Chapter 4. Analysis of Building Energy Performance

Transcription

1 Chapter 4 Analysis of Building Energy Performance 128

2 4.1 Introduction This chapter deals with energy modeling and simulation of the baseline models for the buildings to assess energy performance of the buildings. Building energy modeling and simulation are the best means to achieve reduced energy cost, improved indoor thermal conditions etc. at a much lower cost compared to field tests of actual implementation. Therefore simulation technique for building energy conservation is of significant interest and benefit to engineers. Energy simulation programs can be used to analyze proficient energy efficiency measures before the building is constructed. Simulation studies require a reference case to serve as a benchmark for comparison and assessment of the building energy performance. Based on the initial phases of literature review and data collection, the base models have been developed for all selected proposed commercial buildings under study. There can be two basic stages of energy analysis tools. Simplified energy calculations and detailed energy calculations. Simplified energy calculations are represented by the degree-day method which estimates for energy consumption related to small buildings and the modifiedbin-method, which can be used with better accuracy for estimating the energy consumption of larger buildings. Hour to hour energy simulation provided by detailed energy calculations helps to simulate the energy consumption in a building and its sub systems for every hour of an average weather year 1. Analysis of building energy performance using simulation program and method has been elaborated in this chapter for the proposed ten commercial buildings. 4.2 Energy Analysis Using Simulation Methods and Techniques Nowadays computer simulation has become popular, which offers flexible building energy analysis tool. Building design parameters used as the inputs and energy consumption profiles provided by the simulation are termed as the outputs. The climate zone remains the boundary condition for any of the simulation system and stimulates the basic driving potential for the variation of building loads. Building simulation allows users to evaluate all kinds of effects and changes in an incredibly less time with greatly lesser cost 2. Computer simulation program and method required to carry out building energy simulation has been elaborated in this chapter. 129

3 4.3 Energy Modeling and Simulation of Buildings The commercial buildings have been modeled using the equest-3.63b energy analysis software. The equest-3.63b uses the building energy simulation engine developed by US Department of Energy (DOE). The equest-3.63b energy modeling software allows for a graphical display of all the 3-dimensional geometry entered in the application to describe the building. The proposed commercial buildings under study (ECBs) have been modeled in detail to assure the accuracy and reliability of analysis work. The study objective has been accomplished by evaluating breakdowns in energy use patterns and the energy efficiency performance of the proposed commercial buildings Analysis through Building Energy Simulation The purpose and function of the building energy simulation analysis was to evaluate the distinctiveness of all test building s energy systems related to characteristics and to identify the patterns of the energy usage by the buildings. It can be used to study the impact of proposed building modifications on building energy use. It can also be used to evaluate the outcome of design with unconventional materials which can straight away be evaluated to see how much and in which manner they effect annual energy consumption of the buildings. This could lead to support energy efficient design choices without sacrificing comfort conditions. The equest-3.63b software has been used to develop a base case and for an energy simulation analysis using energy efficiency measures. The building characteristics and related documents such as architectural, electrical and mechanical drawings have been collected through the questionnaires Base Case Formulation The required base case was developed for simulation model that would represent similar energy consumption pattern as well as magnitude. Input parameters influencing building energy performance in terms of energy consumption has been changed within justified and reasonable ranges through the comparison process to 130

4 achieve good match between the simulated and designed values. Fundamentally the properties of materials and constructions have been presented with consistency since the existing data sets for investigated buildings were found to be similar. Preferably, the base model is developed by the data accumulated through actual, detailed survey and meeting with the facility staff, project design teams and the data provided by them. However, detailed building surveys are usually very limited, and the available data are often incomplete for detailed simulation needs. Therefore, certain assumptions have been made to select and determine the necessary inputs for the reference energy conservation buildings. Table 4.1: Characteristic of the base case model Characteristic Wall Construction Wall U-Value in Btu/hr ft 2 F Roof Construction Roof U-Value in Btu/hr ft 2 F Glass Type, U-Value, Glass SHGC and Glass SC Base Case Values 230mm normal brick wall, 19mm plaster on each side, U-Value mm China mosaic tiles, 15mm Brickbat coba, 150mm RCC slab and 20mm Inside Plaster, U-Value 0.33 SGU 6 mm, U-Value 0.968, SHGC 0.51, SC 0.59 Chiller EIR and COP EIR , COP 5.4 Relative Humidity 50% - 70% Conditioned Space Temp. in C for Summer Conditioned Space Temp. in C for Winter 22 o 28 o 20 o 24 o Parking LPD W/ft Remaining all Other Design Parameters and Operation of Facilities Same as the facility i.e. according to design and operation of particular facility Although some similarities in the design parameters of proposed test buildings were found but there were still many of the characteristics and design parameters which were different such as location, occupancy, size, shape, floor area, percentage of conditioned area, maximum capacity of persons, envelop characteristics, window wall 131

