The Value of Reflective Wall Coatings André Desjarlais Oak Ridge National Laboratory 17 February 2011.

The Value of Reflective Wall Coatings

André Desjarlais

Oak Ridge National Laboratory

17 February 2011

OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

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Presentation summary

Is energy efficiency in buildings and walls important? Some statistics……

What research is going on to measure energy benefits of “Cool” walls?

What are the energy savings of this technology?


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Energy is the defining challenge of our time

The major driver for Climate change National security Economic competitiveness Quality of life

Incremental changes to existing technologies cannot meet this challenge Transformational advances

in energy technologiesare needed

Critically dependent on the best science and technology

3 Managed by UT-Battellefor the Department of Energy

Global energy consumptionwill increase 50% by 2030


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0

10000

20000

30000

40000

50000

60000

70000

80000

90000

0 5 10 15 20 25 30

Per Capita Electricity (MWhr/yr)

Pe

r C

ap

ita G

DP

($

/yr)

United States

Chile

Canada

Czech Republic

Italy

Norway

Japan

China

Russia

Sweden

Source: Energy Information Administration and United Nations Statistics Division

North American countries can improve their efficiency


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Improvements in energy efficiency of the economy have been essential to the stabilization of U.S. energy consumption . .

Wood

Qua

drilli

on B

tu

Natural gas

Estimated energy savings

Petroleum

Coal

Non-hydro renewablesNon-hydro renewables

NuclearNuclear

HydroHydro

Source: Energy Information Administration, U.S. Bureau of Economic Analysis


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Buildings energy use is large and growing

Industry377 MMTC

(25%)

Buildings658 MMTC(43%)

34% of Natural Gas Directly (55% Incl. Gen)34% of Natural Gas Directly (55% Incl. Gen)

73% of U.S. Electricity73% of U.S. Electricity

40% of U.S. Primary Energy Consumption40% of U.S. Primary Energy Consumption(39% of U.S. Carbon Emissions)(39% of U.S. Carbon Emissions)

Source: 2007 Buildings Energy Data Book. Tables 1.1.3, 1.2.3, 1.3.3

0

500

1000

1500

2000

2500

3000

1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005

Sa

les

(B

illio

n k

Wh

)

Buildings

Industry

Source: EIA Annual Energy Review, Table 8.9, June 2007

Buildings Drive Electricity Supply Buildings Drive Electricity Supply InvestmentInvestment

0

5

10

15

20

25

30

35

40

45

1980 1985 1990 1995 2000 2005

Year

Qu

ads

Industrial

Transportation

Buildings Total

Buildings Energy Use Growing FastestBuildings Energy Use Growing Fastest


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The building envelope is the key!!

Heating23%

Cooling13%

Lighting18%

Ventilation3%

Water Heating10%

Electronics7%

Appliances12%

Computers2%

Other12%

Has Impact on 57% of Existing

Loads

• 133 Billion $/yr• 13.9% US Energy• 3.5% Global Energy

▪ $133 Billion Annually

▪ 13.9% of U.S. Energy

▪ 3.5% of Global Energy


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Quiz

With Comfort and Energy Efficiency in mind, which car do you select to drive during the

summer?


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Proof of concept


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Solar energy spectrum


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Critical properties

ReflectanceReflectance ((solarsolar) E) Emittancemittance ((IRIR))


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Net Heat Flux into Building

solar It Reflected

solarIt Absorbed)

IItt

Total SolarIrradiation hair(tair-ts) IRR

Net InfraredRadiation

with R=(Ts4-Tsurr

4 )

Convection

solar and IR are both very important!


