Solar Geometry

Summary

The video explores the fundamentals of solar geometry and its implications for building design. It explains the Earth's relationship with the sun, detailing the concept of solstices and equinoxes. Key concepts like solar radiation, solar time versus local time, and sunpath diagrams are explained. The video shows how solar angles affect building orientation and design with a focus on shading and temperature control. Examples from different latitudinal locations in India are provided to illustrate these impacts.

Highlights

• Solar geometry involves understanding the Earth-Sun relationship 🧭🛠️
• Key solar events like solstices and equinoxes shape our climate 🌄🌅
• Mapping the sun's path is crucial for efficient building design 📐🏗️
• Solar radiation impacts building orientation and energy efficiency 💡🔆
• Practical examples show how latitude affects solar exposure in India 🇮🇳🌞

Key Takeaways

• Understand the Earth-Sun relationship and its influence on climate and design 🌍☀️
• Learn about solstices, equinoxes, and how they're vital to solar geometry 🌞
• Discover how solar angles and sunpaths are projected and used in architecture 🚀🏛️
• Differentiate between solar time and local time and their significance ⏰🕰️
• Explore practical examples of solar design implications in different regions of India 🏡🇮🇳

Overview

In this module, we dive deep into the fascinating world of solar geometry. First, we unlock the secrets of how the Earth and Sun waltz around each other and what that means for our climate. Key solar events such as solstices and equinoxes are explained, shedding light on their importance in predicting and harnessing solar energy.

Next, we uncover the art of mapping the sun's path through the sky with sunpath diagrams – a tool that's indispensable for architects and builders. We learn the differences between solar and local time, both crucial for accurately predicting solar exposure and its implications on design.

To bring theory into practice, we take a virtual journey through various locations in India, understanding how local climates and latitudes influence building strategies. These examples highlight the ingenious ways solar geometry can be used to enhance energy efficiency and comfort in architectural design.

Chapters

• 00:00 - 00:30: Introduction to Building Science In this chapter, an introduction to the course 'Principles and Applications of Building Science' is provided. It marks the beginning of the course and sets the stage for the forthcoming modules.
• 00:30 - 01:30: Solar Geometry and Earth-Sun Relationship The chapter focuses on the intricate relationship between solar geometry and Earth's interaction with the Sun, specifically through sunpath diagrams. It discusses the differences between solar time and local time, exploring the implications of solar radiation for both measurement and effect. In the context of building design, the chapter highlights how solar geometry plays a crucial role in architectural considerations. Additionally, it revisits known concepts, aiming to deepen the understanding of the Earth-Sun relationship.
• 01:30 - 04:30: Solar Geometry in Building Design The chapter 'Solar Geometry in Building Design' explores the significance of the Sun as a source of energy influencing Earth's climate. It emphasizes two key concepts: the apparent movement of the Sun, described by solar geometry, and the flow of energy (heat and light) from the Sun to Earth. These principles are crucial for understanding climatic building design.
• 04:30 - 06:30: Sun Path and Solar Radiation The chapter "Sun Path and Solar Radiation" explores the basics of solar geometry and the energy flows associated with it. It emphasizes the heliocentric view where the sun is at the center, and the Earth moves around it over 365 days. The Earth's constant axial tilt at 23 and 1/12° relative to the equatorial plane impacts how solar radiation interacts with buildings, which is crucial for architectural planning.
• 06:30 - 08:30: Impact of Latitude and Longitude on Solar Time The chapter discusses the impact of latitude and longitude on solar time, focusing on solstices. It describes the Northern Solstice, occurring on June 21st and 22nd, as a time when daylight is at its maximum and night time at its minimum in the northern hemisphere, often referred to as the Summer Solstice. Conversely, the Winter Solstice, or the Southern Solstice for the northern hemisphere, occurs on December 22nd, when day lengths are at their shortest.
• 08:30 - 11:30: Understanding Solar Radiation The chapter 'Understanding Solar Radiation' discusses the concept of the Earth's axial tilt and its impact on seasonal changes. It explains that a 23.5° tilt is commonly associated with the term Southern Solstice in the Northern Hemisphere, also known as the Winter Solstice, which occurs when the shortest day and longest night of the year happen, usually bringing minimum temperatures. Additionally, the transcript mentions the Equinox, a period where there is 0° axial tilt, occurring twice a year around the third week of March and September.
• 11:30 - 16:30: Solar Temperature and Building Implications The chapter discusses the critical dates necessary for understanding solar geometry, including the summer solstice in the Northern Hemisphere, two equinoxes in March and September, and the winter solstice. It highlights the differences in temperature associations between the Northern and Southern Hemispheres.
• 16:30 - 19:30: Design Implications and Optimal Building Orientation This chapter discusses the design implications and optimal building orientation in relation to solar geometry, focusing on regions near the equator, such as India and parts of Asia. It explains the impact of the Northern and Southern solstices, detailing how these affect seasonal changes in sunlight exposure at different latitudes, specifically between the Tropic of Cancer and the Tropic of Capricorn. The aim is to understand how these factors should influence architectural design to enhance efficiency and comfort level.
• 19:30 - 20:30: Summary and Conclusion In this chapter, the discussion focuses on 'Summary and Conclusion' where the implications of solar geometry on design are emphasized. It begins with mapping the sun's position, which involves adopting a Locos Centric Theory and understanding two specific angles that help project the sun's movement on a two-dimensional plane. These angles form the basis of a trigonometric projection. The first angle discussed is the altitude angle, which is considered regardless of any orientation.

