Low Energy Cooling in Multi-Storey Buildings for Hot, Arid Climates
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LOW ENERGY COOLING IN MULTI-STOREY BUILDINGS FOR HOT, ARID CLIMATES by AMIRA M. MOSTAFA B.Arch. Cairo University 1984 SUBMTITED TO THE DEPARTMENT OF ARCHITECTURE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN ARCHITECTURE STUDIES AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY JUNE 1989 @ 1989 Amira M. Mostafa. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly copies of this thesis document in whole or in part Signature of Author Amira M. Mostafa Department of Architecture: May 9, 1989 Certified by 7Ti'mohy Johnson Principal Research Associate of Building Technology: Thesis Supervisor Accepted by iMSTITU 9~ASSAC!iUSEFT8 an Beinart MASSVXHUSEM INSN E Chairman: Departmental Co1 'ttee for Graduate Students OF TECHN4O!OGY JUN 0' 198 Rotch tWAMW '77 7 77 I7 LOW ENERGY COOLING IN MULTI-STOREY BUILDINGS FOR HOT, ARID CLIMATES ii LOW ENERGY COOLING IN MULTI-STOREY BUILDINGS FOR HOT, ARID CLIMATES by AMIRA M. MOSTAFA Submitted to the Department of Architecture on May 9th, 1989 in Partial Fulfillment of the Requirements for the Degree of Masters of Science in Architecture Studies ABSTRACT This thesis discusses passive and low energy cooling strategies and systems in hot arid climates. The choice of a certain strategy, as well as determining the appropriate cooling schemes for such a context becomes of prime importance in developing the optimum energy conscious building design. The motivation for working in this area of research stems for the need facing architects to start developing a serious sense for energy considerations in their architectural design, especially in existing and multi-storey buildings. Here, in this research, the different factors that govern the control of heat gain through the envelope of the building will be analyzed. Also, solutions to minimize the cooling load for dwellings will be suggested/provided; by means of selecting the adequate cooling systems (evaporative, convective, and radiative) that promote the optimum desired thermal comfort. This research concludes its technical analysis with an architectural design for two schemes; The first is a cooling system that can be applied to new buildings, or retrofitted to existing ones. It uses evaporative coolers and solar chimney systems at day- time. It also uses night-time forced ventilation to cool the ordinary slab. The second can be applied in new buildings. It uses evaporative coolers and solar chimney systems at day-time. It also uses night-time forced ventilation through cored slabs. This design, and these schemes, are perceived as a starting point for further development and more research. Thesis Advisor: Prof. Timothy Johnson Tide: Principal Research Associate of Architecture iii To my love, best friend, husband, and father of my Mariam and Muhammad... Yasser El-Quessny. The one who taught me to live and think Art and Architecture. If it wasn't for his support, love, help, encouragement I would not have reached this state of accomplishment. iv ACKNOWLEDGEMENT With all the respect and gratitude, I would like to thank my supervisor Timothy Johnson; whom through his guidance, encouragement, and expertise I learned a lot about the research subject and methodology, as well as about myself. I am proud to be one of his students. I would like also to express my gratitude to Prof. Leon Glicksman, Prof.Eric Dluhosch, Prof. Harvey Bryan, and Reinhard Goethert for their valuable comments on my work. To my friends who made my stay in the States rather pleasant. To Yasser for his hard work on editing this thesis. To Ayman , Ahmed, and Adil for their invaluable help. And last but not least to my teachers at Cairo University "Architecture Department " for their encouragement and recommendations . V Table of Contents ABSTRACT PREFACE xi CHAPTER.1. EXAMPLES OF PASSIVE AND LOW ENERGY SOLAR DESIGN 1 A. Historical Responses to Cooling Needs 1 B. Passive and Low Energy Cooling (recent solutions) 4 B.1. Bateson Building 4 B.2. Princeton Professional Park 8 B.3. Office Block in the Egyptian Sahara 9 CHAPTER.2. STRATEGIES FOR SUPPLEMENTING PASSIVE/LOW ENERGY A. Heat Gain in Buildings 11 A. 1. Heat Gain from Building Envelope 11 A.1.1. Windows 12 A. 1.2. Solar Control and Shading Devices for Windows 13 A.2. Heat Gain from Ventilation and Infiltration Loads 13 A.3. Heat Gain from Electric Lighting 13 A.4. Internal Heat Gain from Building Occupants 14 B. Thermal Comfort for People inside their Dwellings 15 C. Cooling Strategies 19 C. 1. Evaporative Cooling 19 C. 1.1. Direct Evaporative Coolers 19 C. 1.2. Indirect Evaporative Coolers 24 C. 1.3. Two-stage Evaporative Coolers 27 C.2. High Mass Cooling with Night Ventilation 28 C.3. Natural Ventilation (promoting air movement within the building) 32 C.3. 