Passive cooling techniques -...
Transcript of Passive cooling techniques -...
© Environmental Design Solutions Pvt. Ltd.
Environmental Design Solutions Pvt. Ltd
Delhi Mumbai Pune Bangalore Chennai New York
Passive cooling techniques theory and practice
Thoughtful Cooling TOT Workshop on Cooling Interiors Efficiently and Sustainably
Deepa Parekh
Rachana Sansad, Mumbai | 9th January, 2015
© Environmental Design Solutions Pvt. Ltd.
Energy efficient buildings are designed in response to
sun and climate
Passive cooling techniques 2
© Environmental Design Solutions Pvt. Ltd.
Buildings are designed to keep occupant comfortable
Definition of thermal comfort parameters has an impact on
energy efficiency
Passive cooling techniques 3
© Environmental Design Solutions Pvt. Ltd.
India has a predominantly warm climate
Hot dry cooling
Hot humid cooling
Composite cooling
+ heating
Temperate cooling
Cold heating
Passive cooling techniques 4
© Environmental Design Solutions Pvt. Ltd.
Energy end-use in buildings in India
Passive cooling techniques 5
Lighting, 30%
Air Conditioning, 7%
Fans, 35%
Evap. Cooling, 4%
Refrigerator, 13%
TV, 4%
Others, 7%
BAU split up of Residential building energy use
Lighting , 59%
Air Conditioning, 31%
Others, 10%
BAU split up of Commercial end use
Commercial buildings Residential buildings
There is an estimated 30-50% energy savings potential in these buildings
© Environmental Design Solutions Pvt. Ltd. Passive cooling techniques 6
Patna Chennai
Jaipur Nagpur
12% comfortable hours 2% comfortable hours
14% comfortable hours 15% comfortable hours
© Environmental Design Solutions Pvt. Ltd.
Passive design might not help solve 100% of the problem, but it certainly
will reduce the demand for energy consumption
Passive cooling techniques 7
© Environmental Design Solutions Pvt. Ltd.
Key objectives in passive cooling
①Reduce demand for cooling
• Avoid overheating
②Reduce the energy required for cooling
• Integrate passive cooling techniques
Passive cooling techniques 8
© Environmental Design Solutions Pvt. Ltd.
Room A vs Room B
All Brick walls
You need a 1 ton AC to cool the room
COOLING LOAD = x
All Glass
You need a 3 ton AC to cool the room
COOLING LOAD = 3x
9
© Environmental Design Solutions Pvt. Ltd.
Room A vs Room B
Mr. A is using the AC for 5 hours a day
Energy consumption = y
Mr. B never shows up for work
Energy consumption = 0
10
© Environmental Design Solutions Pvt. Ltd.
LOADS vs ENERGY
Static
As a result of DESIGN
Loads for identical buildings in the same location will be the same
Thus, it all depends on the DESIGN !
Units: kW/sqm or sqft
Dynamic
As a result of USE
Energy consumption for identical buildings in the same location can be different.
Thus, it all depends on the USER !
Units: kWh/sqm or sqft
11
© Environmental Design Solutions Pvt. Ltd.
Key objectives in passive cooling
①Reduce demand for cooling
• Avoid overheating
②Reduce the energy required for cooling
• Integrate passive cooling techniques
Passive cooling techniques 12
© Environmental Design Solutions Pvt. Ltd.
Techniques to avoid overheating
Objectives:
①Resist heat gain
②Promote heat loss
Passive cooling techniques 13
© Environmental Design Solutions Pvt. Ltd.
Building bioclimatic chart
Passive cooling techniques 14
Integrates architectural strategies with human comfort needs
© Environmental Design Solutions Pvt. Ltd.
Building bioclimatic chart
Passive cooling techniques 15
15.7% comfortable hours
© Environmental Design Solutions Pvt. Ltd.
Building bioclimatic chart
Passive cooling techniques 16
15.7% comfortable hours Add passive strategies shading High thermal mass Direct evaporative cooling Natural ventilation Internal heat gain 54.3% comfortable hours
© Environmental Design Solutions Pvt. Ltd.
Techniques to avoid overheating
①Reduce heat gain
①Using thermal mass construction
②Reduce exposed surface
③Adding insulation
Passive cooling techniques 17
© Environmental Design Solutions Pvt. Ltd.
