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Green Building:Energy Efficient Air-Conditioning


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This powerpoint illustrates the research done on the passive cooling methods of earth tube systems and solar chimneys in Florida\'s sub-tropical climate.

Green Building:Energy Efficient Air-Conditioning

  1. 1. Passive Cooling in Florida Applying the passive cooling techniques of natural ventilation and earth tube cooling to Florida’s subtropical climate Jack Vitek Stetson University Department of Environmental Science April 8th, 2009
  2. 2. Introduction  Conditioning homes in subtropical climates consumes more energy than any other building/structural cost  The implementation of passive cooling techniques would drastically reduce our energy consumption  “Air conditioning is commonly used to achieve thermal comfort in commercial buildings in the hot and humid Southeast Asian Region. Typically, air-conditioning accounts for 60% of electricity consumption in such situations.” – Vangtook, Chrarattananon (2005)  The research and analysis was done to determine whether the passive cooling techniques of earth tube systems and natural ventilation can passively cool a building in a subtropical climate like Florida
  3. 3. Study Area: Comparing Climates  Florida  Warm and humid Average climate with high Temp annual precipitation  Similar Climates Average  Southeast Asia Humidity (India, China, Thailand)  Australia  Sub-Tropical South America Average Rainfall
  4. 4. Expected Findings  Research shows that far less energy is consumed when the passive cooling techniques are incorporated with conventional HVAC systems than without them in regions similar to Florida  Furthermore, it seems the use of multiple passive cooling methods will further increase the energy efficiency and conditioning efficiency of the building  However, passive cooling methods, when used alone, do little to maintain constant humidity when compared to conventional methods
  5. 5. Background: Conventional Methods  HVAC Systems: A conventional method of cooling and conditioning the climate within a give area. The three functions of heating, ventilating, and air-conditioning are closely interrelated.  If solar chimneys, EAT systems are “passive” techniques because the require no energy, HVAC systems would be considered “active”.
  6. 6. Background: Passive Cooling Techniques Passive solar cooling: “the removal of heat of the building environment by applying the natural processes of elimination of heat to the ambient atmosphere by convection, radiation and evaporation or to the adjacent earth by conduction and convection (Jain, 277).” Most Common Techniques: Water-roof evaporation, solar chimneys, earth to air transfer systems, vegetative shading, vegetative roof Techniques Researched: Natural Ventilation (solar chimneys), earth to air transfer systems
  7. 7. Background: Earth to Air Transfer Systems Picture 1 Picture 2 “An earth tube is a long, underground metal or plastic pipe through which air is drawn. As air travels through the pipe, it gives up or receives some of its heat to/from the surround soil and enters the room as conditioned air during the cooling and heating period.” – Lee, Strand (2007)
  8. 8. Background: Earth to Air Transfer Systems  Importance of Tube Length  The longer the tube is underground, the longer the air inside the tube is exposed to the soil condition through the pipe walls (Figures to right) “As the pipe length increases, the inlet air temperature decreases due to the fact that the longer pipe provides a longer path over with heat transfer between the pipe and the surrounding soil can take place give the same overall heat transfer coefficient of earth tube.” – Lee, Strand (2007)
  9. 9. Background: Earth to Air Transfer Systems  Importance of Pipe Depth  The temperature of the soil depends on its depth, therefore making the depth of Picture 3 the pipe very important “As the pipe depth increases, the inlet air temperature decreases, indicating that the earth tube should be placed as deeply as possible.” – Lee, Strand (2007)
  10. 10. Background: Earth to Air Transfer Systems  Importance of Air Velocity  Importance of Pipe Radius (inside pipe)  Increased pipe radius allows  Increased air velocity inside for more air intake, and by the tube limits the amount doing so, limits the amount of air to pipe contact of time air can be conditioned  “As the pipe radius increases, the earth tube inlet air temperature  “As the air flow rate increases also increases due to the face that the inlet air temperature higher pipe radius results in a increases in all locations, lower convective heat transfer since the air spends less time coefficient in the pipe inner in the tube and thus in surface and lower overall heat transfer coefficient of earth tube contact with the lower soil system.” – Lee, Strand (2007) temperature.” – Lee, Strand (2007)