1. Motive Force Caused by Wind Blowing onto the Facade 32 C.3.2. Thermal Motive Force 32 vi CHAPTER.3. APPLICATION OF COOLING SYSTEMS A. Cooling Load Calculations 35 A. 1. Definitions and Symbols (of terminology used in this chapter) 35 A.2. Overall Coefficient of Heat Transmission for Roofs and walls ,and peak heat gain for roofs 37 A.2. 1. Overall Coefficient of Heat Transmission for Existing Roof 37 A.2.2. Overall Coefficient of Heat Transmission for Redesigned Roof 38 A.2.3. Peak Heat Gain for Existing Building 41 A.2.4. Peak Heat Gain after Redesigning the Building 42 A.2.5. Overall Coefficient of Heat Transmission for Walls 42 A.3. Heat Gain through Glass 45 A.3. 1. Peak Heat Gain through Glass by Solar Radiation in Existing Building 45 A.3.2. Peak Heat Gain through Glass By Solar Radiation after Redesigning the Building 46 A.4. Peak Sensible Heat Gain from People 48 A.5. Peak Heat Gain from Internal Light 48 A.6. Summary Of Peak Heat Gain 49 B. Selecting Cooling Systems 50 C. Cooling Systems and Schemes 51 C. 1. Scheme One 51 C. 1.1. Using High Mass Cooling with Night Ventilation 54 C.1.2. Supplementary Cooling 54 C.1.3. Forced Night Ventilation of Thermal Mass 55 C.2. Scheme Two 56 C.2. 1. Night-time Forced Ventilation 56 C.2.2. Day-time Use of Evaporative Coolers 57 C.2.3. Sizing the Evaporative Cooler 59 C.2.3. 1. Using Two-stage Evaporative Cooling 59 C.2.3.2. Using Indirect Evaporative Cooler Only 60 C.2.4. Stack-effect Ventilation by Means of the Solar Chimney 63 C.2.4. 1. Design Decisions with Respect to Building Materials of the Solar Chimney 63 C.2.4.2. Velocity of Air inside the Duct due to the Stack-effect 65 C.2.4.3. The Duct Size of the Solar Chimney 65 C.2.4.4. Volume of Air Flow into the Solar Chimney (for one apartment) 66 C.3. Scheme Three 68 C.4. Scheme Four 69 C.4. 1. Designing Decisions with Respect to Building Materials of the Solar Chimney 69 C.4. 1. Velocity of Air inside the Duct 69 C.4.3. The Duct Size of the Solar Chimney 69 C.4.3. Volume of Air Flow into the Solar Chimney (for one apartment) 70 vii C.5. Summary for Designing the System 70 C.5. 1. Solar Chimney (Scheme Two) 70 C.5.2. Evaporative Cooler (Scheme Two) 71 C.5.3. Solar Chimney (Scheme Four) C.6. Evaluation of the Four Cooling Scheme 72 CHAPTER.4. DESIGN SYNTHESIS 73 APPENDICES Appendix .A. 107 Appendix .B. 111 Appendix .C. 115 Appendix .D. 116 Appendix .E. 117 Appendix .F. 118 BIBLIOGRAPHY 122 viii List of Figures Index Title/Description Page Fig. 1. Pharaonic House of Neb-Amun 1 Fig.2. House of Muhibb Al-din Muwaggi (Cairo/Egypt) 2 Fig.3a. The Bateson Summer Operation 5 Fig.3b. The Bateson Central Atrium 6 Fig.4. The Bateson Building's Heating and Cooling devices 7 Fig.5. Princeton Professional Park 9 Fig.6. Office Block in Egypt 10 Fig.7. Bioclimatic chart(s) 15 Fig.8. Bioclimatic and Cooling Strategies 16 Fig.9. Plotting monthly maximum and minimum DBT and RH for Alexandria/Egypt 18 Fig.1Oa. Evaporative Cooling Tower with wetted baffles 20 Fig. 10b. Details of Cooling Systems (designed by Hassan Fathy) 21 Fig. 11. Direct Evaporative Cooler 22 Fig. 12. Indirect Evaporative Cooling Process 24 Fig. 13a. Schematic Design of dry surface evaporative Cooler 25 Fig. 13b. Schematic Design of dry surface evaporative Cooler 26 Fig. 14. Two-stage Evaporative Cooler 27 Fig. 15. Solar Chimney system (developed by R. Haisley) 33 Fig. 16. Details of Existing Roof 37 Fig. 17. Details of Redesigned Roof 38 Fig. 18. Alternative Wall Design(s), and the selected one(s) 42 Fig. 19a. South-east and north-west orientations of windows (showing shading devices) 46 Fig. 19b. South and south-west orientations (showing shading devices) 47 Fig.19c. West and east orientations (showing shading devices) 47 Fig.20. Plotting Cairo's Summer time design conditions on the Bioclimatic chart (in order to determine the cooling system to be used) 50 Fig.21. Schematic Design of the Cooling Schemes 52 Fig.22. Dimensions of Proposed Cored Slab 53 Fig.23. Plotting Two-stage Evaporative Cooling Process on Psychrometric Chart 58 Fig.24. Plotting Indirect Evaporative Cooling Process on Psychrometric Chart 62 Fig.25. Scheme Four 76 Fig.26. Day-time Operation 77 Fig.27. Night-time Operation 78 ix Fig.28. Cored Concrete Slab (as one of the cooling devices) 80 Fig.29. Section Through External Wall (showing operation of its openings) 81 Fig.30a. Window Design 82 Fig.30b.