Techniques to avoid overheating
①Reduce heat gain ④Form and orientation
⑤Reduce WWR
⑥Use shading devices
⑦Reduce heat gain through glazed areas
⑧Minimize heat gain around the building
Passive cooling techniques 18
© Environmental Design Solutions Pvt. Ltd.
All these strategies do not cool, they reduce overheating.. they reduce cooling demand..
Passive cooling techniques 19
© Environmental Design Solutions Pvt. Ltd.
Passive cooling systems
These transfer heat from the building to natural energy sinks, such as the air, water, earth or outer space. Implementation of these systems in buildings reduces energy needed for cooling.
Passive cooling techniques 20
© Environmental Design Solutions Pvt. Ltd. Passive cooling techniques 21
Bihar Museum, Patna
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 22
Bihar Museum, Patna
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 23
Bihar Museum, Patna
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 24
Bihar Museum, Patna
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 25
Bihar Museum, Patna
© Environmental Design Solutions Pvt. Ltd.
Bihar Museum, Patna
Passive cooling techniques 26
ASHRAE Std 55 Comfort Model For conditioned areas
Adaptive Comfort Model For naturally ventilated areas
Thus various design strategies will have to be combined within the premise of both comfort models to achieve thermal comfort with reduced systems loads in the building throughout the year.
© Environmental Design Solutions Pvt. Ltd.
Passive cooling systems
These transfer heat from the building to natural energy sinks, such as the air, water, earth or outer space. Implementation of these systems in buildings reduces energy needed for cooling.
Passive cooling techniques 27
© Environmental Design Solutions Pvt. Ltd.
Nocturnal ventilative cooling
Concept Night time cooling of
the thermal mass that gets heated up in the day time Heat absorption of
the thermal is more efficient during the day
Passive cooling techniques 28
© Environmental Design Solutions Pvt. Ltd.
Stack ventilation
Passive cooling techniques 29
-Natural ventilation strategy CONCEPT -Works on the principle of thermal buoyancy -Hot air rises through the stack drawing the cool air inducing the air movement
© Environmental Design Solutions Pvt. Ltd.
Solar chimney
Passive cooling techniques 30
CONCEPT Glazed or black colored surface on the stack increases solar heat gain and accelerates rise in temperature in the stack
© Environmental Design Solutions Pvt. Ltd.
Earth tubes
Passive cooling techniques 31
Air intake
Heat exchange with earth
Conditioned air supplied to buildings
CONCEPT: -Ground temperatures at about 3 to 4m do not vary through the year -Earth is a very large heat sink and can be used to exchange heat
© Environmental Design Solutions Pvt. Ltd.
Earth tubes
Passive cooling techniques 32
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 33
Climate responsive design - daylight
- night cooling of thermal mass
-natural ventilation
-wind and solar supported chimney
- ground heat exchanger
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 34
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 35
Climate concept summer night
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 36
Climate concept winter day
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 37
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 38
© Environmental Design Solutions Pvt. Ltd.
French School, Damascus, Syria
Passive cooling techniques 39
© Environmental Design Solutions Pvt. Ltd.
Miramar college police station, san diego, California
Thermal chimney performance goals ① Integrate with a whole building natural
ventilation system (exterior windows, interior openings – doors, grills, interior windows)
② Meet minimum OA requirements during operation
③ Maintain comfort when outdoor air conditions permit
④ Don’t exceed 160 fpm through openings ⑤ Provide mixed mode HVAC operation
Passive cooling techniques 40
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 41
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 42
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 43
© Environmental Design Solutions Pvt. Ltd.
Passive cooling techniques 44
0
1
2
3
4
50
60
70
-20
0
20
0
1
2
3
0
2
4
6
21 TueMay 2002
22 Wed 23 Thu 24 Fri 25 Sat 26 Sun 27 Mon
Temperatures, Heat Gains and Energy Consumption - Miramar Police Station, Building 1EnergyPlus Output 20 May - 27 May, Hourly Student
Fuel (k
BT
U/h
)T
em
pera
ture
(°F
)H
eat
Bala
nce (
kB
TU
/h)
Syste
m E
nerg
y (
kB
TU
/h)
Tota
l fr
esh a
ir (
ac/h
)
Time/Date
System Fans Heat Generation (Gas)
Air Temperature Radiant Temperature Operative Temperature Outside Dry-Bulb Temperature
Glazing Walls Ceilings (int) Floors (int) Ground Floors Partitions (int) Roofs Doors and vents Internal Natural vent.External Air Occupancy Solar Gains Exterior Windows Zone/Sys Sensible Heating Zone/Sys Sensible Cooling
Zone Heating
Mech Vent + Nat Vent + Infiltration
Shoulder period - Whole Building Results – NV maintains 1 to 6 ACH during occupied periods.