5 ratio, HVAC system design, lighting, type of chillers and maximum capacities, various building loads etc. These different characteristics and design parameters make each building unique. Each selected building was having various different bases of building energy performance. It was difficult to assess the impact of proposed energy efficiency measures on all different buildings together. It was significantly understood to have some a common basis to evaluate the effect of energy efficiency measures on all test buildings together. For the accomplishment of research objectives and subject point of view it was essential to make all these building on a common platform called base case. Therefore a base case for each building was developed so that results of simulation have common basis of comparison to be made. In the base case some of the most common design practices in Indian commercial building has been adopted and some times assumed in design to establish base cases which have been given in table 4.1, remaining all other detailed characteristics and design parameters used were same as per the actual characteristics and design of the each particular building given in the description of buildings earlier Input Data The questionnaire was the key source for providing the input data. As well as each zone of each building has been also investigated through architectural, electrical and mechanical drawings with the cooperation of the facility design team for getting information about lighting, equipment and number of people etc. required for data input in equest for detailed energy modeling and simulation. Building Envelope (Wall, Roof and Glazing) Especially large commercial building s envelope comprising wall, roof and window glazing have huge impact on the energy efficiency as well as it provides thermal comfort condition with in the facility. Therefore it becomes very essential to determine the energy efficient characteristics of the building envelope. To come up with this rationale, the building architectural engineering drawings were reviewed to get details of wall, roof and glazing characteristics. 132

6 Envelope Parameters Wall System Wall U Value (Btu/hr ft 2 F) Roof System Roof U Value (Btu/hr ft 2 F) Table 4.2: Summary of base case building envelope characteristic ECB-01 ECB-02 ECB-03 ECB-04 ECB mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm Window area (ft 2 ) Wall area (ft 2 ) Window Wall Ratio 31% 9% 19% 11% 52% Roof area (ft 2 ) Window Glazing SGU 6 mm SGU 6 mm SGU 6 mm SGU 6 mm SGU 6 mm Glass U Value (Btu/hr ft 2 F) Glass Shading Factor (SHGC) Glass Shading Coefficient (SC) Operation of Facility :30AM-09:30PM Summer 10:00AM-09:00PM Winter 09:30AM-07:00PM Summer 10:00AM-07:30PM Winter 09:30AM-10:00PM Summer 09:30AM-10:00PM Winter 10:00AM-07:30PM Summer 10:00AM-07:30PM Winter 10:00AM-07:30PM Summer 10:00AM-07:30PM Winter 133

7 Envelope Parameters Wall System Wall U Value (Btu/hr ft 2 F) Roof System Roof U Value (Btu/hr ft 2 F) ECB-06 ECB-07 ECB-08 ECB-09 ECB mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side 230 mm brick with 19 mm plaster on each side Cont. 230 mm brick with 19 mm plaster on each side mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm 25 mm China mosaic tiles, 15 mm Brickbat coba, 150 mm RCC and inside plaster layer of 20 mm Window area (ft 2 ) Wall area (ft 2 ) Window Wall Ratio 19% 11% 23% 21% 18% Roof area (ft 2 ) Window Glazing SGU 6 mm SGU 6 mm SGU 6 mm SGU 6 mm SGU 6 mm Glass U Value (Btu/hr ft 2 F) Glass Shading Factor (SHGC) Glass Shading Coefficient (SC) Operation of Facility :30AM-06:30PM Summer 10:00AM-07:00PM Winter 10:00AM-07:30PM Summer 10:00AM-07:30PM Winter 10:00AM-09:00PM Summer 10:00AM-09:00PM Winter 10:00AM-07:30PM Summer 10:00AM-07:30PM Winter 09:30AM-09:30PM Summer 10:00AM-09:00PM Winter 134

8 Important information, for instance, type of insulation in walls and roofs, type of window and its characteristics were obtained using building architectural engineering drawings, building construction materials technical specifications and bills of quantity (BOQ). The details of the wall, roof and glazing used in baseline case has been shown in table 4.2 Internal Loads (Occupants, Equipment, Lighting) The usual equipment used in the facilities were personal computers, small and large printers, photocopy machines, few scanners, coffee machines, task lights etc. To calculate equipment and lighting power densities, following procedure was adopted with the help of ASHRAE standard 3. For each zone of the floor, total number of equipment and lighting fixtures was counted by using ASHRAE standards; the power densities of equipment and lighting were calculated. Total number of occupants taken from questionnaire was as per the HVAC heat load calculations. The equipment power density has been also taken from the questionnaire which was in the range of 0.75 W/ft 2 to 2.0 W/ft 2. The researcher has not claimed any savings in the equipment power density (EPD) and has kept same in all parametric runs. Interior lighting power densities have been taken from the lighting floor plans provided by the project design teams. The quantities, details and specifications of the lighting fixtures, marked on the lighting floor plans have been used as inputs. HVAC Systems Information about HVAC systems, air handling units (AHU s) and chillers were collected through questionnaire and with the cooperation of respondents of that facility or its design team. Generally the constant air volume (CAV) systems were used for air conditioning and low COP open centrifugal chillers were used for providing the chilled water to the facility. There were some facilities which have variable speed drive air handling units and chillers with better coefficient of performance. The quantities, details and specifications of the air handling units, chillers, secondary chilled water pumps, primary chilled water pumps, condenser water pumps, cooling towers have been taken from the questionnaire, HVAC floor plans, HVAC BOQ and HVAC technical specifications. The details have been given in table

