Sep 10, 2011 - water cooler, refrigerator, coffee maker and vending machine. The list of ...... A solar ejector cooling system using refrigerant R134a in.
University of Technology, Sydney Faculty of Engineering and Information Technology
Architectural Modifications: Performance Assessment of the Solar Cooling System for a Small Size Office Building
By Ahmed Y Taha Al-Zubaydi BSc Mechanical Engineering
Thesis submitted for fulfillment of requirements for the degree of Master of Engineering
CERTIFICATE OF AUTHORSHIP/ ORIGINALITY
I certify that the work in this thesis has not previously been submitted for a similar degree nor has it been submitted as part of requirements for any other degree except as fully acknowledged within the text. I also certify that the thesis has been written by me. Any help that I have received in my research work and the preparation of the thesis itself has been acknowledged. In addition, I certify that all information sources and literature used are referenced in the thesis.
Ahmed Y Taha Al-Zubaydi
This thesis is dedicated to the memory of my father, my beloved mother, my lovely wife Sarab, my sweet daughters Basma and Tanya, ɅɀȾɊȷȲȾȺȽɊȲȿȵȷɃȺȶȿȵɄ¡¡ȲȿȵɅȹȶȺȿɄɁȺɃȲɅȺɀȿɀȷȞɀȵ¡
ACKNOWLEDGEMENTS I would first like to thank my research supervisor, Mr. John Dartnall, for his support and guidance. John gave me the opportunity to gain research experience by enabling me to participate in several researches throughout the course of my master degree. I would also like to thank my associate supervisor Dr. Jafar Madadnia for his support. A special thanks to Associated Professor Guang Hong and Professor John Reizes for their help and advice. Special thanks also to Ms. Phyllis Agius for her continuous help and kindness. Thanks to Ms. Sue Felix for the editorial advice, her language and illustration of the thesis is highly ĂƉƉƌĞĐŝĂƚĞĚ͘dŚŝƐƚŚĞƐŝƐǁŽƵůĚŶ͛ƚďĞŐŽŽĚǁŝƚŚŽƵƚŚĞƌŚĞůƉ͘ Thanks to all my colleagues and friends, with special thanks to Mr Mohamed Khaled Abu Mahmoud, Dr. Maan Takruri, and every one in Room 1.23.14 for the friendly environment and help offered. Thank you to my Mother and brothers for instilling within me an appreciation for education, and willingness to face and conquer challenges. The love of family is a precious gift that I feel honoured and blessed to hold. A special thanks to all my family and friends who have been understanding and supportive throughout this endeavour, spurring me on with encouragement and acts of love. Thanks to my daughters Basma and Tanya for filling my life with joy and happiness. Finally, and most importantly, I wish to express my sincerest appreciation for my wife, Sarab M Mansoor. Her encouragement and complete faith in my ability to excel in this work was an integral part of my success. Her decisive help was crucial to completing this thesis, and without her support touches I would be far from reaching my goals. Her unfailing love and commitment have enabled me to maintain balance despite the demands of this research, and also helped me to grow emotionally, spiritually, and academically. Thank you, my love.
TABLE OF CONTENTS CERTIFICATE OF AUTHORSHIP/ORIGINALITY..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ŝ /d/KE͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ ͙͙͙͙͙͙͙͙͙͙ ii ACKNOWLEDGMENT͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘ iii d>K&KEdEd^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ iv >/^dK&&/'hZ^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘..viii >/^dK&d>^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘.xv ZKEzD^EZs/d/KE^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ǆǀŝŝŝ ^dZd͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘ǆǆŝŝ d,^/^Khd>/E͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘xxiv Wh>/d/KE͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘xxv 1. CHAPTER 1: INTRODUCTION͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘ϭ 1.1. BACKGROUND͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͘.͙..͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͘͘ϭ 1.2. SOLAR COOLING͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘͘͘Ϯ 1.3. BUILDING ENERGY EFFICIENCY͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘ϱ 1.4. AIM AND OBJECTIVES K&d,^dhz͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘ϱ 1.4.1. /D͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϱ 1.4.2. OBJECTIVES͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘ϱ 1.5. METHODOLOGY͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϲ 1.6. SIMULATION PROGRAMS͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϵ 1.7. REFERENCES͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘ϭϬ 2. CHAPTER 2: LITERATURE Zs/t͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭϮ 2.1. INTERNATIONAL RESEARCHES ON SOLAR THERMAL COOLING SYSTEMS͙͙͙͙͙͙͙͙.͙͙͙͘͘ϭϮ 2.1.1. HISTORY BACKGROUND..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϭϮ 2.1.2. ZEdtKZ>^/K&&/h/>/E'͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘46 22.214.171.124. EXTERNAL WALLS͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘46 126.96.36.199. INTERIOR WALLS͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϰϳ 188.8.131.52. ZKK&͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϰϴ 184.108.40.206. SLAB-ON-GRADE FLOOR͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϰϵ 220.127.116.11. FENESTRATION͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϱϬ 4.4.3. VENTILATION AND INFILTRATION͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘51 4.4.4. h/>/E'>K^E^,h>^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘52 18.104.22.168. OCCUPANCY IN THE OFFICE BUILDING͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϱϮ 22.214.171.124. EQUIPMENT AND LIGHTING IN THE OFFICE BUILDING͙͙͙͙͙͙͙͙͙͙͙͙͘ϱϯ
4.5. ENERGY ANALYSIS..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͘͘͘57 4.5.1. SIMULATION RESULTS OF BUILDING LOADS: SMALL SIZE K&&/h/>/E'DK>͙͘57 4.5.2. /&&ZEd/d/KEdtEdZE^z^EKWE^dh/KZ^h>d^͙͙͙͙͙͙͙͙͙͙͘͘͘62 4.5.3. COMPARISON OF COOLING LOAD RESULTS FOR BASIC CONDITIONS AND /DWZKsDEdK&d,h/>/E'͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘62 4.6. ^hDDZz͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘64 4.7. REFERENCES͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘65 5. CHAPTER 5: SOLAR COOLING SYSTEM CONFIGURATION AND MODELLING͙͙͙͙͙͙͙͙͙͙͙͘...66 5.1. /EdZKhd/KE͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘66 5.2. SOLAR COOLING SYSTEM ^/'E͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘͘͘67 5.3. ^//E'd,D/EKDWKEEd^K&d,^K>ZKK>/E'^z^dD͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘..70 5.3.1. ^KZWd/KE,/>>Z;,Ϳ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘70 5.3.2. ^K>Zd,ZD>K>>dKZ^;^Ϳ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘72 5.3.3. STORAGE dE>/E'/EWhd^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͘132 B. WWE/y͗h/>/E'EZ'z^/Dh>d/KEt/d,dZE^z^͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘143 B.1. INTRODUCTION ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘143 ͘Ϯ͘h/>/E'DK>>/E't/d,dZEh/>͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘143 B.3. ^/Dh>d/KEK&h/>/E'>K^t/d,dZE^z^^/Dh>d/KE^dh/K͙͙͙͙͙͙͙͘..͙͙..160 ͘ϰ͘Z&ZE^͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘163 C.
APPENDIX C; MODELS DESIGN WITH GOOGLE SKETCHUP AND OPENSTUDIO͙͙͙͙͙͙͙͙͘͘͘͘͘164 ͘ϭ͘/EdZKhd/KE͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͘ϭ64 ͘Ϯ͘/E&KZDd/KEKEh/>/E'h^͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͘͘͘164 ͘ϯ͘/EdZ&K&'KK'>^/d/KE^͙͙͙͙͙͙͘ϭϴϱ vii
LIST OF FIGURES &ŝŐƵƌĞϭ͘ϭ͘^ŽůĂƌŽŽůŝŶŐdĞĐŚŶŽůŽŐŝĞƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘͘͘ϰ &ŝŐƵƌĞϭ͘Ϯ͘^ƚĞƉƐŽĨƉƉůŝĞĚDĞƚŚŽĚŽůŽŐǇ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙8 Figure 3.1. Vapour-Compression Refrigeration Cycle ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙...20 &ŝŐƵƌĞϯ͘Ϯ͘ďƐŽƌƉƚŝŽŶDĂĐŚŝŶĞƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘21 Figure 3.3. Single Effect Machine Pressure-dĞŵƉĞƌĂƚƵƌĞŝĂŐƌĂŵ͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͘....24 Figure 3.4. Single-ĨĨĞĐƚ^ƚĞĂŵ&ŝƌĞĚǇĐůĞŝĂŐƌĂŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.͙͙͙...25 Figure 3.5. Double-Effect Machine Pressure-dĞŵƉĞƌĂƚƵƌĞŝĂŐƌĂŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘..͙͙͘͘26 Figure 3.6. Double-ĨĨĞĐƚ^ƚĞĂŵ&ŝƌĞĚǇĐůĞŝĂŐƌĂŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘27 Figure 3.7. Triple- Effect Absorption Chiller P-dŝĂŐƌĂŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͘͘ 28 Figure 3.8. Absorption Chillers vs. ĂƌŶŽƚǇĐůĞKWƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͘͘28 Figure 3.9. Vapour-Absorption Refrigeration ǇĐůĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙.͙..29 &ŝŐƵƌĞϰ͘ϭ͘ůŽĐŬŝĂŐƌĂŵŽĨƵŝůĚŝŶŐ>ŽĂĚ^ŝŵƵůĂƚŝŽŶWƌŽĐĞƐƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘38 Figure 4.2. Meteonorm V. 5.1. Console Panel͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙...40 Figure 4.3. TMY3 to TMY2 Formatter Software from NERL..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘40 &ŝŐƵƌĞϰ͘ϰ͘dZE^z^ŽŵƉŽŶĞŶƚdǇƉĞϴϵĞ>ŽŐŽ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘41 Figure 4.5. ǀĞƌĂŐĞDŽŶƚŚůǇĂŶĚŶŶƵĂůDĂǆŝŵƵŵĂŶĚDŝŶŝŵƵŵdĞŵƉĞƌĂƚƵƌĞƐ͙͙͙͙͘..͙͙͙͙͙41 &ŝŐƵƌĞϰ͘ϲ͘KƵƚĚŽŽƌdĞŵƉĞƌĂƚƵƌĞĨŽƌ^ǇĚŶĞǇŽŶ,ŽƵƌůǇĂƐĞĚ^ŝŵƵůĂƚŝŽŶ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙42 Figure 4.7. Relative Humidity for Sydney on Hourly Based Simulation͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘42 Figure 4.8. Direct Normal Radiation ĨŽƌ^ǇĚŶĞǇŽŶ,ŽƵƌůǇĂƐĞĚ^ŝŵƵůĂƚŝŽŶ͙͙͙͙͙͙͙͙͙͙͙͙͙͙43 Figure 4.9. Global Horizontal Radiation for Sydney on Hourly Based SimulatiŽŶ͙͙͙͙͙͙͙͙͙͙͙...43 Figure 4.10. Diffuse Radiation on Horizontal ĨŽƌ^ǇĚŶĞǇŽŶ,ŽƵƌůǇĂƐĞĚ^ŝŵƵůĂƚŝŽŶ͙͙͙͙͙͙͙͙͙44 &ŝŐƵƌĞϰ͘ϭϭ͘ǆŽŶŽŵĞƚƌŝĐsŝĞǁŽĨ^ŵĂůůKĨĨŝĐĞƵŝůĚŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘45 Figure 4.12. Floor Plan for a Small Size Office Building DŽĚĞů͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘45 &ŝŐƵƌĞϰ͘ϭϯ͘^ŵĂůů^ŝǌĞKĨĨŝĐĞƵŝůĚŝŶŐŽŶƐƚƌƵĐƚŝŽŶ>ĂǇĞƌƐĨŽƌǆƚĞƌŶĂůtĂůů͙͙͙͙͙͙͙͙͙͙͙͙͙͘46 viii
Figure 4.14. Outline Type of Interior Walls in Small Size Office Building͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..47 Figure 4.15. Small Size Office ƵŝůĚŝŶŐZŽŽĨ^ƚƌƵĐƚƵƌĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙..48 Figure 4.16. Outline Type of Slab on Grade Floor in Small Size Office Building͙͙͙͙͙͙͙͙͙͙͙͙...49 &ŝŐƵƌĞϰ͘ϭϳ͘sĞŶƚŝůĂƚŝŽŶĂŶĚ/ŶĨŝůƚƌĂƚŝŽŶĂŝůǇ^ĐŚĞĚƵůĞĨŽƌ^ŵĂůů^ŝǌĞƵŝůĚŝŶŐDŽĚĞů͙͙͙͙͙͙͙͙͘͘51 FigƵƌĞϰ͘ϭϴ͘KĐĐƵƉĂŶĐǇĂŝůǇ^ĐŚĞĚƵůĞĨŽƌĂ^ŵĂůů^ŝǌĞKĨĨŝĐĞƵŝůĚŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ 52 Figure 4.19. Lighting Daily Schedule for Small Size KĨĨŝĐĞƵŝůĚŝŶŐDŽĚĞů͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͘.54 Figure 4.20. Plug Load Daily Schedule for Small Size Office Building DŽĚĞů͙͙͙͙..͙͙͙͙͙͙͙͙͙͙55 Figure 4.21. HVAC Daily Schedule for Small Size KĨĨŝĐĞƵŝůĚŝŶŐDŽĚĞů͙͙͙͙͙͙͙͙..͙͙͙͙͙͙..͙͘͘56 Figure 4.22. Small Size Office Monthly Load Summary for ĂƐĞϭ͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙.͙͙͘58 Figure 4.23. Medium Size Office Monthly Load Summary for ĂƐĞϮ͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͘͘58 Figure 4.24. Small Size Office Monthly Load ^ƵŵŵĂƌǇĨŽƌĂƐĞϯ͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͘͘60 Figure 4.25. Small Size Office Monthly Load Summary for ĂƐĞϰ͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙.͙͙͘61 Figure 4.26. Small ^ŝǌĞKĨĨŝĐĞƵŝůĚŝŶŐ'ƌĂƉŚŽĨDŽŶƚŚůǇŽŽůŝŶŐ>ŽĂĚƐĨŽƌĂĐŚĂƐĞ͙͙͙͙͙..͙͙͘͘62 &ŝŐƵƌĞϰ͘Ϯϳ͘^ŵĂůů^ŝǌĞKĨĨŝĐĞƵŝůĚŝŶŐ'ƌĂƉŚŽĨŶŶƵĂůdŽƚĂůŽŽůŝŶŐ>ŽĂĚƐĨŽƌĂĐŚĂƐĞ͙͙͙͙͙͘ 63 Figure 4.28. Small Size Office Building Graph of Annual Saving in Total Cooling Loads for Each Case.64 Figure 5.1. Solar Cooling System Facility Schematics͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͘68 Figure 5.2. Solar Cooling Facility TRNSYS Studio Arrangement͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙.69 Figure 5.3. Solar Fraction Value Change with Collector Inclination ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϳϴ Figure 5.4. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based ŽŶĂƐĞϭĐŽŽůŝŶŐůŽĂĚƐͿ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͘..79 Figure 5.5. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based ŽŶĂƐĞϮĐŽŽůŝŶŐůŽĂĚƐͿ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͘ϴϬ Figure 5.6. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based on CĂƐĞϯĐŽŽůŝŶŐůŽĂĚƐͿ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͘ϴϬ Figure 5.7. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based ŽŶĂƐĞϰĐŽŽůŝŶŐůŽĂĚƐͿ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͘ϴϭ Figure 5.8. Global 'ƌĞĞŶŚŽƵƐĞ'ĂƐŵŝƐƐŝŽŶƐďǇ'ĂƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙ϴϴ ix
Figure 6.1. Calculated Costs for Solar Cooling System and Reference System in Basic Mode.͙͙.....99 Figure 6.2. Calculated Costs for Solar Cooling System ĂŶĚZĞĨĞƌĞŶĐĞ^ǇƐƚĞŵŝŶĂƐĞϮ͙͙͙͙͙.͙͙100 Figure 6.3. Calculated Costs for Solar Cooling System ĂŶĚZĞĨĞƌĞŶĐĞ^ǇƐƚĞŵŝŶĂƐĞϯ͙͙͙͙͙.͙͙100 Figure 6.4. Calculated Costs for Solar Cooling System ĂŶĚZĞĨĞƌĞŶĐĞ^ǇƐƚĞŵŝŶĂƐĞϰ͙͙͙͙͙.͙͙101 Figure 6.5. Solar Collector Useful Energy in Case 1 ŽŽůŝŶŐ>ŽĂĚƐ͕ƵŝůĚŝŶŐĂƐŝĐDŽĚĞů͙͙͙͙͙͙͘͘ϭ02 Figure 6.6. Solar Collector Useful Energy in Case 2 Cooling Loads, Modified Double Glazed tŝŶĚŽǁƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘ϭ02 Figure 6.7. Solar Collector Useful Energy in Case 3 ŽŽůŝŶŐ>ŽĂĚƐ͕KǀĞƌŚĂŶŐ^ŚĂĚŝŶŐ͙͙͙͙͙͙͙͙ϭ03 Figure 6.8. Solar Collector Useful Energy in Case 4 Cooling Loads, Double Glazed Windows with KǀĞƌŚĂŶŐƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϭ03 Figure 6.9. Annual Saving in Operation Costs by Using Solar Cooling System for the Basic Building ŽŶĚŝƚŝŽŶ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ05 Figure 6.10. Annual Saving in Operation Costs by Using Solar Cooling System and Double Glazing in ^ĐĞŶĂƌŝŽϮƵŝůĚŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘...͙͙͘ϭ05 Figure 6.11. Annual Saving in Operation Costs by Using Solar Cooling System and Overhang Shading ŝŶ^ĐĞŶĂƌŝŽϯƵŝůĚŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ06 Figure 6.12. Annual Saving in Operation Costs by Using Solar Cooling System, Double Glazing and Overhang Shading ŝŶ^ĐĞŶĂƌŝŽϰƵŝůĚŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ06 Figure 6.13. Payback Periods for Solar Cooling System for Scenario 1 (Basic Building Condition)͙͘͘108 &ŝŐƵƌĞϲ͘ϭϰ͘WĂǇďĂĐŬWĞƌŝŽĚƐĨŽƌ^ŽůĂƌŽŽůŝŶŐ^ǇƐƚĞŵĂŶĚƚŚĞŽƵďůĞ'ůĂǌŝŶŐĨŽƌ^ĐĞŶĂƌŝŽϮ͙͙͙108 Figure 6.15. Payback Periods for Solar Cooling System and the Overhang Shading for Scenario 3.͙ϭ09 Figure 6.16. Payback Periods for Solar Cooling System, Double Glazing and Overhang Shading for ^ĐĞŶĂƌŝŽϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ09 &ŝŐƵƌĞϲ͘ϭϳ͘>ŝĨĞǇĐůĞŽƐƚĨŽƌ^ŽůĂƌŽŽůŝŶŐ^ǇƐƚĞŵŝŶ^ĐĞŶĂƌŝŽϭ;ĂƐŝĐƵŝůĚŝŶŐŽŶĚŝƚŝŽŶͿ͙͙.͙110 Figure 6.18. Life Cycle Cost for Solar Cooling System and DoƵďůĞ'ůĂǌŝŶŐŝŶ^ĐĞŶĂƌŝŽϮ͙͙͙͙͙͙͘͘ϭ11 Figure 6.19. Life Cycle Cost ĨŽƌ^ŽůĂƌŽŽůŝŶŐ^ǇƐƚĞŵĂŶĚKǀĞƌŚĂŶŐ^ŚĂĚŝŶŐŝŶ^ĐĞŶĂƌŝŽϯ͙͙͙͙͘͘112 Figure 6.20. Life Cycle Cost for Solar Cooling System, Double Glazing and Overhang Shading in ^ĐĞŶĂƌŝŽϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ12 Figure 6.21. Net Present Values for Solar Cooling Systems in Scenario 1 (Basic Building x
ŽŶĚŝƚŝŽŶͿ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ13 Figure 6.22. Net Present Values for Solar Cooling Systems and Double Glazing for Scenario 2͙͙͙ϭ14 Figure 6.23. Net Present Values for Solar Cooling System and Overhang Shading in Scenario 3͙͙.115 Figure 6.24. Net Present Values for Solar Cooling System, Double Glazing and Overhang Shading in ^ĐĞŶĂƌŝŽϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ 115 Figure 6.25. The Saving in CO2 Gas Emission for Solar Cooling System, Double Glazing and Overhang ^ŚĂĚŝŶŐŝŶ^ĐĞŶĂƌŝŽϭ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ 117 Figure 6.26. The Saving in CH4 'ĂƐŵŝƐƐŝŽŶďǇ^ŽůĂƌŽŽůŝŶŐ^ǇƐƚĞŵŝŶ^ĐĞŶĂƌŝŽϭ͙͙͙͙͙͙.͙͙͙117 Figure 6.27. The Saving in N2K'ĂƐŵŝƐƐŝŽŶĨŽƌ^ŽůĂƌŽŽůŝŶŐ^ǇƐƚĞŵŝŶ^ĐĞŶĂƌŝŽϭ͙͙͙͙͙͙͙͙͘͘ϭ18 Figure 6.28. The Saving in CO2 Gas Emission by the Solar Cooling System and Double Glazing in ^ĐĞŶĂƌŝŽϮ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ19 Figure 6.29. The Saving in CH4 Gas Emission by the Solar Cooling System and Double Glazing in ^ĐĞŶĂƌŝŽϮ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ19 Figure 6.30. The Saving in N2O Gas Emission by the Solar Cooling System and Double Glazing in ^ĐĞŶĂƌŝŽϮ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ20 Figure 6.31. The Saving in CO2 Gas Emission by the Solar Cooling System and Overhang Shading in ^ĐĞŶĂƌŝŽϯ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ21 Figure 6.32. The Saving in CH4 Gas Emission by the Solar Cooling System and Overhang Shading in ^ĐĞŶĂƌŝŽϯ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ21 Figure 6.33. The Saving in N2O Gas Emission by the Solar Cooling System and Overhang Shading in ^ĐĞŶĂƌŝŽϯ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ22 Figure 6.34. The Saving in CO2 Gas Emission by the Solar Cooling System, Double Glazing and Overhang Shading in Scenario ϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ23 Figure 6.35. The Saving in CH4 Gas Emission by the Solar Cooling System, Double Glazing and KǀĞƌŚĂŶŐ^ŚĂĚĞŝŶ^ĐĞŶĂƌŝŽϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ23 Figure 6.36. The Saving in N2O Gas Emission by the Solar Cooling System, Double Glazing and Overhang Shading ŝŶ^ĐĞŶĂƌŝŽϰ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ24 &ŝŐƵƌĞ͘ϭ͘dZEƵŝůĚ^ƚĂƌƚtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘143 &ŝŐƵƌĞ͘Ϯ͘EĞǁŽŶĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘144 &ŝŐƵƌĞ͘ϯ͘ŽŶĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘144
&ŝŐƵƌĞ͘ϰ͘ZĞŐŝŵĞĂƚĂtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙...͙͙͘͘145 &ŝŐƵƌĞ͘ϱ͘/ŶĨŝůƚƌĂƚŝŽŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙.͙͙145 Figure B.6. New /ŶĨŝůƚƌĂƚŝŽŶdǇƉĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..146 &ŝŐƵƌĞ͘ϳ͘ŝƌŚĂŶŐĞŽĨ/ŶĨŝůƚƌĂƚŝŽŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘146 &ŝŐƵƌĞ͘ϴ͘sĞŶƚŝůĂƚŝŽŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͘͘͘147 Figure B.9. New Ventilation Type tŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙.͙͙͘147 &ŝŐƵƌĞ͘ϭϬ͘ŝƌŚĂŶŐĞŽĨsĞŶƚŝůĂƚŝŽŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..148 &ŝŐƵƌĞ͘ϭϭ͘,ĞĂƚŝŶŐtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ 149 &ŝŐƵƌĞ͘ϭϮ͘EĞǁ,ĞĂƚŝŶŐdǇƉĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙.͙͙͙͘͘149 Figure B.13. Heating- ZŽŽŵdĞŵƉĞƌĂƚƵƌĞŽŶƚƌŽůtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙150 &ŝŐƵƌĞ͘ϭϰ͘ŽŽůŝŶŐtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘150 &ŝŐƵƌĞ͘ϭϱ͘EĞǁŽŽůŝŶŐdǇƉĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘151 Figure B.16. Cooling-ZŽŽŵdĞŵƉĞƌĂƚƵƌĞŽŶƚƌŽůtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘151 &ŝŐƵƌĞ͘ϭϳ͘ŽŵĨŽƌƚtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.͙͘͘152 &ŝŐƵƌĞ͘ϭϴ͘EĞǁŽŵĨŽƌƚdǇƉĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͘͘152 Figure B.19. The Zone GĂŝŶƐtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙153 &ŝŐƵƌĞ͘ϮϬ͘dŚĞŽŶĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘.154 &ŝŐƵƌĞ͘Ϯϭ͘tĂůů>ŝďƌĂƌǇtŝŶĚŽǁŝŶdZEƵŝůĚ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙. 155 Figure B.22. Wall Type Manage Window͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘.155 Figure B.23. TRNSYS Layer Library Window͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘ϭ56 Figure B.24. New Layer Type Window͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘ϭ56 Figure B.25. New Wall Type Window͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.157 Figure B.26. Windows Panel ŝŶŽŶĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘159 &ŝŐƵƌĞ͘Ϯϳ͘KƵƚƉƵƚĂƚĂtŝŶĚŽǁŝŶdZEƵŝůĚ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘. 159 &ŝŐƵƌĞ͘Ϯϴ͘dǇƉĞϱϲǆƚĞƌŶĂů;Ύh/Ϳ&ŝůĞĂůůŝŶŐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.͙͙͙͙͘160
