heat island group, lawrence berkeley national laboratory 11 arthur h. rosenfeld former commissioner,...
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Heat Island Group, Lawrence Berkeley National Laboratory11
Arthur H. RosenfeldFormer Commissioner,
California Energy CommissionGuest Faculty Scientist,
Lawrence Berkeley National Lab
[email protected] Phone: 510-527-1060
Cell Phone: 916-205-3965Cell Phone: 916-205-3965
This talk available on CoolWhitePlanet.org
Cool Roofs Cool Your Buildings, Cool Roofs Cool Your Buildings, Your Cities, and OUR PLANETYour Cities, and OUR PLANET
Washington DC, May 2010
Ronnen Levinson, Ph.D.Acting Leader, Heat Island GroupLawrence Berkeley National Lab
[email protected]. 510-486-7494
http://CoolColors.LBL.gov
Heat Island Group, Lawrence Berkeley National Laboratory2
I. Urban heat islands and cool roofsI. Urban heat islands and cool roofs
Heat Island Group, Lawrence Berkeley National Laboratory33
Summer in the citySummer in the city
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summer urban heat island
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Bird’s eye view of urban land useBird’s eye view of urban land use
Tree Cover 13%
Sidewalk 5%
Barren Land 8%
Misc. 6%
Road 22%
Parking Area 12%
Grass 15%
Roof 19%
Area by Land-Cover Category Above the Canopy
~ 1 km2
The surface of Sacramento, CAis about
• 20% roofs• 30% vegetation• 40% pavement
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Reflective roofs stay cooler in the sunReflective roofs stay cooler in the sun
50
40
30
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10
0
0.0 0.2 0.4 0.6 0.8 1.0
Tem
pera
ture
Ris
e (°
C)
Galvanized Steel
IR-Refl. Black
Blac
k Pa
int
Gre
en A
spha
lt Sh
ingl
e
Red
Clay
Tile
Lt. R
ed P
aint
Lt. G
reen
Pai
nt
Whi
te A
spha
lt S
hing
leW
hite
Asp
halt
Shi
ngle
Al R
oof
Coa
t.
Opt
ical
Whi
teO
ptic
al W
hite
Whi
te P
aint
Whi
te P
aint W
hite
Cem
ent C
oat.
Whi
te C
emen
t Coa
t.
Solar Absorptance
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White roofs, cool-colored roofsWhite roofs, cool-colored roofs
flat, white
pitched, white
pitched, cool & colored
OLD NEW
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AC savings ~ 10%
AC savings ~ 15%
AC savings ~ 5%
AC savings ~ 10%
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Potential U.S. white-roof benefits Potential U.S. white-roof benefits
• Retrofitting 80% of U.S. air-conditioned commercial buildings (2.1B m2) would annually save– $735M– 6.2 Mt CO2 (=1.2M cars)
– 9.9 kt NOx (=0.6M cars)
– 26 kt SO2
– 126 kg Hgthrough energy conservation
• Product lifetime energy savings has present value of
$11B
New York Times, 30 July 2009
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Heat Island Group, Lawrence Berkeley National Laboratory8
II. Cool roofs of tomorrowII. Cool roofs of tomorrow
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Advanced cool-colored asphalt shinglesAdvanced cool-colored asphalt shingles
Prototype cool asphalt shingles• use new coating process• offers wide color palette• reflect up to 35% of sunlight• can save up to 60% more energy
today’s cool asphalt shinglesreflect ~ 25% of sunlight
CourtesyElk Corporation
Solar reflectance ≥ 25%
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Advanced white roof coatings, membranesAdvanced white roof coatings, membranes
• White roof coatings, membranes soil rapidly, lose solar reflectance (SR)
– initial SR ~ 0.80– aged SR ~ 0.55
• How to keep white roofs clean and reflective?
– reduce leaching of plasticizers
– decrease surface roughness & stickiness
– photocatalyticself-cleaning
– photoinduced hydrophilicity
White metal roof stays clean,saving 70% more energy than
soiled white coating.
both roofs exposedfor 9 years in Florida
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III. White roofs around the worldIII. White roofs around the world
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White is “cool” in BermudaWhite is “cool” in Bermuda
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……in Santorini, Greecein Santorini, Greece
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……in Hyderabad, Indiain Hyderabad, India
…and widelyin the state of Gujarat, India.
