gsep’s cool roofs and pavements working group · energy balance of roof (4th march, 2012,...

GSEP’S Cool Roofs and Pavements Working Group 2

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Global Climate Benefits of Cool Roof

Vishal Garg, IIIT- Hyderabad


M.L. Fischer1, F. Salamanca1, S. Menon1,2, S. Tonse3, V. Garg4, J. Mathur5, K. Niranjan4, B. Shah6, M. Naja7, KP Singh8

1LBNL, 2Climateworks, 3TST Consulting, 4IIIT Hyderabad, 5 MNIT Jaipur, 6Winbuild Consulting, 7 ARIES,

8GB Pant University

Acknowledgements We gratefully acknowledge the ARM program, Dr. Ram Sagar (ARIES), and Rao Kotamarthi (GVAX, PI) for advice and assistance. This work is supported by the US Dept. of Energy Offices of Efficiency and Renewable Energy , and Science under contract DE-AC02-05CH11231

Earth System Cooling with Reflective Roofs

ARIES Obsevatory

Pantnagar University


EERE/SC study verifies predicted global cooling benefit of white roofs in warm urban climates •  USDOE-Indian collaboration measured

atmospheric radiation and building heat budgets at two sites in N. India, June 2011- March 2012

•  Combination of satellite remote sensing, airborne, and surface measurements show

1)  Heat loads are reduced to buildings, improv ing indoor comfor t fo r occupant s o f un -cond i t ioned buildings in warm climates

2)  Radiative transfer models capture predicted benefit of white roofs

Original and White Coated Roofs

Maximum alCtude ~30 km

Balloon-‐Borne Sounding System: Thermodynamic state of atmosphere, wind speed and direcCon

ISRO aircraO (~7-‐8 km flying alCtude)

Ground-‐based instruments

Satellite footprint ranges from 1 m to 1 km

Roof-‐top instruments



Earlier work •  Menon et.al (2010)

•  Negative radiative forcing – 18.2 W/m2 for 0.1 increase in Albedo •  uncoupled global land surface model

•  Millstein et.al (2011) •  Negative radiative forcing– 18.4 W/m2 for 0.1 increase in Albedo •  coupled global land surface model

Scope of the project •  To experimentally verify the increase in out going solar radiation at TOA •  Predict the outgoing solar radiation using a Radiative Transfer Model

(RRTMG)

Introduction


•  Pantnagar; 29.03 0N, 79.49 0E, 235m above sea level

•  Agricultural and Industrial area •  Aerosol and Gaseous emissions

•  residential cooking, •  diesel vehicles

Methodology

Surface monitoring: 2 white roofs and 2 dark roofs

Four-component radiometers During the process of Whitening Data monitoring on dark roof

Heat flux sensor


Methodology

•  Nainital; 29.36 0N, 79.46 0E, ~ 1940 m above sea level

•  Central Himalayan region •  Site has lower aerosol loading compared

to Pantnagar but still significant AOD relative to background sites

Surface monitoring: 2 white roofs and 2 dark roofs

Data monitoring on dark roof Data monitoring on white roof

Temperature sensor on Dark roof


Pantnagar •  21st October •  26th December •  20th March

Methodology

Naintal •  13th October •  21st December •  20th March

True color image of light (PW1, PW2) and dark (PD1, PD2) roofs at the Pantnagar site taken the

21st OCT 2011

True color image of light roofs (NW1, NW2) and dark roofs (ND1, ND2) at the Nainital site taken the

20th MARCH 2012.

Satellite Measurements of SW↑TOA Radiation: 6 shots


Soiling of Roof

Pantnagar Nainital

•  Roof reflectivity increased by paint application •  Continuous measurements capture temporal variations

White roofs=W1, W2 Black roofs=B1, B2


Shortwave Outgoing Solar Radiation - Pantnagar

0

100

200

300

400

500

PW1 PW2 PD1 PD2

21st October

0

50

100

150

200

250

PW1 PW2 PD1 PD2

26th December

Reflected Solar RadiaCon at surface Reflected Solar RadaCon at TOA

0

50

100

150

200

250

300

350

400

PW1 PW2 PD1 PD2

20th March

α=0.41

α=0.56

α=0.1 α=0.28

α=0.3 α=0.08

α=0.67 α=0.62

α=0.3

α=0.11

α=0.44 α=0.42

Incoming Solar RadiaCon 637 W/m2



Reflected Solar RadiaCon at surface

Reflected Solar RadiaCon at TOA


Shortwave Outgoing Solar Radiation - Nainital

0

100

200

300

400

500

600

NW1 NW2 ND1 ND2

13th October

0 100 200 300 400 500 600

NW1 NW2 ND1 ND2

21st December

0 100 200 300 400 500 600 700

NW1 NW2 ND1 ND2

20th March

α=0.34

α=0.76

α=0.06 α=0.12

α=0.38 α=0.71

α=0.06 α=0.1

α=0.11 α=0.07

α=0.7

α=0.39




Reflected Solar RadiaCon at surface

Reflected Solar RadiaCon at TOA


IKONOS Quantifies Global Cooling Benefit



•  White roofs reduce total (shortwave & thermal) net radiation loading by ~ 200 W m-2 in fall, 2011 (many times typical building heat loads)