Figure B.29. TRNSYS ^ŝŵƵůĂƚŝŽŶ^ƚƵĚŝŽtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘.͙͙͙͙͙161 Figure B.30. Monthly Summary &ŝůĞĂƚĂǆĂŵƉůĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.162 Figure B.31. Online Plotter Hourly Loads Graph Example͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙163 Figure C.1. Display List to Draw ĨƌŽŵ'ŽŽŐůĞ^ŬĞƚĐŚhƉ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙165 Figure C͘Ϯ͘KƉĞŶ^ƚƵĚŝŽdĞŵƉůĂƚĞDŽĚĞůƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘166 Figure C.3. First Step in Sketching ƚŚĞ&ůŽŽƌWůĂŶ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙166 Figure C.4. Set the Core Zone Outline ǁŝƚŚKĨĨƐĞƚKƌĚĞƌ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.167 Figure C͘ϱ͘^ŬĞƚĐŚŝŶŐƚŚĞWĞƌŝŵĞƚĞƌŽŶĞƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘167 Figure C.6. Create Space from &ůŽŽƌWůĂŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙167 Figure C.7. 3D Geometry for &ŝƌƐƚ&ůŽŽƌ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘168 Figure C͘ϴ͘^ŬĞƚĐŚƚŚĞWůĞŶƵŵ&ůŽŽƌWůĂŶ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘168 Figure C͘ϵ͘ϯ'ĞŽŵĞƚƌǇŽĨ&ŝƌƐƚ&ůŽŽƌĂŶĚWůĞŶƵŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.169 Figure C.10. 3D Geometry of a Three-floor ƵŝůĚŝŶŐǁŝƚŚWůĞŶƵŵƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͘169 Figure C͘ϭϭ͘^ƵƌĨĂĐĞDĂƚĐŚŝŶŐtŝŶĚŽǁŝŶKƉĞŶ^ƚƵĚŝŽ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.170 Figure C͘ϭϮ͘KĨĨŝĐĞƵŝůĚŝŶŐϯ'ĞŽŵĞƚƌǇŝŶŽŶƐƚƌƵĐƚŝŽŶZĞŶĚŝŶŐDŽĚĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.170 Figure C.13. Single Space Selection Vieǁ͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..171 Figure C͘ϭϰ͘^ĞƚtŝŶĚŽǁƚŽtĂůůZĂƚŝŽdŽŽůĂƌĐĐĞƐƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ 171 Figure C͘ϭϱ͘^ĞƚtŝŶĚŽǁƚŽtĂůůZĂƚŝŽtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ 172 Figure C.16. 3D Geometry of Office Building with EǆƚĞƌŶĂůtŝŶĚŽǁƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘172 Figure C͘ϭϳ͘^ĞƚƚƚƌŝďƵƚĞƐĨŽƌ^ĞůĞĐƚĞĚ^ƉĂĐĞtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͘͘173 Figure C.18͘KƉĞŶ^ƚƵĚŝŽ/ŶƐƉĞĐƚŽƌtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙͙173 Figure C.19͘'ůĂǌŝŶŐDĂƚĞƌŝĂů^ƉĞĐŝĨŝĐĂƚŝŽŶĚŝƚŝŶŐtŝŶĚŽǁŝŶKƉĞŶ^ƚƵĚŝŽ/ŶƐƉĞĐƚŝŽŶ͙͙͙͙͙͙͙͘174 Figure C.20. Adding an KǀĞƌŚĂŶŐĨŽƌǆƚĞƌŶĂůtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͘174 Figure C.21. Toolbar Access to Add Overhang by Projection Factor in OpenStudio Plug-ŝŶ͙͙͙͙͙͘175 Figure C.22͘KƉĞŶ^ƚƵĚŝŽWĂŶĞůtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͘ 176
Figure C.23͘KƉĞŶ^ƚƵĚŝŽ^ŝŵƵůĂƚŝŽŶtŝŶĚŽǁ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͘ 177 Figure C.24͘KƉĞŶ^ƚƵĚŝŽĂƐŝĐZĞƐƵůƚƐsŝĞǁĞƌ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙..177 Figure C.25͘ZĞƐƵůƚƐsŝĞǁĞƌtŝŶĚŽǁŝŶKƉĞŶ^ƚƵĚŝŽWĂĐŬĂŐĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙178 Figure C.26͘WĞƌŝŵĞƚĞƌŽŶĞϭŶŶƵĂůŽŽůŝŶŐĂŶĚ,ĞĂƚŝŶŐ>ŽĂĚƐŽŶ,ŽƵƌůǇĂƐĞƐ͙͙͙͙͙͙͙͙͙͘178
LIST OF TABLES Table 1.1. List of important studies used as a ŐƵŝĚĞůŝŶĞŝŶƚŚŝƐƉƌŽũĞĐƚ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϳ Table 2.1. Most recent studies in the literature ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϭϲ dĂďůĞϯ͘ϭKWĂŶĚŽƉĞƌĂƚŝŶŐƚĞŵƉĞƌĂƚƵƌĞƌĂŶŐĞ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘28 Table 4.1. Materials for small size office building exterior walls ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͘.47 Table 4.2. Small size office building overall U-factor for external wall ͙͙͙͙͙͙͙͙͙͙͙..͙͙..͙͙.͙47 Table 4.3. Small size office building interior walls materials ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙...48 Table 4.4. Small size office building roof cladding materials͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘49 Table 4.5. Small size office building roof overall U-factor (W/m2͘ŬͿ͙͙͙͙͙͙͙͙͙͙͙͙͙...͙.͙͙......49 Table 4.6. Small size office building slab-on-grade materials cover͙͙͙͙͙͙͙͙..͙͙͙͙.͙͙͙͙͙͙͘͘50 Table 4.7. Small size office building slab-on-grade overall U-factor (W/m2͘ŬͿ͙͙͙͙͙..͙͙͙.͙.͙͙͘͘.50 Table 4.8. Windows areas and orientations for the small size office building baseline models.͙͙͙͘͘50 Table 4.9. Office activity level related to sensible and latent heat gain ͙.͙͙͙͙͙͙͙͙͙͙͙..͙͙......52 Table 4.10. Design values for ůŝŐŚƚůĞǀĞůƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ 53 Table 4.11. Design values for lighting power in energy-efficient ƐǇƐƚĞŵƐ͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͘͘.53 Table 4.12. Lighting power density calculation.͙..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘.54 Table 4.13. Cooling & heating load summary for medium size building office basic mode͙͙͙͙͘͘͘͘͘͘57 Table 4.14. Cooling & heating load summary for medium size building office with modified glazing mode...͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.....59 Table 4.15. Cooling & heating load summary for medium size building office with overhang mode..͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.60 Table 4.16. Cooling & heating load summary for medium size building office with a combination of double glazed windows and overhang mode.͙͙͙͙͙͙͙.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..͙͘61 Table 4.17. Cooling load saving percentage comparison͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.64 Table 5.1. Specification data of HWAR-L30 and SC30 absoƌƉƚŝŽŶĐŚŝůůĞƌƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘͘71 dĂďůĞϱ͘Ϯ͘ǀĂĐƵĂƚĞĚƚƵďĞƐŽůĂƌƚŚĞƌŵĂůĐŽůůĞĐƚŽƌƐ͛ƐƉĞĐŝĨŝĐĂƚŝŽŶĚĂƚĂ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘72
dĂďůĞϱ͘ϯ͘^ƉĞĐŝĨŝĐƚĂŶŬǀŽůƵŵĞƉĞƌƐŽůĂƌĐŽůůĞĐƚŽƌĂƌĞĂŝŶƉƌĞǀŝŽƵƐƐƚƵĚŝĞƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘74 Table 5.4. Solar collectors ƐůŽƉĞĂŶĂůǇƐŝƐŽƵƚƉƵƚƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϳϴ Table 5.5 Emission ĨĂĐƚŽƌƐĨŽƌƚŚĞĐŽŶƐƵŵƉƚŝŽŶŽĨŶĂƚƵƌĂůŐĂƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϴϵ Table 6.1. Total cost summary ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͘....93 Table 6.2. Profitability indicators for double glazing ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘ϵϲ Table 6.3. Profitability indicators for overhang ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.....96 Table 6.4. Profitability indicators for the mixed modification ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙ϵϲ Table 6.5. ^ƵŵŵĂƌǇŽĨŝŶĚŝĐĂƚŽƌƐ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙..97 Table 6.6. SCS component costs͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͙͙͙ϵϴ Table 6.7. Study results summary.͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.͙͙͙͙͘͘͘ϭ27 Table A.1. Sydney 2011 outdoor temperature in degrees Celsius throughout the year, making the ĂǀĞƌĂŐĞŵŽŶƚŚůǇĂŶĚĂŶŶƵĂůŵĂǆŝŵƵŵĂŶĚŵŝŶŝŵƵŵ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙.132 Table A.2. Sydney 2011 outdoor temperature specified hourly temperature on hottest days of each month in the ǇĞĂƌ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ 132 Table A.3. Relative humidity in percent of the city of ^ǇĚŶĞǇ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘. 133 Table A.4. Monthly solar radiation, direct, global and diffuse in Wh/ m² of the city of ^ǇĚŶĞǇ͙͙͙134 Table A.5. Usable area of the small size office building ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ 134 Table A.6. Fenestration U-factor and solar heat gain coefficient (SHGC) visible light transmittance (VLT) values for the small size office building baseline models͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ϭ35 Table A.7. Minimum ventilation rates in breathing zone for medium size office building form Standard 62.1-ϮϬϭϬ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘͘135 Table A.8. Ventilation rates per zone for small size office building ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘..136 Table A.9. Hourly occupancy schedule for small size office building model͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘.137 Table A.10. Lighting schedule for small size office building model͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙ 138 Table A.11. Plug load calculations for small size office building model͙͙͙͙͙͙͙͙͙͙..͙͙͙͙͙͙ϭ39 Table A.12. Plug load schedule for small size office building model͙͙͙͙͙͙͙͙͙͙͙.͙.͙͙͙͙͙..140 Table A.13. HVAC schedule for small size office building model͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘ϭ41 xvi
Table A.14. Cooling & heating thermostat schedule for small size office building model͙͙͙͙͙͘͘͘ϭ42 Table D.1. Total cost for double glazed surface ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘180 Table D.2. Overhang window shading measurements ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘180 Table D.3. Overhang unit costs excluding GST͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘180 Table D.4. Double glazing, overhang shading and mixed maintenance costs with rate 1%...............181 Table D.5. Double glazing return rates ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘.182 Table D.6. Rates of return for the overhang shading ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘183 Table D.7. Rates of return for the mixed modification ͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͙͘͘184
ACRONYMS AND ABBREVIATIONS A
Area of surface
ŽůůĞĐƚŽƌ͛ƐNegative first order efficiency coefficient.
Gross area per solar collector set.
air changes per hour
Advanced Energy Design Guide for Small Office Building
American Society of Heating, Refrigerating and Air-Conditioning Engineers
collector specific area (Collector area per kW of chiller capacity)
Australian Bureau of Meteorology
Commercial Building Energy Consumption Survey
Chilled water circuit pump
Carbon tax tariff on electricity
Carbon tax tariff on natural gas
Coefficient of Performance
Conventional reference system coefficient of performance
Specific heat of fluid
Cooling water circuit pump
US Department Of Energy
Energy Efficiency Strategy
Natural gas lower heating value (Energy content factor)
Annual electricity consumed by the reference conventional system
The capital recovery factor
Global Solar radiation
Gross Domestic Product
Heating, ventilation, and air conditioning
Hot water circuit pump
the effective interest rate
International Energy Agency
Illuminating Engineering Society
Lawrence Berkeley National Laboratory
Life Cycle Cost
Lighting Power Density
mass flow rate
Number of solar collectors in series
Equivalent annual natural gas consumption
The annual energy saving
Net Present Value
National Renewable Energy Laboratory
New South Wales
Pacific Northwest National Laboratory
Auxiliary heater capacity
Total annual cooling load
The amount of useful energy collected by the solar collectors
Total heat gain (qt = qs +ql)
The discount rate
outdoor air flow rate per person
outdoor airflow rate per floor area
(m3) (m3/Year) (A$)
Solar cooling system
Solar heat gain coefficient
Solar hot water circuit pump
The year of specific operating cost determined.
Hot water tank
Typical meteorological year
Natural gas tariff
Coefficient of transmission
Tank specific volume (Tank volume per collector area)
Variable air volume
Visible light transmittance
Auxiliary heater efficiency
Efficiency of the Gas operated power plant
ABSTRACT Across the world, governments, organisations and individuals are seeking to obtain the most effective, cheapest and environmentally clean power sources. During the last decade, air conditioning systems that use renewable energies have undergone significant development. This expansion has been driven, in large part, by successive periods of extreme solar heat and increased demand for the comfort of summer air conditioning in residential and commercial buildings. Most of Australia's greenhouse gas emissions (about 50%) come from the burning of fossil fuels for energy (e.g., for electricity and transport). For this reason, looking for a reduction in the energy used in buildings as well as looking for alternative power sources to fossil fuels should be explored. This project presents approaches to increasing the performance of a solar cooling system by improving the energy efficiency of the building for a typical small-sized Australian office building in Sydney, New South Wales (NSW). Solar cooling systems with a thermally driven LiBr-H2O single-effect absorption chiller that utilises the solar thermal energy provided through evacuated tube solar thermal collectors and thermal back-up is a popular system among solar cooling applications around the world. In this study, the performance of a similar system is evaluated and compared with a conventional cooling system in terms of energy, economic and environmental aspects. The aim of this project was to examine a solar air conditioning system with absorption chiller contributions in a small office building cooled in different thermal efficiency scenarios by demonstrating and evaluating specific architectural improvements to the basic model of the building. These improvements took the form of double-glazed windows, overhanging window shades, and a combination of double-glazed windows and overhanging shades in the environment of Sydney, NSW. TRNSYS and OpenStudio/EnergyPlus software with the graphical interference of Google SketchUp for building energy modelling and simulation were used. To achieve an efficient usage for the building under consideration, the project was divided into two main blocks. The first block included the design and simulation of the building to evaluate a set of proposed architectural improvements, with the aim of achieving optimal intake. For the second block, energy and economic assessments were performed to choose the best alternative application. The building underwent simulation under four different scenarios: the baseline scenario (i.e. the current situation); the introduction of an overhang on the north side of the building; the modification of existing glazing of 4 mm to a double glass and finally a combination of the two modifications: overhang and glazing options. The analysis of the energy and environmental performance of the solar cooling system was based on the system solar fraction and the CO2 foot print. The modelling and simulation of the solar cooling system was carried out by the TRNSYS program in the four different scenarios. The results show that the combination of double glazing with overhang shade is the best option for increasing the thermal efficiency of the building and reducing the cooling load. The favourable assessment of performance of the solar cooling system is indicated by both the equivalent natural gas saved rate (3307 m3/year) and the solar fraction (0.804). In addition, the environmental performance of the system shows positive results by saving more than 69 Tonnes of CO2/year, which is the optimum value compared to other scenarios. xxii
Economically, the window overhang shade is the preferred option as an architectural modification in terms of initial cost, net present value and payback period. However, the economic performance of the solar cooling system studied was not competent when compared to the reference system (vapour compression). The LCC (life cycle cost) calculations show that the solar cooling system values are 40% more than those of the reference system. However, the NPV (net present value) results were found to be negative values after the 25-year life span, indicating that there is no significant profit reward at the end of the term of operation. The PBP (payback period) results, by contrast, show that the solar cooling system will return its value in a lesser period than the proposed life span of 25 years. In conclusion, by applying different architectural modifications for the building envelope, cooling loads can be reduced significantly. However, the window overhang shade is found to be the best option in terms of economic performance. The contribution of the solar cooling system shows that the system is not practical in all four scenarios. This may be due to the high initial cost of the system, even though it is found to be efficient in saving energy and is capable of reducing greenhouse gas emissions.
THESIS OUTLINE Chapter 1 presents a general overview: a brief background to solar cooling technologies, a brief introduction to the importance of building efficiency, a description of the aim and objectives of the thesis, and the methodology utilised in this study to obtain results. Chapter 2 includes two literature reviews: the first focuses on the studies conducted worldwide on solar thermal cooling systems and applied absorption chillers. The second literature review focuses on studies conducted in Australia describing the recent state of the art of various solar cooling technologies in general. Chapter 3 describes the different types of absorption chiller technology and a mathematical analysis. The environmental advantages of absorption chillers and the types of used of fluids are also presented. Chapter 4 describes a small office building subject of the study specifications and geometry, with a brief description of the software used in energy simulations (i.e. TRNSYS and OpenStudio). The simulation results are presented with an analysis of the four different scenarios (Basic building model, Double glazing modification, Overhang window shade modification, and a combination of both modifications). The weather data and its effect in building modelling are also included in this chapter. Chapter 5 describes the modelling of the solar cooling system. The system components used for simulation by the TRNSYS software are defined, and the definitions of component parameters, component sizing, and the optimisation method are explained in detail. Detailed descriptions of the economic and environmental analysis are also given in this chapter. Chapter 6 describes the simulation results of the analysed system in different scenarios and the variation of thermal energy gained by the solar collectors with different area and tank sizes in the four different building scenarios. Moreover, the operational cost saving and equivalent natural gas consumption for a full year period for a number of systems͛ was calculated. An economic analysis was performed using three different methodologies (PBP, LCC and NPV). The environmental impact of the system was calculated and analysed (CO2, N2O and CH4 emissions). The findings of this project are discussed in this chapter and related to the general literature. Chapter 7 concludes the key findings of this study and highlights the issues that challenge solar cooling system applications, and suggests solutions to improve performance. General recommendations are also made to help strengthen the implementation of solar cooling technology.
PUBLICATION Al-Zubaydi, A.Y.T. 2011, 'Solar Air Conditioning and Refrigeration with Absorption Chillers Technology in AustraliaʹAn Overview on Researches and Applications', Journal of Advanced Science and Engineering Research, vol. 1, no. 1.
1.1. BACKGROUND The use of renewable energies for air conditioning systems has undergone significant development during the last decade. This expansion has been driven, in large part, by successive periods of extreme solar heat and increased demand for the comfort of summer air conditioning, especially in residential and commercial buildings. The use of electric air conditioner units can lead to peak power consumption during the summer, but the power consumption of these devices and their mode of operation severely tests the capacity of electricity transmission networks and greatly increases the risk of unexpected electrical power cuts or "blackout" across the country. The development of High Efficiency Energy Buildings has contributed to reduced dependence on fossil fuels for space heating; this energy, however, is usually produced by burning oil, coal, or gas. Renewable energy resources such as geothermal or solar thermal energy can provide heating in some high efficiency buildings. The reinforced insulation of high efficiency buildings helps to reduce heat loss in winter, while in summer the same insulation prevents the infiltration of accumulated heat in the building, so a controlled cooling system or ventilation becomes a necessity. Between 1970 and 1980, the progress made in operating solar thermal panels for the production of domestic hot water (DHW) demonstrated the maturity of solar technology and the technical reliability of the solar source. This has paved the way for more complex systems by exploiting solar energy for space heating and DHW in new systems known as Combisystems. Task 26 of the International Energy Agency (IEA) has been dedicated to the study of combisystems and their performance (IEA 2013). Three tasks have been performed by the IEA (International Energy Agency) to enrich the knowledge of solar cooling and heating systems, and they are: -
Task 25: Solar assisted air conditioning of buildings (1999-2004) (IEA 2004).
Task 38: Solar air conditioning and refrigeration (2006-2010) (IEA 2010).
Task 48: Quality assurance & support measures for solar cooling systems (2011-2015)(IEA 2012).
In general, cooling demand peaks in summer at the same time as the maximum availability of solar radiation. Solar energy is a source of a renewable, non-polluting and cost-free energy which is potentially very suitable for cooling buildings. However, cooling by absorption chiller technology is reported to be about 70% less efficient than mechanical compression systems. Nevertheless, it is still useful when the energy source is free, as in the case of solar source energy. In Australia, several solar cooling production facilities are in operation (Al-Zubaydi 2011); their cooling capacities vary between 18 kW and 300 kW. In general, the majority of these installations are pilot projects for research and development. Recently, low-power absorption chillers have been introduced, with cooling capacities between 5 kW and 15 kW which primarily target consumers in the residential sector and small businesses. In addition, these new devices are already predestined for the solar market. The low coefficient of performance (COP) of absorption technology will no longer be an obstacle if the energy supplied to the system is theoretically free.