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Walmart store in Chico, CAWalmart store in Chico, CA
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Congratulations to UC DavisCongratulations to UC Davis
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White roofs are popular in Tucson, AZWhite roofs are popular in Tucson, AZ
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……and in and in Punta Gorda, FLPunta Gorda, FL
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Washington, DC (Federal) has problemsWashington, DC (Federal) has problems
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Heat Island Group, Lawrence Berkeley National Laboratory202020
PentagonPentagon
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IV. Cooling our planetIV. Cooling our planet
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Solar-reflective surfaces cool the globeSolar-reflective surfaces cool the globevia “negative radiative forcing”via “negative radiative forcing”
Source: Intergovernmental Panel on Climate Change (IPCC)
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White roofs cool your buildings and citiesWhite roofs cool your buildings and citiesand (this is NEW)… our planet!and (this is NEW)… our planet!
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GLOBAL COOLINGGLOBAL COOLING: making 100 m: making 100 m2 2 (1000 ft(1000 ft22) of gray ) of gray roofing white offsets the roofing white offsets the emissionemission of 10 t of CO of 10 t of CO22
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Study(available at
CoolWhitePlanet.org)
Method Cloudcover esti-
mation
CO2 offset(atmos-pheric) per 100
m2
CO2 offset(emitted)per 100
m2
World-wide potential
CO2 offset (emitted) from cool
roofs
CO2 offset compared to
Akbari et al. 2009
1 Akbari et al. 2009 (LBNL) calculation ~ 50% 5.5 t 10 t 24 Gt 100%
2 Menon et al. 2010 (LBNL)GCM + land use model
(summer only) GCM 7 t 13 t 30 Gt 130%
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Oleson et al. 2010 (NCAR)[CO2 values from private communication between
Oleson & Menon]
GCM + urban canyon model GCM 7 t 13 t 30 Gt 130%
4 VanCuren et al. 2010 (CARB) measured solar radiation
not needed 3 t 5 t Addresses CA only;
coastal CA is foggy. 50%
3 papers and 1 memo estimate tonnes of CO3 papers and 1 memo estimate tonnes of CO22 offset by 100 moffset by 100 m22 (1000 ft (1000 ft22) of white roofing ) of white roofing
It is assumed that of 1 tonne of CO2 emitted only 0.55 tonnes remain in the atmosphere after one year,so the atmospheric and emitted columns are just in the ratio of 0.55/1.
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How much COHow much CO22 equivalent is offset if we equivalent is offset if we
whiten all eligible urban flat roofs world-wide?whiten all eligible urban flat roofs world-wide?
• Answer: 15 gigatonnes (Gt)– one third of a year’s worldwide emission– gigatonne = billion metric tons
• If implemented over 15 years (the life of a roof or a program) this is ~ 1 Gt/year.
• 1 Gt/year is equivalent to offsetting the emissions of 250 million cars for 15 years. – There are about 600 million passenger cars world wide,
and they each emit ~ 4 t CO2/year.
Heat Island Group, Lawrence Berkeley National Laboratory27
V. What to do nowV. What to do now
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StrategiesStrategies
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Building standardsBuilding standards
For planning purposes, follow the lead of the California Public Utilities Commission and internalize externalities. Currently it’s only $10/tonne CO2, but it’s a start.
Thus, California already plans to incorporate externalities when optimizing building standards.
Externalities justify cool roofs on non-air conditioned buildings.
Apply externalities also to cool pavements, vehicle roofs, even train roofs.
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100 Cool Cities would 100 Cool Cities would coordinatecoordinatemany initiatives and trade associationsmany initiatives and trade associations
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100 Cool Cities initiative100 Cool Cities initiative
DOE should offer:• U.S. technical support to promote local study
teams in China, India, etc.• Cash incentives to first 10 cities• Funding for Cool Cities staff in U.S.
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AgreementsAgreements
Well before the July Ministerial Conference, DOE and State Department should convince5 - 10 charter countries to sponsor an agreement to promote Cool Roofs.
Interested countries already include Brazil, China, India, and Australia.
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Resources on the webResources on the web
• Cool White Planet– CoolWhitePlanet.org
• Cool Colors Project– CoolColors.LBL.gov
• Heat Island Group– HeatIsland.LBL.gov
• Cool Communities Project– CoolCommunities.LBL.gov
• Roof Savings Calculator– RoofCalc.com
• Cool Roof Rating Council− CoolRoofs.org
• Cool California– CoolCalifornia.org
• EPA Heat Islands– epa.gov/hiri
• Energy Star Cool Roofs– EnergyStar.gov
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