9 Table 4.3: Summary of base case building systems characteristics Type of System ECB-01 ECB-02 ECB-03 ECB-04 ECB-05 HVAC System Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled screw chiller Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled screw chiller No. of Chillers Two chillers 200 TR Two chillers 750 TR Capacity of Chiller in TR each, One chiller 716 TR each, One chiller 300 TR Chiller EIR Chiller COP Chiller Compressor One Speed One Speed One Speed One Speed One Speed HVAC pumping arrangement Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Secondary CHW pumps Constant Speed Constant Speed Constant Speed Constant Speed Constant Speed Number of AHU AHU & CT fan motor One Speed One Speed One Speed One Speed One Speed Elevator load(kw) Exterior Lighting load (kw) Car Park fan load (kw) NA Lights used in whole LED / T5 / Fluorescent LED / T5 / Fluorescent T5 / Fluorescent Lamp building provided by Lamp Lamp T5 / Fluorescent Lamp T5 / Fluorescent Lamp Lighting Power Density Office 2.0, Retail 3.5, Office 2.3, Retail 3.7, (LPD) W/ft 2 Office 2.5, Parking 0.5 Parking 0.5 Parking 0.5 Office 2.0, Parking 0.5 Office 1.5, Parking 0.5 Relative Humidity 50 % - 70 % 50 % - 70 % 50 % - 70 % 50 % - 70 % 50 % - 70 % Conditioned Space Temp. Range in o C For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o 136

10 Type of System ECB-06 ECB-07 ECB-08 ECB-09 ECB-10 HVAC System Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Each conditioned space provided CAV AHU controlled, served by water cooled electric open centrifugal chiller Cont. Each conditioned space provided CAV AHU controlled, served by water cooled electric hermatic chiller No. of Chillers Capacity of Chiller in TR Chiller EIR Chiller COP Chiller Compressor One Speed One Speed One Speed One Speed One Speed HVAC pumping arrangement Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Primary / Secondary Pumping Secondary CHW pumps Constant Speed Constant Speed Constant Speed Constant Speed Constant Speed Number of AHU AHU & CT fan motor One Speed One Speed One Speed One Speed One Speed Elevator load(kw) NA Exterior Lighting load (kw) NA NA 27.5 Car Park fan load (kw) NA NA 80 Lights used in whole LED / T5 / Fluorescent LED / T5 / Fluorescent LED / T5 / Fluorescent T5 / Fluorescent Lamp T5 / Fluorescent Lamp building provided by Lamp Lamp Lamp Lighting Power Density (LPD) W/ft 2 Office 2.4, Parking 0.5 Office 3.0, Parking 0.5 Office 2.5, Retail 3.7, Office 3.0, Retail 4.5, Office 2.5, Parking 0.5 Parking 0.5 Parking 0.5 Relative Humidity 50 % - 70 % 50 % - 70 % 50 % - 70 % 50 % - 70 % 50 % - 70 % Conditioned Space Temp. Range in o C For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o For Summer 22 o -28 o For Winter 20 o -24 o 137

11 Review of Design Drawings Architectural floor plans, elevations and sectional drawings were reviewed in a systematic and careful way to get data about proposed construction details of walls, roofs and window etc. Also engineering drawings were analyzed to get information about glazing and other details about lighting systems from lighting floor plan etc. The HVAC system drawings were investigated to check for the total number of air handling units, their power consumption, chiller system and its power consumption. The details about the timing schedule of air handling units (AHU) and their other details, chiller and condenser schedules and pump schedule have been also used as input data Buildings Thermal Zoning A thermal zone can be defined as an enclosed area in a building which is meant to have the same thermal conditions and by having its own thermostat controls. Dividing the building into proper thermal zones was very essential to analyze HVAC system loads and their operational profiles. In order to reduce the actual zoning complexity of the case study modeling for energy simulation and the thermal zones have been modified from those specified in the HVAC layout. Retails, shops, showrooms, office, corridor, restaurant and lift lobby have been typically considered as conditioned spaces and restrooms, plant rooms, mechanical and electrical rooms, store, stairs were considered as unconditioned thermal zones. The sample ground floor thermal zones of all the selected facilities are shown in figure 4.1 (a) to figure 4.1(j). Figure 4.1: (a) Thermal zones for ground floor of ECB