Australia still has shortcomings in research into solar cooling technologies, either by numerical modelling or by a combination of modelling and experimentation. In concluding, a connection is established between the air conditioning system and a numerical test; in which modelling of the missing parts of the building or system performance should be considered. This combination aims to enhance research outcomes before embarking on expensive long-term experiments. On the other hand, renewable energy systems of Heating, Ventilation and Air Conditioning (HVAC) are becoming increasingly attractive prospects for domestic and tertiary sectors. These technologies can, in some circumstances, make a building independent of the needs of air conditioning or hot water (Fong et al. 2010). However, detailed studies on solar air conditioning systems are rare, as their patterns and design methodology are not yet at the forefront of technology, which could discourage potential consumers. This project summarises the results of the numerical study conducted in the work of the thesis on solar multifunction multi-source systems. As a first step, we discuss in detail the topic of solar systems and their development and production technology absorption cooling. Then, we introduce a suggestion on developing the thermal efficiency of a building by targeting a reduction in the cooling load. We present a numerical model developed from a hydraulic scheme proposed and improved by successive simulations. Finally, we discuss the problem of the optimal design of two main components: the surface of solar panels and the volume of thermal storage. In general, the system design can be achieved by optimising the parameters, and the algorithm can be chosen, in turn, to be adapted later to the studied system. However, in this project, two optimisation methods have been applied to model a solar air conditioning system: a hybrid algorithm proposed for building simulation problems, and an optimisation algorithm based on the design of a theoretical system, which is a novelty in this area. Furthermore, the two algorithms were compared with each other in terms of optimisation and a parametric study was devised as the basis for validating the performance of each algorithm. 1.2. SOLAR COOLING The utilisation of solar energy in cooling applications was explored thousands of years ago, in both active and passive modes. In terms of active cooling, the process of an evaporating water pond on a flat roof with a solar heat process was used in Roman times to cool the water and the roof underneath (Florides et al. 2002). Using the thermal inertia of a building, its ventilation and shading are examples of passive cooling (McVeigh & Sayigh 1992). The capacity for passive cooling is usually related to the architecture of the building. An appropriate building design can save a considerable amount of energy, although this is not always sufficient to provide thermal comfort. Active solar cooling technologies are therefore used to achieve a balance. The introduction of thermal-driven air conditioning and refrigeration technologies encouraged engineers to run these systems using solar thermal energy from the early days of absorption chillers, when Mouchot produced ice cubes by utilising solar thermal energy in 1878. However, the availability of cheap energy and the lack of advanced and efficient solar thermal collectors are considered to be the main reasons for this application being disregarded for decades. Many accumulated motives renewed interest in solar cooling applications in the second half of the 20th century. Trombe and Foex (Trombe & Foex 1957) reported a successful test for a lab experiment in which absorption chillers were powered with solar thermal energy, which was followed by many 2
researchers, e.g. Nakahara et al (Nakahara, Miyakawa & Yamamoto 1977). However, many contemporary researches cover the different aspects of solar refrigeration technologies, and such studies can be significant in decision making in the first stage of selecting a solar cooling system (Henning 2007). The purpose of solar cooling is not limited to air conditioning alone; refrigeration for food preservation is usually presented as a second purpose (Mokhtar et al. 2010). Cooling, refrigeration and air conditioning are actually promising and bright future applications for solar energy technologies. The high demand for air conditioning impacts the electricity network and the environment, which affects our quality of life. On hot summer days, the electricity grid increasingly faces the danger of overload due to the high use of air conditioners, which may cause service disruption and severe economic impact. Associated with the high use of energy, air conditioning plays a significant role in environmental pollution in the form of greenhouse gas emissions ʹ with the resultant climate change impacting not only our environment, but also our health and productivity (Papadopoulos, Oxizidis & Kyriakis 2003). KĨƚŚĞŵĂŶǇǁĂǇƐŽĨŝŶĚŝǀŝĚƵĂůůǇĂĚĚƌĞƐƐŝŶŐĂŝƌĐŽŶĚŝƚŝŽŶŝŶŐ͛ƐŝŵƉĂĐƚƵƉŽŶ the grid and the environment, solar air conditioning (or solar cooling) is found to be a solution that provides cooling, addresses peak loading, and does so with reduced environmental impact. Solar air conditioning is highly attractive because increased cooling is needed precisely when solar intensity is strong and higher ambient temperatures are present. There is a notion that the present cost of this equipment is still prohibitive, not only for the solar cooling equipment and solar collectors themselves, but also for the required backup systems. In fact, even though they cannot compete with conventional technologies, the indirect benefits in terms of image and marketing this technology are often forgotten. The concept itself is highly marketable ʹ to generate cooling using the sun. Solar cooling systems can be classified into two main categories according to the energy used to drive them. Figure [1.1.] illustrates common solar cooling technologies:
Solar Cooling Processes
Photovoltaic Peltier System
Thermal Driven Systems
Photovoltaic Compression System
Heat Transformation Systems
Solid sorbents (rotary wheels, fixed bed process)
Figure 1.1. Solar Cooling Technologies With reference to Figure [1.1.] the solar cooling technology systems can be divided into: 1. Electrical systems I.
Vapour compression systems.
Thermoelectric systems (Peltier system).
2. Thermal systems I.
Heat Transformation systems:
a. Open cycles. b. Closed cycles. II.
a. Rankine process. b. Ejector system. ¹ Stirling systems can be categorised as either electrical or thermal systems, because Stirling systems can be driven by thermal energy for generating electricity or vice versa. In the context of solar energy, Stirling systems are used to generate electricity using parabolic dish collectors. Stirling systems are among the main competitors of PV cells.
Electrical systems utilise PV cells, but thermal systems utilise solar thermal collectors of various types. In recent years, solar thermal powered cooling systems have been successfully implemented all around the world. In order to reduce global warming and peak demand for electricity during summer months, solar cooling applications will become widespread at an increasing rate. 1.3. BUILDING ENERGY EFFICIENCY The efficiency of buildings, including public administration buildings, is considered to be an objective of national scope that aims to accelerate a national policy in the field of energy. In addition, it creates the conditions for a revival of productive sectors that have a strong impact on the national economy (E3 2013). The criteria for intervention and the mechanisms which will enable the realisation of this plan of action for upgrading the energy efficiency of public buildings are intended to improve and develop new legal standards, as well as leading to a significant reduction in energy bill costs. The benefits created by the intervention measures are particularly due to savings in energy consumption. Therefore, there will be a need to intervene with the involvement of disbursing Energy Services Company that can make use of support measures in these cases, such as access to the Revolving Fund. The implementation of the plan that determines the economic effects that are important in the construction phase of the interventions in the phase regime in terms of output growth will enable the creation of value economic added, employment, and an overall increase in GDP. For the identification of the measures contained in this Plan of Action, reference was made to the legal framework, the measures in the approval (NSW and national), and various reports on energy efficiency products by associations and public and private organisations in NSW and nationally. 1.4. AIM AND OBJECTIVES OF THE STUDY This project is motivated by the present needs of Australia for renewable energy sources and the fact that energy prices in the country have increased significantly in the past few years. Furthermore, hotels and offices in the country use more than 40% of their energy for air conditioning purposes. Therefore, solar-assisted air conditioning systems are a logical approach to reducing energy demand and lowering peak electricity demands for local power stations. 1.4.1. AIM The aim of this project is to examine a solar air conditioning system with absorption chiller contributions operating in a small office building in the climate of Sydney, NSW. The project considers different thermal efficiency scenarios and demonstrates specific architectural improvements. 1.4.2. OBJECTIVES The objectives are listed according to their significance as follow: 1. To calculate the building cooling load saving by applying different architectural improvements, which are: 5
A. Double glazed windows. B. Overhang window shades. C. Combination of double glazed window and overhang shades. 2. To calculate the energy saving and greenhouse gas emission reduction, as part of the international trend toward greenhouse gases emission reduction. 3. To evaluate the economic performance of the architectural improvements and solar cooling system in different settings by applying: A. LCC, life cycle cost methodology. B. NPV, the net present value methodology. C. PBP, the payback period methodology. 1.5. METHODOLOGY The experimental part of this study is excluded for several reasons, but principally for lack of financial support. Accordingly, the only available approach to obtain the operating data of a solar cooling system at the selected location (Sydney) for a small size office building, which is the subject of this study, was to use computer simulation software. The majority of studies discussed in the literature review (Chapter 2) validated the TRNSYS program for carrying out the energy system simulation. TRNSYS (Duffy et al. 2009; Klein et al. 2006) was used for the yearly simulations and an integrated model of the overall system was developed in TRNSYS. Since energy consumption and performance investigations of environment dependent systems such as building HVAC and refrigeration systems, solar collectors and cooling towers, usually require weather information, typical meteorological year (TMY) data was generated for use in the analysis of the system parameters. TRNSYS is a flexible simulation tool designed to simulate the transient performance of thermal energy systems and building energy simulation by modelling building heating, cooling, lighting and ventilating. The simulation of the building and energy system provide the required data flow necessary for energy, economic and environmental performance assessment. Table 1.1 lists the most important references, selected from the studies and works discussed in the literature review (Chapter2), that are used as methodology guides for this project. In this study, the building descriptions, cooling loads, energy saving, economic calculations, payback period and environmental impact were based on the equation used and validated against the results of these works.
Table 1.1. List of important studies used as a guideline in this project Authors
Solar cooling systems rules of thumb.
Thornton, Brian A. (Thornton et al. 2010) Small office building modelling and cooling Wang, Weimin loads calculations. Lane, Michael D. Huang Y. Liu, Bing Calise, F. (Calise, d'Accadia & System modelling and component sizing and d'Accadia, M. Dentice Vanoli 2011) optimisation. Vanoli, L. Economical and Environmental Analysis. Calise, F. (Calise, Dentice System modelling and component sizing and Dentice d'Accadia, M. d'Accadia & Palombo optimisation. Palombo, A. 2010) Economical and environmental analysis. Hang, Yin (Hang, Qu & Zhao Solar cooling system exergy calculations. Qu, Ming 2011) Zhao, Fu Sullivan, W.G. (Sullivan, Wicks & Economic assessment calculations. Wicks, E.M. Koelling 2011) Koelling, C.P. (Book) Department of Climate (DCCEE 2012) Environmental assessment calculations. Change and Energy Efficiency (Report) Figure 1.2. Describes the steps of the applied methodology validated by (Hang, Qu & Zhao 2011),(Monné et al. 2011), (Tsoutsos et al. 2010) and (Joudi & Abdul-Ghafour 2003). The steps of the applied methodology are described in the following points: 1- Data collection: i-
Building characteristic data collection: the description of the building including the dimensions and size, geometry, nature of activity, orientation, wall type and materials, window type and window to wall ratio, lighting, internal heat loads, occupation, loads schedules, ventilation type, and comfort conditions for heating and cooling. All of them are important for completing step 2 and the rest of the process.
Geographical Location Data. The location data are essential in the simulation process in order to draw the meteorological data from special software (i.e. Meteonorm).
Meteorological data collection for the study location (solar radiation, ambient temperature and humidity ratio). The TRNSYS software weather library contains typical meteorological yearly files (TMY2) for different locations worldwide, and the weather data for selected locations were selected from the software library. 7
2- Building simulation: the building simulation is an essential step in system design decision making. The load calculations for heating and cooling indicate the maximum loads and sizing of the main components of the solar cooling system, specifically the chiller cooling capacity. The building is modelled with the TRNBuild application in the TRNSYS program and simulated with TRNSYS Studio in the assigned weather conditions of the specific location. 3- Sizing the solar cooling system components: according to the data from the building simulation, the size of the absorption chiller should be decided first. All other component sizing subsequently took place, i.e. cooling tower capacity, storage tank volume, auxiliary boiler power and thermostat set temperature. As a result, the solar collector area was determined. 4- The outputs of the TRNSYS program were evaluated to achieve the maximum energy and economic results. The results evaluations included: the solar fraction value, the optimisation procedure, changes in the solar collector surface, the fluid flow rate, storage tank volume, auxiliary boiler power and thermostat set temperature, and the cooling tower type and capacity. 5- In the last stage, the optimum results from step 4 were analysed. Further calculations were made, e.g. the environmental benefits of the solar cooling system, the system costs and the life cycle of the system. In this stage, we found the answers for the study questions.
Step2: Building simulation x Building load calculation
Step3: Sizing system main components x Absorption chiller x Solar collector area x Storage tank x Auxiliary heater x Pumps and pipes
Step1: Data collection x Building description; x Location; x Meteorological data;
Step4: Evaluation of TRNSYS results x Energy x Economy x Environment
Step5: Optimization and analysis
Figure 1.2. Steps of Applied Methodology (Hang, Qu & Zhao 2011)
1.6. SIMULATION PROGRAMS In this Study, two simulation software packages are suggested to use based on similar studies and references i.e. Henning (Henning 2004). These programs are: TRNSYS TRNSYS (TRaNsient SYstem Simulation Program) is one of the most flexible energy simulation programs available nowadays with its advanced modular system. This simulation package has been used for more than 30 years for HVAC analysis and sizing. Due to its modular approach, TRNSYS is extremely flexible for modelling a variety of energy systems in differing levels of complexity. Supplied source code and documentation provide an easy method for users to modify or add components not in the standard library; extensive documentation on component routines, including explanation, background, typical uses and governing equations; supplied time step, starting and stopping times allowing choice of modelling periods. The TRNSYS includes a components library with hundreds components cover a various energy aspects (HVAC, Solar PV, Wind turbines, etc.). The standard included library could be extended with additional advanced libraries according to the field of simulation, moreover a new add- on components may be created using the package programming language (FORTRAN), Components can also be written in C++. Starting from TRNSYS version 17, the graphical interference for users through the Google SketchUp is available. But still, the software is a high cost commercial package. TRNSYS is primarily an equation solving program based on standard numerical techniques. However, validation does become important for the individual components in TRNSYS. The University of Wisconsin, TRNSYS website contains long lists of validation publications and articles related to TRNSYS or its components. EnergyPlus The EnergyPlus is a free licensed whole building energy simulation program that engineers, architects, and researchers use to model energy and water use in buildings. With EnergyPlus Modelling the building professionals can optimise the building design and energy efficiency by simulate the performance of a building. The EnergyPlus models heating, cooling, lighting, ventilation, other energy flows, time-steps less than an hour, modular systems and plant integrated with heat balance-based zone simulation, multizone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems, and water use. To improve the EnergyPlus functionality, an Add-Ons created to make the package more user ʹ friendly, these add-ons includes OpenStudio application suite and The Legacy OpenStudio Plug-in for SketchUp. OpenStudio is a cross-platform (Windows, Mac, and Linux) collection of software tools to support whole building energy modelling using EnergyPlus and advanced daylight analysis using Radiance. OpenStudio includes graphical interfaces along with a Software Development Kit (SDK). The Legacy OpenStudio Plug-in for SketchUp makes it possible for architects and engineers to perform EnergyPlus simulations using SketchUp, a user-friendly 3-D drawing interface. 9
1.7. REFERENCES Al-Zubaydi, A.Y.T. 2011, 'Solar air conditioning and refrigeration with absorption chillers technology in AustraliaʹAn overview on researches and applications', Journal of Advanced Science and Engineering Research, vol. 1, no. 1. Calise, F., d'Accadia, M.D. & Vanoli, L. 2011, 'Thermoeconomic optimization of solar heating and cooling systems', Energy Conversion and Management, vol. 52, no. 2, pp. 1562-73. Calise, F., Dentice d'Accadia, M. & Palombo, A. 2010, 'Transient analysis and energy optimization of solar heating and cooling systems in various configurations', Solar Energy, vol. 84, no. 3, pp. 432-49. DCCEE 2012, National Greenhouse Accounts Factors - July 2012, Commonwealth of Australia. Duffy, M., Hiller, M., Bradley, D., Keilholz, W., Thornton, J., GmbH, T. & Stuttgart, G. 2009, 'TRNSYSʹ Features and functionalitity for building simulation', Building Simulation 2009, no. 2009, pp. 1950- 4. E3 2013, Energy Efficiency Strategy - Australia, Energy Rating Florides, G.A., Kalogirou, S.A., Tassou, S.A. & Wrobel, L.C. 2002, 'Modelling, simulation and warming impact assessment of a domestic-size absorption solar cooling system', Applied Thermal Engineering, vol. 22, no. 12, pp. 1313-25. Fong, K., Chow, T., Lee, C., Lin, Z. & Chan, L. 2010, 'Comparative study of different solar cooling systems for buildings in subtropical city', Solar Energy, vol. 84, pp. 227ʹ44. Hang, Y., Qu, M. & Zhao, F. 2011, 'Economical and environmental assessment of an optimized solar cooling system for a medium-sized benchmark office building in Los Angeles, California', Renewable Energy, vol. 36, no. 2, pp. 648-58. Henning, H.-M. 2004, Solar-Assisted Air Conditioning in Buildings, A Handbook for Planners, Springer Wien / New York. Henning, H.-M. 2007, 'Solar assisted air conditioning of buildings - an overview', Applied Thermal Engineering, vol. 27, no. 10, pp. 1734-49. IEA 2004, Task 25: Solar Assisted Air Conditioning of Buildings. IEA 2010, Task 38 - Solar Air-Conditioning and Refrigeration. IEA 2012, Task 48: Quality Assurance & Support Measures for Solar Cooling Systems. IEA 2013, Solar Heating and Cooling Programme. Joudi, K.A. & Abdul-Ghafour, Q.J. 2003, 'Development of design charts for solar cooling systems. Part I: Computer simulation for a solar cooling system and development of solar cooling design charts', Energy Conversion and Management, vol. 44, no. 2, pp. 313-39. Klein, S.A., Beckman, W.A., Mitchell, J.W. & Duffie, J.A. 2006, TRNSYS 16. A Transient System Simulation Program, University of Wisconsin-Madison. McVeigh, J.C. & Sayigh, A.A.M. 1992, Solar air conditioning and refrigeration, Oxford : Pergamon Press. Mokhtar, M., Ali, M.T., Bräuniger, S., Afshari, A., Sgouridis, S., Armstrong, P. & Chiesa, M. 2010, 'Systematic comprehensive techno-economic assessment of solar cooling technologies using location-specific climate data', Applied Energy, vol. 87, no. 12, pp. 3766-78. Monné, C., Alonso, S., Palacín, F. & Serra, L. 2011, 'Monitoring and simulation of an existing solar powered absorption cooling system in Zaragoza (Spain)', Applied Thermal Engineering, vol. 31, no. 1, pp. 28-35. Nakahara, N., Miyakawa, Y. & Yamamoto, M. 1977, 'Experimental study on house cooling and heating with solar energy using flat plate collector', Solar Energy, vol. 19, no. 6, pp. 657-62. Papadopoulos, A.M., Oxizidis, S. & Kyriakis, N. 2003, 'Perspectives of solar cooling in view of the developments in the air-conditioning sector', Renewable and Sustainable Energy Reviews, vol. 7, no. 5, pp. 419-38. Sullivan, W.G., Wicks, E.M. & Koelling, C.P. 2011, Engineering Economy, Pearson.
Thornton, B.A., Wang, W., Lane, M.D., Y., H. & Liu, B. 2010, Technical Support Document: 50% Energy Savings for Small Office Buildings, PNNL-19341, Pacific Northwest National Laboratory, Richland, WA. Trombe, F. & Foex, M. 1957, 'The production of cold by means of solar radiation', Solar Energy, vol. 1, no. 1, pp. 51-2. Tsoutsos, T., Aloumpi, E., Gkouskos, Z. & Karagiorgas, M. 2010, 'Design of a solar absorption cooling system in a Greek hospital', Energy and Buildings, vol. 42, no. 2, pp. 265-72.
This chapter involves an extensive review of existing literature on the solar thermal system internationally and in Australia. This chapter consists of two literature reviews: the first (Section 2.1) focuses on studies done worldwide on solar thermal cooling systems with applied absorption chillers. The second (Section 2.2) focuses on the studies conducted in Australia and describes the recent state of the art of various solar cooling technologies in general. 2.1.
INTERNATIONAL RESEARCHES ON SOLAR THERMAL COOLING SYSTEMS
2.1.1. HISTORY BACKGROUND The interest in solar cooling energy dates back to the 19th century, when Ferdinand Carré (18241894) used the principles developed by Michael Faraday (1791-1867) to build the first thermal cooling machine for the production of ice in 1850, using a solution of water and sulphuric acid, which modified to an ammonia and water solution. In 1878, Mouchot used Carré’s machine to produce ice with the hot water supplied from a solar thermal collector at the World Trade Fair, Paris, France. Trombe and Foex (Trombe & Foex 1957) built a prototype of a solar refrigerating system by applying an ammonia-water absorption chiller (NH3-H2O) in which the ammonia solution was directly heated with sun radiation (direct fired). This system was able to produce ice at a rate of up to 6 kg/day when a 1.5 m² cylindro-parabolic mirror was applied as the heat source. The main aim of the experiment was to compare the results to the earlier work of V.A. Baum who produced ice in larger quantities with the aid of a high power solar installation constructed in Uzbekistan in 1956. Since Trombe and Foe ’s e peri e t at Montlouis Laboratory, many researchers started theoretical and experimental assessments for a different layout of solar cooling systems, utilising absorption chillers as the main technology. 2.1.2. RECENT WORKS The design and optimisation of a solar driven cooling system with a LiBr-H2O absorption chiller for the hot weather of Cyprus was undertaken by Florides (Florides et al. 2002). This system was simulated with TRNSYS to size and optimise the main components (i.e. solar thermal collectors’ area, thermal storage tank). The optimised system consisted of a 15 m² compound parabolic collector titled at 30º from horizon with a 0.6 m³ hot water storage tank to operate a 3.5 RT (11 kW) cooling capacity chiller. The system was able to reduce the CO2 emission by more than 20% compared to a conventional system; however, the economic performance of the system was less than expected due to the small collector area and fuel prices. In 2007, the authors re-evaluated the same system performance (Florides & Kalogirou 2007). The results indicated that due to the high cost of fuel, a large part of the building load could be covered more efficiently with solar energy than with the conventional system. Thus, renewable energy forms can economically replace part of the fuel energy as fuel prices increase. Henning’s work (Henning 2007) focused on the analysis of different solar cooling technologies in terms of type and thermodynamic performance, presenting the latest developments of closed and opened heat driven cooling cycles. Solar assisted air conditioning can lead to remarkable primary energy savings if the systems are properly designed. Improvements in the performance of thermally 12
driven chillers and open cooling cycles play a key role in approaching economic feasibility. The installed system data indicate an inadequacy in the hydraulic and control design of both systems. At Camegie Mellon University in the United States (US), the performance of the solar cooling system with absorption chiller was subjected to study by Qu et al. (Masson, Qu & Archer 2007; Qu et al. 2007). Their study modelled the system and simulated the performance with TRNSYS to investigate the quantity of solar energy collected as well as the effect of thermal storage vessels on the syste ’s efficiency. The priority of the designed process should be to focus on the efficacy of the system rather than the efficiency. The performance of the designed system (even after optimisation) was lower than the performance of the same system without storage with an optimum collectors orientation. The control strategy of the heat rejection system (cooling tower) was the subject of a study by Kuhn et al. (Kühn, Ciganda & Ziegler 2008). This study examined different control strategies for a solar cooling system and aimed to investigate its effect, developing a new control strategy that used the cooling water temperature as a control parameter. The result showed the possibility of saving up to 50% of electricity consumed by the cooling tower fan by using the appropriate control strategy in sunny weather. In addition, it provided a high cooling capacity in low irradiation weather by controlling the stable chilled water outlet temperature by adjusting the cooling tower temperature. Mateus and Oliveira (Mateus & Oliveira 2009a) applied the TRNSYS software tool on an assessment basis to evaluate the prospective performance of a solar assisted air conditioning system for heating and cooling. Diverse building models were utilised: office, hotel and residential which performed in different European climates to analyse the energetic and economic performance. The results showed that it was possible to save CO2 emissions and the total cost with the solar air conditioning system. However, promising economic outcomes resulted when natural gas was adopted as a backup energy for the system. The minimum cost was usually achieved when the solar fraction value was between 20% and 60%. An exploitation costs reduction (35% to 45%) resulted in an annual solar fraction of 60%. In Greece, the performance assessment by an exergy analysis for a solar cooling system installed in a medical centre, beside the environmental and economic appraisal of the installation, was investigated by Koroneos et al. (Koroneos, Nanaki & Xydis 2010). A 70 kW capacity absorption chiller from Yazaki with 0.7 average COP, linked to 291 m² solar thermal collector fields, and a cooling tower of 70 kW capacity and hot water storage tank of 50 lt/m² of collector area was used. The study showed that the COP of the system could be optimised by decreasing the exergy losses from the system. However, the economic study showed that with a 70 kW cooling capacity system assisted by a 9 ² solar ther al collector’s area, the payback period could only be competitive with government subsidies to reduce the time to half. The significant reduction of peak electricity load during the cooling season could lead to great environmental profits due to the reduction of polluting emissions. Reunion Island is an Indian Ocean island with semi-tropical weather and limited power resources, where Marc et al. (Marc et al. 2010) presented a system demonstration, the design and control characters, and then analysed the results of the first experimental season and its effect on reducing power consumption. A system of 30 kW capacity cooled with 80 kW cooling tower was used to provide the cooling for four classrooms with a total area of 170 m². The solar cycle of a 90 m² 13
double-glazed flat plate collector and 1500 m³ hot water storage tank were also used. The results of the first seaso ’s a al sis assisted the solution of experiential problems after commissioning, as well as helping to investigate the component with higher energy consumption. Moreover, the experiments showed the success of the system in fulfilling the cooling needs of the four classrooms without an auxiliary backup system,. In addition, thermal comfort was achieved. Calise et al. (Calise, Dentice d'Accadia & Palombo 2010; Calise, Palombo & Vanoli 2010) conducted two studies based on a transient simulation model of three different solar assisted cooling and heating system layouts utilising an absorption chiller in Italian climates (three different locations). The simulation was performed using the TRNSYS software and the economic model was developed with a full set of equations. The studies can be considered as calculation guidelines for the optimisation of solar cooling systems. The optimisation of systems parameters and results analysis showed optimistic results in energy saving but no profitability. It also showed the importance of selecting the accurate pump nominal flows, and the volume of the hot water storage tank beside the set point of the auxiliary boiler to achieve economic and environmental goals by lowering the amount of consumed energy. In both studies, the annual primary energy saving was chosen as the optimisation objective function, while technical designed parameters such as collector slope, pump flows, set-point temperatures and tank volume were selected as optimising system design variables. Another study by Calise (Calise 2010) investigated a different layout of a solar assisted air conditioning system based on the auxiliary unit and used different building models in three locations in Italy. The study was simulated with TRNSYS software to assess the most suitable type of building and climatic condition to maximise the solar air conditioning system performance in both cooling and heating. Although the system was designed to cover 20% of the maximum cooling load, a solar fraction of 27.7% in summer was recorded. However, a winter solar fraction of 46.2% indicated that the system was capable of achieving a primary annual energy saving of 64.7%. The study was used as the design basis for a pre-commercial, optimised prototype solar air conditioning system in south Italy for experimental analysis and simulation results validation. Most of the studies cited above analysed the operation and design of solar assisted air conditioning systems in cooling mode only. This could be because such plants were supposed to be installed in buildings that do not required space heating. Similar works are mainly decisive on the energy analysis, while the economic element was often barely investigated except for limited studies (Mateus & Oliveira 2009b). The authors investigated the possibility of a combination of solar absorption cooling and heating systems for different types of buildings in different locations. The layouts considered varied in the type of backup systems and type of collectors used. The use of evacuated tube collectors helped to minimise the solar collectors’ field area by 30-50% according to the location, compared to the flat plate collectors. The gas boiler as a backup system resulted in a further reduction in area of 3-9%,. However, the best energy obtained during the optimisation process was for a storage capacity range of 0.05-0.11 m³ for every 1 m² of collector area. The solar fraction at optimised results reached up to 60%. However, when the emission savings became high, the system performance is not valuable when evaluated on an economic basis only. Generally, the environmental performance of the system is based on the calculation of the carbon dioxide emission during the operating phase alone, whereas the carbon dioxide emissions throughout other life cycle phases of solar assisted air conditioning systems are neglected, i.e. the 14
emission of carbon dioxide resulting at both the components manufacturing stage and the system installation stage. This could be due to the complexity of the estimation and calculation procedure. However, equivalent or greater emission may result in similar phases for conventional systems (Hang, Qu & Zhao 2011). The majority of the above-cited studies and evaluations were conducted in a European environment. The rise of fossil fuel prices alongside international efforts to reduce greenhouse gas emissions has encouraged countries such as the US to call for new researches into solar cooling systems. Studies by Qu et al. (Qu, Archer & Yin 2008; Qu et al. 2007) and Hang et al. (Hang, Qu & Zhao 2011) have enriched the knowledge for North American environments. Hang et al. accomplished an energetic, economic and environmental appraisal on a solar assisted air conditioning system using a benchmark model office building developed by the US DOE [Department of Energy], in Los Angeles, California. The authors set the equivalent uniform annual cost (EUAC) as an indicator for economic performance, while the solar fraction for the energetic and life cycle carbon dioxide reduction was set for the environmental evaluation. A solar fraction value of 83% and optimum cost of carbon footprint reduction of $0.75 per kg resulted when the area of the solar collector and hot water storage tank volume were 280 m² and 11 m³ respectively. Although the study showed no saving in economic terms it was able to reduce the life cycle CO2 up to 80%. Similar studies which evaluate solar cooling projects in Mexico and Chile have also been published in the past two years (Ortiz, Mammoli & Vorobieff 2008; Vidal, Escobar & Colle 2009). Despite its high potential for energy savings in all the cited studies or programs, solar assisted air conditioning technology is still not been investigated sufficiently, and that may be due to its inadequate commercial availability and/or to the high capital costs. However, due to the international trend towards the use of renewable energy, a reduced carbon footprint, the constant increase in energy prices in the near future and the expected carbon tax scheme, all these parameters would promote the utilisation of solar cooling systems in the near future. The comparisons between other solar cooling systems and the solar cooling system with absorption chiller usually lean to the thermal solar system with absorption chillers. A study by Hartmann et al. (Hartmann, Glueck & Schmidt) described a comparison between the solar cooling system assisted by a Photovoltaic solar panels and the thermal solar cooling system. The results showed that the solar cooling system with PV panel might perform with higher economic and energetic outputs than solar thermal systems, which could be due to the use of flat plate collectors and an adsorption chiller in their simulation. In contrast, another study by Kim and Ferreira (Kim & Infante Ferreira 2008) compared all commercially available solar air conditioning systems on the basis of initial cost and performance. The results estimated that a solar air conditioning system with solar thermal collectors and absorption chiller was the most suitable cost compared with other systems in solar cooling technology. Unlike other solar cooling systems, the solar thermal air conditioning system with absorption chillers can cover the heating loads with the same efficiency as cooling loads. A recent study in Italy (Calise, d'Accadia & Vanoli 2011) investigated a different layout of a solar assisted air conditioning system based on the auxiliary unit and different building models in three different locations. A transient simulation with TRNSYS software to assess the most suitable type of building and climatic condition to maximise the solar air conditioning system performance in both cooling and heating were used. 15
The cost of a solar air conditioning system is a significant factor in decision-making. The high cost is always considered as the main restriction in the adoption of the system as an economical alternative to the conventional system. Boopathi and Shanmugam (Boopathi Raja & Shanmugam 2012) pointed to practical suggestions for applying modifications to the solar air conditioning system with LiBr absorption chillers, to reduce the operating costs for long-term operations. The operation cost reduction results in improving the s ste ’s economic parameters throughout the life span. Such modifications included the limitation of the electrical components and placing the generator heat exchanger inside the hot water storage. The studies listed in Table 2.1 performed the latest studies related to the absorption system and concluded that the units are realistic for comfort cooling. Table 2.1. Most Recent Studies in the Literature Authors
Marc, Olivier Anies, Guillaume Lucas, Franck Castaing-Lasvignottes, Jean G. Anie P. Stouffs J. Castaing-Lasvignottes
(Marc et al. 2012)
Developed a numerical model to simulate the thermodynamics performance and analyse the data of solar cooling system.
