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Sustainable ArchitectureProf. Avlokita AgrawalDepartment of Architecture and PlanningIndian Institute of Technology, RoorkeeLecture – 40Energy Efficiency - VGood morning. Welcome back to this last lecture on Energy Efficiency in sustainablebuildings as part of this online ongoing course on Sustainable Architecture and I am yourinstructor Dr. Avlokita Agrawal, Assistant Professor at Department of Architecture andPlanning, IIT Roorkee.So, in the previous lecture we looked at the compliance approach for meeting up with variouscriteria set for energy efficiency in buildings and most of these criteria we followed fromECBC when we are talking about buildings energy efficient buildings in Indian context. Oneaspect of the compliance which was left was interior lighting power.(Refer Slide Time: 01:08)So, continuing from the previous lecture we will quickly look at what are the compliancecriteria for meeting up with interior lighting power. So, whenever we are talking about theinterior lighting power we are talking about the prescriptive requirements for the installedelectric wattage for interior building lighting. Now, this implies that to achieve the desiredilluminance the illuminance levels how much of the power electric power will be consumedand that is what we call as if the lighting power density.So, the LPD of an overall interior lighting system is calculated. When we are talking aboutthe compliance approach we have 2 types of compliance approach.(Refer Slide Time: 02:05)One we have for different spaces within a building. So, we call it a space function method.Now, in this space function method we have different functions assigned to the spaces. Forexample, an enclosed office area, an open plan office area or some conference or multipurpose hall or a classroom or a lecture room, for the lobby of a hotel, for emergency in ahospital for recovery and like that so this there is a huge table there is a long table and foreach of these spaces for each of these space and function lighting power density has beenprescribed.So, if you are looking at an open plan office and LPD which is 11.8 Watts per meter only formeeting up with the interior lighting requirement is prescribed. So, whenever we are talkingabout the offices the open plan area of the office will have to meet up with the LPD given asthis. Now, when we would. So, there are 2 compliance approaches; one is the space functionmethod and in this method all areas in a building specifically will have to meet up with thelighting power density requirement as prescribed here for each area.So, there is different LPD for the circulation in different LPD for the open plan officedifferent LPD for this enclosed office, for toilets, for the common areas and like that and wehave to meet up with them individually. So, this is quite rigid. So, in the space functionmethod for each space in the building the desired LPD will have to be achieved.(Refer Slide Time: 04:03)When we do that so, suppose this is for a particular building. These are the different types ofareas which are there and the total area for each of these spaces and based upon the LPDrequirements which are given which are taken from the ECBA we calculate the total lightingpower allowance which is which can be achieved which can be taken for each space andbased upon this the lighting system will have to be designed, the luminaries will have to bepicked up. Now, here the LPD of each space will have to be met individually.However, if we calculate the if we know the total lighting power allowance for the buildingwe can also go to the building area method where instead of meeting up with the LPDsindividually while maintaining the given illuminance levels as per NBC. The total LPD of thebuilding which is also as per the function of the building the type of the building the LPD canbe met.So, instead of meeting up with the individual spaces we can achieve the LPD as desired asprescribed for the total building. So, within the interior lighting power there are these 2approaches space function method and building area method. Now, when we are talkingabout lighting power this was for interior lighting, artificial lighting. We also havecompliance approach for the exterior lighting power. (Refer Slide Time: 05:48)Exactly, in the same manner as we have for interior lighting power we have the prescriptionsfor the exterior lighting applications. For example, building entrance with canopy, buildingentrance without canopy exit, building facade, driveways and parking pedestrians and likethat and then we have the power limits the LPDs. So, this is 10 Watt per meter square of thecanopied area. For driveways and parkings we have 1.6 Watts per meter square which iswhich we can clearly see that it is much lesser than that of the interior lighting power becausemore lighting is required.And just as the compliance for interior lighting is shown we will show the compliance for theexterior lighting. Based upon the total area of say the driveway or the parking and the wattagethe power consumed to light up the entire driveway up and parking and calculating the LPD.So, again we have to meet up the LPD requirement the lighting power requirement for each ofthe spaces in the exterior of the building to comply with the exterior lighting powerrequirement as per ECBC.So, when we are looking at this ECBC compliance as I had briefly explained in the previouslecture there are 3 compliance approaches so, far we have seen the prescriptive approach.