameter and when you put the value of nu or the frequency which is c by lambda c is the speed of light and the lambda is the wavelength. So, basically when you actually simplify this equation you will get the simplified expression that is equal to e is the energy of the photon incoming photon in is equal to 1.24 divided by the wavelength in the lambda and this wavelength should be given in micrometer and this energy will be given in electron hold. So, when we talk about the solar spectrum we can talk about the spectrum in terms of the wavelength of the photon. So, solar spectrum value of the wavelength varies from about 400 nanometer 380 nanometer to be precise and it will go all the way into infrared where the wavelength is in the couple of micrometer. So, 4 micrometer 3 micrometer or we can talk about the energy how to find out the energy you can use this formula to find out the energy. Many times we refer to the photon also by the color. So, we say it is a blue photon we refer to as a green photon we referred as a red photon or we referred as a infrared photon. So, when we say it is a blue photon so what is the energy of the blue photon the wavelength of the blue photon. So, this is one calculation that you will also do in the tutorial. So, basically when we say the blue photon we are saying that the wavelength of the photon is or the lambda of the photon is 400 nanometer or we will say 0.04 micrometer I want to calculate the energy. So, energy is 1.24 divided by lambda and it should be micrometer. So, I should divide it by 0.4 how much is this how much this will be if you divide 1.24 divided by 0.4 you will get about 3.1 electron volt. So, your energy about that so this is a proximate number more precise calculation you can do using the calculator. So, you can do this similarly you say I have a let us say green photon will have let us say wavelength of green photon is 515 nanometer green photon will have the 515 nanometer wavelength you can say it is 0.55 micrometer and similarly you can calculate the energy of the green photon using this and you will get that this number is again about more than 2 electron volt or 2.5 electron volt. So, you can calculate this in this way you can actually represents a photon by its wavelength you can represent photon by its color and you can represent photon by its energy also. So, the energy of the photon in a solar spectrum varies between higher side that is ultraviolet photon will have energy of about 3.5 electron volt and at the lower side as you go from ultraviolet to the blue light to the green light and the lower yellow and the red light and infrared radiation the energy decreases wavelength increases energy decreases. So, the at the infrared side the energy of the photon will be only about 0.3 electron volt. So, the range of photon energy varies from lower side 0.3 electron volt higher side about 3.5 electron volt. So, then I was talking about the solar radiation and we have learned about the solar constant which is the which is the solar radiation outside the earth atmosphere it is called the extra terrestrial solar radiation, but what we are interested is in what reaches the earth surface what we are interested in what is the solar radiation available in earth surface. So, while the solar radiation it passes the atmosphere and actually goes through certain interaction or it may not go through interaction. So, if it does not go through any interaction with the atmosphere it is called the direct radiation. So, if the light is coming directly it is called the direct radiation if the solar light comes this ray comes and it gets scattered because of the particles in the atmosphere it may be gas particle it may be you know dust particle it may be some other molecules of CO2 O2 etcetera water vapors it may result in scattering and because of that the angle or the direction of the light reaching the surface will change and therefore, you have the diffuse radiation. So, this is the direct radiation and you have the diffuse radiation sometime what happens that ray coming may get absorbed in the atmosphere and may never reach the earth surface then it is get absorbed. So, then we have two types of radiation one is called the direct radiation coming to the earth surface without any interaction and the other is the diffuse radiation which is coming to the earth surface by some interaction and therefore, the angle of the radiation is not fixed. The light that comes inside our room through the windows are actually a diffuse radiation that comes inside. So, this is one thing direct radiation and diffuse radiation and the sum of the two radiation is the total radiation falling on a given surface and the sum of the two radiation is called the global radiation. So, you normally when you want to find out we have the what is called the direct radiation plus diffuse radiation and the sum of the two is a global solar radiation. So, normally we are interested in the global solar radiation. There is one other terminology that we should use here and learn here is kind is the distance that is travelled by the rays in the atmosphere. So, when we are talking about the solar radiation outside the earth atmosphere means the distance travelled is 0 and therefore, the distance travelled by rays in earth's atmosphere is called air mass AM. The distance travelled by the rays on the earth's atmosphere is called air mass or abbreviated as AM. This is the one term which we will use many times now onwards. So, please note it carefully air mass is the distance travelled by the solar radiation in the earth's earth atmosphere. So, when you are talking about solar radiation outside the earth's atmosphere distance travelled is 0 and therefore, the solar radiation is referred as a air mass 0 