ENERGY SAVING OF VARIABLE AIR VOLUME SYSTEMS C3Q8AT4JWA Basnayake Mudiyanselage Buddhika Kalum Suchinthana Bandara (07/8320) Dissertation submitted in partial fulfillment of the requirements for the degree Master of Science >5S / / Department o f Electrical Engineering . ^ C O ^ - ^ > ] University of Moratuwa "\ Sri Lanka University of Moratuwa • l l l l l l l October 2011 100840 uciODerzutt 10C84C DECLARATION OF THE CANDIDATE & SUPERVISOR I declare that this is my own work and this dissertation does not incorporate without acknowledgment any material previously submitted for a Degree or Diploma in any other University or institution of higher learning and to the best of my knowledge and belief it does not contain any material previously published or written by another person except where the acknowledgement is made in the text. Also, I hereby grant to University of Moratuwa the non-exclusive right to reproduce and distribute my dissertation, in whole or in part in print, electronic or other medium. I retain the right to use this content in whole or part in whole or part in future work (such as articles or books). The above candidate has carried out 'research for the Masters Dissertation under my supervision. Signature Name of the Candidate : B. M. B K. S. Bandara Signature Name of the Supervisor : Professor Lanka Udawatta i Abstract Air conditioning is very common in modern buildings. It was originally purposed to maintain thermally comfortable environments for people inside the building. So far, human thermal comfort is not only the criteria adapted to given the control and operation of a system. Most of the commercial buildings in Sri Lanka are sick buildings and having extremely high energy consumption of 50% to 65% of the total power consumption for air conditioning. The main reasons to have less energy efficiency of central air conditioning systems are over selection of the equipments, poor maintenance and improper controlling. Although having over selected equipment such as chillers, pumps and air handling units of particular installation, the energy usage can be optimized by accommodating a proper control system. The objective of this research is a conceptual development for air distribution cycle in order to improve the energy saving of existing variable air volume (VAV) system while maintaining the human comfort at a highest level. This will be only a functional modification of the system (programming concept), any additional sensing elements and or controlling elements will not be required to achieve the results. Any Specialized Building Management System Contractor can use this programming concept in their system with own programming languages or functional blocks. Only the requirement is that the VAV controller shall be connected to air handling unit controller via a communication bus and the few parameters from VAV controllers shall be transmitted to the particular air handling unit (AHU) controller. Generally in VAV air distribution system, thought-out the running period of the AHU, the duct static pressure set point is constant and Variable Speed Drive will be modulated by Direct Digital Controller (DDC) in order to maintain the duct static pressure at the set point. The research describes about the concept of the duct static pressure set point to varying (resetting) according to the actual demand of the total VAV Units which are connected to the particular VAV AHU. This will be an adaptive control loop for pressure set point. At the end of the research (under the result), the actual site experimental data is given for the power consumption of "Fixed Duct Static Pressure Set Point VAV Control System" Vs "Proposed adaptive control of pressure set point VAV Control System". The conclusion and analysis of the dissertation shows 6% of the energy saving from the adaptive control system compare to the fixed duct static pressure set point. Key Words: Duct Static Pressure, VAV Energy Efficiency, Static Pressure Set Point and VAV AHU. ii ACKNOWLEDGEMENT I wish to acknowledgement and express my sincere thanks to my supervisor Prof. Lanka Udawatta for the technical support and advise he gave me to work on a research having a greater opportunity to save energy which in the Air Conditioning Industry of Sri Lanka. I am also grateful to Dr. Karunadasa and all other members of Department of Electrical Engineering, University of Moratuwa for the support given to me from the beginning of Electrical Installation Msc Class. I would also like to thank all reviewers who attended in the progress review presentation for giving me their valuable comments and guidance. Without the help and support given by my colleagues Nihal Silva, Nirosh Perera, and Priyantha Bernard, who worked with me on HNB Head Office Project, I would not have been to able to complete this research project in time and I am very thankful to them for their support. Finally I wish to thank my parents and my brother for unwavering and resolute support given while this dissertation is being prepared. 