(Refer Slide Time: 07:18)Where each building system or component should have a specific performance value whichcomes from directly from the prescriptive tables of ECBC. For this one it requires very littleenergy expertise you do not need to perform simulations or much calculation and all we haveto do is select the right kind of material which meets up with the prescriptive requirements ofthe ECBC and our job is done.But often to meet up with the prescriptive requirements of ECBC we have to select the highperformance materials. So, for example if you want to have a fenestration which has a u valueof 0.3 and then shgc of 0.27 it would directly imply that we have to select a double glazedwindow with a Louis coating or with selective coating. Now, that will prove to be a littlecostlier as compared to say a single clear glass building where we can provide proper shading.So, the second approach in the compliance as per ECBC was trade off method where we cantrade off the performance of one component of envelope with the other component of theenvelope. So, just as I was explaining here that in case we do not want to select a very highefficiency material as in the case of fenestration as I was just talking about. Instead ofinvesting in the performance of fenestration I may improve the performance of the roof if Iknow that there is more amount of heat which is going to be transferred through the roof ascompared to the fenestration based upon my design.In certain other design it may be the other way around that the fenestrations become moreimportant and the roof is not as important. So, I decide this trade off based upon my designand then using the equations the calculations which are given for the trade off we prove thatthe performance the on low performance factor of the proposed building is better than the thatof the base case building.The third approach is whole building performance approach where we will use the simulationtools whole building simulation tools. So, that there are different tools which are availableone of such simulation tool we will learn at length in subsequent lectures in the last 2 weeksof our course here. In this type of compliance approach whole building performance approachwe create a computer model, a simulation model of the proposed building and then we inputthe properties of all the materials which are proposed all the on loop systems HVAC systems,lighting systems, the electrical power systems, pumps everything.So, all the energy consuming components will be input in this whole building performancemethod. And the overall performance factor for the proposed building will be calculated andfor compliance it will be shown that the proposed building performs at least equal or betterthan that of the base case building. So, in this case it is not necessary that only theperformance of the envelope of the building is considered.Here, all the energy components both passive as well as active components are collectivelytaken into account and the overall performance of the building is proved to be better. So, wewill look at this whole buildings performance method in the last 2 weeks through the detailsof assimilation tool how to use a simulation tool.(Refer Slide Time: 11:41)So, this is to summarize the ECBC compliance process. We have looked at the differentapplicable building systems envelope, HVAC, lighting, electrical power and service hot waterand pumping. So, we have minimum mandatory requirements for each one of these. Aftercomplying after following these mandatory requirements we can choose any of thecompliance approaches we can go ahead with the prescriptive approach or for envelope wecan go for the trade of option.In case of trade off the mandatory requirements and the prescriptive requirements for all othercomponents will be kept as the same. They will have to be met using the mandatory andprescriptive approach only. The third one is this whole building performance approach whereall the components for all the components of building systems energy systems and buildingsthey can be changed, but the overall performance of the building needs to be complied with.(Refer Slide Time: 12:45)So, in the last 2 lectures we will be looking at the whole building energy simulation where thetool takes into account the building shape and geometry climate, heat loads, equipmentefficiencies and it calculates the hourly energy consumption and based on that the annualenergy consumption is arrived at and then we compare the performance of the proposed caseversus the base case.In addition to the energy efficient building the concept of reducing the demand of energy inbuildings the new concept and it is the concept which is quite relevant today. So, when wewere looking at the energy scenario of the world and we looked at how the future scenario forenergy is going to be. We saw that in order to contain to or contain the global warming at theindustrial levels of the global temperatures we will have to construct all our new buildings asnet 0 energy buildings. Now, what is a net 0 building?