Solar Geometry Transcription

• 00:00 - 00:30 [Music] [Music] welcome to the course principles and applications of building science this is the first module here we will start with
• 00:30 - 01:00 solar geometry mainly we will talk about Earth and relationship sunpath diagrams and what is the consequence of it on the solar time and local time how they are different solar radiation specifically we will look at how to measure and what are its implications finally we will look at how does that affect how does that affect building design what are the design implications to start with we'll look at Earth Sun relationship some of this we already know we will relate it more with
• 01:00 - 01:30 climatic building design the climate of Earth as you know is driven by the energy input from the Sun Sun is a source of energy there are two essential aspects that person has to understand one is the parent movement of the Sun or you know if you take a geocentric theory it is apparent movement of the sun where the sun's position is that is a solar geometry we typically refer as and number two is the energy flow from the Sun be it heat energy be it light energy it is energy flow from Sun to the Earth
• 01:30 - 02:00 and how to handle it whether you will include it in the building or exclude it in the building so two primary things one is the solar geometry number two is the energy flows associated with it considering a heliocentric view you have sun in the center Earth is moving around it 365 days the axis which is subtended with the equatorial plane and the sun this particular angle the tilt of Earth is 23 and 1 12° this is constant tilt as the Earth moves around you start getting
• 02:00 - 02:30 two typical extremes one is called Northern solistes that is when 23 and 12° plus that is on June 21st and 22nd it happens that is the day times are maximum the night times are minimum in the northern hemisphere typically we call Northern solistes for countries or locations in northern hemisphere this is called Summer solistes on the other side winter solistes are the Southern solistes for northern hemisphere which is called which occurs on December 22nd
• 02:30 - 03:00 that is - 232° tilt typically this is referred as Southern solce for locations in northern hemisphere we refer to this as winter solistes this is where you know you get the shortest day and longest night typically we get minimum temperatures in this particular season apart from this when Earth is typically you know there is a 0° tilt you call it as Equinox it occurs twice that is March third week of March and third week of
• 03:00 - 03:30 September so there are four important dates which are critical if we have to understand solar geometry first is Northern solistes are summer solistes for Northern Hemisphere next is two equinoxes which occurs in March and September and the last one is winter solists or Southern solists which occurs mean which typically is a minimum temperatures associated with Northern Hemisphere it is exactly the opposite for sou southern hemisphere here so
• 03:30 - 04:00 during Northern solists they have Winters and during Southern solest they have their Summers so we have equator here Tropic of Cancer and Tropic of Capricorn 23 and 12° North 0° and 23 and 12° South so we are talking primarily about India or Asian part so primarily we will look at what happens around here and what is the impact of the solar geometry on this particular our particular location
• 04:00 - 04:30 so if we have to understand more or if we have to derive some implications of the solar geometry on our design we have to start mapping the sun position the first step is to get into a Locos Centric Theory and get two typical angles to map the sun's position on a two dimensional plane sun is a 3D movement moving so from that you are deriving two typical angles from which you can project it is a trigonometric projection first thing is the altitude angle wherever whichever orientation it
• 04:30 - 05:00 is you typically take a horizontal plane and you mark the position of the sun the angle which is subtended with the horizontal plane is called altitude angle higher the altitude angle sun is towards your head that is 90° means sun is just above your head typically you know if you say East and West you get very low altitude angles next is azimat angle which you can take either North or South as reference many cases you take North as a reference and wherever the sun's position is irrespective of its
• 05:00 - 05:30 altitude angle where it is located you typically project it down and take the angle difference between are the angle subtended from north for example when sun is right on the Eastern side you can say it is 90° or towards the West it will be 37 270° if you are taking North as a reference point if you have to really calculate altitude angle and azimo Tangle these are trigonometric calculations so you need few indicators like declination which we talked about
• 05:30 - 06:00 earlier you need the hour angle from solar Moon then you will need the number of day of year so with these things there are some formulas we are not going to work out as a part of this module but if somebody is interested these are if you know these three to four numbers it is easier to locate the position of the sun it is easy to calculate altitude and azimat angles we will go more with a graphical representation given the shorter duration of these specific modules let us consider two specific