(Anies, Stouffs & CastaingLasvignottes 2012) (Gomri 2013)
Developed a numerical model to simulate the thermodynamics performance and analyse the data of solar cooling system.
Gomri, Rabah Djelloul, A Draoui, B Moummi, N Hang, Yin Du, Lili Qu, Ming Peeta, Srinivas
(Djelloul, Draoui & Moummi 2013) (Hang et al. 2013)
Simulation of solar air conditioning system with a single stage LiBr- H2O absorption chiller. Transit simulation of Solar air conditioning system. Applied the CDD method in the optimisation of the solar cooling system performance outputs.
Performance evaluation and system control could be achieved with alternative numerical models, rather than the commercially available packages, to compare the experimental records against the theoretical calculations. Studies by Marc et al. (Marc et al. 2012) and Anies et al. (Anies, Stouffs & Castaing-Lasvignottes 2012) developed a simple numerical model based on the thermodynamic principles of absorption chillers (as presented in Chapter 4) to simulate and analyse the performance of a solar cooling system, then compared the results against the data from the experimental work of a system employing a 4.5 kW absorption chiller. Similar modelling can be useful for the optimisation of system components, if both studies show compatibility between the experimental and computed results. Gomri (Gomri 2013) analysed the performance of a solar assisted air conditioning system with a natural gas heater backup. The results were obtained by modelling and simulating the system subject to the weather of Constantine, in eastern Algeria. With a flat plate collector as the solar 16
energy provider, a 10 kW capacity absorption chiller performance showed that, by increasing the condenser area, the generator temperature could optimise the COP of the absorption chiller and the exergetic efficiency of the system. Another study of the performance of a solar cooling system in the Algerian weather by Djelloul et al. (Djelloul, Draoui & Moummi 2013) presented a literature review of solar air conditioning systems with absorption chillers and a brief TRNSYS simulation. Yin Hung et al.’s study (Hang et al. 2013) proposed an evolutionary method based on previous studies (Hang, Qu & Ukkusuri 2011); (Hang, Qu & Zhao 2011). The proposed method (Central Composite Design) examined the overall performance of the solar air conditioning system from economic, energy and environmental aspects. The solar cooling system with a single stage absorption chiller to cover the cooling demand of the benchmark medium sized office building was simulated under four different weather data locations in the US. The results of the life cycle cost of the solar air conditioning system with cooling and heating loads of the building indicate that the higher loads would lead to fewer life cycle costs. This may be due to the higher saving in operating costs. Based on the results of the other studies, this study is conducted to investigate the feasibility of building thermal efficiency improvements in the performance of solar cooling systems in a small office building in the weather conditions of Sydney, NSW. 2.2.
NATIONAL RESEARCHES ON SOLAR THERMAL COOLING SYSTEMS
A large number of reviews on solar cooling systems have been published internationally. In Australia, however, recent reviews of the status of the technology and the application of solar cooling systems are lacking. Therefore, there is a need to explore those studies that have been conducted in Australia, along with the applications utilised in Australia. This has been presented in a published paper (Al-Zubaydi 2011) presented in APPENDEX E.
Al-Zubaydi, A.Y.T. 2011, 'Solar air conditioning and refrigeration with absorption chillers technology in Australia–An overview on researches and applications', Journal of Advanced Science and Engineering Research, vol. 1, no. 1. Anies, G., Stouffs, P. & Castaing-Lasvignottes, J. 2012, 'Modelling and experimental validation of a solar cooling installation', ECOS 2012 - The 25th International Conference on Efficincy, Cost, Optimization, Simulation and Enviromental Impact of Energy Systems June 26-29, 2012, Perugia, Italy. Boopathi Raja, V. & Shanmugam, V. 2012, 'A review and new approach to minimize the cost of solar assisted absorption cooling system', Renewable and Sustainable Energy Reviews, vol. 16, no. 9, pp. 6725-31. Calise, F. 2010, 'Thermoeconomic analysis and optimization of high efficiency solar heating and cooling systems for different Italian school buildings and climates', Energy and Buildings, vol. 42, no. 7, pp. 992-1003. Calise, F., d'Accadia, M.D. & Vanoli, L. 2011, 'Thermoeconomic optimization of solar heating and cooling systems', Energy Conversion and Management, vol. 52, no. 2, pp. 1562-73. Calise, F., Dentice d'Accadia, M. & Palombo, A. 2010, 'Transient analysis and energy optimization of solar heating and cooling systems in various configurations', Solar Energy, vol. 84, no. 3, pp. 432-49. Calise, F., Palombo, A. & Vanoli, L. 2010, 'Maximization of primary energy savings of solar heating and cooling systems by transient simulations and computer design of experiments', Applied Energy, vol. 87, no. 2, pp. 524-40. Djelloul, A., Draoui, B. & Moummi, N. 2013, 'Simulation of A Solar Driven Air Conditioning System for a House in Dry and Hot Climate of Algeria', Courrier du Savoir, no. N°15, pp. 31-9. Florides, G. & Kalogirou, S. 2007, 'Optimisation and cost analysis of a lithium bromide absorption solar cooling system', Clima 2007. Florides, G.A., Kalogirou, S.A., Tassou, S.A. & Wrobel, L.C. 2002, 'Modelling and simulation of an absorption solar cooling system for Cyprus', Solar Energy, vol. 72, no. 1, pp. 43-51. Gomri, R. 2013, 'Simulation study on the performance of solar/natural gas absorption cooling chillers', Energy Conversion and Management, vol. 65, no. 0, pp. 675-81. Hang, Y., Du, L., Qu, M. & Peeta, S. 2013, 'Multi-objective optimization of integrated solar absorption cooling and heating systems for medium-sized office buildings', Renewable Energy, vol. 52, pp. 67-78. Hang, Y., Qu, M. & Ukkusuri, S. 2011, 'Optimizing the design of a solar cooling system using central composite design techniques', Energy and Buildings, vol. 43, no. 4, pp. 988-94. Hang, Y., Qu, M. & Zhao, F. 2011, 'Economical and environmental assessment of an optimized solar cooling system for a medium-sized benchmark office building in Los Angeles, California', Renewable Energy, vol. 36, no. 2, pp. 648-58. Hartmann, N., Glueck, C. & Schmidt, F.P., 'Solar cooling for small office buildings: Comparison of solar thermal and photovoltaic options for two different European climates', Renewable Energy, vol. In Press, Corrected Proof. Henning, H.-M. 2007, 'Solar assisted air conditioning of buildings - an overview', Applied Thermal Engineering, vol. 27, no. 10, pp. 1734-49. Kim, D.S. & Infante Ferreira, C.A. 2008, 'Solar refrigeration options - a state-of-the-art review', International Journal of refrigeration, vol. 31, no. 1, pp. 3-15. Koroneos, C., Nanaki, E. & Xydis, G. 2010, 'Solar air conditioning systems and their applicability--An exergy approach', Resources, Conservation and Recycling, vol. In Press, Corrected Proof. Kühn, A., Ciganda, J. & Ziegler, F. 2008, 'Comparison Of Control Strategies Of Solar Absorption Chillers', paper presented to the EUROSUN 2008, 1st International Congress on Heating, Cooling and Building, Lisbon, Portugal. 18
Marc, O., Anies, G., Lucas, F. & Castaing-Lasvignottes, J. 2012, 'Assessing performance and controlling operating conditions of a solar driven absorption chiller using simplified numerical models', Solar Energy, vol. 86, no. 9, pp. 2231-9. Marc, O., Lucas, F., Sinama, F. & Monceyron, E. 2010, 'Experimental investigation of a solar cooling absorption system operating without any backup system under tropical climate', Energy and Buildings, vol. 42, no. 6, pp. 774-82. Masson, S., Qu, M. & Archer, D. 2007, 'Performance Modeling of a Solar Thermal System for Cooling a d Heati g i Car egie Mello U iversit ’s I tellige t Workplace', Energy Sustainability 2007, June 27-20, 2007, ASME, Long Beach, California. Mateus, T. & Oliveira, A. 2009a, 'Energy and economic analysis of an integrated solar absorption cooling and heating system in different building types and climates', Applied Energy, vol. 86, no. 6, pp. 949-57. Mateus, T. & Oliveira, A.C. 2009b, 'Energy and economic analysis of an integrated solar absorption cooling and heating system in different building types and climates', Applied Energy, vol. 86, no. 6, pp. 949-57. Ortiz, M., Mammoli, A. & Vorobieff, P. 2008, 'A TRNSYS Model of a Solar Thermal System with Thermal Storage and Absorption Cooling', 2008 ASEE Gulf-Southwest Annual Conference, The University of New Mexico - Albuquerque. Qu, M., Archer, D. & Yin, H. 2008, 'Experiment Based Performance Analysis of a Solar Absorption Cooling and Heating System in Carnegie Mellon University', Energy Sustainability 2008, August 10-14, 2008, ASME, Jacksonville, Florida USA. Qu, M., Archer, D.H., Yin, H. & Masson, S. 2007, 'Solar Absorption Cooling and Heating System in the Intelligent Workplace', ASME Conference Proceedings, vol. 2007, no. 47977, pp. 647-55. Trombe, F. & Foex, M. 1957, 'The production of cold by means of solar radiation', Solar Energy, vol. 1, no. 1, pp. 51-2. Vidal, H., Escobar, R. & Colle, S. 2009, 'Simulation and optimization of solar driven air conditioning system for house in Chile', ISES Solar World Congress 2009: Renewable energy shaping our future, ISES, Johannesburg, S.Africa.
3. ABSORPTION CHILLERS 3.1. INTRODUCTION The absorption chiller is defined as a refrigerating machine which uses the absorption cycle as its work cycle. Absorption is a chemical process involving the separation of one or more components of a gas mixture with the aid of a liquid solvent, with which it forms a solution. This process involves a mass transfer of solute A through gas B, which diffuses and is at rest, into a liquid C, also at rest (Kuehn & Coleman 2005). In this project, water (H2O) is the solute absorbed in lithium bromide (LiBr). The absorption chiller was invented by Nairne in 1774 and the system was improved by Carré in the second half of the 19th century to produce ice, based on producing a decrease in vapour pressure by using an ammonia/water cycle. There were no fundamental changes to the system till the 1950s, when the use of absorption chillers was reduced as a result of the production of electricity at very low cost. Since the 1970s, as a consequence of rising energy prices, the industry has encouraged and promoted energy conservation, and more specifically, residual heat sources (eg: exhaust gas turbines used in heated water in cogeneration plants). These heat sources can be used for absorption machines, and accordingly their promotion has increased in recent years, especially in the United States and Japan in the field of air conditioning. Currently, the application of this technology is focused on meeting the demand for refrigeration and air conditioning in large buildings with areas with a high energy demand (Balaras et al. 2007; García Casals 2006; Henning 2007). 3.2. THERMODYNAMIC FUNDAMENTALS OF THE ABSORPTION CHILLER The absorption refrigeration cycle can be easily explained by comparing the cycle to the basic vapour compression cycle. The schematic diagram of the standard vapour compression refrigeration cycle is introduced in Figure 3.1. The main components in this cycle are: condenser, evaporator, throttling valve, and compressor. QE 3
4 Evaporator Expansion Valve
Figure 3.1. Vapour-Compression Refrigeration Cycle 20
In the vapour compression refrigeration cycle, refrigerant is added to the compressor. The hot, high pressure refrigerant vapour is then forced from the compressor to the condenser (1) where heat (QC) is extracted from the refrigerant to the ambient air (or water), causing the condensation of the refrigerant into a liquid. The liquid refrigerant is throttled through the expansion valve (2) which reduces its pressure to evaporator pressure. A percentage of the low pressure liquid refrigerant where part of the refrigerant boils and evaporates cooling down the liquid refrigerant to the evaporator temperature (TE). The cool vapour and liquid refrigerant mixture enters the evaporator unit (3) and absorbs heat with amount of (QE) from air or water and create a cooling affect. The added heat (QE) will cause the cool low pressure mixture to boil and evaporate, after which it will be pumped to the compressor (4) to repeat the refrigeration cycle. In the absorption refrigeration system, much like the vapour compression system, the refrigerant will flow through a condenser and will be throttled through an expansion valve and evaporated by an evaporator, but the refrigerant compression method is replaced by a generator and absorber, as shown in Figure 3.2 in the next section. 3.3. COMPONENTS OF ABSORPTION MACHINE The absorption chiller ideally consists of a generator, a condenser, an evaporator and an absorber. In addition to an expansion valve between the condenser and evaporator, which is responsible for reducing the pressure between these two units, there is another bottleneck with the same function as in vapour- compression located between the generator and the absorber and a pump that drives the solution from the absorber to the generator. Figure 3.2 is a pictorial representation of these elements.
5 W Pump
Figure 3.2. Absorption Machines (Kuehn & Coleman 2005)
The functions of each component are as follows. Generator: The main function of the generator unit is to supply the refrigerant vapour to the rest of the system at high pressure and temperature. The vapour is formed by separating the refrigerant (e.g. water in H2O/LiBr Machines) from the absorbent (LiBr). An internal heat exchanger immersed in the mixture of the refrigerant and absorbent within the generator unit is used to circulate the fluid with high energy and temperature supplied from the heat source (e.g. steam or hot water). The added heat will cause the dilute mixture to boil, release the refrigerant as a vapour, and make the absorbent mixture more concentrated. The vapour flows to the next element, the condenser, while the concentrated mixture of absorbent travels back to the absorber unit. Condenser: The process of refrigerant vapour condensation is performed in the condenser unit by the extraction of heat from the refrigerant vapour to the cooling water running in pipes within the condenser unit (in a water cooled system) or the air (in an air cooled system). The refrigerant vapour condenses on the cooling fluid pipes, liquefies and drops to the bottom of the condenser unit, where it is collected and carried to the expansion valve device. Usually, the cooling water rejects heat to the surrounding area using a cooling tower, after which its flow inside the condenser unit resumes. Expansion Valve: The hot side of the absorption machine is under high pressure, while the refrigeration side is under low pressure, and the expansion device maintains this pressure difference. As the liquid refrigerant travels through the expansion device, its pressure is reduced from the high pressure level of the condenser to the low pressure level of the evaporator. This pressure reduction forces a portion of the refrigerant liquid to boil into a vapour, cooling the rest of the refrigerant mixture to the low evaporator temperature before it flows to the evaporator unit. Evaporator: The purpose of the evaporator unit is to cool the circulating water. The refrigerant mixture is delivered from the expansion device at an evaporative pressure of about 870 Pa absolute. It absorbs the heat from the circulating water running in tubes inside the evaporator unit; the water is chilled and the refrigerant is evaporated and migrates continuously to the absorber unit. Any obstruction of the vapour inside the evaporator unit will increase the pressure inside the vessel and cause an increase in the refrigerant boil temperature, in which case the desired cooling effect cannot be achieved. Absorber: The main purpose of the absorber unit is to enable the refrigerant vapour to be absorbed by the concentrated absorbent solution returned from the generator unit. As more and more refrigerant is absorbed by the absorbent solution, its absorption ability decreases, forming a weak absorbent solution that is pumped to the generator to repeat the cycle. In the modelling of an absorption machine, the following assumptions were considered: 22
Thermodynamic equilibrium in each of the transformations. Heat exchangers are of infinite area. The feed temperature of the diluted solution is the same temperature of the generator.
There are two distinct areas: the high pressure formed by the generator and the condenser and the low pressure formed by the evaporator and the absorber. In addition there are two cycles, the refrigerant cycle and the absorption cycle. More detailed operation of the absorption chiller is described below. A heat source provides heat QG, with the generator temperature TG, separating the refrigerant from the solution (point 1). The refrigerant vapour at the temperature and pressure TG and PC respectively is fed to the condenser where it condenses at the temperature and pressure TC and PC respectively (point 2). The liquid refrigerant undergoes isenthalpic expansion in the expansion valve and is partially transformed into steam; the pressure decreases until it reaches PE (point 3). The refrigerant boils in the evaporator temperature (TE) and pressure PE (point 4). The refrigerant vapour, at temperature (TE) and pressure (PE), is fed into the absorber where it is absorbed by the dissolution temperature (TA) and pressure (PE). As the absorber and condenser transfer heat to the environment, it is usually comply that (T = TC). The hot solution at temperature (TG) and pressure (PC) from the generator (point 7), passes through the throttle valve and returns to the absorber at the temperature (TG) and pressure (PE) (point 8), where it mixes with the existing solution in the absorber. This temperature (TC) and pressure (PE) (point 5), is pumped to the generator pressure (PC), where it is heated to the temperature TG (point 6) and continues the cycle. In the condenser, the refrigerant changes to a liquid, giving up its latent heat (QC) to an exterior fluid, whereas in the evaporator, the refrigerant boils at low pressure and absorbs heat (QE), which cools the exterior fluid. The set-absorber thermo-chemical compressor pump is so called because it performs the same function as the mechanical compressor when steam from the evaporator enters the absorber and exits as saturated steam in the superheated steam generator as well as the working fluid cycle mechanical compression.
3.4. TYPES OF ABSORPTION CHILLER Absorption chillers can be classified by the type of heat supplied to the generator unit, i.e. direct- or indirect-fired systems, or by the number of cycles within the machine, i.e. single-, double- or tripleeffect (Kuehn & Coleman 2005). A. SINGLE EFFECT Single-effect absorption chillers are machines with a single absorption cycle, in which the refrigerant transfer is made through the machine’s major components (Generator, Condenser, Evaporator and Absorber) to produce the cooling effect, as described in the Pressure-Temperature diagram in Figure 3.3.
Weak Solution TE
Strong Solution TG
Figure 3.3. Single Effect Machine Pressure-Temperature Diagram (Kuehn & Coleman 2005)
The single-effect absorption cycle requires low pressure, lower temperature steam or hot water (7595 °C) from the heat supply to activate the generator unit, and thus these systems are desirable where waste heat or hot water from solar thermal collectors are available. The thermal efficiency (COP) is limited in the range of 0.6-0.7 for single-effect LiBr/H2O absorption chillers (Figure 1.8) (Balaras et al. 2007; Henning 2007). The low COP value restrains the cost competitiveness of singleeffect systems.
Figure 3.4. Single-Effect Steam Fired Cycle Diagram [YORK] In this project, we study the heat that is capable of conveying the heated water through solar evacuated tube collectors for single-effect machine starts.