12 Figure 4.1: (b) Thermal zones for ground floor of ECB-02 Figure 4.1: (c) Thermal zones for ground floor of ECB-03 Figure 4.1: (d) Thermal zones for ground floor of ECB

13 Figure 4.1: (e) Thermal zones for ground floor of ECB-05 Figure 4.1: (f) Thermal zones for ground floor of ECB-06 Figure 4.1: (g) Thermal zones for ground floor of ECB

14 Figure 4.1: (h) Thermal zones for ground floor of ECB-08 Figure 4.1: (i) Thermal zones for ground floor of ECB-09 Figure 4.1: (j) Thermal zones for ground floor of ECB

15 4.3.5 Baseline Case Energy Modeling and Simulation The foremost rationale behind this step was to develop base case models which represent the existing energy usage and operating conditions for the building. The major tasks which have been performed during this process were as follows: To obtain and review architectural, mechanical and electrical drawings; To obtain all occupancy and operating schedules for equipment (which includes lighting and HVAC systems); and To develop a base-case model for building energy usage All the collected data was used in equest-3.63b software including the construction of walls and roofs, details of glazing, schedules including people, equipment, lighting, outside air, set point temperatures and the schedule of HVAC systems. (.BIN) weather files have been for energy modeling purpose. Any accurate building modeling which uses any computer simulation tool consists of the following steps. The first step is to accurately survey the building thermal characteristics and define representative thermal zoning scheme and finally enter these parameters into the simulation tool very carefully. Available architectural drawings were used in combination with an interview with the facility design team and through a survey. The second step involves simulating the energy model using relevant weather file and finally, potential energy efficiency measures, which can be evaluated using the simulation model. In order to investigate the impact of HVAC operation techniques on annual energy consumption and thermal comfort conditions, the selected facilities were modeled and simulated using equest-3.63b energy simulation program. The simulation was performed using the corresponding city s (.BIN) weather data file. The initial base case model was developed considering the following assumptions: 1. The partition walls were assumed as adiabatic layers with no heat energy transfer between the different separated thermal zones. 2. In order to minimize deviation, the complexity is reduced and for adhering to program limitation total number of zones per floor can be reduced. Shops and offices with identical operation and characteristic were grouped to form a single zone. 142

16 3. In view of the fact that each entrance had a lobby before joining into the main zone, the infiltration rate through the entrance was assumed to be minimal. 4. The air-conditioning system, operating as per the facility operating schedule provided by the project design team in the questionnaire. 5. Exterior lighting was considered to be part of energy consumption as it plays significant role in the total annual energy consumption. 6. All office and retail area have been usually served by constant air volume (CAV AHU) air handling systems. 7. Since any variations in thermostat design were not informed, the thermostat setting was assumed to be the same at all times of the year. A typical base case of ECB-01 has been modeled using base case input data in equest-3.63b has been shown as screenshot in figure 4.2. Figure 4.2: Screenshot of the energy model of ECB-01 building in equest Performance of Base Case Models Simulations Analysis of the simulation results of the base models have been an essential requirement for understanding the important components and elements of the model. 143

17 The annual electricity consumption of the base cases was compared with each other to assess the existing design building energy performance. The results obtained for annual energy consumption through the initial simulation of the base case have been tabulated and presented in table 4.4. S. No. Base Cases of ECB s Table 4.4: Base cases annual energy consumption Building Energy Consumption in kwh Building Energy Consumption in kwh/ft 2 year 1 ECB ECB ECB ECB ECB ECB ECB ECB ECB ECB Input Data and Techniques of Energy Efficiency Measures The input data was required to be modified in the form of energy efficiency measures to investigate the impact of the proposed energy efficiency measures (EEMs) in all the test energy conservation buildings (ECBs). The base case and modified design data as well as operational techniques, which have been implemented as EEMs, are tabulated in table 4.5. The impact of improving the building envelope parameters i.e. reducing the building envelope overall heat transfer coefficient was required to reduce the building heat load, this has resulted in the reduced cooling demand and hence the reduced energy consumption or increased energy efficiency. The Energy Efficiency Measures EEM-4 to EEM-9 lead to improved HVAC system. These energy efficiency measures has provided efficient running of HVAC systems which leads to reduced energy 144