radiation. When the sun is exactly vertical on the head top of the head then the distance travelled by the sun rays is exactly equal to one air mass thickness of one air mass and it is referred as air mass 1 and the corresponding to the that is referred as the air mass 1 spectrum. Solar spectrum which is directly coming when the sun is exactly on my top of my head is the air mass 1 spectrum. But we know that the sun ray sun is very for a very small amount of time sun is on the overhead normally the sun is in the morning it has a very low angle then it comes to the overhead in the evening it goes to the other side and therefore, most of the time the distance travelled by the sun rays is more than one air mass. So, if you for example, if the angle made by the sun rays with respect to vertical is theta then the distance travelled is this this is the distance travelled and this distance travelled air mass is given can be given by 1 over cos theta very simple trigonometry you can also find out that the distance travelled at any angle is given by a m 1 over cos theta. So, once you know your theta you can find out what is the distance travelled by the. So, if this is our surface this is a small sphere and this is my vertical in if the rays are coming at some angle like this this is my theta. So, I am interested in this distance I am interested in what is the distance x and to y here. So, this is my distance and this is the air mass which is can be given by 1 over 1 over cos of theta. So, once you know the theta you can find out the air mass simple. So, I hope this is very clear to all of you because we are going to use this term air mass several times. So, when air mass is 0 I told about. So, we are talking about the solar radiation outside the amount of solar flux a radiation is 1376 watt per meter square air mass is 1 which is overhead 1105 when is air mass 1.5 this is corresponding to the angle which is of 48 degree with respect to the vertical. So, vertical is this. So, if you make a 48 degree like this then then air mass travelled is 1.5 and at under that some condition you get 1000 watt per meter square and you may many of you know already that solar PV cells and modules are actually characterized for 1000 watt per meter square of solar radiation. So, this is the standard radiation which is used for characterization. So, when you buy a solar PV module the manufacturer guarantees you the module output is let us say module is 100 watt P they guarantee that module output is 100 watt only under 1000 watt per meter square air mass 1.5 spectrum. So, that is the importance of the air mass the PV people use it for characterization and for the rating of the PV module also when people tell about the record efficiencies or the cell efficiencies these efficiencies are for the air mass 1.5 spectrum. So, please take a note of that also carefully. Now, we have the global solar radiation and global solar radiation is sum of the diffuse and direct and normally there is 10 to 15 percent of the diffuse solar radiation depending on the sky. If there is a cloudy condition your diffuse solar radiation will be higher if the sky is clear your diffuse solar radiation will be lower. So, this is what is the spectrum we will get. Remember why we are doing all this exercise about the solar radiation because first of all it is useful to know this. So, that I know how my solar cell is working. Secondly it is useful to know so that I know how to install my solar PV module so that I can collect as much solar radiation as possible. So, this is the spectrum that you get the line is the black body fitting the yellow curve is the actual curve outside the earth atmosphere and the red curve is the amount of solar radiation received on the earth surface. Here you have the watt per meter square per nanometer wavelength and x axis is the wavelength in nanometer. Now, you can see that there are this deeps here and this deeps as I said because of the absorption of the radiation in the earth atmosphere. So, here corresponding element is also written. So, water vapor absorbs at about you know 1200 nanometer 1400 nanometer CO2 absorbs also some portion and this is what is the spectrum that we get on the earth or surface and this is by the way corresponding to air mass 1.5 spectrum. This spectrum is shown here is air mass 1.5 out of the total radiation we receive about 7.6 percent which is the wavelength 0.15 to 0.38 comes in the ultraviolet radiation 48 percent comes in the visible spectrum. So, most of the solar radiation we receive is actually in the visible range starting from 318 nanometer or 0.38 micrometer to 0.72 micrometer infrared radiation 0.72 to 4 micrometer 43. The question here is how can we measure this radiation at a given time how much solar radiation is falling on earth surface how can we measure this and in your experiment that you are going to do in the afternoon not this afternoon, but some other afternoon you will do may be today afternoon some people already will do that we have provided you a solar cell with the characteristic and the current output of a solar cell in a short circuit model actually give you the amount of solar radiation falling. In practice how do we people measure the solar radiation in using a pyronometer. The pyronometer is a is a as having two glass domes there is a metal as a metal which is sitting there. So, what you do in the pyronometer is you have the you have a metal sensor which is sitting there this metal sensor then you have the glass dome 1 and 2 glass dome this glass domes are there to protect this metal from the environmental contact. So, when the solar radiation falls on this detector it heats up. So, the more solar radiation falling on it more heating will cause. So, the temperature the temperature