• 06:00 - 06:30 examples to get a better picture of these solar movements first let us take a location Sagar typically northern part of India the latitude is 34.1 De North and longitude is 74.8 De East first let us look at what is the impact of change in Latitude so we will be considering Sagar first followed by trandum which is in the southern tip of India so first the next we will look at longitude where we will talk about the solar time how to calc
• 06:30 - 07:00 local derive local time from that so we will look at that first let us take a look at the latitude of the place 34° North there are three images this is summer solists where you have you know here we are referring to the Northern solistice or summer solist is here sun's position it rises somewhere then at this point then it moves traverses sets here typically you get sun right above the head this is on Summer solistice
• 07:00 - 07:30 it never crosses towards the northern side it is slightly tilted towards South but still you get sun from the Northeast and Northwestern side during the morning and evening times during Equinox if you see sun moves you know the sun rises here moves along and then sits in this point so typically you get sun rising exactly in the East sitting exactly in the west during Equinox but it traverses a you know it has a southern Traverse it
• 07:30 - 08:00 rises in the East traverses through South and sets in the West Winter solest you have further lower altitude angle here we are talking about three altitude angles this altitude angle is high slightly less you know slightly lesser and winter solest is December 21st here we have typically the least possible altitude angle you don't get sun directly on the east or the West it is mostly somewhere close to Southeast and South West and it has a southern
• 08:00 - 08:30 Traverse this is the case of 34° north latitude take a look at trandum this is 8.5 de north latitude much closer to Equator so when we looked at SRI nagar it is off Tropic of Cancer it is further north of Tropic of Cancer here we are talking about a location South of Tropic of Cancer much closer to the Equator if you look at the sun movement it has you know the sunrise happens somewhere close to Northeast sits somewhere close to to
• 08:30 - 09:00 Northwest it traverses not directly through South it is somewhat off the center point that is it has a slightly Northern Traverse during summer solistes it is further off so this is a center point this is South this part is North so it has a typical Northern Traverse what implication this has if you have a northern wall which has large Windows typically during summer especially in latitudes like this say 11° 10° or even you know 15° 13° north latitude you will
• 09:00 - 09:30 have solar incidence on your Northern faat and Northern Windows during summer months the lower you go towards equator like typically the case of 8° 8 and 12° north latitude you will have up to 4 4 and half months you will have solar incidence on your Northern wall so when you are blindly following a code which says or a textbook which says Sun traverses from east to west through South Northern wall or Northern f s are
• 09:30 - 10:00 you know free of direct solar radiation it might be misleading you have to closely look at what latitude it is which decides because critical months like Summers like May June July where solar radiation is also more temperatures are also more you are going to get direct solar radiation on your Northern facade here during Equinox East and West a slight Southern traverses noted it is slightly off the center point slightly traverses towards the South winter solistes the altitude angle
• 10:00 - 10:30 if you compare with shagar is not as low as you looked at shagar you don't get such a low steep penetration of solar radiation it is slightly higher in terms of altitude angle in all the three cases the altitude angle is much higher compared to 34° that is the location shagar which we talked about now let us look at something called sunpath diagram which is highly useful if you are designing a building specifically for shading devices are locating orienting
• 10:30 - 11:00 your building for anything to start with sunpath diagram is a basic requirement it is nothing but a projection a two- dimensional projection of a 3D movement mostly we refer to stereographic projection there are other types like orthographic we will look at few of them I mean just for an example primarily we are working with a stereographic projection there are other things as I said like spherical orthographic but mainly we are looking at a stereographic projection you need two specific angles
• 11:00 - 11:30 that is Altitude angle and azimat angle to locate or map the position of the sun now coming back to our two example cities shagar and trandum the solar movement can be mapped like this we looked at in the three dimension now this is what we were talking about this is your Traverse of Sun during your summer solistice this is your Traverse of Sun during winter solistice Equinox
• 11:30 - 12:00 occurs somewhere here we will look at the components more in detail this is for trandum like I said this is a Center Point these are month lines so if you see up to 4 months easily you will get direct solar radiation or solar incidence on Northern facade if you have to assess a northern facade Northern facade will fall somewhere in this Center Line again Southern facade you have to take this as a center line and see how many months or how much duration you have solar incidents on your Southern firstart so typically in this