18 consumption in these end use heads. The details of the major input data for base cases and each of the energy efficiency measure (EEM) has been represented in table 4.5. Component Wall System Wall U Value (Btu/hr ft 2 F) Roof System Roof U Value (Btu/hr ft 2 F) Window Glazing Table 4.5: Input data for base cases and EEMs All Base Cases 230 mm brick wall with 19 mm plaster on both side of wall Energy Efficiency Measures (EEMs) Insulated wall with 230 mm brick wall with 19 mm plaster on both side of wall, 26 mm extruded polystyrene (XPS) insulation between the exterior plaster & brick wall Flat concrete slab 150 mm, 15 mm brickbat coba, 25 mm China mosaic tiles, and inside plaster layer of 20 mm Insulated roof with flat concrete slab 150 mm, 100 mm brickbat coba, 60 mm over-deck extruded polystyrene(xps) insulation, 25 mm China mosaic tiles, and inside plaster of 20 mm Single glazed unit (SGU) 6 mm Efficient glazing (DGU) 6 mm exterior glass, 12 mm air gap, 6 mm interior glass Glass U Value (Btu/hr ft 2 F) Glass Solar Factor (SF or SHGC) Glass Shading Coefficient (SC) Chiller EIR & COP EIR , Energy efficient chiller COP 5.40 EIR , COP 6.1 Chiller Compressor One speed One speed Primary Chilled Water Pumps Constant speed Constant speed Secondary Chilled Water Pumps Constant speed VFD control AHU Fan Motor One speed VFD control Cooling Tower Fan Motor One speed VFD control Supply Air Temp. 55 F Reset control Chilled Water Supply Temp. 44 F Reset control Conditioned Space Temp. Range in o C For summer 22 o -28 o For winter 20 o -24 o For summer 22 o -28 o For winter 20 o -24 o Relative Humidity 50 % - 70 % 50 % - 70 % Lights used in whole building provided by Fluorescent/ LED/ T5 lamp LED / T5 lamp Car Parking LPD in W/ ft 2 LPD 0.5 Energy efficient lighting LPD 0.15, Lux

19 Typically the lighting power density was designed in the range from 0.3 to 0.5 W/ft 2 for car park or basement area. The LPD for these spaces was designed at a very high value. It can be designed at 0.15 W/ft 2 which has provided very comfortable results having lux around The LPD of 0.15 W/ft 2 can be achieved by using CFL or T5 lamps or with a combination of both. It provides significant savings in the building car parking lighting as shown in table EEMs Impact on Building Energy Efficiency The simulation results of the energy efficiency measures have shown the impact on building energy performance by reduced energy consumption. The models simulation results have shown that by implementing all energy efficiency measures together the huge savings in energy consumptions up to 28% has been achieved in ECB-02 which is an office building having conditioned area of ft 2 and situated in New Delhi under composite climate zone. The EEMs simulation results for energy consumption in kwh have been shown in table 4.6. The details of annual energy saving applying individual energy efficiency measure over base case have been tabulated in table 4.6. The reduced annual electricity consumption from the base cases was compared in all energy conservation buildings (ECB s) to assess the improved building energy performance. The simulation results obtained after the implementation of each individual EEM on the base cases have been presented in table Implementation of appropriate EEMs The annual electricity consumption of the proposed cases (EEMs) was compared with baseline cases energy consumptions to develop an understanding about the building energy performance characteristics. Simulation results of annual energy consumption has been tabulated in table 4.5 which reveal that all ten (10) proposed energy efficiency measures has potential to save annual energy consumption. The percentage of savings shown by EEM-01, EEM-02 and EEM-03 together was in the range of 2% to 15%, EEM-04 to EEM-09 together leads to energy saving in the range of 8% to 23%. 146

20 S. No. Base Case and EEMs Table 4.6: EEMs and base cases annual energy consumption in kwh Energy Consumption Applying Individual EEM (kwh) 1 Base Case EEM EEM EEM EEM EEM EEM EEM EEM EEM EEM

21 S. No. Base Case and EEMs Table 4.7: EEMs and base cases annual energy consumption in kwh/ft 2 year Energy Consumption Applying Individual EEM (kwh/ft 2 year) 1 Base Case EEM EEM EEM EEM EEM EEM EEM EEM EEM EEM

22 The last EEM-10 was showing maximum savings around 2%. The ranges in which energy efficiency measures have been provided savings gave an impression of feasibility to provide significant energy saving opportunities in through implementation. Although all EEMs were providing energy savings but the prominent and potential energy efficiency measure was EEM-06 i.e. VFD on AHU s. Therefore all ten proposed EEMs has been decided to be implemented on all ECB s for cost benefit analyses in lateral phase. All the proposed EEMs have been implemented in the base case design to improve the buildings energy efficiency. 4.7 Evaluation of EEMs Simulation Results On the basis of the evaluation of annual energy use pattern and economics of the building, all proposed energy efficiency measures (EEMs) for the building were analyzed. As a result energy efficiency measures were classified into three categories on the basis of magnitude of investment as shown in table 4.8. These categories comprise: (a) Low investment measures (b) Medium investment measures (c) Major investment measures All aforesaid three categories of energy efficiency measures have been discussed in details as follows: (a) Low Investment Measures: The low investment measures were those which can be implemented either through operational means or without the need for significant alteration in building systems and with a very low investment amount which would be less than rupees 8 lacs (i.e. an average of investment required for implementation of EEM across all ECB s). Therefore these measures do not necessitate significant cost for their implementation in the buildings. 149

