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

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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Questions
Thank You