Ten Years at the Calif. Energy Commission & White Roofs to Cool your Building, your City and

(this is new !) Cool the World

UC Sustainability Committee UCOP, Oakland, Sept 29, 2011

Arthur H. Rosenfeld, Former Commissioner California Energy Commission.

Distinguished Scientist Emeritus Lawrence Berkeley National Lab.

AHRosenfeld@LBL.gov 510 495-2227

Presentation available at www.ArtRosenfeld.org

Filename UC Sustainability fm IEA Annex 53 LBNL fm Carnegie DC fm Russian Talk 6-5-11 + DR from EE Summit Sacto. Path DinnerTalk Life at CEC. ARPA-E

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Summer in the city

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summer urban heat island

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Bird’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,  CA  is  about  

•   20%  roofs  •   30%  vegeta;on  •   40%  pavement  

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Reflective roofs stay cooler in the sun

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Tempe

rature  Rise  (  °C)  

Galvanized Steel

IR-­‐Refl.  Black  

Black  Pa

int  

Green  Asph

alt  S

hingle  

Red  Clay  Tile  

Lt.  R

ed  Paint  

Lt.  G

reen

 Paint  

Whi

te A

spha

lt Sh

ingl

e

Al R

oof

Coa

t.

Opt

ical

Whi

te

Whi

te P

aint

Whi

te C

emen

t Coa

t.

Solar  Absorptance  =  1  –  Solar  Reflectance  

Solar  Reflectance  1.0   0.8   0.6   0.4   0.2   0.0  

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White roofs, cool-colored roofs save money

flat,  white  

pitched,  white  

pitched,  cool  &  colored  

OLD   NEW  

AC  savings  ≈  15%  

AC  savings  ≈  10%  

AC  savings  ≈  5%  

Chicago Heat Wave 1995, 739 Deaths The most lethal floor was the top floor of a building

with a black roof

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European Heat Wave 2003, 30,000 Deaths Moscow-Centered Heat Wave 2010,~10,000 Deaths

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White roofs around the world

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…in  Santorini,  Greece  

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…in  Hyderabad,  India  

…and  widely  in  the  state  of  Gujarat,  India.  

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Walmart  store  in  northern  California  

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University of California 9 campuses viewed by

Google Earth

University of CA at Berkeley

University of CA at Davis

University of CA at Irvine

University of CA at Los Angeles

University of CA at Merced

University of CA at Riverside

University of CA at San Diego

University of CA at Santa Barbara

UCSF Parnassus Campus

Cooling our planet

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Solar-­‐reflec=ve  surfaces  cool  the  globe  via  “nega=ve  radia=ve  forcing”  

Source:  Intergovernmental  Panel  on  Climate  Change  (IPCC)  

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GLOBAL  COOLING:  making  100  m2  (1000  I2)  of  gray  roofing  white  offsets  the  emission  of  10  t  of  CO2  

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How much CO2 equivalent is offset if we whiten all eligible urban flat roofs world-wide? (i/ii)

• Answer:  24  Gigatonnes  (Gt)  – 2/3  of  a  year’s  worldwide  emission  – Gigatonne  =  billion  metric  tons  

• If  implemented  over  20  years  (the  life  of  a  roof  or  a  program)  this  is  ≈  1.2  Gt/year.  

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How much CO2 equivalent is offset if we whiten all eligible urban flat roofs world-wide? (ii/ii)

•  Offset  is  equivalent  to  taking  300  million  cars  off  the  road  for  20  years.    – There  are  about  600  million  passenger  cars  world  wide,  and  they  each  emit  ≈  4  t  CO2/year.  

In terms of avoided power plants

Full white roof potential can offset the emissions from 500 medium-sized coal fired power plants or 1,000 medium-sized gas fired power plants.

That is just the albedo effect – if the building is air conditioned, it will avoid comparable real CO2 back at the power plant. 27

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Global Cool Cities Alliance could unite many initiatives and trade associations

A UC White Roof Information Exchange

•  For facilities staff to exchange experience between campuses, with the Heat Island Group at LBNL, and with Global Cool Cities Alliance

•  Sample topics for “flat” (low-slope) roofs: –  Initial cost premium for choosing white? –  Does white have a longer service life than dark? –  Annual maintenance? –  Annual A/C savings (as a fraction of cooling load of space under

roof)? –  Complaints about glare? –  Cost-effectiveness of cisterns to hold and use storm water?