• 12:00 - 12:30 case your Northern facade is going to have solar incidence for more duration whereas here it is only for 2 to 3 months that too slightly in the mornings and evenings which is which can be prevented or abstracted through a vertical shading system here you will also need a horizontal shade on your Northern wall in order to avoid direct solar radiation during summer in Laboratories this particular thing is studied using heliodon you might have heard of this name this is a device where you can set the solar position everything is adjustable you can set
• 12:30 - 13:00 latitude longitude solar position then mean typically these are lights which cause Shadows you can put your model and you can assess what is a shadow of penetration what is a solar incidence these things can be experimentally assist in this module we are going to look at this is a you know graphic 3D graphic which is generated by a software called ecotect we will be primarily using for demonstrations we will be using the models from EOTech as well as Associated tool called solar tool which
• 13:00 - 13:30 helps us to graph graphically represent a three-dimensional Sun Path so similar thing which we are going to look at this is a solar tool which I was talking about here we are talking about the solar path this is a stereographic projection there are different types of projections as I said spherical liid distance stereographic orthographic wall Rams you can also look at tabular mapping of it there are key components here the peripheral line represents the aimal angle which we talked about then
• 13:30 - 14:00 the concentric line talks about altitude angle these are the date lines month lines summer to inter solistice and these things are the hour lines so knowing these date and hour lines you can locate a sun's position at a particular Point other than this this particular tool lets you set the date and time say for example if we are setting June 21st then you will have summer solist is here for a particular
• 14:00 - 14:30 time you will know where the sun's position is when you change it to Winter that is December Sun position changes here you can also change the latitude of the place simply now it is 34° that is for shagar if I change it to trivandrum location the solar path that is a total Sun Path diagram varies this is during December and this is during June a simple representation of sun Movement we will look at the Shadow and Shadow assessments further in detail so far we
• 14:30 - 15:00 have been dealing with the latitude of a location and how it affects the sun's movement now in this section we will talk about the impact of longitude and primary considerations which we have to give so for this one major thing we have to understand is the difference between solar time and the local time the time used in the Solar chart is a general solar time it coincides with the Lo local clock time only at a reference longitude for a particular time zone say if you take the case of India we don't
• 15:00 - 15:30 have different time zones there is one time zone across the country though we have a vast extent from west to the east we have only single time zone the reference longitude for India is 82.3 De East latitude east longitude if you take a country like us they have a different time zones as you go from east to west of United States the time zone varies for example they have half an hour to 1 hour time adjustment every time zone as you move from east to west for a basic
• 15:30 - 16:00 understanding every degree of longitude you move it means a time difference of 4 minutes we'll use this in further calculations to understand this better let us consider two locations first is Mumbai which is 73 73° east longitude on the western side of India number two is thear which is 95° east longitude which is farther east of India Mumbai lies west of India's reference longitude that is 82° reference line it lies west of
• 16:00 - 16:30 reference line by 9.5 or 9° 30 minutes whereas diar lies on the east of India's reference longitude by 12° and 30 minutes another thing which has to be factored in the calculation is the equation of time correction it can be done like I said earlier it can be done numerically but I'm showing you a graphic indicator the simple graph which tells you how to find out the correction time correction this has along the X x axis it has a number of day that is day
• 16:30 - 17:00 of the year starts from zero it goes to 365 366 then on the y axis we have the equation of time correction this depends on the day of the year considered for example if you take 26th January it comes somewhere here 26th day of the year the time correction will be -13 minutes if you take 26th October or 27th October which is somewhere around the 300th day of the year the time correction will be plus 17 minutes using
• 17:00 - 17:30 this what we can do if you take the same case of Mumbai and the buar the calculation goes like this say for example if I have to establish what is a local solar noon what time the local noon occurs in Mumbai noon is 12:00 minus 38 minutes this 38 comes from this 9° 30 minutes if you multiply that for every longitude Dee it is 4 minutes so if you multiply you will get 38 minutes minus 13 because I'm calculating it for 26th January whereas if I'm calculating