B. DOUBLE EFFECT Double-effect machines consist of two generators of refrigerant, the high temperature generator (GA) and low temperature generator (GB), two heat recovery of the solution (RA and RB), a condenser and a liquid sub-cooler, an expansion valve, an evaporator and an absorber. The necessary equipment is the same as in the single-effect machine, but in this case the generator is divided into two as shown, in Figures 3.5. and 3.6. The high pressure zone consists of the evaporator and the absorber, while the low pressure zone consists of the condenser and the generator. Configurations can be found in series the two zones by furnishing the same flow generator solution successively low and high. Double-effect absorption chillers require a high temperature – pressure steam or hot water – to operate (120 °C - 160 °C). Their use is limited to either waste heat recovery, or to locations where high pressure steam is available, or situations when gas is cheaper than electricity (for direct fired systems). Their combinations with solar thermal harvesting systems are rare due to the need for more advanced and higher cost solar thermal collectors and thermal storage tanks. Though the COPs of double-effect chillers are higher than for single-effect chillers (0.7-1.5), the cost of additional components is much higher, because they require larger heat exchangers, more complicated control systems and special materials to avoid corrosion (Balaras et al. 2007; Henning 2007).
P High-Temperature Condensor
Figure 3.5. Double-Effect Machine Pressure-Temperature Diagram (Kuehn & Coleman 2005)
Second-Sta ge Genera tor
First Stage Generator
Steam In (1100 kPa, 184 °C)
Condensate Out (110 °C) 144 °C
Condenser 8 kPa
37 °C Cool i ng Wa ter 35 °C
7.2 °C Chilled Water
Condens a te Hea t-Excha nger
12.8 °C System Water
Absorber 29.4 °C Cooling Water
Hi gh-Tempera ture Hea t-Excha nger
168 °C, 61.95% 76 °C
46 °C, 61.8%
Low-Tempera ture Hea t-Excha nger
57 °C, 64.5%
Di l ute Sol uti on Pump 39 °C, 50.5%
Figure 3.6. Double-Effect Steam Fired Cycle Diagram (Kuehn & Coleman 2005)
C. TRIPLE EFFECT An extra stage can be added to the double-effect absorption system by adding a higher temperature generator and condenser to the two generators and two condensers that already exist in the doubleeffect absorption chiller. Each stage works as an independent high temperature cycle and the vapour is condensed in each condenser, flowing to the evaporator to achieve the cooling effect.
P High-Temperature Condensor
Middle-Temperature Condensor Middle-Temperature Generator
Low-Temperature Condensor Low-Temperature Generator
Figure 3.7. Triple- Effect Absorption Chiller P-T Diagram (Kuehn & Coleman 2005) Typical operating values of the two machines are: Table 3.1 COP and operating temperature range (Henning 2007) Machine type Single effect Double effect
COP 0,6-0,7 1,2-1,5
Temperature Range (° C) 75-90 120-160
1.6 1.4 1.2
0.6 0.4 0.2 0 50
Figure 3.8. Absorption Chillers vs Carnot Cycle COPs (Henning 2007)
THERMODYNAMIC ANALYSIS OF SINGLE- EFFECT ABSORPTION CHILLER
The thermodynamic parameter that defines the behaviour of the absorption chiller is the coefficient of energy efficiency or coefficient of performance (EEC or COP) (Balaras et al. 2007; Henning 2007; Kuehn & Coleman 2005; Mittal, Kasana & Thakur 2006). The expression of this term is: Eq.(3.1)
The procedure for calculating (COPideal) or (COPmax) (Balaras et al. 2007; Kuehn & Coleman 2005; Mittal, Kasana & Thakur 2006) makes the following assumptions: 1) 2) 3) 4)
The machines operate on a Carnot cycle (ΔU = 0). All processes are reversible (ΔS = 0). Closed systems (absorbent does not evaporate from the generator). Sign of heat and work: - W > 0 : system does work. - W < 0 : system receives outside work.
The generator temperature is maintained between 80 and 100 oC to avoid crystallisation of the lithium bromide. This temperature is maintained by using low pressure steam when the collected useful heat is not sufficient. The heat is rejected in the absorber by the cooling water and the cycle is repeated.
Refrigerant Vapor Generator 7 Weak 3 Solution 4
Absorber 10 E
Figure 3.9. Vapour-Absorption refrigeration Cycle
For a closed absorption system as shown in Figure 3.9, the energy balance equation is: 𝑊
The work required to pump the liquid W p vdp is very small and can be ignored. The entropy changes within the generator heating medium (SG) ' Eq(3.3) environment (SO) , Eq(3.4) and refrigerant substance (SE ) , Eq(3.5) As all the process are reversible, according to the second law of thermodynamics the total entropy change (S ) is greater than or equal to zero: Eq(3.6) or Eq(3.7) By re-arranging equations (4.7) and (4.4), we get: Eq(3.8) Rewriting equation (3.1), the COP is given by: Eq(3.9) For a complete reversible system, COPmax is given by: Eq(3.10) The thermodynamic analysis of an absorption cooling system can be carried out by taking a control volume around each component and applying the following three equations to any part of the system: 1- Mass balance: Eq(3.11) 2-
Material balance: Eq(3.12) 30
Energy balance: Eq(3.13)
Referring to Figure. 3.9, the mass, substance and energy balance equations on the different components can be written as: Generator: Eq(3.14) Eq(3.15) Eq(3.16) Absorber: Eq(3.17) Eq(3.18) Eq(3.19) Condenser: Eq(3.20) Eq(3.21) Eq(3.22) Evaporator: Eq(3.23) Eq(3.24) Eq(3.25) Heat exchanger
Eq(3.26) Eq(3.27) Eq(3.28) Eq(3.29) Eq(3.30)
Where points 1,2, .. ...... refers to the positions shown in Figure (3.9), h is the specific enthalpy in kJ/kg, x is the concentration in kg of LiBr per kg of solution, and m is the mass flow rate in Kg of solution per unit of time. It can be seen from the figure that h7 = hr (enthalpy of refrigerant), m7 = mr (flow rate of refrigerant), x3 = xr concentration of refrigerant in LiBr), xL = xab (concentration of LiBr in absorbent). Using the above equations, the mass flow rates, the amount of heat required by the generator, the rejection by the condenser and absorber, and the cooling produced in the evaporator can be calculated. The COP of the cooling system will be:
Eq(3.31) Eq(3.32) Eq(3.33) Eq(3.34) Eq(3.35)
where qrefrig is the cooling effect supplying the refrigeration unit and the flow rate of the absorbent is: Eq(3.36) while the flow rate of the solution (
) calculated by equation (3.36)
The rate at which heat must be supplied to the generator QsuP is obtained from the heat balance: Eq(3.37) This requirement, which determines the size of the solar collector, probably represents the maximum heat load the refrigeration unit must supply during the hottest part of the day. The coefficient of performance COP is: Eq(3.38) The rate of heat transfer in the other three heat exchanger units – the liquid heat exchanger, the water condenser, and the generator – is obtained from the heat balances: 1- For the liquid heat exchanger this gives Eq(3.39) where q1-2 is heat transferred from the absorbent stream to the refrigerant absorbent stream. 2- For the water condenser, the rate of heat transfer q7-8 to the environment is Eq(3.40) 3- Absorber: The rate of heat removal from the absorber can be calculated from an overall heat balance on this system: Eq(3.41)
For system optimisation, the life cycle cost needs to be calculated. The next chapter describes the parts of the system and the properties of the absorption chiller, and presents the system cost evaluation method. 3.6. WORKING FLUIDS The absorption cooling thermodynamic system employs a solution of usually two or three components, essentially called refrigerants and absorbents (Kuehn & Coleman 2005). A refrigerant is a chemical substance that absorbs heat from a fluid to lower temperature. The properties that a refrigerant must hold are: a) High latent heat of vaporisation, to reduce as much as possible the mass flow of refrigerant that will be circulated through the plant, with a consequential reduction in size as well as losses in piping and heat exchangers. b) The condensing pressure and condensation temperature must not be too high, to avoid installation difficulties which will enable refrigerant leaks. High condensing pressure and condensation temperature also increase the cost of the pump and the equipment located in high pressure areas requires high mechanical strength. c) Vapour pressure at the evaporation temperature should not be too low because if it is less than atmospheric, sealing problems occur and decrease the efficiency of the air intake cycle, resulting in the appearance of corrosion and the formation of ice crystals. d) The specific volume of the refrigerant vapour pressure of evaporation must be reduced to decrease the size of the pump. e) Low freezing temperature so that it does not solidify in normal working conditions. f) High thermal conductivity to reduce the heat exchange surfaces as far as possible. g) Reduced viscosity to decrease the pressure drop in pipes and heat exchangers. h) Behaviour must be inert to the material constituting the installation. i) It must be cheap, to decrease costs and keep the total price of the machine as low as possible. The absorbent is a substance having an affinity with the coolant. This affinity allows the coolant in vapour state to be absorbed by the absorbent by increasing the concentration of coolant in solution. The properties that must met are: a) b) c) d)
Stability at the working temperatures of the cycle. Easily soluble in the refrigerant. Boiling point higher than the refrigerant to allow easy separation. The crystallisation temperature of the eutectic formed in the refrigerant must be low to avoid crystal formation. e) Low chemical aggression to prevent corrosion in the system. f) Cheap and low toxicity. Because the working fluid is a solution, the cycle characteristics and performance will depend on the physical properties of the fluid, which are: a) Suitability to the cycle temperatures and pressures. 33
b) c) d) e) f)
Absorption friendly refrigerant. Rapid trend to equilibrium. Easy separation of the pure refrigerant. Low volatility of the absorbent. Low viscosity.
The principal commercial solutions used are the ammonia water pair [NH3 (Refrigerant) - H20 (absorbent)] and lithium bromide-water [LiBr (absorbent) - H2O (refrigerant)]. The first is used in air conditioning systems with high and low power, while the second is used in air-conditioning systems with medium and high power. 3.7.
ENVIRONMENTAL CONSIDERATIONS OF ABSORPTION CHILLERS
The absorption chiller is an alternative means of generating energy for sustainable development because: -
It has low CO2 emissions and can run on waste heat sources or low-emission fossil fuels. This will reduce the greenhouse effect on Earth. Using solar energy as heat source for the absorption chiller is currently under investigation (Henning 2007) . It has lower ozone depletion potential, because the refrigerant materials used (water, ammonia, etc.) when released to the atmosphere are combined with oxygen free radicals, thus favouring the maintenance of the ozone layer. There is an increasing development of the absorption cycle to achieve machines able to work with equal or better efficiency than the machines of mechanical compression.
By employing waste heat or a renewable source of energy absorption, it is necessary to assess the available heat and energy flux of the machine for it to operate without interruption. Comparing both energy flows will determine whether the heat source is capable of driving the machine or whether it will be necessary to use another source. To evaluate the available heat and reliability, it is necessary to know the temperature and flow of the source, and the continuity of supply or temporary variations, which depend on the charging rate of the process by which it is generated. The classification of the absorption chiller, its operating principles and working fluids have been presented in this chapter. The focal point of this study is to model a single-effect absorption chiller, therefore other absorption chiller configurations were not considered. Nevertheless, other types of absorption chiller have the same fundamental principles as single-effect absorption chillers.
3.8. REFERENCES Balaras, C.A., Grossman, G., Henning, H.-M., Infante Ferreira, C.A., Podesser, E., Wang, L. & Wiemken, E. 2007, 'Solar air conditioning in Europe--an overview', Renewable and Sustainable Energy Reviews, vol. 11, no. 2, pp. 299-314. García Casals, X. 2006, 'Solar absorption cooling in Spain: Perspectives and outcomes from the simulation of recent installations', Renewable Energy, vol. 31, no. 9, pp. 1371-89. Henning, H.-M. 2007, 'Solar assisted air conditioning of buildings - an overview', Applied Thermal Engineering, vol. 27, no. 10, pp. 1734-49. Kuehn, T.H. & Coleman, J.W. 2005, 2005 ASHRAE Handbook: Fundamentals, ASHRAE. Mittal, V., Kasana, K. & Thakur, N. 2006, 'Modelling and simulation of a solar absorption cooling system for India', Journal of Energy in Southern Africa, vol. 17, no. 3, p. 65.
BUILDING SPECIFICATIONS AND COOLING LOADS
4.1. INTRODUCTION In this chapter we study the energetic simulation of a building using the OpenStudio plugin for Google SketchUp 8 and TRNSYS software package. A small office building model was investigated (D.O.E. Benchmark building for a small size office, (Thornton et al. 2010)). During the drafting of the project, we followed the rules governing the development of projects in order to acquire the highest quality in each of its component sections. The energy efficiency of buildings can be defined as the reduction in energy consumption while maintaining the same energy services, without affecting the comfort and quality of life, continuing to protect the environment, ensuring supply, and promoting sustainable use. The wise use of energy results in cost savings and positive effects on the environment. In light of the above, to achieve an efficient energy use for the building under consideration, the project was divided into two main blocks: the first block is described in this chapter and includes the design and simulation of the building. The evaluation of a set of proposed architectural improvements designed to achieve optimal intake was also considered in this study. In the second block (Chapter 6), energy and economic assessments were performed to choose the best alternative application. In the first block, we analysed the building to enable us to specify all the information on weather, rainfall, climatic data, solar radiation and more. Moreover, we detailed the building's occupancy level and defined the structural characteristics of the building and the construction materials. Once the components had been defined, the geometry inside the building was defined to indicate the usable area of each zone that was planned. The determination of the requirements for each area was based on the occupancy of these areas. These requirements were: the metabolic activity, specified ventilation and other thermal loads for each of the areas that make up the building. All requirements were based on the ASHRAE Standard for Office Buildings (ASHRAE 2004). In this same block, we also presented a brief description of the OpenStudio plugin for the Google SketchUp program from the National Renewable Energy Laboratory (NREL), and a short guide to the basic steps to create three-dimensional models (Appendix A). A simulation model using the OpenStudio program, along with the TRNSYS software package (Appendix B), was broken down for the current situation of the building, which detailed the features corresponding to the thermal loads being considered. The building underwent simulation under four different scenarios: the first corresponded to the baseline scenario, i.e. the current situation. The remaining three corresponded to each of the proposed improvements included in this project, i.e. introducing an overhang on the north side of the building, modifying the existing 4mm glazing by using double glass, and finally a combination of both these previous improvements. Once the results had been obtained from the simulations of the first block, energetic assessments of the results obtained for each of the three proposed improvement for reducing energy consumption were performed.
The HVAC components were added to the models to estimate the energy required for the air conditioning system in each model, in order to calculate the carbon footprint and compare the energy saving with the absorption chiller system utilising solar thermal energy. 4.2.
The objectives were outlined in Section 1.4.2. 4.3.
DESCRIPTION OF THE PROCESS
4.3.1. CALCULATION AND SIMULATION PROGRAMS ENERGYPLUS – An engine for calculating the heating and cooling loads needed to maintain set points in a thermal control HVAC system. ENERGYPLUS is a stand-alone free simulation program without a “user friendly” graphical interface. The program reads input and writes output as text files. GOOGLE SKETCHUP – A three-dimensional model using the 3D drawing program Google SketchUp with the design characteristics identified in the previous section. OPENSTUDIO – Plugin for GOOGLE SKETCHUP and ENERGYPLUS which makes it easy to use Google SketchUp to create and edit the building geometry in EnergyPlus input files. TRNSYS – Simulation software for system performance, including HAVC Systems performance and solar thermal systems. The TRNSYS 16 software package was used in this study. In this version there is a lack of graphic interference, unlike TRNSYS 17. TRNBuild – An application within the TRNSYS software package used to create and edit the nongeometry information in the TRNSYS building model. In TRNBuild, the building design characteristics are used to create the building model with a manual data entry before the energy simulation with TRNSYS Studio is conducted. This software is commercial package. MICROSOFT EXCEL – Program used to calculate the budget and perform the economic feasibility study. 4.3.2. BLOCK DIAGRAM OF PROCESS This chapter is structured in two main blocks, as specified in the introductory section (Section 4.1). The first block, which corresponds to the definition phase of the model and simulation, consists of three phases. The simulation results obtained in the first block are detailed below using a block diagram (Figure 4.1). Study of buildings A search process to obtain all the features of the model to simulate, following the guidelines and regulations. Simulation results Results were obtained from the input parameters for occupation, outside temperature, relative humidity, etc., using the EnergyPlus/OpenStudio and TRNSYS calculation programs.
Comparison of the results The results of the simulation model from the two different energy assessment software packages were plotted for comparison. The results were also energetically evaluated in parallel for the various proposals and a series of performance indicators was calculated in a later stage (Chapter 6). Energy consumption of conventional systems The energy consumed by the HVAC equipments for the different models was estimated from the EnergyPlus/OpenStudio program. The results were compared to the energy saving, economic and environmental assessments for the proposed solar thermal cooling system employing an absorption chiller at a later stage (Chapter 6).
Initial Phase Preliminary Analysis
Intermediate Phase Definition of the model and simulation
Final Phase evaluation of the results
Comparison of the results obtained
Figure 4.1. Block Diagram of Building Load Simulation Process 4.3.3. WEATHER STUDY This section details the characteristics of the weather conditions in the location of the building under study to obtain as much detail as possible for accurate simulation. This can be done by referring to, and following, the appropriate regulations. 126.96.36.199. LOCATION/WEATHER CONDITIONS The building model selected for this study was the United States (US) Department of Energy’s baseline benchmark building model for small office prototype (ASHRAE 2004; Thornton et al. 2010) under the climatic conditions of Sydney, NSW. Sydney is the capital city of New South Wales, and a 38
major city in Australia, located at 33.86S, 151. 20E, 66 metres above sea level and in the time zone GMT+10. It experiences year-round moderate weather. 188.8.131.52. AMBIENT CLIMATIC DATA Full information on the climatic environment of the city of Sydney is required, with climatic data for at least the summer and winter seasons providing the most extreme hot and cold temperatures. The US Department of Energy, Energy Efficiency & Renewable Energy website (http://www.eere.energy.gov/) provides the weather data for more than 2,000 locations around the world in different file formats including RMY format (Australia Representative Metrological Year Climate Files), readable by the EnergyPlus/OpenStudio software package. This data format was created by the Department of the Environment and Water Resources, Australia Greenhouse Office, Canberra, ACT, Australia. The compressed file contains more than one file; the file that will later be run in EnergyPlus/OpenStudio to simulate the weather conditions in Sydney has a .*EPW extension. The .STAT extension retrieved offers a rich amount of data such as the geometric situation of the city coordinates. The TRNSYS software package requires the weather data files to be in TMY2 format (Typical Meteorological Year). The TMY2 sets are data sets of hourly values of solar radiation and meteorological elements for a 1-year period. The TRNSYS Weather files library package contains TMY2 files for most of the Australian weather stations. The TMY2 data are derived from the 19611990 database. More accurate performance and economic analyses of energy systems are possible when the TMY2 data are based on more recent and accurate data. Generally, we can create an updated TMY2 weather data file using the weather data available on the Australian Bureau of Meteorology website (http://www.bom.gov.au) and the Meteonorm Software package from Meteotest (http://www.meteotest.com/) (Figure 4.2). A simpler method is available, however, by using a Microsoft Office Excel macro for reading TMY2 data files, available at the Solar Energy Laboratory- University of Wisconsin Madison – Website for free [http://sel.me.wisc.edu/trnsys/weather/tmy2data.htm]. This macro enables the user to open the TMY2 files on an Excel sheet, edit and save it as a modified TMY2 file. A third and more accurate way to create TMY2 files readable by TRNSYS 16 is to convert the TMY3 modified weather files updated on a weather database for the period 1991-2005, using free TMY3 to TMY2 conversion software from the National Renewable Energy Laboratory Website [http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/]. By following very simple steps including the selection of the TMY3 file, the output TMY2 file, process and an updated TMY2 data file based on the weather database between 1991-2005 will be ready to use by TRNSYS16 (Figure 4.3).
Figure 4.2. Meteonorm V. 5.1. Console Panel
Figure 4.3. TMY3 to TMY2 Formatter Software from NERL. Finally, the TRNSYS Studio Type 89e [Figure 4.4] component can be used to read weather data files in the EnergyPlus / ESP-r format (.EPW). It assumes that the first line of the data file corresponds to the start time of the simulation.
Figure 4.4. TRNSYS Component Type 89e Logo. 184.108.40.206. OUTDOOR TEMPERATURE Annual ambient temperature records for Sydney NSW are available from the Australian Bureau of Meteorology (B.O.M.). Table A.1 and Figure 4.5 list the average temperature records for Sydney in 2011 on a monthly basis, with maximum and minimum dry bulb temperatures recorded.
Figure 4.5. Average Monthly and Annual Maximum and Minimum Temperatures (Source:(B.O.M.))
The outdoor temperature hourly records for the hottest day in each month are listed in Table A.1. Figure 4.6 shows the hourly records of ambient temperatures in Sydney weather using the B.O.M. data records in the TRNSYS software.
Figure 4.6. Outdoor Temperature for Sydney on Hourly Based Simulation 220.127.116.11. RELATIVE HUMIDITY The Bureau of Meteorology database provides another important parameter, which is relative humidity (%). Table A.2 lists the relative humidity as a percentage for the hottest days of each month in Sydney. The hourly humidity ratio is shown in Figure 4.7.
Figure 4.7. Relative Humidity for Sydney on Hourly Based Simulation
18.104.22.168. SOLAR RADIATION Monthly solar radiation (Direct, Global and Diffuse Radiation) on a horizontal surface in Wh/m2 is listed in Table A.3. The hourly instant values for solar radiation are presented in Figure 4.8, Figure 4.9 and Figure 4.10.
Figure 4.8. Direct Normal Radiation for Sydney on Hourly Based Simulation
Figure 4.9. Global Horizontal Radiation for Sydney on Hourly Based Simulation
Figure 4.10. Diffuse Radiation on Horizontal for Sydney on Hourly Based Simulation 4.4. OFFICE BUILDINGS UNDER STUDY: THE ASHRAE SMALL SIZE OFFICE BUILDING MODEL 4.4.1. GEOMETRIC DESCRIPTION The small office prototype from the ASHRAE Advanced Energy Design Guide for Small Office Building (AEDG-SO)(ASHRAE 2004) is a building with two identical floors [Figure 4.11]. Similar to the medium sized office prototype, each floor has four perimeter zones and one core zone. The floor area of each is 930 m2 (30.5 m x 30.5 m) [Figure 4.12] with a total office space area of 1860 m2 and a perimeter zone depth of 3.6 m. The percentages of floor area are: Perimeter 30%, Core 70%. The floor to floor height is 4 m (2.75 m floor to ceiling height and 1.25 m plenum above ceiling). The window to wall ratio is 20% with a glazing sill height of 1 m.
Figure 4.11. Axonometric View of Small Office Building
Figure 4.12. Floor Plan for a Small Size Office Building Model
In total, the building is divided into 10 thermal zones; as a summary, specifications of the useful surfaces of each zone are shown in Table A.4.
4.4.2. CONSTRUCTION DATA OF THE SMALL SIZE OFFICE BUILDING This section details the construction aspects of the building with the characteristic data of the small size office model, and the construction materials of which it is composed. The ASHRAE office building office construction is based on the data provided by the CBECS (Commercial Building Energy Consumption Survey) (CBECS 2003) to meet ASHRAE Standard 90.1-2010 Section 4.3 Prescriptive Building Envelope Option(ANSI/ASHRAE/IESNA 2010). 22.214.171.124. EXTERNAL WALLS An envelope is a set of elements of the building that face adversity from the outside; the outer surface waterproof and designed to reduce noise and reflect light. The wall consists of a multi-layer construction [Figure 4.13]: 200 mm concrete block (1842 kg/m3), R-0.15 K·m2/W, and rigid insulation held in place with metal clips. The baseline building insulation thickness varies by climate, and in some warmer climate zones, insulation is not required. The interior layer is a 13 mm gypsum board (if baseline insulation is required), R-0.08 K·m2/W.