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Cool UC Information Exchange

•  Sample topics for pavements: –  Why give repaved asphalt a superblack coating?

•  Does anybody know how to overcome this practice? –  Consideration of light-colored aggregate for “asphalt” roads?

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•  If you have experience and/or ideas with cool roofs or pavements, please contact Benjamin Mandel with thoughts on these issues: •  BHMandel@LBL.gov •  (516) 672-2680

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Resources on the web

•  Art  Rosenfeld’s  website  –  ArtRosenfeld.org  

•  Cool  Colors  Project  –  CoolColors.LBL.gov  

•  Heat  Island  Group  –  HeatIsland.LBL.gov    

•  Cool  Communi;es  Project  –  CoolCommuni;es.LBL.gov    

•  Roof  Savings  Calculator  –  RoofCalc.com    

•  Global  Cool  Ci;es  Alliance  −  GlobalCoolCi;es.org  

•  Cool  Roof  Ra;ng  Council  −  CoolRoofs.org  

•  Cool  California  –  CoolCalifornia.org  

•  EPA  Heat  Islands  –  epa.gov/hea;sland  

•  Energy  Star  Cool  Roofs  –  EnergyStar.gov  

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Sunlight — more than meets the eye

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1.0

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Wavelength (nm)

Nor

mal

ized

Sol

ar Ir

radi

ance

near-infrared visibleUV

Solar  Irradiance  Distribution

■ 6.6% ultraviolet (300 - 400 nm) ■ 44.7% visible (400 - 700 nm) ■ 48.7% near-infrared (700 - 2500 nm)

Air Mass 1 Global Horizontal (AM1GH) Solar Irradiance

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White, cool color, warm color

white roof

cool red roof

gray roof 0.0

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1.0

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Wavelength (nm)

Refle

ctan

ce

0.0

0.5

1.0

1.5

2.0

Irradiance (W m

-2 nm-1)

white membraneG:sol=0.82,uv=0.12,vis=0.90,nir=0.83

red tileG:sol=0.39,uv=0.07,vis=0.20,nir=0.60

400 nm line

700 nm line

Duro-Last membrane (dark gray[LBNL]/matte)G:sol=0.23,uv=0.09,vis=0.26,nir=0.22

(G) AM1GH Solar Irradiance, ASTMG173-03 (uv=7%,vis=45%,nir=49%)

nir visuv

sol=300-2500 nm; uv=300-400 nm; vis=400-700nm; nir=700-2500 nm

cool red (Rsol=0.39)

standard white (Rsol=0.82)

solar irradiance

dark gray (Rsol=0.23)

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Cool colored roofs available today

cool clay tile R ≥0.40

Courtesy

MCA Clay Tile

cool metal R ≥0.30

Courtesy

BASF Industrial Coatings

Courtesy American Rooftile Coatings

+0.37 +0.29 +0.15 +0.23 +0.26 +0.29

cool concrete tile R ≥0.40!

standard concrete tile!(same color)!

solar reflectance gain =!

cool fiberglass asphalt shingle R ≥0.25 Courtesy

Elk Corporation

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Resources on the web

•  Art  Rosenfeld’s  website  –  ArtRosenfeld.org  

•  Cool  Colors  Project  –  CoolColors.LBL.gov  

•  Heat  Island  Group  –  HeatIsland.LBL.gov    

•  Cool  Communi;es  Project  –  CoolCommuni;es.LBL.gov    

•  Roof  Savings  Calculator  –  RoofCalc.com    

•  Global  Cool  Ci;es  Alliance  −  GlobalCoolCi;es.org  

•  Cool  Roof  Ra;ng  Council  −  CoolRoofs.org  

•  Cool  California  –  CoolCalifornia.org  

•  EPA  Heat  Islands  –  epa.gov/hea;sland  

•  Energy  Star  Cool  Roofs  –  EnergyStar.gov