111 TABLE OF CONTENTS Declaration of the Candidate & Supervisor Abstract Acknowledgement Table of Content List if Figures List of Tables List of Abbreviations 1. Introduction 1.1 Type of Air Conditioning Systems 1.2 Constant Air Volume (CAV) System 1.3 Variable Air Volume (VAV) System 1.4 Motivation 1.5 Objective and Scope 2. Theoretical Background 2.1 Characteristics of Fan 2.2 Bernoulli 's Equation 2.3 Duct Designing and Air Distribution 2.4 Variable Speed Drive 2.5 Insulation Class of Motor and Speed Limitation 2.6 Duct Layout of Variable Air Volume System 2.7 Direct Digital Controllers 3. Research Design 3.1 Selection of a Suitable Building 3.2 The System Architectures 3.3 Functional Description 3.4 Theory of Operations and VAV AHU Fan Characteristics (Calculation Basis) with the Existing Control Function (Fixed Duct Static Pressure Set Points iv 3.5 Theory of Operations and VAV A H U Fan Characteristics 42 (Calculation Basis) with the Proposed Adaptive Control Duct Static Pressure Set Point Function 3.6 Adaptive Control for Pressure Set Point Varied Function 44 4. Actual Site Experimental Data 48 4.1 The selected 1 l k W VAV AHU Fan Characteristics 48 (Experiment Basis) 4.2 Sample Calculation of Power Consumption 56 5. Results and Calculation 58 5.1 Result 59 5.2 Calculation 69 6. Analysis 71 6.1 Analysis 71 6.1.1 Human and Equipment Heat Load 71 6.1.2 Heat Load from Outside and Ventilation 71 6.1.3 Heat Load from Radiation via Glass & Windows 72 7. Conclusion 77 References List 79 v LIST OF FIGURES Page Figure 2 .1 . General Fan Characteristics 9 Figure 2.2: Trunk and Branch System 15 Figure 2.3: Spider System 16 Figure 2.4: Radial System 17 Figure 2.5: Perimeter Loop System 17 Figure 2.6: Speed - Torque Curve for an Induction Motor 19 Figure 2.7: Typical Block Diagram of a VSD 20 Figure 2.8: Motor Insulation Class 23 Figure 2.9: Duct Layout of one Simple Run with Short Takeoffs 25 Figure 2.10: Duct Layout of Complex Duct Runs with 25 Multiple Branches Figure 3.1: The System Architecture of the Central Air 31 Conditioning System Figure 3.2: The System Architecture of Building Management 33 System Figure 3.3: Constant Volume Air Handling Unit 34 Figure 3.4: Variable Volume Air Handling Unit 38 Figure 3.5: Variable Volume Box 40 Figure 3.6: Physical Network Diagram of Adaptive Pressure 46 Set Point Control Loop Figure 3.7: Control Algorithm Block Diagram of Adaptive 47 Pressure Set Point in DDC Figure 4 .1 : Fan Characteristics for Fixed (Constant) Duct 54 Pressure Values Figure 4.2: Fan Characteristics for Different Duct Pressure 55 Values (Fixed Speed) Figure 6 .1 . Variation of Outdoor Condition during the Sampling 74 Periods Figure 6.2: Variation of Average Outdoor Enthalpy during the 76 Sampling Periods 4 vi LIST OF TABLES Pag Table 2.1 Temperature Class and Maximum Operation Temperature 22 Table 2.2. Minimum Speed Limitation Vs Temperature Tolerance Class 23 Table 2.3 DDC Contact Convention 28 Table 3.1 AHU On/Off Schedule 35 Table 3.2: Schedule of Adaptive Control 45 Table 4.1 Fan Characteristics for Fixed Speed of 100% 48 Table 4.2. Fan Characteristics for Fixed Speed of 90% 49 Table 4.3: Fan Characteristics for Fixed Speed of 80% 50 Table 4.4: Fan Characteristics for Fixed Speed of 70% 51 Table 4.5: Fan Characteristics for Fixed Speed of 60% 52 Table 4.6: Fan Characteristics for Fixed Speed of 50% 53 Table 4.7: The Power Consumptions of AHU Fan for Different Air Flow 57 Rates Table 5.1: Total Power Consumption for 400 Pa, on 26 t h Oct 2009 59 Table 5.2: Total Power Consumption for 400 Pa, on 27 t h Oct 2009 60 Table 5.3: Total Power Consumption for 400 Pa, on 28 t h Oct 2009 61 Table 5.4: Total Power Consumption for 400 Pa, on 29 t h Oct 2009 62 Table 5.5: Total Power Consumption for 400 Pa, on 30 t h Oct 2009 63 Table 5.6: Total Power Consumption with Adaptive Control Duct Static 64 Pressure Set point on 17 t h Oct 2009 Table 5.7: Total Power Consumption with Adaptive Control Duct Static 65 Pressure Set point on 18 t h Oct 2009 Table 5.8: Total Power Consumption with Adaptive Control Duct Static 66 Pressure Set point on 19 t h Oct 2009 Table 5.9: Total Power Consumption with Adaptive Control Duct Static 67 Pressure Set point on 20 t h Oct 2009 Table 5.10: Total Power Consumption with Adaptive Control Duct Static 68 Pressure Set point on 21 Oct 2009 vn f Table 5.11: Total Power Consumption for Five Days with Fixed Duct Static Pressure Set Point of 400 Pa Table 5.12 Total Power Consumption for Five Days with Adapting 69 69 Control Duct Static Pressure Set Point Table 6 .1: Variation of Outdoor Relative Humidity and Dry Bulb Temperature during the Data Gathering Period of Adaptive 72 Control Table 6.2: Variation of Outdoor Relative Humidity and Dry Bulb 73 Temperature during the Data Gathering Period of Fixed Pressure Set Point Table 6.3: Variation of Average Outdoor Air Enthalpy during the Data 74 Gathering Period of Adaptive Control Table 6.4. Variation of Average Outdoor Air Enthalpy during the Data 75 Gathering Period of Fixed Pressure Set Point viii LIST OF ABBREVIATIONS Abbreviation Description A Ampere AC Alternative Current ASHRAE American Society of Heating, Refrigerating and Air- conditioning Engineers B M S Building Management System CAV Constant Air Volume CFD Computational Fluid Dynamics Co2 Carbon Dioxide DC Direct Current DDC Direct Digital Control DW/142 Specification for Sheet Metal Ductwork Addendum-A D X Direct Expansion EMI Electromagnetic Interference g Gravity Acceleration H V A C Heating Ventilation and Air Conditioning Hz Hertz IAQ Indoor Air Quality kW Kilo Watt 1/s Liters per Second m Meter m/s Meters per Second m/s2 Meters per Square Second mA Milliamp N/m2 Newton per Square Second N E M A National Electrical Manufacturer Association °C Celsius ix p Pa PI RH R P M S M A C N A V VAV VFD VSD z A . Pressure Pascal Proportional-Integral (PI) control Relative Humidity Revaluation per Minutes Sheet Metal and Air Conditioning Contractors Association Velocity, Voltage Variable Air Volume Variable Frequency Driver Variable Speed Diver Height 4k X