Figure 4.13. Small Size Office Building Construction Layers for External Wall The features of all wall materials are listed in Table 4.2. 46
Table 4.1. Materials for small size office building exterior walls Construction
Rigid board insulation
To obtain the thermal performance of the exterior wall mass, the wall is assumed to be within US climate zone 3B of ASHRAE 90.1-2007 standard. Table 4.3 shows the overall U-factor value for selected wall. Table 4.2. Small size office building overall u-factor for external wall Zones
Overall U-factor (W/m2-K)
126.96.36.199. INTERIOR WALLS The small size building model interior walls that separate the building zones consist of gypsum board layers with airspace in between according to ASHRAE Standard 90.01-2010 (ANSI/ASHRAE/IESNA 2010) [Figure 4.14].
Figure 4.14. Outline Type of Interior Walls in Small Size Office Building
As with the values obtained for the materials of the exterior walls, the constructive elements of the interior wall and their characteristics are listed in Table 4.4. Table 4.3. Small size office building interior walls materials
Construction Thickness R-Value
Wall air space resistance
188.8.131.52. ROOF The roof is defined as a cover to the closure system on the top of a building. The ASHRAE small size office building model roof is a flat roof formed by the following construction layers [Figure 4.15]:
- Continuous rigid insulation - Metal deck
A single-ply membrane of EPDM (ethylene-propylenediene- terpolymer) is used as an exterior finish and a grey EPDM is used in the baseline, with a solar reflectance value of 0.23 and a thermal emittance of 0.87, based on the database of the Lawrence Berkeley National Laboratory [LBNL 2009:http://eetd.lbl.gov/coolroofs/].
Figure 4.15. Small Size Office Building Roof Structure The constructive elements of the roof materials and their characteristics, and the roof thermal performance data, are listed in Table 4.5 and Table 4.6, respectively.
Table 4.4. Small size office building roof cladding materials (Thornton et al. 2010) Construction Thickness R-Value
Rigid insulation (continuous)
Varies according to thickness (usually 2.6 K.m2/W)
Table 4.5. Small size office building roof overall u-factor (W/m2.k). (Thornton et al. 2010) Zones Overall U-factor (W/m2-K)
184.108.40.206. SLAB-ON-GRADE FLOOR The baseline model of a small size office prototype uses unheated slab-on-grade floors; the ground floor base assembly consists of a concrete slab over a modelled sand layer and is covered with carpet, in accordance with CBECS results and ASHRAE 90.1 standard requirements (ANSI/ASHRAE/IESNA 2010; CBECS 2003) for a mon-residential building. The outermost layer of the surface consists of the following layers [Figure 4.16]:
Figure 4.16. Outline Type of Slab on Grade Floor in Small Size Office Building The slab-on-grade floor layer characteristics and thermal performance are listed in Table 4.7 and Table 4.8, respectively.
Table 4.6. Small size office building slab-on-grade materials cover (CBECS 2003) Construction Thickness R-Value
Table 4.7. Small size office building slab-on-grade overall U-factor (W/m2.k).
Overall F-factor (W/m-K)
220.127.116.11. FENESTRATION The ASHRAE model for a small size office building window-to-wall ratio is set to 20%; similarly, the window-to-wall ratio in this project was set to 20%. Windows 1.5 m high, 1.8 m wide and with a height from the floor of 1.22 m were distributed equally around the building perimeter at the rate of eight windows per exterior wall (Figure 4.11), with no external shading. The type of glass meets ASHRAI 90.1 requirements for a non-residential building: vertical glazing 31.1-40%, and U fixed value (Thornton et al. 2010). Windows were glazed according to the specification listed in Table A.5. The total area of windows for each climatic zone are listed in Table 4.9. Table 4.8. Windows areas and orientations for the small size office building baseline models Zone CORE_BOTTOM
CORE_TOP PERIMETER_TOP_ZN_3 PERIMETER_TOP_ZN_2 PERIMETER_TOP_ZN_1 PERIMETER_TOP_ZN_4 PERIMETER_BOT_ZN_3 PERIMETER_BOT_ZN_2 PERIMETER_BOT_ZN_1 PERIMETER_BOT_ZN_4 TOTAL
Gross Wall Area [m²]
Window Glass Area [m²]
554 554 90 90 90 90 90 90 90 90
0 0 84 84 84 84 84 84 84 84
0 0 16.8 16.8 16.8 16.8 16.8 16.8 16.8 16.8
4.4.3. VENTILATION AND INFILTRATION Infiltration is defined as the uncontrolled leakage of air to a conditioned space from an unconditioned space due to pressure difference (ANSI/ASHRAE 2010). The air infiltration in any building occurs through doors, windows, floors, ceiling and walls. According to McQuiston (McQuiston, Parker & Spitler 2000), the rate of infiltration through the exterior walls of a building is 0.29 air changes per hour (ACH). This infiltration occurs 24 hours a day. The EnergyPlus input design infiltration is calculated as 1.02 E-3 m3/s·m2 of an above-grade exterior wall surface area. The infiltration schedule that is input to EnergyPlus/OpenStudio is assumed to have a full infiltration rate when the HVAC system is scheduled ‘off’ and 25% infiltration when the HVAC system is switched ‘on’. Ventilation is the process of supplying or removing air from the conditioned space to control air contaminants, humidity and/or temperature levels within the space. The ventilation rates for each space in the office building are listed in ASHRAE Standard 62.1-2010 (ANSI/ASHRAE 2010), as shown in Table A.6. Since ASHRAE Standard 62.1-2004, the amount of outdoor air required for ventilation in each space is no longer based on the number of people in the space alone, as was the case in previous versions of the standards, but on the number of people and the floor area of the space. In Table A.6, the Rp is the outdoor air flow rate per person [L/(s·person)] and Ra is the outdoor airflow rate per floor area [L/(s·m2)]. The default values of the combined air flow for ventilation in L/(s·person) for an office space is 8.5 L/(s·person) and the occupant density for an office space of 5 person/93 m2 (5 person/1000 ft2) were used to calculate the amount of ventilation air required for each space (Table A.6). The total outdoor ventilation rate supplied to the building is 558.8 L/s when the ventilation system is on. The ventilation system is turned on two hours prior to people entering the building (i.e., 06:00) and is shut off two hours after the last occupants have left (i.e., 23:00). The daily schedule I s presented in Figure 4.17. The calculated ventilation rates for each space are given in Table A.7. According to PNNL work (Thornton et al. 2010) , the EnergyPlus input design infiltration is calculated as 1.02 E-3 m3/s·m2 of an above-grade exterior wall surface area, equivalent to the base infiltration rate of 9.14 E-3 m3/s·m2 of an above-grade envelope surface area at 75 Pa. Infilteration
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Figure 4.17. Ventilation and Infiltration Daily Schedule for Small Size Building Model
4.4.4. BUILDING LOADS AND SCHEDULES 18.104.22.168. OCCUPANCY IN THE OFFICE BUILDING The space occupants are a source of internal heat load. According to ASHRAE Standard 62.1-2010 (ANSI/ASHRAE 2010) and the ASHRAE Handbook of Fundamentals, the number of people who may be in a room for an extended period of time is based on the space type, as shown in Table 4.15. The density of occupants in an office space is 5 person/93 m2 (5 person/1000 ft2). As calculated in Table 4.16, the total number of occupants in the office building is 100 persons. The PNNL study for small size office building model (Thornton et al. 2010) assumed that the proportion used area of a typical small office building is 44% of the total floor area (818 m2). With a work station area of 9m2 per person, according to the ASHRAE Handbook of Fundamentals (ASHRAE 2009), the total occupancy results in 88 people at peak time. The heat gain from people is a parameter of the activity level of office occupants. The ASHRAE 2009 Fundamentals Handbook (ASHRAE 2009) contains tables for the sensible and latent heat emitted by occupants at different activity levels. Table 4.10 lists examples of activity levels in office buildings. In the case of a small size office building, all 10 thermal zones are considered as office spaces. Accordingly, the total heat gain is 132 W/person, for the seated, light work, typing activity level [Table 4.9]. Table 4.9. Office activity level related to sensible and latent heat gain Zone
Activity Seated, light work, typing
Associated Heat Gain qs = 74 W, ql = 58W
Total Heat Gain qt =132 W
Seated, light work, typing
qs = 75 W, ql = 75W
qt =150 W
Seated at rest
qs = 60 W, ql = 40W
qt =100 W
Figure 4.18 and Table A.8 (Thornton et al. 2010) illustrate the occupancy schedule of an office space. The building is not used for the first seven hours of the day, and is 95% occupied during working hours (09:00 – 17:00), with half the people leaving the building during the lunch hour.
Figure 4.18. Occupancy Daily Schedule for a Small Size Office Building 52
22.214.171.124. EQUIPMENT AND LIGHTING IN THE OFFICE BUILDING Apart from the internal heat loads created by people, other internal charges within the system are caused by lighting, electrical and electronic equipment. These are called plug loads. For the study and simulation of an air conditioning system, ventilation and air conditioning (HVAC) is essential to clearly define internal design loads with a realistic schedule, similar to understanding occupation loads. LIGHTING The ventilation system should be designed taking into account the internal heat loads caused by the lighting system, which is assessed according to light levels determined by typical design values given in Table 4.10 of the IES Lighting Handbook (Thornton et al. 2010). These averages are based on the surface area of the premises. Typical values for energy-efficient systems are given in Table 4.11 based on ASHRAE Standard 90.1-2010 (ANSI/ASHRAE/IESNA 2010). The office light level is a value of 400 lux for offices, but the lighting power equivalent value is 10 W/m2 (Table 4.11). Table 4.10. Design values for light levels (DiLaura et al. 2011) Type of use
Light level in lux
Single office room with window Open plan offices Conference room
300 to 500 400 to 600 200 to 300
400 400 300
Table 4.11. Design values for lighting power in energy-efficient systems Light level in lux 50 100 200 300 400 500
Lighting power specified in W/m2 Default typical range 2.5 to 3.23 3.5 to 4.54 5.5 to 7.6 7.5 to 7.58 9.0 to 12.5 11.0 to 15,2
The lighting power value used by Thornton et al. (Thornton et al. 2010) for internal lighting is 10.76 W/m2 (1 W/ft2) for all areas, based on ASHRAE Standard 90.1-2010 (ANSI/ASHRAE/IESNA 2010). Table 4.12 shows the method used to estimate the Lighting Power Density (LPD) value. The lighting schedule of an office space can be found in Table A.9 and Figure 4.19. On weekdays, 15% of the lights in the office building are usually in use outside working hours; this percentage is reduced to 10% at weekends and holidays. 90% of the lights are utilised during working hours.
Table 4.12. Lighting power density calculation Space Type Office – open plan Office – private Conference meeting Corridor/Transition Active storage Restrooms Lounge/Recreation Electrical/Mechanical Stairway Lobby Other Weighted LPD for the whole building
Percentage of Floor Area1 15% 29% 8% 12% 14% 4% 2% 2% 3% 6% 5% 100%
Baseline LPD (W/m2) 11.8 11.8 14 5.4 8.6 8.6 12.9 16.1 6.5 14 10.8 10.8
Figure 4.19. Lighting Daily Schedule for Small Size Office Building Model
EQUIPMENT The plug loads of a typical office space are related to the office equipment: computers and monitors, fax machines, printers and copiers, as well as facilities equipment such as refrigerators, microwaves, water heaters and coffee machines. The lights and plug loads have a negative effect on the cooling load and a positive effect on the heating load in addition to their effect on electrical energy consumption, i.e. higher plug loads and internal lighting load will increase the cooling load of the space and decrease the heating load.
As explained earlier, the workstations cover an area of 818 m2 (44% of the total area of the office building), with each work station occupying 9.3 m2. Occupancy was set at 88 persons with a computer allocated to each. Based on two tenants using the building, each had one computer server, laser printer, fax machine, water cooler, refrigerator, coffee maker and vending machine. The list of equipment presented by Thornton et al. (Thornton et al. 2010) is shown in Table A.10. The plug loads schedule of a small sized office space can be found in Table A.11 and Figure 4.20.
Figure 4.20. Plug Load Daily Schedule for Small Size Office Building Model
HVAC System In this study, the HVAC system for a small sized office building is different from the conventional system assigned in the small sized office prototype used by Thornton et al. (Thornton et al. 2010). A single packaged rooftop variable air volume (VAV) air-conditioning system was used instead of a single cooling unit per zone. A gas furnace at the main air handling unit with electrical resistance reheating was selected as the heating system. Table A.12 and Figure 4.21 illustrate the HVAC hourly scheduling; Table A.13 shows the thermostat temperature setting for heating and cooling. The HVAC system thermostat set points are 24 °C for cooling and 21 °C for heating during office hours and 26.7 °C for cooling and 18.3 °C for heating for off hours.
1.2 1 0.8 0.6 0.4 0.2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Figure 4.21. HVAC Daily Schedule for Small Size Office Building Model OVERHANGS A simple overhang can reduce the room temperature by 2°C to 5 °C depending on its area and orientation. Thus, the outer overhang shade is considered to be a real environmental benefit and a solution for future energy savings. During summer months, the sun is much higher, thus the fall of solar rays is more perpendicular to the ground and an overhang shade prevents the entry of such rays into the building through windows. Installing an outdoor overhang reduces energy consumption and the greenhouse effect. The European Parliament, for instance, has considered sun protection as a solution to reduce energy costs in buildings since 2002. Indeed, before operating the air conditioner, it is preferable to apply overhangs to reduce the room temperature by a few degrees. The results of this study show that this simple gesture can reduce the power consumption of air conditioning by 10% to 20%. If the overhang is also equipped with an automatic control system, the indoor temperature can be adjusted during summer, meaning that no air conditioning would be required at certain times of the day. In parallel, the architectural concept of recent years (passive house, positive home) has tended to use more windows to make the most of the heat and light gained naturally from the sun. Exterior overhangs are involved at this stage to optimise the impact of solar radiation and limit the use of air conditioning or artificial lighting.
The results obtained from the simulation using TRNSYS 16 [Appendix B] and OpenStduio/EnergyPlus [Appendix C], i.e. the cooling loads of the building, are presented in this section. 4.5.1. SIMULATION RESULTS OF BUILDING LOADS: SMALL SIZE OFFICE BUILDING MODEL CASE 1: BASIC MODEL SIMULATION RESULTS The baseline model of the small size building in this study was described and the building structure and loads were defined in Section 4.5. This building uses single layer glass of 4 mm thickness for all windows, with no overhangs to protect the windows from sunlight. The baseline model cooling load results are used as a reference value to compare with the simulated results of other scenarios. The simulation results of the monthly cooling loads over the year under baseline conditions are shown in Table 4.13. The results show that the total cooling load was around 64000 kWh. As shown in Figure 4.22, the minimum cooling load value in July was 66.32 kWh. By contrast, the highest power points are in December and January, specifically in January with a value of 12450 kWh. The graph becomes a parabola with its maximum at the ends and the minimum in the middle [Figure 4.22]. In winter, however, the cooling power is decreased. Table 4.13. Cooling & heating load summary for medium size building office basic mode Month January February March April May June July August September October November December Annual Sum or Average Minimum of Months Maximum of Months
TRNSYS:DISTRICTCOOLING [KWh] 12450.00 10990.00 9648.00 4607.00 1905.00 353.10 66.32 555.50 1743.00 5012.00 6712.00 10160.00
OPENSTUDIO:DISTRICTCOOLING [KWh] 11205.00 10440.50 10130.40 4146.30 1714.50 317.79 63.00 538.84 1620.99 5312.72 7383.20 10566.40
64201.92 66.32 12450.00
63439.64 63.00 11205.00
14000.00 12000.00 10000.00 8000.00 6000.00 4000.00 2000.00 0.00 1
Figure 4.22. Small Size Office Monthly Load Summary for Case 1 CASE 2 SIMULATION RESULTS WITH BUILDING MODIFIED GLAZING The first architectural improvement proposed to reduce the load calculation was the installation of double glazing in all windows in the building. The total area was 134.4 m2 of double glazing. This improvement featured double-glazed windows, each having 6 mm glass separated by an Argon gas space of 16 mm (Model 2SHA AR-3 TRNSYS American window library), with a U-value of (1.26 W/m2.k) and SHGC of (0.212) to replace the original clear single glazing of 4 mm thickness (U-value of (3.2 W/m2.k) and SHGC of (0.39)). The new glazing is intended to maintain the required indoor temperature within a correct and useful range. TRNSYS [kWh]
12000.00 10000.00 8000.00 6000.00 4000.00 2000.00 0.00
Figure 4.23. Medium Size Office Monthly Load Summary For Case 2
With an annual total cooling load of 56898.54 kWh, a reduction percentage of 11.3% was recorded from the cooling load of the basic building case. In January, the peak for cooling was recorded as 11060.00 kWh (Table 4.14 and Figure 4.23).
Table 4.14. Cooling & heating load summary for medium size building office with modified glazing mode Month January February March April May June July August September October November December Annual Sum or Average Minimum of Months Maximum of Months
TRNSYS:DISTRICTCOOLING [KWh] 11060.00 9818.00 8745.00 4267.00 1741.00 290.00 22.74 394.80 1458.00 4306.00 5836.00 8960.00
OPENSTUDIO:DISTRICTCOOLING [KWh] 9954.00 9327.10 9182.25 3840.30 1566.90 261.00 21.60 382.96 1355.94 4564.36 6419.60 9318.40
56898.54 22.74 11060.00
56194.41 21.60 9954.00
CASE 3: SIMULATION RESULTS BASELINE MODEL WITH OVERHANG The second architectural improvement for the building envelope was to install overhangs to the single-glazed windows. The intention of this improvement was to obtain a further reduction in cooling energy. The most important feature of an overhang is the outright rejection of solar radiation during the summer months. Overhangs with an external shading factor of 0.5 were added to all windows of the building. The calculated results in cooling loads observed throughout the year are shown in Table 4.15 and Figure 4.24. The addition of overhangs to the small office building base model resulted in a reduction of the annual building cooling load of 18.9% compared to the cooling load of the basic building conditions (Case 1), and an 8.5% reduction compared to the case of the modified glazed windows (Case 2) (Table 4.15). The building improvement by adding overhangs resulted in a significant cooling load reduction. This result seems to be compatible with ASHRAE Standard (ANSI/ASHRAE/IESNA 2010; ASHRAE 2009).
12000.00 10000.00 8000.00 6000.00 4000.00 2000.00 0.00
Figure 4.24. Small Size Office Monthly Load Summary for Case 3 Table 4.15. Cooling & heating load summary for medium size building office with overhang mode Month January February March April May June July August September October November December Annual Sum or Average Minimum of Months Maximum of Months
HEATING:DISTRICTHEATING [KWh] 10690.00 9447.00 8246.00 3750.00 1283.00 173.40 6.50 193.60 1120.00 3611.00 5138.00 8404.00 52062.50 6.50 10690.00
COOLING:DISTRICTCOOLING [KWh] 10476.20 8974.65 8081.08 3412.50 1372.81 156.06 7.80 201.34 1041.60 3827.66 5651.80 8740.16 51943.66 7.80 10476.20
CASE 4: SIMULATION RESULTS WITH THE COMBINATION OF OVERHANG AND MODIFIED GLAZING The small office building model with modified double-glazed (6-16-6) windows in combination with external overhang shade is the fourth and final improvement. The monthly cooling load in a year-long period is listed in Table 4.16 and Figure 4.25. The results show that the annual cooling load was 21.6% less than Case 1, 11.5% less than Case 2, and 3.3% less than Case 3. The monthly cooling loads were reduced by a similar rate in most cases. With a total cooling load reduction of 21.6% of the basic mode, this case (Case 4) must be considered the most energy efficient of all the cases. From Table 4.16 and Figure 4.25, the cooling load variation by 60
month can be analysed. These values will be used in future stages for the energy economic analysis (Chapter 6). Table 4.16. Cooling & heating load summary for medium size building office with a combination of double-glazed windows and overhang mode Month January February March April May June July August September October November December Annual Sum or Average Minimum of Months Maximum of Months
TRNSYS:DISTRICTCOOLING [KWh] 10090.00 8971.00 7981.00 3796.00 1401.00 202.90 6.66 230.20 1134.00 3542.00 4971.00 7997.00
OPENSTUDIO:DISTRICTCOOLING [KWh] 9585.50 8253.32 8380.05 3530.28 1499.07 182.61 6.33 223.29 1054.62 3754.52 5468.10 8316.88
50322.76 6.66 10090.00
50254.57 6.33 9585.50
12000.00 10000.00 8000.00 6000.00 4000.00 2000.00 0.00
Figure 4.25. Small Size Office Monthly Load Summary for Case 4
4.5.2. DIFFERENTIATION BETWEEN TRNSYS AND OPENSTUDIO RESULTS By comparing the simulation results, a difference of 2-3% on average was reported between the results obtained from the TRNSYS and OpenStudio simulations. However, the results should both be considered in the light of further calculations because TRNSYS was used to simulate the performance of the absorption chiller, while Openstudio was used to calculate the electrical power required to cool the building with a vapour compression air conditioning system. This difference between the results of the TRNSYS and OpenStudio simulations may be due to: 1- The creation of a new window type in TRSNSYS with Windows 5 software (LBL 2012). 2- The shadow effect calculation in the OpenStudio plugin graphical interference with Google SketchUp. 3- The advanced calculation of heat transfer by radiation between building the sky. In this study, we validated the results obtained from OpenStudio by comparing our result with the results obtained by Thornton et al. (Thornton et al. 2009; Thornton et al. 2010). Both studies used OpenStudio to simulate the building energy consumption. The TRNSYS simulation results of this study were validated against the results obtained by a variety of studies (e.g. (Vidal, Escobar & Colle 2009); (Thomas & André 2009); and (Utrick 2009). 4.5.3. COMPARISON OF COOLING LOAD RESULTS FOR BASIC CONDITIONS AND IMPROVEMENTS OF THE BUILDING The following is a comparison of the results of the building’s basic conditions and the results of the three architectural improvements relating to double glazing, overhang, and the combination of double glazing and overhang. Once we analysed the simulation results we created a comparative Figure 4.26 and 4.27 that show the difference between the various cases. CASE 1
14000 12000 10000 8000 6000 4000 2000 0
Figure 4.26. Small Size Office Building Graph of Monthly Cooling Loads for Each Case
Figure 4.26 shows the monthly cooling loads in the four different cases. The cooling load is highest in the second case (double glazing window improvement) compared to the other two modification cases. This is mainly related to the properties of the double glazing window which allows solar radiation to pass through, but prevents heat transfer to the outside. Accordingly the cooling load is increased. ANNUAL TOTAL COOLING LOAD [kWh] 70000 60000 50000 40000 30000 20000 10000 0 CASE 1
Figure 4.27. Small Size Office Building Graph of Annual Total Cooling Loads for Each Case Figure 4.27 shows the annual cooling loads in four different cases. The total annual cooling load values for the baseline condition (Case 1) was 64201.92 kWh; for the improved double glazing (Case 2) it was 56898 kWh; for the original window with overhang (Case 3) it was 52062.5 kWh; and for the combined double glazing and overhang (Case 4), it was 50322.76 kWh. Figure 4.28 shows the cooling load savings in kWh for the three types of improvement to the building envelope compared to the baseline case (Case 1). The cooling load saving for Case 2 was 7303.38 kWh (11.4%); for Case 3 it was 12139.42 kWh (18.9%); while for Case 4 it was 13879.16 kWh (21.15%). These figures are useful for calculating the saving in electricity consumption and greenhouse gas emissions in the various cases apart from the cost estimation, payback period and life span (Chapter 6).
ANNUAL SAVING IN COOLING LOAD [kWh] 16000 14000 12000 10000 8000 6000 4000 2000 0 CASE 2
Figure 4.28. Small Size Office Building Graph of Annual Saving in Total Cooling Loads for Each Case 4.6.