© Environmental Design Solutions Pvt. Ltd. Passive cooling techniques 45
0
20
40
60
70
80
90
-40
-20
0
20
-80
-60
-40
-20
0
0
1
2
3
27 TueAug 2002
28 Wed 29 Thu 30 Fri 31 Sat Sep 2 Mon
Temperatures, Heat Gains and Energy Consumption - Miramar Police Station, Building 1EnergyPlus Output 26 Aug - 2 Sep, Hourly Student
Fuel (k
BT
U/h
)T
em
pera
ture
(°F
)H
eat
Bala
nce (
kB
TU
/h)
Syste
m E
nerg
y (
kB
TU
/h)
Tota
l fr
esh a
ir (
ac/h
)
Time/Date
System Fans Chiller (Electricity)
Air Temperature Radiant Temperature Operative Temperature Outside Dry-Bulb Temperature
Glazing Walls Ceilings (int) Floors (int) Ground Floors Partitions (int) Roofs Doors and vents Internal Natural vent.External Air Occupancy Solar Gains Exterior Windows Zone/Sys Sensible Heating Zone/Sys Sensible Cooling
Sensible Cooling Total Cooling
Mech Vent + Nat Vent + Infiltration
Summer period - Whole Building Results – NV system maintains ACH above min OA requirements and typically provides 2 ACH.
© Environmental Design Solutions Pvt. Ltd.
Airflow Results (7am to 6pm, Mon-Sat)
Passive cooling techniques 46
Zone Summer Period (Aug 26 – Sep 2)
Winter Period (Jan 7 - 14)
Shoulder Period (May 20 – 26)
Max ACH Max Airspeed (fpm)
Max ACH Max Airspeed (fpm)
Max ACH Max Airspeed (fpm)
1.1 5.4 77 7.7 110 14.5 207
Kitchen 9.2 36 12.7 50 21.9 87
2.3 6 37 7.8 48 18.5 113
2.4 33.4 60 25 45 46.5 83
2.5 20.1 68 16.1 54 31.7 107
2.8 2.8 43 5.7 87 6.1 93
Maximum airspeeds are all acceptable (<160 fpm) for nearly all spaces so breeze is mostly imperceptible. Zone 1.1 rises slightly above this limit but should not negatively impact comfort (still < 300 fpm)
© Environmental Design Solutions Pvt. Ltd.
Sizing the thermal chimney
Passive cooling techniques 47
© Environmental Design Solutions Pvt. Ltd.
Wind tower/ wind catcher
Passive cooling techniques 48
CONCEPT: -Aids comfort ventilation -Capture the natural breeze and direct it inside the buildings -the tower inlet is oriented towards the prevailing breezes -The air isn’t necessary cooled but the circulation creates a fan-like condition
© Environmental Design Solutions Pvt. Ltd.
Passive downdraught cooling
Passive cooling techniques 49
CONCEPT: -Similar to wind catcher, but this is a cooling strategy -Water is sprinkled at the top of the tower -When air moves through the tower, the water droplets evaporate picking up the heat the air -Cool air falls down and enters the building
© Environmental Design Solutions Pvt. Ltd.
Passive downdraught cooling
Passive cooling techniques 51
© Environmental Design Solutions Pvt. Ltd.
Passive downdraught cooling
Passive cooling techniques 52
© Environmental Design Solutions Pvt. Ltd.
Summary
①Focusing on reducing building loads is key to achieving energy efficiency
②This is very much a design issue !
③This should become a business as usual ‘way of working’
④Low energy cooling techniques combined with conscious usage is the key to reduce GHG emissions.
Passive cooling techniques 53
© Environmental Design Solutions Pvt. Ltd.
Thank You
Environmental Design Solutions Pvt. Ltd
Delhi Mumbai Pune Bangalore Chennai New York
Passive cooling techniques 54