• 17:30 - 18:00 it for say as a example I stated 26th October or 27th October the correction will be in positive it will be plus say 17 minutes here it is minus33 so this comes to 119 subtract this from 12 so you will get 51 minutes so local solar noon at Mumbai occurs 51 minutes later than Indian Standard time because it lies to the west of the reference longitude the case of diar the same way if we
• 18:00 - 18:30 calculate we find that the local solar Moon occurs 37 minutes earlier than the Indian Standard Time if India were to have different time zones from east to west then the time zone adjustments will be something like half an hour to 45 minutes for each time zone if one were to divide the country into three different time zones we'll look little bit more in detail about solar radiation two main measures are there number one is radians wat per M Square most
• 18:30 - 19:00 commonly used it is a instantaneous flux or energy flow earlier it used to be called solar intensity it's now called radians wats per square meter it can be horizontal it can be vertical and number two is IR radiation which means the energy quantity integrated over a specific time it can be per day per hour or per year total or for a specific season it is measured in wat hour per M Square looking a little bit more into the detail of solar radiation itself the
• 19:00 - 19:30 sun surface is around 6,000 de Centigrade peak of its radiation emission occurs at 550 nanom wavelength so this is a solar Spectrum we know three major things one is a visible spectrum then you have ultraviolet and infrared once the sun's energy hits Earth's atmosphere part of it is reflected back part of it is absorbed part of it is transmitted whatever component is absorbed is reradiated then after entering the air atmosphere the ground absorption are
• 19:30 - 20:00 water bodies they absorb part of it they reflect part of it whatever is absorbed is reemitted what comes in comes in as shortwave radiation once it is absorbed and then reradiated it goes back as long wave radiation these long wave radiations are trapped by the cloud cover which we generally call greenhouse effect where this radiated long wave radiation gets trapped in the Earth's atmosphere there is a large variation in a ation among different locations of the
• 20:00 - 20:30 Earth this is for three main reasons one is the angle of incidence we know the coine law which states that the steeper the angle of incidence the difference will be more number two is the atmospheric depletion again it is a factor of the angle of incidence for example if it is in the polar region the same Sun's radiation have to Traverse a long distance across the atmosphere cutting through so there is a factor which varies between 2 and 7 then number three is the duration of
• 20:30 - 21:00 sunsh sunshine for example earlier we said summer solists versus winter solists or the northern solce versus Southern solists where the sun's duration of sunshine considerably varies between June 21st and December 22nd so this has a considerable impact on the irradiation let us come back to the example of shagar which is 34° north and 74.8 de east longitude you take the same Sou wall wall surface I put some windows and
• 21:00 - 21:30 some shading systems here if you take the solar radiation incidence on a winter this is winter solce you have a steep Southern Sun this is where the solar radiation incidence occurs if you see in this scale this portion corresponds to somewhere around 3,000 wat hours this is for a particular day on the instance of December 22nd this is what is the solar radiation which occurs on the southern surface this is a total
• 21:30 - 22:00 solar radiation one more thing we have to remember is this total solar radiation has two components one is a direct radiation and other is a diffuse radiation for example consider this surface at this point of time this is around noon this particular surface is not getting any direct solar radiation but still the radiation will be there because of diffuse components diffuse radiation will still have some impact on these surfaces total radiation net radiation will be minimum lesser consider the case of trandum which is 8
• 22:00 - 22:30 and 12° north latitude this is again winter solistice the southern sun is not as steep as you found in shagar it is slightly with a higher altitude angle carefully look at this numbers the total solar radiation incident on a southern facad which is somewhere around 6,000 wat hours so the solar incidence you receive on the southern faad considerably varies between the northern part of India that is a location like
• 22:30 - 23:00 shagar versus dandrum now let us not worry about now let us not worry about what climate condition it is shagar has a colder climate versus trandum has a war and humid climate now we are not getting into the climate classification that is part of a different module the subsequent modules but just the solar radiation intensity considerably varies on a given building facade how do we account for this particular solar radiation in our building related calculation the main parameter which is