Comparative energy studies were required to address the study objective, namely, to calculate the building cooling load savings by applying different architectural improvements to ensure the optimal cooling load calculation of a building by means of enhancing the thermal efficiency of the building. The results obtained for each of the proposed architectural improvements have been evaluated in this chapter and summarised in the table below (Table 4.17). This table details the reduction of energy required for the cooling load in the baseline model and the three suggested cases correspond to the construction conditions and climate of the building. Table 4.17. Cooling load saving percentage comparison. Small Size Office Building Model Improvement Type
Mixed (Overhangs + Double Glazing)
Cooling Load Saving %
The results show that the best option for reducing the building cooling load is to replace single layer glass with double glazing and to install overhangs for all windows. The results also demonstrate, however, that the cooling loads were slightly higher during the winter months with the installation of double-glazed windows, which is due to the properties of double glazing. As a result, the heating load of the building would be reduced during winter. The cost study of each option performed in this project (Chapter 6) will be the decision-making guide in the process of selecting between the three suggested modifications to the building. However, the most important factor is to study and evaluate the effect of the cooling load reduction on the size and performance of the solar cooling system with absorption chiller. 64
ANSI/ASHRAE 2010, ANSI/ASHRAE Standard 62.1-2010, Ventilation for Acceptable Indoor Air Quality, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, Georgia. ANSI/ASHRAE/IESNA 2010, User’s Manual for ANSI/ASHRAE/IESNA Standard 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings. , American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, Georgia. ASHRAE 2004, Advanced Energy Design Guide for Small Office Building, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, Georgia. ASHRAE 2009, 2009 ASHRAE Handbook -- Fundamentals (SI) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, Georgia. B.O.M., Bureau of Meteorology, viewed 24/12 2012. CBECS 2003, 'Commercial Buildings Energy Consumption Survey 2003', Energy Information Administration of U.S. Department of Energy, Washington, D.C., viewed 16/10/2012. DiLaura, D.L., Houser, K.W., America, I.E.S.o.N., Mistrick, R.G. & Steffy, G.R. 2011, The Lighting Handbook: Reference & Application, Illuminating Engineering Society of North America. LBL 2012, WINDOW - Lawrence Berkeley National Laboratory, viewed 25/12 2012. McQuiston, F.C., Parker, J.D. & Spitler, J.D. 2000, Heating, ventilating, and air conditioning: analysis and design, John Wiley & Sons. NREL, National Renewable Energy Laboratory, viewed 24/12 2012. Thomas, S. & André, P. 2009, 'Dynamic simulation of a compelet solar assisted conditioning system in an office building using TRNSYS', paper presented to the Eleventh International IBPSA Conference, Glasgow, Scotland, July 27-30, 2009, viewed 28/7/2010. Thornton, B.A., Wang, W., Lane, M.D., Rosenberg, M.I. & Liu, B. 2009, Technical Support Document: 50% Energy Savings Design Technology Packages for Medium Office Buildings, PNNL-19004; Other: BT0201000, Pacific Northwest National Laboratory, Richland, WA. Thornton, B.A., Wang, W., Lane, M.D., Y., H. & Liu, B. 2010, Technical Support Document: 50% Energy Savings for Small Office Buildings, PNNL-19341, Pacific Northwest National Laboratory, Richland, WA. Utrick, J.B. 2009, Energy and Buildings: Efficiency, Air Quality and Conservation, Nova Science Pub Incorporated. Vidal, H., Escobar, R. & Colle, S. 2009, 'Simulation and optimization of solar driven air conditioning system for house in Chile', ISES Solar World Congress 2009: Renewable energy shaping our future, ISES, Johannesburg, S.Africa.
SOLAR COOLING SYSTEM CONFIGURATION AND MODELLING
This chapter discusses the design, modelling and simulation of a solar thermal cooling system with absorption chiller. The essential elements of the model are presented with a theoretical description of their models, the modelling method of the simulation model of a multifunction solar system and a method for estimating the power consumption of the model components. The method of estimating the consumption of the reference system without recourse to renewable solar energy is also presented. In the absence of experimental data, this system was used to validate the numerical model, at least from the theoretical point of view. As mentioned in Chapter 1 and the Literature Review (Chapter2), the system components vary according to several parameters, including the cooling load, building location and orientation, cost management as well as weather data (i.e. solar radiation). The rules of thumb are usually applied to prefigure the configuration of system components, and then the system optimisation procedure determines the final system design. Besides the published studies such as Calise et al. (Calise, d'Accadia & Vanoli 2011) and Ortiz et al. (Ortiz et al. 2010), the design handbooks for solar thermal systems were used as a starting point in the design procedure of this project (GermanSolarEnergySociety 2005; Henning 2004). To simulate the real time performance of solar assisted air conditioning system, it is possible to use specially-designed software (TRNSYS). The Transient System Simulation Program, or TRNSYS, which commercially available since 1975, is software intended to analyse the transient performance of thermal energy systems where behaviour is time-varying, with a considerable degree of accuracy (Klein et al. 2006). Due to Its modular nature, TRNSYS software is very flexible, easy to use and allows the addition of mathematical models which are not included in the standard library (if this is necessary to allow the simulation to be more realistic). A system as defined in TRNSYS consists of a series of components, connected in a suitable manner to be able to simulate the performance of the work specified. TRNSYS contains in its interior a series of subroutines (subroutines) written in FORTRAN language. Each subroutine contains a model of a system component which must have a number that shows the function (Type number). By specifying the parameters (time-independent values) and the input data (time-dependent values), the model can calculate the output functions of time. The outputs thus obtained can be used as input for other components that contain a different mathematical model. The module technique minimises the complexity of the simulation of the system, because it reduces a great problem to a number of smaller problems, each of which can be solved independently and easily. To put together a whole system, or to assemble the types used in a specific project, the user generates an input file (*.DCK) that guides TRNSYS in connecting the various subroutines. Based on the input files, TRNSYS calls the components and iterates at each time step to solve all the equations of the system. The sampling time ranges from seconds to hours, depending on the process studied and defined a priori by the user. The user can easily create an individual component of TRNSYS to model all the new technology that is generated with the passage of time. Certainly, the user will first need to verify that the model to be simulated is not among the 72 components of the standard library provided upon purchase or in TESS libraries. 66
5.2. SOLAR COOLING SYSTEM DESIGN The data collected in Chapter 4 (i.e. weather data and building cooling loads) are the main factors in designing the parameters of the solar cooling system components. The accurate selection and sizing of the system’s component are important issues. In medium-size systems, simple layouts are generally applied to reduce the total cost and improve performance. Accordingly, less complicated components can be used: single speed pumps and gas fired boilers are employed as backup units. In larger systems, more efficient components are applied; the additional cost is added to the system’s capital cost but results in higher efficiency. The type of solar collector (e.g. flat-plate, evacuated tube, etc.), the chiller type (single stage or double stage absorption chiller), hot water storage tank, auxiliary unit power, and cold water storage tank (if any), are the components to be sized according to the data collected. The solar cooling facility layout to be examined in this study consists of the basic components used in similar studies (Assilzadeh et al. 2005; Calise, Dentice d'Accadia & Palombo 2010; Florides & Kalogirou 2007; Florides et al. 2002a; Hang, Qu & Zhao 2011; Li & Sumathy 2001). The schematic of the solar cooling system is shown in Figure 5.1. The description of each plant component is reviewed in the following: -
Evacuated-tube solar thermal collectors field (SC);
Hot water storage tank (TK);
Gas- fired boiler as an auxiliary backup unit (AH);
A LiBr/H2O single stage absorption chiller (ABS);
Wet type cooling tower (CT).
Multi- zone capacitance building (Bld).
Single-speed pump for solar hot water circuit (SWP);
Single-speed pump for hot water circuit (HWP);
Single-speed pump for cooling water circuit (CWP);
Single-speed pump for chilled water circuit (CHWP);
SC AH TK
Figure 5.1. Solar Cooling System Facility Schematics Figure 5.2 shows the TRNSYS studio arrangement for a solar cooling system. As can be seen, more components could be added from the TRNSYS library to perform an advanced simulation. The controller in the solar loop is a feedback controller with hysteresis (ON/OFF function). This controller operates the solar pump (P1) whenever the tank (TK) lower side temperature is low and/or the solar collector water temperature is higher than the set point. Other components are also required for system modelling in TRNSYS such as thermostat unit, integrators, weather database, psychometric calculator, printers, and plotters.
Figure 5.2. Solar Cooling Facility TRNSYS Studio Arrangement
5.3. SIZING THE MAIN COMPONENTS OF THE SOLAR COOLING SYSTEM The size selection of the components for the above layout depends on several variables; the solar collector type is a parameter of the collector type efficiency, the required operation temperature of the solar cooling unit and the solar radiation in the specified location. The capacity of the chiller is a parameter of the building maximum cooling load. The determination of the auxiliary heater capacity is based on the capacity of the absorption chiller. Rules of thumb are usually applied to estimate the solar thermal collector type and areas; the chiller capacity is selected based on the cooling loads of the building from Section 4.6, as well as the auxiliary heater and the cooling tower capacity. 5.3.1. ABSORPTION CHILLER (ABS) According to the cooling load calculation for the small size building model subject of study, the maximum daily cooling powers required were 75 kW (73 W/m²) for the building basic condition, 66 kW for the glazing modified case, 67 kW for the building with overhang case and 62 kW for the building with double glazing and overhang case. The available single stage water fired absorption chiller capacity was 105 kW (30 tons). The products of two manufacturers were investigated: 1- HWAR-L30, manufacturer: World Energy Co., Ltd / CHP Solution Inc. Korea. 2- WFC-SC30, manufacturer: Yazaki Inc., Japan. A brief comparison between specifications of the two models is listed in Table 5.1. From this table, it can be seen that the SC30 chiller is the best choice, because the flow rate of the three loops is much less compared to the value of HWAR-L30, which leads to less power consumption for the total plant. The cooling water temperature is higher in the HWAR-L30, which means that the cooling tower requires a higher rejection capacity. Finally, the hot water temperature requirement is less and more flexible for the SC 30, which means that less heat is required to operate a system utilising this chiller. The YAZAKI SC30 chiller power consumption is specifically done by the solution pump, which consumes 310 Watts only, while the consumption of the solution pump in the HWAR-L30 model is about 2.4 kW. Another important factor that plays a vital rule in the selection of the chiller are the dimensions, making the smaller chiller more attractive. The total volume of the SC30 unit is about 60% less than that of the HWAR-L30 unit. All the above parameters are good indicators that the YAZAKI SC30 single stage, water fired, absorption chiller should be selected for our system.
Table 5.1. Specification data of HWAR-L30 and SC30 absorption chillers Model
Pressure drop through evaporator
Pressure drop through (Condenser/Absorber)
Pressure drop through (Generator)
3PH,460 V,60 HZ
3PH,208 V, 60 HZ
186.6 x 55.4 x 94
63 x 54.3 x 80.5
Chilled Water Inlet/outlet temperature
Cooling water* Inlet
Hot water Inlet
Electrical Consumption Dimensions (Length x Width x Height) *Heat rejection 256 kW
5.3.2. SOLAR THERMAL COLLECTORS (SC) Hot water with a temperature range of 70-95 °C is required to operate the chiller in our system layouts. Solar thermal collectors were the source of hot water (backup with auxiliary heater in SCS). For this hot water temperature range, the evacuated tube solar thermal collector was selected due to its high efficiency compared to the flat-plate type, and its simplicity compared to the parabolic trough type. Also, its cost was at a midpoint between the costs of the other two types (Duffie & Beckman 2006; Hang, Qu & Zhao 2011) . Table 5.2 lists the specifications data of the solar thermal collector applied in this study. The same data were used by Hang et al.(Hang, Qu & Zhao 2011). Table 5.2. Evacuated tube solar thermal collectors’ specification data Factor Collector intercept efficiency (
Negative first order efficiency coefficient ( ) Negative second order efficiency coefficient (
Evacuated tube collector
1.919 m x 2.16 m = 4.15 m²
A set of calculations was required to estimate the solar thermal collector parameters within the complete solar cooling system. The slope of the collector is the angle between the collector surface and the horizontal (0°= horizontal); the angle is positive when facing towards the collector surface azimuth. As a general rule, the performance of the collector is somewhat optimised when the collector slope is set to the latitude 33.87°S for Sydney (Kuehn & Coleman 2005). The number of solar evacuated tube collectors in a series is one of the parameters required in TYPE 71 in the TRNSYS model of solar evacuated tube collectors in the TRNSYS library. This parameter is used to identify the number of collectors that are hooked up in a series arrangement, where the output of the first collector is the inlet to the second collector. The equations (5.1), (5.2) and (5.3) were used to calculate the number of solar collectors in the series (Hang, Qu & Zhao 2011).
Where: The amount of useful energy collected by the solar collectors in Watts. Optical efficiency of the solar collector. Specific heat of fluid in J/kg.°K. Collector’s Negative first order efficiency coefficient. Collector’s Negative second order efficiency coefficient. Collectors’ inlet water temperature in °C. Collectors’ inlet water temperature in °C. Collectors’ inlet water temperature in °C. G
Global Solar radiation in W/m². Water flow rate through the solar collector in kg/s. Gross area per solar collector set in m².
Number of solar collectors in series.
The solar collector input and output temperatures ( ) were considered as having the same values as the hot water loop temperatures for the absorption chiller, i.e. (95 °C and 82 °C respectively). The water mass flow rate was also considered as the hot water flow rate within the chiller generator unit (7.2 kg/s). The ambient temperature and the global solar radiation were determined in Chapter 4 (26 ºC, 930 W/m² for Sydney). Values for , , and are listed in the collector specification sheet (Table 5.2). The rules of thumb are usually used to estimate the primary area collector ( ), and the following equation was used to set the value of the collector area from which the optimisation process was started (Henning 2004): Eq(5.4)
Where: Collector area in (m²) Nominal cooling capacity (Watt) Collector efficiency The coefficient of performance of the solar thermal chiller G
Global Solar radiation in W/m²
The presented data were: G= 930 W/m² for Sydney, Accordingly, the value of the collector area was: = 278 m² for Sydney (approximately) [
= 105 kW,
= 0.623, and
is the collector specific area (collector area required per kW of cooling capacity). 73
According to Henning (Henning 2004) and Argiriou (ASHRAE 2009), the average value of a specific collector area is between 1 to 6 m²/kW. The value of was calculated by the equation below: Eq(5.5)
5.3.3. STORAGE TANK (TK) The system under study included a hot water storage tank in a solar loop. The thermal performance of the energy storage tank is subject to thermal stratification. The stratified tank modelling is represented by the assumption that the tank is divided into fully-mixed equal volume segments Nnumber, where N ≤ 15 and the value of N determines the degree of stratification. No stratification effects are present if the N value is equal to 1 and the tank is considered as a fully-mixed tank. The pressure relief valve is necessary to avoid the boiling effect of the hot water in the tank. The loss of sensible energy through the valve is considered within the model, whereas the mass loss is neglected. The storage tank volume in previous studies ranged from 40-110 litres per m² of solar thermal collector area. Table 5.3 lists the values of specific tank volumes in selected studies. In this study, the optimisation of the tank volume was achieved by changing the specific tank volume from 40 l/m² to 120 l/m² against the solar collector area. Table 5.3. Specific tank volume per solar collector area in previous studies Reference
Storage tank specific volume
(Florides et al. 2002b)
(Hang, Qu & Zhao 2011)
(Mateus & Oliveira 2009)
(Koroneos, Nanaki & Xydis 2010)
According to Calise et al. (Calise 2010; Calise, d'Accadia & Vanoli 2011; Calise, Dentice d'Accadia & Palombo 2010; Calise, Palombo & Vanoli 2010) the hot water tank volume is represented by the following equation as a function of the solar collector area ( ): Eq(5.6)
Consequently, the primary tank volumes for our study were 10.64 m³ for Sydney; a rounded up value of 11 m3 was used.
5.3.4. AUXILIARY HEATER (AH) The auxiliary heater is a backup unit that adds heat to the upstream water supplied from the solar loop in the event that the supplied water temperature is lower than required operating temperature of the absorption chiller hot water. The auxiliary heater used in the solar cooling system (SCS) was considered as a natural gas boiler. The set point of the auxiliary heater is another parameter that may affect the efficiency of the solar cooling system; the set point temperature should be as close as possible to the hot water temperature required for the chiller operation. The capacity of the auxiliary heater (AH) is a function of the absorption chiller rated capacity and the coefficient of performance of the absorption chiller. Taking into consideration the energy losses through the auxiliary heater (boiler efficiency ), as represented by Calise et al. (Calise, d'Accadia & Vanoli 2011) in the equation below: Eq(5.7) Accordingly, the auxiliary water heater capacity in this study was estimated as 120 kW. 5.3.5. PUMPS (WP) The circulation pump flow rates in solar cooling facilities play an important role in the system’s performance efficiency. As mentioned earlier, variable speed pumps are more effective, especially if used with a proper control system, but are an extra burden on the initial cost of the system, thus fixed speed pumps are the first choice. In this model four pumps (SWP, HWP, CHWP and CWP) were used. Each pump circulates the water in the different loops within the facility: the SWP (solar water pump) for the solar loop, the HWP (hot water pump) for the hot water loop, CWP (cooling water pump) for the cooling water loop and CHWP (chilled water pump) for the chilled water loop. Each pump mass flow rate is dependent on the specification data of the main component in its loop; accordingly, the SWP mass flow rate is associated with the area of the solar collector, and the flow rate within the solar collector in the specification data, as well as with the environmental condition (i.e. radiation and ambient temperature). The CHWP mass flow rate is dependent on the building maximum cooling load, while the CWP and HWP mass flow rates are dependent on the absorption chiller COP value and other specifications (Calise 2010; Florides et al. 2002a). The mass flow rates for the four pumps were calculated by the following set of equations: Eq(5.8) Eq(5.9) Eq(5.10) Eq(5.11)
5.3.6. COOLING TOWER (CT) A cooling tower is a device in which circulating condenser water from a condenser or cooling coils is evaporatively cooled by contact with atmospheric air. The heat is rejected from the cooling water to the ambient environment when coolant is brought into contact with the ambient air. The type of cooling tower assisting the solar cooling system in this study was an open type. The performance of the open circuit cooling tower fundamentally depends on the wet bulb temperature of the ambient air and slightly depends on the ambient air temperature. The design limits for the cooling water temperature leaving the cooling tower is approximately 3-5 °C above the wet bulb temperature, which is below the ambient air temperature. The water flow rate in the cooling tower is proportional to the cooling load to avoid water congestion; it is usually optional to use a frequency control to synchronise the fan speed with the cooling load. The cooling tower air mass flow rate, cooling capacity and cooling water flow rate are calculated according to the following equations (ASHRAE 2012): Cooling tower air mass flow rate: Eq(5.12) Cooling tower cooling capacity: Eq(5.13) and the cooling water flow rate: Eq(5.14)
The typical design and performance figures for an open-circuit cooling tower are 130-170 m³/h per kW of cooling power, electricity consumption 6-10 W/kW cooling for axial ventilators and 10-20 W/kW cooling for radial ventilators. 5.3.7. CONTROL SYSTEM The solar cooling system requires a sophisticated control strategy to manage the operation of different components. A group of energy and temperature controllers were employed, as follows: A- Solar Loop Controller: The water in the solar loop circulating between the hot water tank and the solar collectors should be controlled by a temperature sensor. The controller sends the ON/OFF signal to the solar pump depending on the set temperature difference between the hot water tank mean temperature and the solar collector output temperature. If the solar collector water outlet temperature is less than or equal to the hot water tank mean temperature, the controller shuts down the pump to prevent heat loss from the tank. B- Hot Water Loop Controllers: The hot water loop controller activates the work of the hot water pump and the auxiliary gas water heater depending on operating status of the absorption chiller and the hot water tank temperature. The hot water pump is activated when there is a cooling demand to supply the absorption chiller with hot water from the 76
storage tank. The water passes through the gas water heater. The auxiliary heater is activated by a temperature sensor that measures the temperature of the water passing through. If the water supplied from the hot water tank is below the minimum temperature required by the absorption chiller (i.e. 88 °C), the controller activates the auxiliary heater to produce hot water at the required temperature. C- Absorption Chiller Controller: The absorption chiller operation is synchronised with the building thermostat signal. If the temperature in the zones is below the set temperature for cooling, the thermostat signals the absorption chiller to activate and the chilled water circulates within the chilled water loop until the zone temperature is lowered to the set point temperature. D- Cooling Water Loop Controller: The cooling tower rejects the heat from the absorption chiller cooling water to improve the COP. The water keeps circulated within the loop (chiller, cooling tower and pump) as long as the temperature of the sump water is higher than the temperature of cooling water required in the chiller specifications data. 5.4.
SYSTEM COMPONENT OPTIMISATION
The solar energy fraction, or solar fraction (SF) is the ratio of solar energy used in the whole system divided by the total energy requirement of the solar cooling plant. Solar fraction is the key parameter to be considered during the optimisation process of the solar-assisted cooling system design for saving primary energy. The SF value should be at least 0.4 (Henning 2004), but it is recommended that solar-assisted cooling systems should be designed with a SF of 0.7-0.8 to save a significant amount of primary energy. The solar fraction (SF) is calculated as follows: Eq(5.12) Where: The useful energy gained by the solar collector (Watts) The rate of energy delivered to the fluid stream by the auxiliary heater (Watts) The collector useful energy and the auxiliary energy are to be integrated on a daily basis, however, daily average solar fraction value to be calculated. 5.4.1. SOLAR COLLECTOR SLOPE The average inclination of a solar collector designed for a hot water system is usually the local latitude minus 15 degrees (Duffie & Beckman 2006; Henning 2004), but for a solar cooling system, an investigation is required to determine the slope angle for each system according to location, solar collector type and system cooling capacity. During the investigation, the optimum slope angle is indicated by the higher value of the solar contribution.
The slope optimisation analysis is accomplished by several running for the system using the TRNSYS with the solar collector area fixed at 033 m², 13 m³ tank volume and average flow rate of 40 kg/hr.m². Changing the slope value starts from (5 ° Slope) and is increased by (5°) steps. Table 5.4 lists results of the optimisation process. As can be seen from the results and Figure 5.3, the optimised slope angle of the solar fraction value was found to be 15 ° in Sydney.