(Refer Slide Time: 14:01)A net zero energy building is a building which has zero net energy consumption whichimplies that whatever energy is going to be consumed in the building the same amount ofrenewable energy will have to be created on site. So, we do not take any energy from outsidethe site and all of it is created on the site itself. Now there are multiple variations within thisnet zero energy building.(Refer Slide Time: 14:35)So, we have a net zero site energy. We have a net zero source energy. We have a net zeroenergy cost and we have net zero energy emissions. Let us quickly look at each of thesedefinitions. The first one is net zero site energy building.(Refer Slide Time: 14:51)Now, here in this type of a building all the energy which is consumed in the building isproduced on site itself. So, this particular picture is in front of a natural biodegradable heart inSadhana forest which is part of the Oroville township. So, in this forest whatever theyconsume in these buildings which are also organic they produce them on the site itself. So,there is no transmission of energy from outside the site to the site and the site at the site thebuilding is net zero energy.(Refer Slide Time: 15:35)The neck is the next is net zero source energy building. So, when we talk about this a sourcezero energy building, it produces at least as much energy as it uses inner year when accountedfor at the source. What it implies is that it will still remain grid connected.It may draw energy from the grid at certain points of their time, but if we calculate it over theenergy use in an year it will produce the same amount of energy at the site at the source itself.So, it will still draw energy during certain periods and certain seasons while it will be givingback to the grid at certain other seasons and times of the year and times of the day. That iswhat net zero source energy building is.(Refer Slide Time: 16:31)A net zero energy cost building is a building where the net cost of the energy of the moneythat the building owner pays to the utility for procuring the energy or vice versa is. Now, thathappens in a case when the building consumes or produces energy at other times of the daywhich are off peak and supplies it back to the grid when it is the peak demand.There by selling the energy generated on site at a higher tariff and drawing more amount ofenergy which is supplied at a lower tariff. So, here we are not only looking at the total amountof energy which is consumed and produced we are also looking at the tariffs of it and sooverall the energy cost of the building comes out to be net zero. So, we are mainly concernedabout the cost of the energy which is consumed in the building.(Refer Slide Time: 17:40)And the last one of these terminologies associated terminologies is a net zero 0 energyemission building. Now a net zero energy emission building produces at least as muchemissions free renewable energy as it uses from emissions producing energy sources. So, forexample, the building is situated in a place where it is dependent upon the energy which isgenerated through the thermal power plant.So, the amount of energy which it is consuming from the energy obtained from the grid whichis largely the thermal power, energy generated through thermal power it produces the sameamount of energy using the renewable sources. So, this has to be equated and then it becomesa net zero energy emission building.(Refer Slide Time: 18:33)So, what is the approach for a net zero energy building. Now before I go into that for all thesevarious definitions the fundamental understanding for us for a net zero energy building is thatthe amount of energy which is consumed in the building an equal amount is producedsomewhere either on the site itself or off the site or somewhere. So, that the overall balance ofthe energy consumed and produced remains equal.So, when we are talking about this net zero building and the approach for it we will first haveto look at the different components energy consuming components in a building. So, we haveHVAC.(Refer Slide Time: 19:19)We have lighting load. We have equipments and appliances. We have hot water requirementand we have nice miscellaneous energy consumption. So, this is what comprises the total ofthis entire energy consumption in a building. For a building to be net zero we have to producethe same amount of energy using renewable energy sources. Once this total energy demand isequal to the amount of energy generated using renewable sources that is when the buildingqualifies to be called as a net zero energy building.(Refer Slide Time: 20:03)However, it does not mean that we continue to increase our demand and also continue toincrease the amount of energy which is generated using renewables. Because renewableenergy is also coming at a cost. It consumed natural resources it is consuming huge amount ofmetal and glass and a lot of transportation is required installation is required. So, the intentshould be to reduce the energy demand first and how do we do that we have seen it enough.First of all using the passive energy conservation measures which are integrated in theirdesign.(Refer Slide Time: 20:46)So, we talked about the building envelope, fenestration, shading devices, the passive heatingand cooling techniques, material choice etcetera. So, all of this we have seen in ourdiscussions so far. So, we reduce the amount of energy which is consumed we reduce theenergy demand.