of this plate will actually tell you how much solar radiation is falling. So, that is the idea of the pyronometer. So, pyronometer work on this principle. Now, you can see the it can take the radiation from all direction it can take this radiation can take this radiation it can take this radiation or radiation can come from any other direction. What does it mean will it measure the direct solar radiation or will it measure the diffuse solar radiation or will it measure the global solar radiation? What should it do? It should actually measure the global solar radiation because it can take the radiation from all directions. So, it will take the diffuse radiation as well as the global solar radiation. So, when we want to make a direct solar radiation only then what we should do we should avoid the diffuse component. When we want to measure the direct solar radiation we want to avoid the diffuse component that can be avoided if you have a long tube the principle remains same if your long tube backside there is a metal sensor that is setting which again the temperature of the metal is proportional to the radiation falling, but now because the tube is long any radiation which is coming from the other direction will not be collected and therefore, you will get only the direct radiation it is called the pyronometer. So, by using the pyronometer and pyronometer you can actually measure the diffuse and direct solar radiation. So, this is I have already shown you how you can do the measurement in the pyronometer. Now, let us see how does the solar radiation vary and some of the important dates which will actually useful for us to find out the inclination of the solar panel for optimum collection. This we know very well that earth is divided in the longitudes and latitudes. Normally, latitudes we go from 0 latitude to 90 degree north latitude from 0 to 90 degree south and in the longitude we go from 0 to 180 degree on either side 0 180 degree east and 0 to 180 degree west. Now, the so if this is my earth surface this is my the plane in which around with this earth is moving. So, around with the earth is rotating now my earth is it is actually inclined it is normally it should be like this, but because my earth axis inclined it is actually like this earth axis is like this and what is this? This is the plane in which there is a motion is taking place between the earth and sun. So, this is the plane in which motion is taking place earth is here it takes rotates in this plane, but it axis is actually tilted. So, that is what we should note here that earth axis is tilted and this tilt is 23.5 degree. So, because of this tilt there is an angle between the equatorial plane equatorial plane is plane of the equator and the plane of revolution. The plane of revolution is one plane in which the earth and sun is always actually in this plane and the equatorial plane is the plane of the equator and this plane will make an angle and this is the reason why there are seasons on the earth surface and this is the reason why you know winter you will get less radiation in summer you will get more radiation things like and let us try to understand that. This is one very nice schematic which is available on the web. So, you can get important terminology for example, here summer. So, you have the winter in the summer. See what is happening this is the north pole here I hope everybody can see north pole is in the dark condition under this situation under this situation north pole is in a bright condition while this two days in this two days which is called spring equinox and autumn equinox. The pole is just at the bisection of a bright part in the dark part of the earth I will come back to that. So, again this is the same thing this is a equinox condition by the way there are two important days equinox is the day when the day length is equal to the night length equinox is the day when the day length is equal to the night length this happens twice in the year. When it happens it happens the equinox is a day length equal to night it happens in the March and it happens in September March 21st September 21st very simple. So, in this position the equator the plane of the equator is the same as the plane of the rotation plane of the revolution. So, basically equator is perpendicular, but there are other days when which the other line the plane line here is the plane of equator and this is the plane of rotation and let me draw you in. So, this is sun and this is the earth. So, this revolution is taking place here this is earth then this is the plane of revolution in which the rotation is taking place. Now, because my earth axis is inclined. So, normally it should have been like this, but axis is inclined. So, actual north is like this. So, perpendicular to this there will be a plane of equator. So, my plane of equator is like this. So, this is the angle that equatorial plane this is equator plane this is the plane of revolution and this is the angle. This is important that there is angle that exist like this. So, on the day of equinox this angle is 0 on some other days which is called the solstice there is the maximum condition this angle this angle this angle I have shown you this angle can vary between this angle can vary between 0 to 23.45 degree it can be either plus 23.45 or it can be minus 20. So, it can become 0 also. So, this is the equinox is the day when the angle is 0 and the solstice is the day when angle is maximum 23.45 this solstice day occurs on 21st December and 21st June these are the two extreme conditions fine how does it affect. So, here I have shown the various angles. So, when you talk about the equinox there is a March equinox March 2021. So, you have the and this angle which I have shown you here by the this angle is