23 (b) Medium Investment Measures: The medium investment measures were those which can be implemented through building design alterations or modifications and with the investment amount between 8 lacs to 20 lacs (i.e. an average of investment required for implementation of EEM in all ECB s). Thus reasonable extra cost would be required for their implementation. (c) Major Investment Measures: The major investment measures were those which require major investment in terms of cost for their implementation such as an investment of rupees 20 lacs or above in the buildings (i.e. an average of investment required for implementation of EEM in all ECB s). These measures can be implemented through system design renewal or retrofitting in proposed design to the commercial buildings. Table 4.8: Level of energy efficiency measures Level of Measures Low Investment Measures Medium Investment Measures Major Investment Measures Energy Efficiency Measures EEM-05 VFD Control on SCHWP EEM-07 VFD on CT Fans EEM-09 CHWST Reset Control EEM-03 Efficient Glazing System EEM-06 AHU Fan VFD Control EEM-08 SAT Reset EEM-10 Car Parking Lower Lighting Power Density EEM-01 Insulated Walls EEM-02 Insulated Roofs EEM-04 Energy Efficient Chillers Description VFD Control on Secondary Chilled Water Pump VFD Control on Cooling Tower Fans Chilled Water Supply Temperature Reset Control Low U-value, Double Glazed Unit Glass with U-value = 0.56 Btu/hr ft 2 F, SF/ SHGC = 0.25 and SC = 0.29 VFD Control on Air Handling Units Supply Air Temperature Reset Control Car Parking Lower Lighting Power Density reduced to 0.15 W/ft 2 with lux around mm extruded polystyrene (XPS) insulation between the exterior plaster and brick wall 60 mm over-deck extruded polystyrene (XPS) insulation Efficient Chiller for HVAC System with COP of 6.1 EIR =

24 EEM-01 : Insulated Wall In this EEM the heat transfer from the exterior walls has been reduced by providing the insulation in the exterior walls. Overall heat transfer coefficient (U-value) of the wall became as Btu/hr ft 2 F (0.698 W/m² K) by using this insulation. The reduced U-value has reduced the building heat gain. For the buildings under study, polystyrene XPS insulation of 26mm thickness has been used in exterior walls. The U-value of walls used in the existing design of buildings was Btu/hr ft 2 F (1.869 W/m² K). As an energy efficiency measure, polystyrene XPS insulation of 26mm thickness was tried using the equest-3.63b simulation program. The use of the polystyrene XPS insulation, the new U-value of walls was reduced to Btu/hr ft 2 F (0.698 W/m² K). The simulation results of insulated walls shown in figure 4.3 and 4.4 in comparison with existing building design i.e. base case. 40 Comparison of Annual Energy Consumption between Base Case and Insulated Wall Energy Consumption in kwh/ft 2 -Year Base Case EEM Figure 4.3: Comparison of annual energy consumption between base case and insulated wall 151

25 The charts elaborate that only three ECB s were capable to save more than 1.5% of electric energy using this EEM which may not be practically cost effective in some of the buildings due to long payback period but in some case due to various building energy design factors it may lead to very good saving as in the case of ECB-07 with more than 10% savings in electric energy consumption. As it can be seen from the comparison between base case and insulated wall (EEM-01) it has been observed that the maximum percentage of energy savings i.e % was obtained in ECB-07 which interprets that proposed level of insulated walls in EEM-01 was considered to be sufficient in comparison to the base model. According to the graph analysis the minimum percentage of energy savings i.e. 0.18% which has been obtained in ECB- 06 which interprets that current level of insulated walls (EEM-01) may be considered to be insufficient in comparison to base model of ECB Percentage Savings by Insulated Wall 10 Percentage EEM Figure 4.4: Savings in energy consumption applying insulated wall (EEM-01) In this EEM, on an average, 2.52% reduction in energy consumption has been achieved by all ECB s. This EEM requires major investment in terms of cost for their implementation in the buildings. EEM-02 : Insulated Roof The heat transfer from the exposed roof has been reduced by providing over-deck insulation in the exposed roof. As an energy conservation measure, over-deck 152

26 extruded polystyrene (XPS) insulation of 60 mm has been used for roof construction using the equest-3.63b simulation program. Comparison of Annual Energy Consumption between Base Case and Insulated Roofs Energy Consumption in kwh/ft 2 -Year ECB-01ECB-02 ECB-03 ECB-04ECB-05 ECB-06 ECB-07ECB-08 ECB-09 ECB-10 Base Case EEM Figure 4.5: Comparison of annual energy consumption between base case and insulated roof 3.0 Percentage Savings by Insulated Roof 2.5 Percentage EEM Figure 4.6: Savings in energy consumption applying insulated roof (EEM-02) 153