(Refer Slide Time: 21:08)Next, we employ the active energy conservation measures that is by using efficient lightingefficient appliances and we reduced our energy demand further. As we go on reducing ourenergy demand the amount of energy the equivalent amount of renewable energy which needsto be produced also keeps going down.So, once we have reduced the energy demand substantially a small amount of renewableenergy will need to be produced and the overall concept and proposition of net zero energybecomes much more feasible. So, it is a 2 step process. First of all reduce the energy demandand whatever that reduced energy demand is we substituted using the renewable energy.(Refer Slide Time: 22:05)This concept of net zero energy is picking momentum across the world and also in India. So,Bureau of Energy Efficiency launched the net zero energy buildings portal NZEB portalwhich is live and a lot of information is available on NZEB portal and a lot of information onhow to achieve this net zero energy status using what are the different passive designstrategies, what are the different active strategies.So, all of that is a very nicely properly summarized and integrated on this NZEB portal youcan go to Bureau of Energy Efficiency and NZEB portal to look for more information onregarding this. So, there are some buildings in our country which have a net zero energystatus. I am picking up some of the case studies relevant case studies more you can find outon net. So, the first case study is the a living laboratory accept university it is in Ahmedabadand it is an office and an educational building. It is a new construction building it wasconstructed new and Ahmedabad is actually a hot dry climate.The total area is approximately 500 square meter and it has a grid connectivity it is not offgrid. So, the first thing that they did was to reduce the EPI Energy Performance Index of thebuilding and they brought it as low as 58 kilo Watt hour per meter square per year. So, if youremember the numbers when we were talking about the standard buildings in India and wesaw that air conditioned building have an EPI of as high as 250 kilo Watt hour per metersquare per year that was the average.This is a substantially low number. This is a very low EPI the moment we have a low EPI itimplies that the amount of renewable energy which needs to be generated on site is also less.And after reducing the EPI the demand energy demand they have generated the renewableenergy with 50 percent of the roof which is covered with solar photovoltaics and thegeneration is equivalent to 70 kilo Watt hour per meter square per year effectivelycompensating for all the energy demand in this building.(Refer Slide Time: 24:37)So, the approach was first of all the first step was passive design strategies incorporation ofthat. So, they talked about the orientation of the building which we have seen as north southbeing the most appropriate and the best orientation, incorporating daylight strategies, addingvision windows, adding clear stories and light shells on south to bring in diffused light alongwith the occupant control so, that there is no requirement for artificial lighting during the day.Using these passive design strategies first level of energy demand reduction has beenachieved.(Refer Slide Time: 25:21)The second was thinking about the active strategies. So, first one was HVAC where instead ofjust air conditioning the entire building throughout the year mixed mode ventilation wasthought to be the was worked out where during the comfortable seasons when the outdoortemperatures and the environment is quite comfortable the mixed mode ventilation wasimplemented incorporated.In addition to that radiant cooling floor and ceiling panels were used added a variablerefrigerant flow device was used for dedicated outdoor air conditioning system which alsohad a very high COP and in it was inbuilt with the carbon dioxide sensors and controls highefficiency air cooled chillers was used and passive cooling in non summer months withunderground tank and evaporate evaporative a fluid cooler were used. All of these togetherreduced the amount of energy which was required to create indoor environmental comfortthermal comfort.And the light the energy requirement was substantially reduced for the HVAC. The same wasdone for daylight for lighting design where first of all most of the spaces were able to achievedaylight autonomy for 75 percent of the time over 90 percent of the spaces which ispractically making the requirement for artificial lighting to be close to 0 and then in additionto that occupancy sensor control of lights was also installed and overall the demand forenergy through the active strategies was further reduced.(Refer Slide Time: 27:15)Once this passive and active strategies were incorporated into the building and the EPI wasreduced to 58 kilo Watt hour per meter square per year renewable energy was further addedwhere the 50 percent of roof was covered with these photovoltaic panels and they were ableto generate the equivalent amount of energy which was consumed in the building therebymaking this entire building as a net zero energy building.