called this angle is called declination angle declination angle angle between the plane of revolution which is joining the center of the sun to the center of earth with the equatorial plane. This is the declination angle declination angle is given in terms of the delta. So, delta value the value of delta can be 0 it can be plus 23.45 or it can be minus 23.45. So, in the equinox day delta is 0 as the position March and September on other condition the solstice day you can see the declination angle is minus 23.45 in one situation when is the equatorial plane is above. So, it is measured in this direction. So, above the equatorial plane sorry above the revolution plane and in this case it is lower. So, it is plus 23.45. So, June is delta is plus consider positive in the June and in the December it is considered negative and all other days it varies from 0 to 23.45 plus and minus how does the sun appears to move actually it is the earth which is revolving, but we feel that sun is moving and therefore it is called the apparent motion of the sun. How does the sun appears to move the sun moves in a plane on a given day this plane makes an angle equal to the latitude angle of the location. What I mean by this this is very important to understand and we will we will focus more light on this also for an observer who is sitting at location. So, this is the earth surface let us say and I am an observer I am standing here. How does a plane how does the how does the sun appears to move moves in a plane. So, what I what I showed you that this is the normal to the plane this is normal to the horizontal surface this is the horizontal surface and this is the normal. At any given location the sun moves in a plane always in a plane which is fixed at an angle. So, this is the angle which is with respect to normal and this angle is equal to the phi again we use this symbol phi very regularly phi is the latitude angle of a location latitude angle of a location. So, I mean Mumbai, Mumbai has a latitude angle of 19 degree if you go to the south then the location like Chennai will have the I think latitude about 8 9 degree if you go north towards Delhi the latitude was 23 degree or so. So, the what I mean the sun moves always in this plane. So, in the morning when sun rises sun is here in the afternoon in the 10 o'clock it will go here then it will go here in the peak position that is the noon position will go here in the 2 o'clock it will come here in the 4 o'clock it will be here and in the sun set will always occur here. So, sun always moves in a plane. So, if you look at perpendicular to the east west if you look at perpendicular to the east west you will find that sun is always moving in a plane and the angle of this plane is equal to the angle equal to the latitude angle with respect to the normal this is this is the important point to note the position of the plane in which sun moves change in a different season the second point the first point is the sun always moves in a plane. So, I am looking at the east west motion my sun is in the morning here then it goes goes goes up I am looking by the perpendicular to the east west direction. So, sun goes up and then comes down, but the position of this plane can change. How what I what do I mean I just let me go to your board. So, this plane this position is actually in the on the day of on the day of equinox but when it reaches. So, the position will become this after sometime position will become this and it goes to the extreme position the sun and this extreme position will refer to the solstice day then plane will start moving back and come here and then will start actually moving the other side it will start moving to the other side and here. So, if one is corresponding to the winter solstice the other will corresponding to the summer solstice. Now, this this plane which is this plane which is depends on the angle of the location. So, if you are leaving a equator the solar the motion of the sun always occurs in a perpendicular. The sun is always here and this position of this changes with respect to observed. If you are in Mumbai then this motion will occur at 19 degree if you go in Europe for example, Europe the latitudes will be 40 degree 45. So, sun will actually move in this and if I continue this analogy what will happen to the north pole sun will actually move horizontally in horizontal plane and that I will show you some schematics. So, if you are at a equinox day remember what is the equinox day day equal to day length equal to night length and you are at zero latitude zero latitude means equator then sun will actually rise here it will set here rise here move here go up and come down. So, at the afternoon time afternoon time sun will be exactly overhead which means there will not be any shadow of this tree there will not be any shadow of this tree. So, notice no shadow of the object at a noon time this will happen on equinox day at zero degree latitude now at some other day what will happen. So, I have represented the same thing here at the equinox zero degree latitude here observer you are sitting here morning sun is here before and afternoon it is here and the noon time it is here because the sun is exactly on top of my head the shadow is not there fine add some other latitude equinox means same day equal day length equal to night length, but at some other latitude not zero not equator now you go to the towards the north pole 20 degree what I said the sun will move in an angle equal to the latitude angle. Now, this is the example of a 20 degree latitude the sun is actually move in a plane which is 20 degree with respect to the normal so like this. So, now in this case sun is moving in this plane. So, starting at the observer before and afternoon here the noon