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Camouflage invisible to night vision

Near Infrared FilmConventional Film


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Conventional vs. infrared pigments


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Regal White Rawhide Slate Blue

Brick Red Charcoal Gray

Hartford Green

Slate Bronze

Standard SR .67

Cool SR .72

Standard SR .47

Cool SR .56

Standard SR .21

Cool SR .33

Standard SR .25

Cool SR .30

Standard SR .14

Cool SR .28

Standard SR .11

Cool SR .28

Standard SR .08

Cool SR .26

Higher reflectance without sacrificing color choice


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Solar energy spectrum


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Overview: scope of work

Compare thermal performance of walls with cool (high infrared reflectance) and standard colors


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IR coating on right stud space and upper half of middle; Non-IR coating on rest except for strip of uncoated primer at bottom

ORNL test site


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ORNL test site Data acquisition continuous for three years

Check consistency of data with program to estimate wall properties from temperature and heat flux measurements. Data very consistent from month to month

Behavior of solar radiation control on vertical walls more complicated than low-slope roofs. Difficult to generalize simply


20

30

50

70

90

110

130

ORNL test site: Non vs IR -- summer day

Hours into July 25, 2005

0 4 8 12 16 20 24

Heat Flux,

Solar/100

[Btu/(h·ft²)]

-1

0

1

2

-2

Temper- ature (°F) Air temp warmer

but wall solar lower vs 4/16/05

Behavior of Non and IR again same at night

Peak temps again consistent with coatings over primer

Non OutsideNon InsideIR OutsideIR Inside

Wall Solar

Non Heat Flux

IR Heat Flux

Air


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Model for wall behavior Seek a model that can be generalized to give

results for whole buildings

Have done extensive validation of a model in DOE 2.2 for a 1100 ft² ranch house

Conventional Wood-Framed Construction Heat/cool with heat pump: 68°F winter; 76°F summer; size heat pump for climate

Occupy with 3 people + Building America energy use profiles


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Model for wall behavior To validate model, generate climatic data from ORNL

weather station records for year of test Use properties of wall materials along with

construction details for test section

Extra gypsum layer(only for validation)

Gypsum wallboard

Fiberglass batt (R-11)

Stucco (1 in.)

Non-vented air space

Oriented strand board

Texcote coatings with different solar reflectance

Measured heat flux

Measured temperatures


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Model generalizations Building America Performance Analysis Resources at

http://www.eere.energy.gov/buildings/building_america/pa_resources.html gives energy use profiles for three occupants (3 BR home). Choose to heat and cool with air-to-air heat pump (76°F cooling; 68°F heating; no setup or setback)

Choose seven different climates to show response of typical house to cooling and mixed climates of interest

0

500

1000

1500

2000

2500

3000

3500

4000

4500

MiamiPhoenix

Las Vegas

Bakersfield

Richmond

Knoxville

Sacramento

CDD65 (°F-day)HDD65 (°F-day)Average Daily Solar (Btu/ft²)

Cities arranged by decreasing cooling degree days

http://www.eere.energy.gov/buildings/building_america/pa_resources.html


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Model generalizations IR reflective coating on conventional walls saves

cooling energy. Savings are 4% to 9% compared to non-IR reflecting walls

Miami

Phoenix

Las Vegas

Bakersfield

Richmond

Knoxville

Sacramento0

1000

2000

3000

4000

5000

6000

4.25.0

5.3

6.2

7.1 7.6 9.0

Annual Electricity for Cooling (kWh)

Non Walls

IR Walls

Walls: Wood Studs + R-11 Batts

% Savings for IR Walls


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Model generalizations IR reflective coating on CMU walls shows larger savings

of cooling energy. Savings are 6% to 13% compared to cooling energy with non-IR reflecting walls

Miami

Phoenix

Las Vegas

Bakersfield

Richmond

Knoxville

Sacramento0

1000

2000

3000

4000

5000

6000 Annual Electricity for Cooling (kWh)

Non Walls

IR Walls

6.46.9

6.7

8.6

10.4 11.013.0

Walls: 8 in. CMU + R-5 Foam

% Savings for IR Walls


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Project summary

Full year of ORNL data validated DOE 2.2 model

Complexity of real wall applications (different orientations, shading and construction) makes generalization very difficult

DOE 2.2 whole building annual energy estimates for ranch house show that IR reflecting pigments save 4% to 13% of cooling energy

The Value of Reflective Wall Coatings

Questions or comments?

The Value of Reflective Wall Coatings André Desjarlais Oak Ridge National Laboratory 17 February 2011.

Documents

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