part 2 - the writing’s on the wall: recent cool wall ......feb 22, 2018 · part 2 - the...
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The Writing’s on the WallRecent Cool Wall Research and Measures
February 22, 2018Hosted by:
U.S. EPA Heat Island Reduction Program
Building Energy and Greenhouse Gas Benefits
Ronnen M. LevinsonLawrence Berkeley National Lab
LBNL Heat Island Group
Source: Lea Suzuki, San Francisco Chronicle, 10 February 2013
Ronnen Levinson*, Pablo Rosado,Sharon Chen, and Hugo Destaillats
Lawrence Berkeley National Lab (LBNL)* [email protected]
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A “cool” wall reflects sunlight to reduce cooling load, save energy, and lower emissions
Wall solar reflectance
• Conventional ≈ 25%• Cool color ≈ 40%• Off or dull white ≈ 60%• Bright white ≈ 80%
14
We used EnergyPlus to model cool-wall heating, ventilation, and air conditioning (HVAC) energy savings
Apartment building Single-family home Large hotel
Small office Medium office Large office
Stand-alone store Strip mall Restaurants (sit-down and fast-food)
15
We evaluated annual energy, cost, and emission savings in each California and U.S. climate zone (> 100K simulations!)
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Cool walls save energy, carbon dioxide in homes, offices, and stores in all California climates + U.S. climates 1 - 4
17omes
Example: Single-family home in Houston, TX
Single-family home
N
Floor area: 220 m² (2,400 ft²)Net wall area: 180 m² (1,900 ft²)Wall albedo: 0.25 → 0.60Building orientation: averaged
$58 (6%) $74 (5%)
$129 (7%)
329 kg (6%)
421 kg (5%)
736 kg (7%)
0
100
200
300
400
500
600
700
800
New (2012) Older (1980s) Oldest (pre-1980)
Annual HVAC energy cost savings ($)
Annual HVAC carbon dioxide equivalent savings (kg)
Savings in pre-1980 homes over 2 times that in new h
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Can scale savings by Solar Availability Factor (SAF)to adjust for shading & reflection by neighboring buildings
Single-family homes (each 6 m tall)
E
S
W
N
30 m6 m
3 m
3 m
𝑅𝑅 = 2SAF ≈ 0.5
𝑅𝑅 = building height 𝐻𝐻 / separation 𝑊𝑊
𝑅𝑅 = 0.2SAF ≈ 0.9
𝑅𝑅 = 1SAF ≈ 0.6 𝑅𝑅 = 2
SAF ≈ 0.5
0.2 1 2 10
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Cool wall products with high solar reflectance (SR) are sold today
Conv
entio
nal
SR 0.0 – 0.1 0.1 – 0.2 0.2 – 0.3 0.3 – 0.4 0.4 – 0.5 0.5 – 0.6 0.6 – 0.7 0.7 – 0.8 0.8 – 0.9
Spec
tral
ly s
elec
tive
L*=34, a*=2, b*=4 dark brown
L*=32, a*=3, b*=7 dark brown
L*=47, a*=1, b*=-1 dark purple-gray
L*=47, a*=0, b*=7 green-gray
0.49 0.51
light gray L*=67, a*=-1, b*=1
0.65
light brown L*=67, a*=5, b*=18
dark brown L*=32, a*=2, b*=6
0.14
0.20
0.81
0.28
0.53
0.36
0.33
0.31
0.24
0.39
0.62
0.66
0.88
off white L*=88, a*=0, b*=12
dark purple-gray L*=48, a*=2, b*=0
0.06
dull white L*=85, a*=-1, b*=1
silver metallic L*=79, a*=-1, b*=-3
L*=32, a*11, b*=3 burgundy
bright white L*=94, a*=-1, b*=3
L*=81, a*=-4, b*=8 light green
bright white L*=98, a*=-1, b*=2
L*=72, a*=1, b*=5 light gray
L*=68, a*=5, b*=17 light brown
lower-tier cool walls(0.40 ≤ SR < 0.60)
higher-tier cool walls(SR ≥ 0.60)
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Wall products are undergoing 2 year exposure in California, 5 year exposure at U.S. sites
04
15
4
46
69
4 611
4
30
55
0
10
20
30
40
50
60
70
retroreflector Al-plasticcomposite
factory-appliedcoating
fabric, vinyl field-appliedcoating
total
CA Exposure US Exposure
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Solar reflectance losses modest (≤ 0.05) after15 months in California, 12 months in U.S.
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(18
mo.
)
Initial albedo
woodconcretemetalfiber cement
Berkeley
Field-applied coatings on...
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(18
mo.
)
Initial albedo
woodconcretemetalfiber cement
Los Angeles
Field-applied coatings on...
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(18
mo.
)
Initial albedo
woodconcretemetalfiber cement
Fresno
Field-applied coatings on...
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(12
mo.
)
Initial albedo
woodconcretemetalfiber cement
Arizona
Field-applied coatings on...
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(12
mo.
)
Initial albedo
woodconcretemetalfiber cement
Florida
Field-applied coatings on...
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Alb
edo
loss
aft
er fi
eld
expo
sure
(12
mo.
)
Initial albedo
woodconcretemetalfiber cement
Ohio
Field-applied coatings on...
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