  11. 11. Background: Earth to Air Transfer Systems Other Important Factors  Soil Temperature – Directly effects air inside tube  Soil Composition – Determines how well soil can hold temperature  Pipe Thickness – Influential in air to soil temperature transfer  Pipe Composition – Influential in air to soil temperature transfer
  12. 12. Background: Natural Ventilation & Solar Chimneys  Buoyancy Driving Force “Natural ventilation is (stack effect) – due to not only regarded as a simple measure to temperature difference provide fresh air for between indoor and outdoor the occupants, air temperatures (Bassiouny necessary to maintain & Koura, 2007) – Picture A acceptable air quality Picture A levels, but also as an excellent energy-saving  Aeromotive – wind driving way to reduce the force - Picture B internal cooling load of housing located in the tropics.”  Solar Chimneys use both - Boonsri, Hirunlabh, types of natural ventilation and Khedari (1999) to passively cool the structure Picture B
  13. 13. Background: Natural Ventilation and Solar Chimneys  Importance of Air Gap  Importance of Solar  Provides area for stack Chimney’s Positioning  Air gap and solar chimney effect to exist between solar chimney and must receive solar radiation building inlet in order for stack effect to occur  Solar Chimneys located on  Usually located in south façade or in roof the south façade of a building are most common due to solar exposure Chungloo & Limmeechokchai (2006)
  14. 14. Background: Natural Ventilation & Solar Chimneys  Importance of Air Gap  Importance of Façade Material  Provides area for stack effect to  Wall material has an influence exist between solar chimney and on the air gap’s ability to building inlet insulate heat, creating the stack  Usually located in south façade or effect in roof  Importance of Ventilation Input &  Importance of Solar Chimney’s Air Gap Output Positioning  Air gap and solar chimney must  The amount of input and output receive solar radiation in order for air allowed must be regulated stack effect to occur (airflow)  Solar Chimneys located on the  Degree of “openness” of south façade of a building are input/out most common due to solar  When the respective vents are exposure opened (time of day) Bassiouny & Koura (2007) Liping & Hein (2006)
  15. 15. Literature Review: Earth to Air Transfer Systems Passive Cooling Tech. Data Source Information Covered Earth to Air Girja Sharan, Rantan Jadhav  Single pass earth tube buried 3 (2000) m below surface, ambient air is pumped through blower  Air at constant velocity Earth to Air Kwany Ho Lee, Richard K. Importance of: Strand (2007) Pipe Radius Air Flow Pipe Length Pipe Depth Earth to Air Jens Pfafferot (2003) Importance of: Ground Temperature Soil Composition Heat Transmission
  16. 16. Literature Review: Natural Ventilation & Solar Chimneys Passive Cooling Tech. Date Source Information Covered Natural Ventilation Wang Liping & Wong Hien Design and importance of façade in natural ventilation Solar Chimney Sudaporn Chungloo & Bundit Solar radiation’s effect on solar chimney Limmeechokchai (2006) Air gaps, stack effect and south facing façades Connect solar chimneys and natural ventilation ACH (Air Changes per Hour) Radiant Cooling Prapapong Vangtook &  Energy consumption of A/C in hot humid climate Surapong Chirarattananon  A/C = 70% energy consumption in (2005) households Solar Chimney Ramadan Bassiouny & Nader  Description of solar chimney  Increase of solar radiation on air gap S.A. Koura (2007) increases air flow rate  Spraying water
  17. 17. Discussion: What Was Learned?  EAT & Natural  2-6 degrees temp. Ventilation produced difference in outdoor and cooler temperatures indoor temperature  No to little energy  Little information consumption addressing the regulation  Combination of passive of humidity and active systems to  Cannot condition a reduce (not eliminate) structure as effectively as energy mechanical methods can  Night Ventilation in hot humid climates
  18. 18. Discussion: Where to Now?  Continued/Increased development of humidity regulation in passive techniques  Increased application of passive cooling techniques alongside mechanical  Promote cost benefits of applying passive techniques  Increased popularity in United States
  19. 19. Questions Thank You