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GSEP’S Cool Roofs and Pavements Working Group 2012 Global Climate Benefits of Cool Roof Vishal Garg, IIIT- Hyderabad

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Page 1: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

GSEP’S Cool Roofs and Pavements Working Group 2

01

2

Global  Climate  Benefits  of  Cool  Roof  

Vishal Garg, IIIT- Hyderabad

Page 2: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

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    

Page 3: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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  

Earth System Cooling with Reflective Roofs

Page 4: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Page 5: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

•  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

Page 6: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Page 7: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Page 8: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

Soiling of Roof

Pantnagar Nainital

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

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

Page 9: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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    

Incoming  Solar  RadiaCon  472  W/m2    

Incoming  Solar  RadiaCon  639  W/m2    

Reflected  Solar  RadiaCon  at  surface  

Reflected  Solar  RadiaCon  at  TOA  

Page 10: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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  

Incoming  Solar  RadiaCon  665  W/m2    

Incoming  Solar  RadiaCon  802  W/m2    

Incoming  Solar  RadiaCon  826  W/m2    

Reflected  Solar  RadiaCon  at  surface  

Reflected  Solar  RadiaCon  at  TOA  

Page 11: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

IKONOS Quantifies Global Cooling Benefit

Earth System Cooling with Reflective Roofs

Page 12: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

•  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)  

Earth System Cooling with Reflective Roofs

Page 13: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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)

Earth System Cooling with Reflective Roofs

Page 14: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Page 15: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

Temperature and Heat Flux (6-31 May 2012)

12°C

04°C

2.3°C

20 W/m2

Page 16: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

y  =  1.4177x  +  12.079  R²  =  0.60923  

-­‐40  

-­‐30  

-­‐20  

-­‐10  

0  

10  

20  

30  

40  

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)

Page 17: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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  

Page 18: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

Daytime monthly mean Temperature and Heat Flux

0  

10  

20  

30  

40  

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  

Dec   Jan   Feb   Mar   Apr   May   Jun   Jul  

Tem

pe

ratu

re °

C

Month

Daytime Monthly mean Indoor surface temperature

Day time – 8:00 to 18:00

-­‐25  

-­‐20  

-­‐15  

-­‐10  

-­‐5  

0  

5  

10  

15  

Dec   Jan   Feb   Mar   Apr   May   Jun   Jul  

He

at

Flu

x (W

/m2)

Month

Daytime Monthly mean Heat Flux

Page 19: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Incoming short wave 707 W/m2

Reflected short wave 76 W/m2

Heat Flux through the roof 21 W/m2

Heat Flux through the roof 43 W/m2

Page 20: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

Page 21: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

Temperature and Heat Flux (1-21 Dec 2011)

0  

10  

20  

30  

40  

50  

0:00  

13:15  

2:30  

15:45  

5:00  

18:15  

7:30  

20:45  

10:00  

23:15  

12:30  

1:45  

15:00  

4:15  

17:30  

6:45  

20:00  

9:15  

22:30  

Tem

pe

ratu

re °

C

Time (Hours)

Underdeck surface temperature

0  

10  

20  

30  

40  

50  

0:00  

13:15  

2:30  

15:45  

5:00  

18:15  

7:30  

20:45  

10:00  

23:15  

12:30  

1:45  

15:00  

4:15  

17:30  

6:45  

20:00  

9:15  

22:30  

Tem

pe

ratu

re °

C

Time (Hours)

Overdeck surface temperature

0  

10  

20  

30  

40  

50  

0:00  

10:30  

21:00  

7:30  

18:00  

4:30  

15:00  

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

Page 22: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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)

Page 23: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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

White Roof surface

Incoming short wave 701 W/m2

Reflected short wave 239 W/m2

Dark Roof surface

Incoming short wave 665 W/m2

Reflected short wave 40 W/m2

Heat Flux through the roof 34 W/m2

Heat Flux through the roof 82 W/m2

Page 24: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

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    

Page 25: GSEP’S Cool Roofs and Pavements Working Group · Energy balance of roof (4th March, 2012, Pantnagar) White Roof surface Incoming short wave 738 W/m2 Reflected short wave 362 W/m2

Vishal Garg, IIIT- Hyderabad

Thank You

[email protected]