Table 5.4. Solar collectors slope analysis outputs* Location
Q Solar (kJ/hr)
Q Aux (kJ/hr)
Solar Contribution (SF)
*For all cases A=300 m², V=10 m³, specific flow rate
= 40 kg/hr.m²
Solar Contribution (SF) 1 0.9
0.8 0.7 0.6 0.5 0.4 0.3 0
COLLECTOR SLOPE (DEGREE)
Figure 5.3. Solar Fraction Value Change with Collector Inclination 78
5.4.2. OPTIMISATION OF THE COLLECTOR AREA AND STORAGE TANK VOLUME To design the system to achieve maximum performance, the optimum sizes of the solar collector area and hot water storage tank volume should be set. The optimal area and storage tank volume is determined by many factors (e.g., system performance, economic analysis and environmental analysis). In this stage, the analysis was based on the system performance alone, specifically for the Sydney location. The TRNSYS software facility is usually utilised to run multiple simulations within a reasonable time to find the optimum sizes of the collector area and hot water storage tank of the solar loop. Similar to a study by Hang et al. (Hang, Qu & Zhao 2011), a variation of the solar collector area from 80 m2 to 420 m2 by 40 m2 interval in sequence with the hot water storage tank volume to the collector area ratio of 0.02 m3/m2 to 0.14 m3/m2 with interval of 0.02 was performed to decide the optimum size of the solar collector area and the hot water storage tank volume. In this study, however, 232 simulations were executed to achieve the results shown in Figures 5.4, 5.5, 5.6 and 5.7. The values of the Qsolar and Qaux were used to calculate the solar fraction value (SF). In all scenarios, the results show that the solar fraction value increased as the collector area increased, although the effect of the hot water tank volume ratio on the solar fraction was limited above the value of 0.04 m3/m2. This result is found to be consistent with other studies (Hang, Qu & Zhao 2011) . Clearly, the results in Figures 5.4, 5.5, 5.6 and 5.7 show that the system SF reached the effective range (above 50%) as the solar collector area was 200 m2 and above. Accordingly, the further calculations started from this point. The value of the maximum solar fraction was 94.2% for a solar collector area of 400 m² and hot water storage tank volume of 56 m³ in the scenario of the combined improvements of the building thermal envelope (double-glazed window + overhangs). Further simulations were recommended to calculate the most suitable sizes. 80 m2
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.02
STORAGE TANK VOLUME RATIO (M3/M2)
Figure 5.4. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based on Case 1 cooling loads)
1 0.9 0.8 SOLAR FACTOR
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
STORAGE TANK VOLUME RATIO (M3/M2)
Figure 5.5. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based on Case 2 cooling loads)
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
STORAGE TANK VOLUME RATIO (M3/M2)
Figure 5.6. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based on Case 3 cooling loads)
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
Figure 5.7. Solar Cooling System Performance with Different Collector Areas and Hot Storage Tank Volume (based on Case 4 cooling loads)
The above values are not considered as the final judgement on the solar cooling system, because the economic and environmental analysis are also required to reach a final decision. The economic data were collected to run the economic calculation (Chapter 6). 5.5. SOLAR COOLING SYSTEM ENERGY PERFORMANCE Solar cooling system research aims to achieve energy consumption reductions. Energy saving is one of the parameters that governs the performance of the cooling system. As explained earlier, the higher SF value means that less auxiliary energy is consumed by the solar cooling system. The energy saving is compared to the energy consumption by the reference conventional system, i.e. the vapour compression system. To compare the energy consumption of each system, the calculations of the gas required to operate both the solar cooling system and the conventional system were required (on the assumption that the grid electricity was generated by gas). To calculate the natural gas consumed by the conventional system, we need to know the electricity used by the system; such values are provided by the Energy Plus /OpenStudio simulation performed in Chapter 4. The electricity consumption by the conventional system and the natural gas required to produce this electricity were calculated by equations (5.13) and (5.14) (Syed et al. 2002): Eq(5.13)
Eq(5.14) Where: Total annual cooling load [kWh] Annual natural gas consumed by the reference cooling system [
Conventional reference system coefficient of performance [-]. Annual electricity consumed by the reference conventional system [kWh]. Natural gas lower heating value (Energy content factor)[kJ/m3]. Efficiency of the Gas operated power plant [%] The values of the equation parameters from previous studies were: reference system COP taken (2.5), natural gas lower heating value (38305 kJ/m3), and efficiency of power plant (58%). The annual natural gas consumed by the reference conventional system was used to evaluate the energy performance of the solar assisted air conditioning system by comparing the amount of natural gas consumed by the system to the amount consumed by the reference system. The annual natural gas consumption of the thermal solar assisted cooling system with absorption chillers was the consumption of the backup auxiliary heater and the gas required to produce the electricity consumed by the electrical components of the system (i.e. cooling tower, refrigerant pumps, and water pumps). The value of the electricity and natural gas consumed by the solar system is given by equations (5.15) and (5.16): Eq(5.15) Eq(5.16) Where: Annual electricity consumption by the solar assisted cooling system [kWh]. Annual electricity consumption by the absorption chiller [kWh]. Annual electricity consumption by the cooling tower unit [kWh]. Annual electricity consumption by the solar loop pump [kWh]. Annual electricity consumption by the hot water pump [kWh]. Annual electricity consumption by the chilled water pump [kWh]. Annual electricity consumption by the cooling water pump [kWh]. Equivalent annual natural gas consumption by the solar assisted cooling system [m3]. 82
Equivalent annual natural gas consumption by the absorption chiller [m3]. Equivalent annual natural gas consumption by the cooling tower unit [m3]. Annual natural gas consumption by the backup auxiliary heater [m3]. Equivalent annual natural gas consumption by the solar loop pump [m3]. Equivalent annual natural gas consumption by the hot water pump [m3]. Equivalent annual natural gas consumption by the chilled water pump [m3]. Equivalent annual natural gas consumption by the cooling water pump [m3]. The above values are calculated by the equations (5.17-5.20): Eq(5.17) where: Annual electricity consumed by the absorption chiller electrical components [kWh] is simulation output (measured in practical systems). Eq(5.18) where: Annual electricity consumed by the cooling tower fan [kWh] is simulation output (measured in practical systems). Is the fan motor efficiency. Eq(5.19) where: Is the energy added by the auxiliary gas heater to the hot water below 85 °C temperature supplying the generator unit in the absorption chiller [kJ]. and in general for pumps: Eq(5.20)
where: Annual electricity consumed by the Pump [kWh] is simulation output (measured in practical
Is the pump motor efficiency. After both NGSC and NGref are calculated, the energy saving of the solar thermal assisted cooling system is given by equation (5.21): NGS = (NGref – NGSCS)
The annual energy saving [m3/Year].
5.6. ECONOMIC ANALYSIS One of the main motivations for this project is seeking to reduce environmental impact without entailing reduced living standards; however, it is necessary to verify that the installation designs are economically feasible. Therefore, once the system parameters have been calculated and the installation components sized, it is necessary to perform an economic analysis to determine whether the installation designed is competitive from the economic perspective. The economic analysis is a comparison between the total costs of the solar thermal-assisted air conditioning system and a conventional electrically driven vapour compression air conditioning system. Cost structures for both systems are required to calculate the total costs. The annual total cost of the system is the accumulation of the initial cost of the system and the operating cost, thus the total cost of the air conditioning system is given by equation (5.22)(Rosenquist et al. 2004): Eq(5.22) where: Is the annual total cost of the air conditioning system [A$/Year]. The specific annual initial cost of the air conditioning system [A$/Year]. The annual operation cost of the air conditioning system [A$/Year]. The annual maintenance cost of the air conditioning system [A$/Year]. The specific annual initial cost is the addition of the system components costs divided by the life span of the system (N [Years]). The equation (5.23) suggested by Calise et al. (Calise, d'Accadia & Vanoli 2011) is used to estimate the initial cost of the solar cooling system: Eq(5.23) where:
The cost of absorption chiller unit including valves and control system [A$]. The cost of cooling tower unit [A$]. The total cost of the solar collector field [A$]. The cost of the hot water tank [A$] The cost of the auxiliary heater [A$]. The cost of water pumps, pipes and plumping [A$] , and calculated by:
Eq(5.24) where: Is the total cost of pipes and plumping [A$] The conventional system in the small sized office benchmark building was a package air-conditioning unit (Thornton et al. 2010), cooled by a cooling tower, with two pumps within the installation (i.e. a chilled water pump and a cooling water pump). The equation (5.25) was used to calculate the specific annual total cost of the conventional system: Eq(5.25) where: The cost of electrical chiller unit [A$]. The operating cost represents the cost of electricity, natural gas, wages of employees, suppliers, water and materials, all of which are incurred in the operation of the system. In the cost of electricity, water and materials have been considered as operating costs. The total cost of electricity and gas is estimated based on the TRNSYS system simulation results. The maintenance cost is the final cost to be estimated for the air-conditioning system. The maintenance cost is difficult to quantify because it depends on a larger number of variables such as local labour rates, labours expenses, the age of the system, length of operation, etc. The maintenance cost is usually calculated at 3% of the investment cost (Eicker & Pietruschka 2009). The operating cost of the solar air-conditioning system was the sum of the cost of the natural gas consumed by the auxiliary heater unit and the cost of electricity consumed by the electrical components, with consideration being given to the carbon tax on gas (per GJ) and electricity (per kWh) consumed, equation (5.26): Eq(5.26) Where: The auxiliary heater natural gas consumed [GJ]. 85
Natural gas tariff in NSW [A$/GJ]. Carbon tax tariff on natural gas in NSW [A$/GJ]. Electricity tariff in NSW [A$/kWh]. Carbon tax tariff on electricity in NSW [A$/kWh]. The operational cost saving in one year is the difference between the operating costs of the reference system and the solar cooling system: Eq(5.27) 5.6.1. PAYBACK PERIOD The payback period is ‘the time the consumer takes to recover the assumed higher purchase expense of more energy-efficient equipment as a result of lower operating costs’ (Rosenquist et al. 2004). Numerically, the payback period is the ratio of the difference in the initial costs of a solar cooling system and a conventional system to the saving in annual operating costs. This result is known as a ‘simple’ payback period, because it does not take into account changes in operating expenses over time or the time value of money; that is, the calculation is done at an effective discount rate of 0 percent. Accordingly, the SBP is given by Rosaler (Rosaler 2002): Eq(5.28) More parameters can change the PBP value, i.e. energy inflation rate; accordingly , the PBP equation can be expanded to a more complex level (Eicker & Pietruschka 2009). The following equation was used to calculate PBP values in this study: Eq(5.29) where: The capital recovery factor calculated by equation (6.30): Eq(5.30) Is the effective interest rate or real rate accounts for inflation rate j and interest rate i and given by: Eq(5.31)
PBPs are expressed in years. If the payback period is greater than the life span of the product, it means that an increased total installed cost is not recovered through reduced operating expenses. 86
5.6.2. LIFE-CYCLE COST The methodology of the life cycle cost (LCC) is commonly proposed to make an overall assessment of configuration choices, considered a time horizon not only limited to the period of delivering the product/service to the end user, but extending the period of use until the disposal of the asset. In addition, it is proposed to evaluate not only the material determinations (costs and benefits) associated with the realisation of the asset and its use, but also to assess the wider implications relating to the effects, harmful or beneficial, that affect the entire system. Rosenquist et al. (Rosenquist et al. 2004) defined the LCC as ‘the total customer expense over the life of an appliance, including purchase expense and operating costs (including energy expenditures)’, and its value is given by equation (5.32): Eq(5.32) Where: Life cycle cost ∑
Sum over the system life-span, from the 1st year to year (N)
The discount rate
The year of specific operating cost determined
5.6.3. NET PRESENT VALUE Net present value is one of the most reliable measures used in capital budgeting. It represents the present value of net cash inflows generated by a project rather than the initial investment on the project. The use of discounted cash inflows means that net present value accounts for the time value of money. Before calculating NPV, a target rate of return is set to be used to discount the net cash inflows from a project. The major component of NPV is the present value of net cash inflows which may be even (i.e. equal cash inflows in different periods) or uneven (i.e. different cash flows in different periods). Where net cash inflows are even, present value can be easily calculated by using the present value formula of annuity. However, if net cash inflows are uneven, it is necessary to calculate the present value of each individual cash inflow separately. We have the following formula for calculating NPV (Brigham & Ehrhardt 2011); When cash flow is even:
Eq(5.33) where: i
is the stated annual interest rate is the cash flow at date (r)
5.7. ENVIRONMENTAL IMPACT ANALYSIS Reducing greenhouse gas emissions is a critical contemporary world issue. It may be the key point in a decision making analysis of different HVAC systems, not only from the environmental point of view, but from an economic viewpoint as well, especially after the carbon tax charges in many countries, including Australia, have been applied. An extra cost is thus added to the operating costs of different HVAC systems depending on their reliance on conventional energy. On a global scale, the key greenhouse gases emitted by human activities are (Figure 5.8):
Carbon dioxide (CO2) - Fossil fuel use is the primary source of CO2. The way in which people use land is also an important source of CO2, especially when it involves deforestation. Land can also remove CO2 from the atmosphere through reforestation, improvement of soils, and other activities.
Methane (CH4) - Agricultural activities, waste management, and energy use all contribute to CH4 emissions.
Nitrous oxide (N2O) - Agricultural activities, such as fertiliser use, are the primary source of N2O emissions.
Fluorinated gases (F-gases) - Industrial processes, refrigeration, and the use of a variety of consumer products contribute to emissions of F-gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).
Figure 5.8. Global Greenhouse Gas Emissions by Gas (IPCC 2007)
The calculation of greenhouse gases is a critical issue due to different greenhouse gases emission levels. The Intergovernmental Panel on Climate Change (IPCC) methodology is usually applied. The following formula is used to estimate greenhouse gas emissions from the combustion of natural gas (DCCEE 2012): Eq(5.34) where: is the emissions of gas type (carbon dioxide, methane or nitrous oxide), from gaseous fuel type (Natural Gas) in (CO2-e tonnes). is the quantity of fuel used (i.e. Natural gas) (m3) Natural gas lower heating value (Energy content factor)[GJ/m3]. The emission factor for each gas type (carbon dioxide, methane or nitrous oxide) (which includes the effect of an oxidation factor) for fuel type (Natural gas) (kilograms CO2-e per gigajoule of fuel type (Natural gas). Table 5.5 lists the emission factors for the consumption of natural gas. The quantity of natural gas used is given by equation (5.12) for the vapour compression system and equation (5.13) for the solar cooling system. By calculating the amount of CO2 emission, another cost known as the carbon tax cost was added to the operating cost, given by equation (5.35): Eq(5.35) where: Carbon tax cost (A$) Carbon pricing (A$/ CO2-e tonnes)
Table 5.5 Emission factors for the consumption of natural gas (NGER 2008) Emission factor Fuel combusted
Energy content factor
(relevant oxidation factors incorporated)
5.8. REFERENCES ASHRAE 2009, 2009 ASHRAE Handbook -- Fundamentals (SI) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, Georgia. ASHRAE 2012, ASHRAE Handbook -- HVAC Systems and Equipment (SI), American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, Georgia. Assilzadeh, F., Kalogirou, S.A., Ali, Y. & Sopian, K. 2005, 'Simulation and optimization of a LiBr solar absorption cooling system with evacuated tube collectors', Renewable Energy, vol. 30, no. 8, pp. 1143-59. Brigham, E.F. & Ehrhardt, M.C. 2011, Financial Management: Theory and Practice, South-Western Cengage Learning. Calise, F. 2010, 'Thermoeconomic analysis and optimization of high efficiency solar heating and cooling systems for different Italian school buildings and climates', Energy and Buildings, vol. 42, no. 7, pp. 992-1003. Calise, F., d'Accadia, M.D. & Vanoli, L. 2011, 'Thermoeconomic optimization of solar heating and cooling systems', Energy Conversion and Management, vol. 52, no. 2, pp. 1562-73. Calise, F., Dentice d'Accadia, M. & Palombo, A. 2010, 'Transient analysis and energy optimization of solar heating and cooling systems in various configurations', Solar Energy, vol. 84, no. 3, pp. 432-49. Calise, F., Palombo, A. & Vanoli, L. 2010, 'Maximization of primary energy savings of solar heating and cooling systems by transient simulations and computer design of experiments', Applied Energy, vol. 87, no. 2, pp. 524-40. DCCEE 2012, National Greenhouse Accounts Factors - July 2012, Commonwealth of Australia. Duffie, J.A. & Beckman, W.A. 2006, Solar Engineering of Thermal Processes, John Wiley & Sons. Eicker, U. & Pietruschka, D. 2009, 'Design and performance of solar powered absorption cooling systems in office buildings', Energy and Buildings, vol. 41, no. 1, pp. 81-91. Florides, G. & Kalogirou, S. 2007, 'Optimisation and cost analysis of a lithium bromide absorption solar cooling system', Clima 2007. Florides, G.A., Kalogirou, S.A., Tassou, S.A. & Wrobel, L.C. 2002a, 'Modelling and simulation of an absorption solar cooling system for Cyprus', Solar Energy, vol. 72, no. 1, pp. 43-51. Florides, G.A., Kalogirou, S.A., Tassou, S.A. & Wrobel, L.C. 2002b, 'Modelling, simulation and warming impact assessment of a domestic-size absorption solar cooling system', Applied Thermal Engineering, vol. 22, no. 12, pp. 1313-25. GermanSolarEnergySociety 2005, Planning and Installing Solar Thermal Systems: A Guide for Installers, Architects, and Engineers, James & James. Hang, Y., Qu, M. & Zhao, F. 2011, 'Economical and environmental assessment of an optimized solar cooling system for a medium-sized benchmark office building in Los Angeles, California', Renewable Energy, vol. 36, no. 2, pp. 648-58. Henning, H.-M. 2004, Solar-Assisted Air Conditioning in Buildings, A Handbook for Planners, Springer Wien / New York. IPCC 2007, Intergovernmental Panel on Climate Change. Klein, S.A., Beckman, W.A., Mitchell, J.W. & Duffie, J.A. 2006, TRNSYS 16. A Transient System Simulation Program, University of Wisconsin-Madison. Koroneos, C., Nanaki, E. & Xydis, G. 2010, 'Solar air conditioning systems and their applicability--An exergy approach', Resources, Conservation and Recycling, vol. In Press, Corrected Proof. Kuehn, T.H. & Coleman, J.W. 2005, 2005 ASHRAE Handbook: Fundamentals, ASHRAE. Li, Z.F. & Sumathy, K. 2001, 'Simulation of a solar absorption air conditioning system', Energy Conversion and Management, vol. 42, no. 3, pp. 313-27. Mateus, T. & Oliveira, A. 2009, 'Energy and economic analysis of an integrated solar absorption cooling and heating system in different building types and climates', Applied Energy, vol. 86, no. 6, pp. 949-57. 90
NGER 2008, National Greenhouse and Energy Reporting (Measurement) Determination 2008, Department of Climate Change and Energy Efficiency, Commonwealth of Australia, F2011C00469. Ortiz, M., Barsun, H., He, H., Vorobieff, P. & Mammoli, A. 2010, 'Modeling of a solar-assisted HVAC system with thermal storage', Energy and Buildings, vol. 42, no. 4, pp. 500-9. Rosaler, R. 2002, Standard Handbook of Plant Engineering, McGraw-Hill Education. Rosenquist, G., Coughlin, K., Dale, L., McMahon, J. & Meyers, S. 2004, 'Life-cycle cost and payback period analysis for commercial unitary air conditioners'. Syed, A., Maidment, G.G., Tozer, R.M. & Missenden, J.F. 2002, 'An economic investigation of solar energy applied to water cooled liquid chillers', 1st International Conference on Sustainable Energy Technologies (12-14 June 2002), Porto, Portugal, pp. 40/70-44/70. Thornton, B.A., Wang, W., Lane, M.D., Y., H. & Liu, B. 2010, Technical Support Document: 50% Energy Savings for Small Office Buildings, PNNL-19341, Pacific Northwest National Laboratory, Richland, WA.
6. RESULTS AND DISCUSSION 6.1.
BUILDING ENVELOPE IMPROVEMENTS
The first part of this study has investigated and discussed the consequences of building thermal efficiency improvement on the basis of energy saving through the reduction of annual cooling loads. Three different improvements were suggested in Chapter 4, i.e. double-glazed windows; overhang shades as a shading device and a combination of the two. The cooling load calculations for the three building improvements, as well as the basic case (the original building envelope), were performed by simulation with two different tools, TRNSYS and OpenStudio. The simulation results for the four cases were discussed and compared Sections 4.6, 4.7 and 4.8. In Section 6.1, the analysis of the building cooling loads simulation results is carried out from the economic and environmental point of view, to evaluate the feasibility of these improvements. 6.1.1. ECONOMIC ANALYSIS In this section, we cover an economic feasibility study for each of the proposed improvements. Once the analysis has been performed, the results will indicate the most suitable solution. For the economic comparison of the proposed improvements and the subsequent selection of one of them, a cost evaluation for each of the proposed improvement alternatives is conducted. For this purpose, a calculation of the costs and initial investment during the useful life of each of the improvements is required. We differentiate the following costs: 1. Construction costs or first investment. 2. Maintenance costs. The period considered for the analysis of profitability logically coincides with the period of service of the variant (lifetime) that corresponds to the years 2012-2037 inclusive. Therefore, a period of 25 years is considered for the double glazing and overhang from the year of commissioning. 6.1.2. ECONOMIC OPTIMISATION 126.96.36.199. COST OF CONSTRUCTION OR INITIAL INVESTMENT The investment costs of the work correspond to the budget minus tax (GST = 10%), and adding them with the cost of drafting the project. For each of the proposed alternatives, the first investment costs were: DOUBLE GLAZING The technical characteristics of the double glazing glass chosen were: colourless float glass 6mm double glazing double glazed window 6 mm in each glass separated by a Argon gas space of 16 mm, similar to Model 2SHA AR-3 in the TRNSYS American window library, with a U-value of 1.26 W/m2.k and SHGC of 0.212, replacing the original clear single glazing of 4 mm thickness (U-value of 3.2 W/m2.k and SHGC of 0.39). Joinery fixation was carried out with support coined by chocks and side
perimeter, and cold sealed with silicone Bioclean supports, including glass cutting and placement of reeds. Costs were obtained from three suppliers: Rome Euro Windows, Magnetitee and Euro Glazing. The cost per unit of glass surface measured in square meters (A$/m2) varied from 140-220 A$/m2. Knowing the unit cost of double glazing with the technical characteristics described above, and taking into the consideration the requirements of the building under study, fenestration Summary section, where the building glass total surface area is calculated by EnergyPlus. The total cost of the double glazing is shown in Table D.1. OVERHANG SHADE To calculate the total cost of the following improvements, the dimensions of the various overhangs located on the North, East and West sides of the building are required. The calculations are based on a window height of 1.5 m and a width of 1.8 m, covering a percentage of 20% of the total area of the external walls (Thornton et al. 2010). Table D.2 shows the calculated dimensions of the metal overhang shading for the building’s windows. Once the measurements of the different overhangs to improve the building envelope were known, the total cost of the overhang investment was calculated. The number of units and the cost of each overhang shade, including labour, were used to calculate the total cost of construction (Table D.3). MIXED DOUBLE GLAZED AND WINDOW OVERHANG SHADING Ultimately, the total cost of the improvement was the combined sum of both costs: Total Cost = Total cost of double glazing + Total Cost of overhang = A$ 35,748 As a result, the following construction costs were obtained (Table 6.1). Table 6.1. Total cost summary Double Glazing Cost Total cost
Overhang Shade Cost
Mixed A$ 35,748
188.8.131.52. MAINTENANCE COSTS For a full assessment of the project investment, construction costs were added to the maintenance costs of the building improvements during the period of service. For instant, regular maintenance of double glazing includes monthly cleaning with soapy water and regular strengthening of the permanent silicone seal at the junction with the surface. On the other hand, for the overhangs used in this study, no maintenance is required for the shade itself, but regular checking of the supports is necessary.
The maintenance costs are considered to be 1% of the investment costs of both the double glazing and overhang shades throughout the service period. Considering the rate of return of 1% over inflation of the money value we get the annual maintenance cost (Table D.4). 6.1.3. ANALYSIS OF PROFITABILITY After obtaining the construction costs and maintenance costs for each improvement throughout the period of study, an evaluation of economic performance was achieved. The building installation consisted of a single packaged rooftop variable air volume (VAV) airconditioning system with a cooling capacity of 79 kW, Type (30 RW 080) from Carrier. To calculate the annual cost of electricity consumption in the current conditions, the following calculations were performed: For the annual electricity consumption recall equations (5.13) and (5.26) to get: Eq(6.1)
A. Basic case From the results obtained in Chapter 4 (Section 4.6.1), the annual cooling load for the small office building in the basic condition scenario was 64201.92 kWh. The electricity tariff in NSW was 0.27 A$/kWh, and the COP of the heat pump was 2.5. Applied to equation (6.1), we obtained: Annual electricity cost (A$) = 64201.92 (kWh) x 0.27 (A$/Kwh) /2.5 = 6,934 (A$) The costs and benefits were determined with respect to the current situation of the building with the following criteria: -
The concept of costs was considered for the construction and maintenance of improvements.
The concept of benefits was considered for the savings in energy consumption and therefore in the bill. B. DOUBLE GLAZING
When the percentage of savings achieved by improving the building with double glazing was known from the loads comparison (Section 4.9), the cost savings from this improvement were calculated: Annual economic savings (A$) = saving percentage (%) x annual electricity cost (A$) = 11.4% x 6,933.80 (A$) = 791 (A$) The annual electricity consumption saving with improved double glazing was A$ 791. If the lifetime of the glass is 25 years, then the consumption savings would be A$ 19,761.
C. OVERHANG SHADE As with the double glazing, the calculation of the annual economic saving with the improved window overhang shade was: Annual economic savings (A$) = saving percentage (%) x annual electricity cost (A$) = 18.9% x 6,933.80 (A$) = 1,310 (A$) The annual consumption saving with improved overhang shade was A$ 1,310. If the life of the overhang shade is 25 years, the savings over the period would be A$ 32,762. D. MIXED DOUBLE GLAZED AND OVERHANG SHADE With the mixed improvement, the annual cost saving was: Annual economic savings (A$) = saving percentage (%) x annual electricity cost (A$) = 21.15 % x 6,933.80 (A$) = 1,467 (A$) The annual energy saving with mixed improvement was A$ 1,467. If the life span of the mixed improvement is 25 years, the energy savings would be A$ 36,662. 6.1.4. PERFORMANCE INDICATORS The performance indicators used for comparative analysis are defined below. For an economically viable alternative, the following conditions must hold: NPV (Net Present Value) must be a positive value. The project return value ratio to the total cost must be more than 1 (B / C> 1). The payback period must be less than the span life years (PBP