27 The U-value of the insulated roof comes out as Btu/hr.ft 2 F (0.359 W/m 2 K) with respect to previous base design U-value of Btu/hr.ft 2 F (1.851 W/m 2 K). The reduced U-value has reduced the building heat gain. From the simulation results, up to 2.8 % energy savings was achieved annually with this EEM. This EEM can be used as major investment in terms of cost for their implementation in the buildings. The results are shown graphically in figure 4.5 and 4.6. EEM-03 : Efficient Glazing System: (Double Glazed Unit Glass for façade) The heat transfer from the single glazed glass is higher than the double glazed unit. The overall heat transfer coefficient (U-value) and solar factor (SF) or solar heat gain coefficient (SHGC) or shading coefficient (SC) has been lower for the double glazed units. The configuration of the double glazed unit used in EEM-03 was 6 mm exterior glass + 12 mm air gap + 6 mm interior glass which can be beneficial in both reducing the energy use and improving the indoor comfort levels. The U-value of window glazing was modified by the use of DGU glass from Btu/hr ft 2 F (5.5 W/m 2 K) to 0.56 Btu/hr ft 2 F (3.182 W/m 2 K) with solar heat gain coefficient 0.25 and shading coefficient The solar heat gain coefficient and shading coefficient used in the base case was 0.51 and 0.59 respectively. As an energy efficiency measure, the existing glazing system use in base case design was replaced using a simulation program with a lower double glazed window glass. The details of window glazing have shown in table 4.9. The simulation results for the use of double glazed window have been shown graphically in figure 4.7 and figure 4.8. Component Window Glazing Glass U Value (Btu/hr ft 2 F) Glass Solar Factor (SF or SHGC) Glass Shading Coefficient (SC) Table 4.9: Specifications for the glazing system All Base Case Single Glazed Unit Single glazed unit (SGU) 6 mm Efficient Glazing System Double Glazed Unit Glass for façade Efficient glazing (DGU) 6 mm exterior glass, 12 mm air gap, 6 mm interior glass

28 Comparison of Annual Energy Consumption between Base Case and Efficient Glazing System 40 Energy Consumption in kwh/ft 2 -Year Base Case EEM Figure 4.7: Comparison of annual energy consumption between base case and efficient glazing system Percentage Percentage Savings by Efficient Glazing System EEM Figure 4.8: Savings in energy consumption applying efficient glazing system (EEM-03) From the figure 4.8, it indicates that on an average, a 2% reduction in energy consumption was achieved per annum. The glazing system plays an important role in 155

29 energy use pattern for the building and for reducing the internal heat gains. From the figure 4.8, indicates that a maximum of 4.11% of energy savings was obtained in ECB-05 which interprets that proposed glazing system in EEM-03 can be considered as sufficient in comparison to its base model. According to the graph analysis the minimum percentage of energy savings 0.07% was obtained in ECB-06 which may be due to the cold climatic zone of ECB-06. It interprets that current level of insulated walls may be considered to be insufficient in the building of cold climate zone. This EEM is medium investment measures which can be implemented through building design modifications with reasonable extra cost of implementation. EEM-04 : Energy Efficient Chillers Chillers are the main part of HVAC systems and play an important role in energy use. The efficiency of the chiller is measured in terms of coefficient of performance (COP). 40 Comparison of Annual Energy Consumption between Base Case and Energy Efficient Chillers Energy Consumption in kwh/ft 2 -Year Base Case EEM Figure 4.9: Comparison of annual energy consumption between base case and energy efficient chillers 156

30 The COP of the chillers being used in general practice is 4.8 or 5.4. The COP is the reciprocal of electric input ratio (EIR). As the COP of the chiller increases, the EIR decreases, this has resulted in reduced energy consumption of the chiller. As an energy efficiency measure, more energy efficient air cooled reciprocating chillers with higher coefficient of performance (COP) of 6.1 (EIR = ) were used and the impact of more energy efficient chillers on energy consumption has been evaluated by using equest-3.63b simulation program. In other words the chillers being used in general practice having COP of 4.8 or 5.4 has been replaced in this EEM with the most energy efficient chillers having COP of 6.1 (EIR = ). 6 Percentage Savings by Energy Efficient Chillers 5 Percentage EEM Figure 4.10: Savings in energy consumption applying energy efficient chillers (EEM-04) As can be seen from the comparison between base case and EEM-04 energy efficient chillers, the minimum percentage of energy savings was 1.78% in ECB-08 and the average percentage of energy savings obtained was around 3% among all test commercial buildings while maximum annual saving was achieved around 5% in ECB-10, which interprets that improved design with energy efficient chillers of COP 6.1 is considerable and appropriate in comparison to the base models. This EEM has been categorized as a major investment measure which can be implemented through system design renewal or retrofitting in proposed design to the commercial buildings. This EEM has feasibility to apply in all the proposed commercial buildings and it can also be applied to similar types of commercial buildings which are in the design stage or under construction. 157