• 23:00 - 23:30 used this solar temperature solar temperature is kind of a inclusive number which if you read this equation this is T out is a outside air temperature in deg Centigrade this is a drivable temperature of outside air Sol air temperature actually includes the effect of air temperature and adds up a small component to it which is inclusive of the main thing Global solar radians wat per met Square absorptivity of a particular surface so say imagine the
• 23:30 - 24:00 same Southern facade which I was talking about if it were to be bright colored say White surface versus a black surface the absorptivity of the surface considerably varies so in that case this particular Factor will vary the third part of this small factor is H KN or the heat transfer coefficient for radiation and convection this is equivalent to the film coefficient on the outside surface of the wall so this particular factor is added to the outside air temperature So Sol air
• 24:00 - 24:30 temperature typically will be equal or more than the Ambient Air Temperature in tropical climates what happens is say imagine if you take a western facade somewhere around 4:00 in the evening there will be an ambient temperature take a case like shagar in June 21st say the ambient temperature is 30° the southern facade which we looked at the solar radiation intensity will be X plus the absorptivity of a surface imagine a white surface there will be a heat transfer coefficient so a small
• 24:30 - 25:00 magnitude say about 4 to 5° will get added up which becomes the solar temperature this is more or less equivalent to the surface temperature of a particular wall I have done some calculations using the same equation take this location this dotted line represents the outside air temperature starts from 6 6:00 this is evening 6 this is a 12-hour graph morning the temperatures are around 27° and goes up to 35° in the evening
• 25:00 - 25:30 there are two other lines in this graph this is time in hours this is temperature there are two other lines this is solar temperature on the Eastern facad this blue line versus this purple line This is a solar temperature and the Western facad interestingly if you notice the Eastern facade the Soler temperature goes as high as 40° early in the morning only around say you know 7 to 9:00 the peak occurs then it cools down comes back Bel below the Ambient Air Temperature whereas on a western
• 25:30 - 26:00 facade the Sol air temperature rise much lower than the ambient temperature and then it picks up in the evening and then it's heat now it gets heated up what is the impact on building design for example if you have to have a wall which is part of a bedroom your bedroom wall is exposed to Eastern side the Sol a temperature will go as high as 40° in the morning then it will cool down so when you want to occupy it somewhere around 9:00 in the night the surface
• 26:00 - 26:30 temperature is not that high so including the time lag which we will discuss later the inside temperatures will be relatively cooler whereas a west facing wall of a bedroom the maximum temperature occurs somewhere around 4:00 to 5:00 in the evening then this will be transmitted in so you will have relatively higher temperature surface inside surface temperature as well as heat gain through that particular wall here we did a small calculation as such solar temperature is dependent on two
• 26:30 - 27:00 main things one we earlier saw the absorptivity of a surface that is represented by a for a brighter surface versus a reflective Surface versus a darker surface number two is it can be modified with the effect of shading what happens in the case of shading moment you have a shading device or a balcony the direct solar radiation is cut but you have to keep in mind the diffus solar radiation still exist so it is not totally negated but but the direct component which is quite significant is
• 27:00 - 27:30 totally negated if you have a full cover of shadding we have calculated the solar temperature ranges for eight orientations there are three cases here the first case this is a dark blue the absorption the solar absor absorptions of the surface is4 which corresponds to a normal white painted or a ivory color painted external wall that is direct solar radiation it doesn't have any shading number two this light blue where we painted the surface with a reflective
• 27:30 - 28:00 coating today we get a lot of reflective commonly called Low Coatings which are done on the wall that is low emissive coating mainly reflective coating has been done for the second case and the third the same wall and additional shading system was added to the first case that is the absorptivity remains there is no reflective coating but additionally a shading system was provided that is the wall is completely shaded you can imagine there is a balcony present in front of the wall so what happens in the first instance
• 28:00 - 28:30 the Sol a temperature for example in the eastern wall goes as high as 47° for a West phing Wall it goes up to 51° this is in a tropical warm humid climate it goes as high as 51° in a West phasing wall whereas when you paint it with the reflective coating it can be brought as low as 41° you will find 10° difference on the external surface or solar temperature instead of reflective coating if you go for a proper shaded west facing wall you can bring it down