position is here though we are day length is equal to night length equinox day length is equal to night length will there be any shadow of the object at the noon position question to all the remote centers will there be any shadow of the objects at the observer in the noon position and the answer is yes because the noon the sun is not exactly overhead it is at some angle it is some angle. So, there will be an there will be a shadow here which is also shown here that now this tree will have shadow and you can continue this analogy. So, I will just so you can continue this and if you go towards the north pole sun will appear as if it is moving in a horizontal plane it will appear as the sun is moving in a horizontal plane. So, this is analogy I hope it is clear to you. So, that was the day and now the solstice day the equinox day when the day length is equal to night length the solstice is extreme position. Now solstice day is 0 degree latitude also the sun is actually not overhead in the afternoon position I will show you how. So, first of all I am talking at 0 degree latitude what does it mean the plane is moving vertically with respect to observer. So, if the observer the sun will be in the horizontal sun's positions are this. Now, this is on equinox day what other day what I said with respect to observer with respect to observer the position of the plane will change the position of the plane is going to change. So, the plane will be here in one case and other case. So, in case of winter it will be here in case of summer it will be here. So, now in winter position sun is here in the noon time. So, it is making some angle. So, there will be a shadow same thing in summer position also sun is here. So, with respect to observer it is making some angle. So, therefore, there will be shadow. So, this is how we can understand the motion of the sun and various planes under the various locations also. So, that is what I am saying that if you are 0 degree latitude same thing I have shown here your sun moves in this plane then the plane itself moves as the time passes the plane itself moves goes to the extreme position then it come back equinox day this is the second equinox and then it goes to this side comes to the extreme condition and then it comes back exactly same thing happens with the plane of the plane in which sun is moving for all other locations in the world. Plane the sun always moves in a fixed plane which is equal to the latitude angle and the plane itself can change with respect to season. So, this is what will happen in one position extreme position is 23.45 degree this side in other position summer it will be 23.45 degree this side. This is example of a 0 degree latitude, but normally all the locations in India is having higher angles. So, in normally higher latitude angle. So, normally our plane will move like this. So, at one place it in one position it is like this phi is the latitude angle of the location and then other location it is going to be like this and the other extreme position is this fine. This angle is phi which is equal to the latitude angle. Now, this angle which is the extreme position, but as I said this angle can change when the plane is near this angle will change and this angle is given by what is called the declination angle. The angle between the center of the sun to center of the earth plane and the equatorial plane is given by the declination angle. The extreme number is 23.45, but this can change. So, here it is the one case and then you can have the another case also. So, for example, so I am talking about a place in India which is having a latitude of 5, this is one angle. Now, this plane position will change. So, let us say this plane has now changed to this location. So, angle with respect to normal remains 5 itself, angle remains 5 itself with respect to normal, but now I am sitting here. My observer is a fixed at a location the only the position of the plane is changing. So, I am sitting here. So, now actually the at the noon time. So, this is the noon position of the sun, the angle made is this. So, this is the phi and this angle is delta. So, the total angle with respect to the normal at the observer location, total angle with respect to normal is phi plus delta. Now, the delta value will change as I said it can be 0, it can be plus 23.45, it can be minus 23.41. So, therefore, we should put a plus and minus. So, the total angle with respect to normal is 5 plus plus or minus delta and depending on the motion of this plane, depending on the motion of this plane which is shifting its position as per the season. So, that is what I showed here. Now, so the question is if I want to collect the maximum amount of solar radiation, how should I install my module? If I want to collect the maximum amount of solar radiation, how should I install my module? The simple answer is that your module should always be perpendicular to the rays. If your rays are coming this way, your module should be like this. If rays are coming from the top, your module should be like this. If rays are coming from this, your module should be like this which means that my position of my module should be changing all the time. From morning it will be different, 10 o'clock, 9 o'clock, 11 o'clock, 12 o'clock, every minute, every second it should be different. But then this is called the trekking of the sun. You have to trek the sun, but many times because of the cause reason it is not possible to trek the sun. You cannot do that and therefore, you would like to install a module at a fixed angle. You fix the module so that you can get the maximum radiation under that condition. So, what is that condition? That we need to find out. So, the condition is that I want to find the angle with respect to the