31 EEM-05 : VFD Control on Secondary Chilled Water Pumps (SCHWP) In this EEM the secondary chilled water pumps has been made equipped with variable frequency drives (VFD). The VFD is used to increase or decrease the pump speed, hence the pump power became according to the load requirement. The typical secondary chilled water pumps were of constant speed, they keep on serving the same amount of chilled water to the building even if there would be less demand of chilled water. This problem has been rectified by the use of variable frequency drive (VFD) control on secondary chilled water pumps. The VFD has reduced the speed of the secondary chilled water pumps whenever the chilled water demand was reduced. 40 Comparison of Annual Energy Consumption between Base Case and VFD Control on Secondary Chilled Water Pumps Energy Consumption in kwh/ft 2 -Year Base Case EEM Figure 4.11: Comparison of annual energy consumption between base case and VFD control on secondary chilled water pumps The power is directly proportional to the cubic power of the speed; hence the power has drastically reduced whenever the speed of the pump was slow down because of the reduced chilled water demand. The cooling load on the building varies because of the changes in the occupancy pattern in a day and changes in the outside weather 158

32 conditions. The purpose of the secondary chilled water pumps was to serve the chilled water to the AHUs / FCUs in the facility. The reduced cooling load of the building has resulted in reduced demand of chilled water. Percentage Percentage Savings by VFD Control on Secondary Chilled Water Pumps EEM Figure 4.12: Savings in energy consumption applying VFD control on secondary chilled water pumps (EEM-05) Since it can be seen from the comparison between base case and EEM-05 it is observed that the maximum percentage of energy savings 3.75% obtained in ECB-09 and the average 1.5% percentage saving obtained in all test ECB s which interprets that the proposed EEM-05 is feasible and can be considered for implementation in the proposed commercial buildings. This EEM has been a low investment measure as it can be implemented through modification in design and operational means without the need for significant alteration in system or building and with a very low investment amount which is less than rupees 2 lacs in the selected ECB s. Therefore this measure does not necessitate significant cost for their implementation in the buildings. EEM-06 : Air Handling Unit Fans VFD Control The AHUs are typically controlled by a thermostat either placed in the path of the return air or in the space served by the AHU. The base cases were designed with constant speed AHU motors. The constant speed motors was designed with constant 159

33 air volume (CAV) system which means that all AHU fans were operated with constant speed. They were designed to supply air conditioned air through a constant volume air supply system to the conditioned zones. The systems were designed to supply enough air to cool the building under design conditions. As an energy efficiency measure, changing the system to a variable air volume (VAV) system by employing variable frequency drives (VFD) has reduced the amount of air supply by all AHU s and resulted in less energy to condition the various zones. Variable speed drive fans have been used in the VAV systems to apply the variable air volume system in the proposed ECB s by using equest-3.63b simulation program. 40 Comparison of Annual Energy Consumption between Base Case and Air Handling Unit Fans VFD Control Energy Consumption in kwh/ft 2 -Year Base Case EEM Figure 4.13: Comparison of annual energy consumption between base case and air handling unit fans VFD control The AHU s were supplying the constant amount of dehumidified air to the conditioned space irrespective of the space demand. In this EEM the AHU fan motor has been equipped and controlled by variable frequency drives (VFD). The VFD has operated all the air handling units fan meter according to load requirements. 160

34 The VFD has reduced the speed of the AHU fan motor whenever the space demand of dehumidified air was reduced. The power is directly proportional to the cubic power of the speed; hence the power has drastically reduced whenever the speed of the fan motor slow down because of the reduced demand of dehumidified air. Percentage Percentage Savings by Air Handling Unit Fans VFD Control EEM Figure 4.14: Savings in energy consumption applying air handling unit fans VFD control (EEM-06) The figure 4.14 indicates that this EEM has been able to save electrical use to 17% as savings obtained in ECB-08 and at an average of more than 9% of savings has been achieved in all ECB s after analysis it interprets that this EEM has been the most efficient EEM among all other EEM under study as compared to their base cases. According to the graph analysis the minimum percentage of energy savings 2% was obtained in ECB-10. This EEM has a medium investment measure as it can be implemented through building design modifications and thus, reasonable extra cost is required for its implementation. This EEM can be feasible to apply in all the proposed commercial buildings and it can also be applied to similar types of commercial buildings which are in the design stage or under construction. EEM-07 : VFD Control on Cooling Tower Fans Typically the fan of the cooling tower used was constant speed fan. Again the cooling tower fan runs continuously irrespective of the outside air temperature and the temperature of the condenser water is being supplied to the chiller condenser. 161