• 28:30 - 29:00 to as low as 37° you have to notice that this is more or less equivalent to a North phasing wall imagine you have a balcony which has a West phasing wall you cannot avoid it the better solution in today's context would be if you are in a design stage you can provide a balcony or deep overhang so as to shade the complete wall it becomes more or less equivalent to a North facing wall forgetting about the wind and other components which we are discussing just with solar radiation this can be made
• 29:00 - 29:30 equivalent to an earth facing wall or if you further don't have choice you have crossed the design stage then the next best alternate would be to look for a reflective coating but this is temporary the coating would last for around 2 to 3 years after which it loses its reflective property it has to be reced there can be a slightly better improvement with reflective coating but with a permanent shading system the whole Solar temperature can be brought down let us discuss about few design implication this particular graph two things this is
• 29:30 - 30:00 again for shagar this is winter solistice and this is summer solists this is the same solar radiation but this is a direct solar radiation graph I have split the whole thing instead of drawing a square I have made a cylindrical structure which is segmented so each of these segment represents a specific orientation say if you want to take just four cardal orientation east west north and south you can refer W hour per m Square this is Radiance at
• 30:00 - 30:30 this particular instants of time this is during winter solistes in shagar this is a southern sun summer solists this is a condition this is for trivandrum the numbers get higher during winter solists and this is during summer solistes even Northern surfaces and North Eastern surfaces get more solar radiation one important thing which we should not forget is the use of for example Northern Windows or North lights as you go down the Tropic of Cancer towards
• 30:30 - 31:00 equator Northern surfaces start receiving solar radiation it is not that Northern surfaces are totally devoid of solar radiation as you get closer to Equator what happens is Sun starts traversing towards your Northern wall as well this is considering a Locos Centric Theory with sun as a moving body you are located here Sun starts moving towards your North if your building facade is this you will still get solar radiation in your Northern facade for at least 4 months for latitudes south of Tropic of
• 31:00 - 31:30 Cancer further you go towards equator it gets more especially on equator there will be equal distribution half of the Year sun will be to the northern side half of the Year sun will be to the southern side to get a better understanding we have this graph the small box rectangle here represents a building's orientation these lines here the red one indicates the solar radiation during summer which is depicted as overheated period the blue one which is shown here this
• 31:30 - 32:00 indicates the solar radiation During the underheated period or the winter season this is an interesting graph which shows that which is a major or you know direction from which higher solar intensity comes during summer this is during winter and the green one is an annual average typically it is understood and agreed upon that your longer surface of the building longer facades of the building should not be placing Facing East and West without
• 32:00 - 32:30 enough solar protection so it is a better idea to orient it the longer surface to orient it towards north and south shorter towards East and West it is understood but still you can go for minor directional changes depending on the location for example in case of shagar the major solar incidents during summer occurs in this direction not exactly in the East but it occurs slightly away from the East and during Winters it is not directly and the South but it is towards little bit towards
• 32:30 - 33:00 East it's not Southeast but slightly ahead of East so in this case the actual right orientation of the building will be a slight tilt rather than just on the plane consider the case of trandum the case changes the maximum solar radiation intensity during summer occurs at 70° so this is where you get maximum solar radiation during summer and during winter you get somewhere around 160° this is where the max maximum occurs so a tradeoff the best orientation would be
• 33:00 - 33:30 would not be just south the longer facing not just facing south but it is somewhere around 160° that is a perpendicular if you draw this should be facing 160° this is where this would be the best case in which the building can be oriented we'll close this session here take a quick recap we studied five important things first thing is the Earth and relationship how it moves around we studied about northern solest equinox and Southern solest the Earth's Tilt then we talked
• 33:30 - 34:00 about how this Earth movement rather Sun movement would be translated into diagrams for quick reference that is sunpath diagrams the stereographic projection how it is built and how it can be used number three we talked about the effect of longitude and time zones we calculated solar time and local time then we talked about the impact of solar radiation we took specific example of a building facad and we were studying it for two different Loc locations geol locations then we studied about the
• 34:00 - 34:30 design implications that is how to orient your building considering the solar radiation before positioning a building itself thank you [Music]
• 34:30 - 35:00 [Music] [Music]