•  Only part of net radiation is returned to space, requiring space-borne measurements and model evaluation

White Roofs Reduce Net Radiation Loading and Heat Flux to Building

~ 200 W m-‐2

Time of day (GMT)



Successful Prediction of Global Cooling Benefit

Close agreement of measured (IKONOS) and modeled (RRTMG) top-of-atmosphere SW radiance for both sites and three seasons demonstrates method can be applied to urban scales

(Salamanca et al., accepted and in press)



W2 B2 Block B

W1 B1 Block A

Center for Basic Sciences and Humanities, Pantnagar University, Uttarakhand

Block A – Biophysics center wing Block B – Environmental science wing W1 & W2: White roofs,B1 & B2: ExisCng roofs

Thermocouple covered with cement and coated white

Pantnagar Site (Concrete Roof)

Warm and Humid (29°C – 4°C) 29.01°N, 79.29°E


Temperature and Heat Flux (6-31 May 2012)

12°C

04°C

2.3°C

20 W/m2


y = 1.4177x + 12.079 R² = 0.60923

-‐40

-‐30

-‐20

-‐10

0

10

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30

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50

60

-‐40 -‐30 -‐20 -‐10 0 10 20 30 Da

rk ro

of (

W/m

2)

Cool roof (W/m2)

Heat Flux

Cool roof -‐ Dark roof Linear (Cool roof -‐ Dark roof)

Heat Flux (May 2012)


0 5 10 15 20 25 30 35 40 45

Tem

pe

ratu

re °

C

Month

Monthly mean outside surface temperature

0 5 10 15 20 25 30 35 40 45

Tem

pe

ratu

re °

C

Month

Monthly mean Inside Surface temperature

Monthly mean Temperature and Heat Flux

-‐15

-‐10

-‐5

0

5

10

15

20

He

at

Flu

x (W

/m2)

Month

Monthly mean Heat Flux

Dark roof Cool roof


Daytime monthly mean Temperature and Heat Flux

0

10

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50

60

Dec Jan Feb Mar Apr May Jun Jul

Tem

pe

ratu

re °

C

Month

Daytime Monthly mean outside surface temperature

0 5

10 15 20 25 30 35 40


Tem

pe

ratu

re °

C

Month

Daytime Monthly mean Indoor surface temperature

Day time – 8:00 to 18:00

-‐25

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-‐5

0

5

10

15


He

at

Flu

x (W

/m2)

Month

Daytime Monthly mean Heat Flux


Energy balance of roof (4th March, 2012, Pantnagar)

White Roof surface

Incoming short wave 738 W/m2

Reflected short wave 362 W/m2

Dark Roof surface



Heat Flux through the roof 21 W/m2



A

B

Aryabhatta Research Institute of Observational Sciences

Nainital site (Metal Roof)

Cold Climate (Summer: 27°C – 10°C, Winter: 15°C – 0°C) 29.22°N, 79.27°E


Temperature and Heat Flux (1-21 Dec 2011)

0

10

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50

0:00

13:15

2:30

15:45

5:00

18:15

7:30

20:45

10:00

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12:30

1:45

15:00

4:15

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6:45

20:00

9:15

22:30

Tem

pe

ratu

re °

C

Time (Hours)

Underdeck surface temperature

0

10

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30

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50

0:00

13:15

2:30

15:45

5:00

18:15

7:30

20:45

10:00

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12:30

1:45

15:00

4:15

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6:45

20:00

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22:30

Tem

pe

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re °

C

Time (Hours)

Overdeck surface temperature

0

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50

0:00

10:30

21:00

7:30

18:00

4:30

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1:30

12:00

22:30

9:00

19:30

6:00

16:30

3:00

13:30

0:00

10:30

21:00

7:30

18:00

4:30

15:00

1:30

Tem

pe

ratu

re °

C

Time (Hours)

Air temperature

-‐200

-‐100

0

100

200

300

400

500

0:00

21:25

18:50

16:15

13:40

11:05

8:30

5:55

3:20

0:45

22:10

19:35

17:00

14:25

11:50

9:15

6:40

4:05

1:30

22:55

20:20

17:45

15:10 He

at

Flu

x (W

/m2)

Time (hours)

Heat Flux


y = 1.6226x + 35.494 R² = 0.84874

-‐200

-‐100

0

100

200

300

400

500

-‐150 -‐100 -‐50 0 50 100 150 200

Dark(W

/m2)

White(W/m2)

Dark(Green) -‐ White roof

Heat Flux - Dark-Cool roof (1-21 Dec 2011)


Energy balance of roof (21st December, 2012,Nainital)

White Roof surface



Dark Roof surface






Results* for Pantnagar

•  Daily mean benefit for albedo increase of 0.1 is ~ 20 Wm-2 for Pantnagar (~ 40 Wm-2 for Nainital)

•  Heat flux reduction of ~ 20 Wm-2 is observed in the month of May

•  Over deck Temperature reduction of 12oC

•  Under deck Temperature reduction of 4oC

•  Indoor temperature reduction of 2-3oC

* These are the preliminary results, further analysis is being carried out for final results


Thank You

[email protected]

gsep’s cool roofs and pavements working group · energy balance of roof (4th march, 2012,...

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