(Refer Slide Time: 27:47)(Refer Slide Time: 27:48)Next case study that we have here is Akshay Urja Bhawan at Panchkula. This is a publicbuilding an office building. Again Panchkula is in is classified to be a hot dry climate. So, thenext building that we have is Akshay Urja Bhawan at Panchkula. This is an office buildingagain a new construction and the overall area for the project is around 5,000 square meter.It is again a grid connected and here if you look at this EPI number it is really impressive it isit has been reduced to 30 kilo Watt hour per meter square per year in this building that is veryvery low and the rest of the energy the this energy was supplied using the renewable energysystems which was generated using the building integrated photovoltaics.(Refer Slide Time: 28:42)So, how they have done. The first step as we have always discussed is the passive strategiesthey have considered orienting the building properly, day lighting allowing for day lighting inmost of the areas. So, the south blazing was provided with horizontal shades and there werealmost no east and west openings and there were reasonable amount of north glazing withvertical shading provided.Doing this almost the all the areas indoors they were they had sufficient amount of daylightavailable. And the courtyard the building has courtyard which is covered with angle whichcan maximize the winter sun on the south for south face while reducing the diffused daylightduring summers. Another passive design strategy was that of ventilation where the south facewas added with solar chimneys to aid the ventilation in some of the non air conditionedspace.So, this entire building was not air conditioned which is which was the most impactfulstrategy in reducing the EPI of the building. In addition to that the construction of thebuilding and the components of the building envelope. So, it had cavity was with insulationand also double glazed windows and aerated concrete blocks were used for walls insulatedroof tiles and thermo tech roof tiles were used. Doing incorporating all these passive designstrategies the energy demand in this building for thermal comfort was reduced in went.(Refer Slide Time: 30:24)In active strategies they placed a lot of importance on ventilation and cooling. So, the entirespace was divided into 3 distinct zones. And the first strategy that they used was maintainingproper set point temperatures as we have seen. So, at 25 degrees plus minus 1 degree in theapex offices and controlled offices and public areas were maintained at 25 plus 3 degreecentigrade and passive zones were maintained at 25 plus minus 5 degree centigrade.And in different zones which is the apex offices, the controlled offices and the passive zonesthey had different strategies. So, in pass in control zones they were cool in summer and chillin monsoon, passive zones were cool in summer and ventilated in monsoons. In the atrium amist system was installed which was which would control with the cooling of the control andpassive zones and the chilled supply chilled waters was supplied at a much highertemperature of 15 degrees while normally it is supplied at a temperature of around 8 degreecentigrade.Once these passive and active strategies were incorporated the EPI which was brought downsubstantially to 30 kilo Watt hour per meter square per year the rest of it was generated usingthe BIPV which was installed on top of the roof in the atrium and it was able to generate thesame amount of energy which was consumed by the building thereby making this building asa net zero energy building. (Refer Slide Time: 31:58)Couple of more buildings are available as case studies and you can learn more about it fromthe NZEB portal, but the approach for all the net zero energy buildings remains the same firstof all we use the passive strategies to reduce the amount of heat gain into the building andalso to reduce the amount of energy consumed for artificial lighting and heating and cooling.And then we add on the active efficient active strategies to further reduce the amount ofenergy which is required and lastly whatever reduced energy demand is it is offset byinstalling renewable energy. So, Indira Paryavaran Bhawan which is in Delhi it is an officebuilding and it has a project area of around 10,000 square meter here also the EPI has beensubstantially reduced and the entire roof of this building is covered with huge rooftop PV andit generates an equivalent amount of energy which it consumes. Another building which is aneco commercial building of a bear material science. (Refer Slide Time: 33:16)It is in Greater Noida. It has an API of around 72 kilo Watt hour per meter square per year,but with the help of the photovoltaic rooftop photovoltaic which is installed on it is roof itgenerates these equivalent amount of energy and much higher amount of energy than what itconsumes. So, it general and this excess energy it gives back to the other is it gives to theother buildings on site.So, it is not just a net zero energy, but it is an energy positive building where it generatesmore amount of energy than it consumes. So, there are a couple of other case studies whichyou can see on the in and NZEB portal and with this we conclude the discussion on a EnergyEfficiency in Sustainable Buildings and we also conclude the lectures of this week. From nextweek onwards we will start discussion on another head related to sustainable buildings andtowards the end of this course we will be learning or software for whole building energysimulation.So, thank you very much for being with us this week. See you next week with a new series oflectures till then bye bye.Thank you.