now either. So, angle with respect to vertical is 90 sorry 5 plus delta or 5 minus delta with respect to vertical, but with respect to horizontal it is 90 minus 5 plus minus delta. So, this is the angle that you want to, this is the angle that you want to install your module so that it will have maximum radiation in the afternoon time. We are actually positioning our collector only with the afternoon time because afternoon is the time when you will get the highest solar radiation. So, afternoon is the time we will get the highest solar radiation. Therefore, whenever we want to install a module in a fixed position we are always considering the afternoon time only. So, here is the note it says noon time position perfectly noon time. So, with respect to vertical if I have module installed at 5 plus minus delta I will get maximum or with respect to horizontal 90 minus 5 plus minus delta. So, this is so this is where we will stop and I will continue this in the next lecture. But you can think about you can ponder about if this is my condition if this is my condition if this is my afternoon position then where should be my module installed. So, this is the let us say this is the winter season and this is the autumn season. So, in autumn season if I want to install my module it should be like this this is my module perpendicular or if I want to install I want to make it suitable for the winter then actually I have to have angle like this. So, that is perpendicular. So, the angle of the module even if it is fixed to collect the highest amount of solar radiation in the afternoon will also change and it will change us for the season and you know from your experience that in the summer sun is sun comes to the overhead position. Therefore, the module should be nearly flat or with some angle in the winter sun actually becomes what we call in our Hindu calendar become Dakshinayan. So, therefore, sun the module has to face towards the south it has to face towards the south and that angle will always be with respect to now I am I am trying to give the angle with respect to horizontal. So, this is the angle of installation. So, it will be 90 minus 5 plus minus delta. This is the angle of installation for a given location on a given day. Now, the phi is fixed your value of phi is fixed, but your delta is changing every day. So, in the next lecture we will learn how the delta is changing. The delta changes from 0 to plus to 23.45 it goes to minus 23.45 and again becomes 0. So, in the next lecture we will actually calculate what is the value of delta and once we do that we can actually find out what is the optimum installation angle of a module. So, that you collect the best possible solar radiation on the afternoon. So, this will continue in the next lecture. I hope when you go back home today in the evening please go through the slide and try to understand the sun earth movement, the concept of air mass, the concept of equinox and solstice and the concept of the motion of sun in a given plane and the fact that sun the plane is angle of the plane is fixed that plane itself moves as per the season. And once we know that we can actually find out what is the best possible inclination of a module. So, that you can collect most amount of solar radiation in the noon time and because the value of delta is changing every day your angle should also change every day, but that is not possible and we will see what we can do. So, I will stop here for the second lecture. Thank you very much and I will take some more questions before we break for the lunch. NIT Surat, can you ask question if there is any question? Yes sir, if we install our solar power plant on a water bed the impact of temperature will increase the efficiency of the power plant. Yeah, I got your question. So, wait for couple of more lectures and you will get the answer. Thank you sir. Hello, Jabalpur. Sir, I am asked a good question, the cost of the solar plant is installation is much more, the cost capacity factor is the solar is very low. So, how can generate a efficient bed to generate per unit cost? How can you have the per unit cost using this method? Okay, so the in order to reduce the per unit cost of course you want you should try to collect as much radiation as possible. One way of collecting the more radiation is actually take your modules as per the moment of the sun. So, if you keep your modules perpendicular to the sun all the time then you are going to collect more radiation, but so that will increase your capacity factor of the plant. So, normally without tracking your plant capacity factor is about 0.151617, but if you do the tracking your capacity factor can increase to 0.2, 0.2122. One last question Varangal. Sir, my question is that in every season can we put our module normal to the sun always? Is that is possible sir? To get the more efficiency of the radiation? Yes, it is possible to put your modules normal to the sun in all the conditions. The only problem is that your module has to be changing its position all the day throughout the season and that mechanism either you can do manually or you can have you know automatic arrangement to do that and moving the modules actually aids to the cost of the system. And many times people find that the tracking solutions which are available commercially right now are not so cheaply available. And therefore, if you look at the all the power plant that are established in India right now are not actually of movable type they are fixed. But yes if you move the module all the time definitely you will get more energy. And people have shown by calculation that if you continuously follow the sun in the two axis you can actually get about 30 to 40 percent extra electricity. Thank you to all of you. See you good bye.