evaluation of greening scenarios to reduce paris city ... · cécile de munck, a lemonsu, v masson,...

Context & methodology

Construction of greening scenarios Benefits for thermal comfort and energy demand in heat wave context Seasonal impacts

Cécile de Munck, A Lemonsu, V Masson, M Bonhomme, J Le Bras [email protected]

ICUC9 – Toulouse 2015

Evaluation of greening scenarios to reduce Paris city vulnerability to future heat waves

VegDUD ANR

Ville Durable 2009

1 – Context 2 – Greening scenarios 3 – Benefits for heat wave 4 – Seasonal impacts

VegDUD ANR Ville Durable 2009

ICUC9-TLSE2015

Viguié et al 20/07 Cassiopée room

2 complementary research projects with similar focus

Objectives : modelling adaptation strategies to urban climate or climate change at the scale of cities modelling the role of vegetation in sustainable urban development focus of both projects : thermal comfort and energy consumption

Recent improvements of Town Energy Balance to address these objectives


CANOPY u, v, T, q, e

Solar protections

Internal loads

Solar gains

Infiltration Ventilation

Atmospheric level

Air conditioning

Heating

Bueno et al. 2012 Ti

ROOF n layers

FLOOR n layers

WALL n

layers

Thermal mass

de Munck et al . 2013

GREENROOF

BEM

Lemonsu et al. 2012

GARDEN

Hamdi & Masson 2008

URBAN CANOPY

Masson 2013

ORIENTATION

de Munck 2013

WATERING

Le Bras & Masson 2015

UWG




Solar protections

Internal loads

Solar gains


Atmospheric level

Air conditioning

Heating


ROOF n layers

FLOOR n layers

WALL n

layers

Thermal mass

BEM

Lemonsu et al. 2012

GARDEN

de Munck 2013

WATERING

Sprinklers

Drip irrigation


GREENROOF

Masson 2013

ORIENTATION


UWG

Hamdi & Masson 2008

URBAN CANOPY

tIrrig = 8 hours at night

Irrig = 25 L m-2 week-1




Solar protections

Internal loads

Solar gains


Atmospheric level

Air conditioning

Heating


ROOF n layers

FLOOR n layers

WALL n

layers

Thermal mass

BEM

Lemonsu et al. 2012

GARDEN

de Munck 2013

WATERING

UTCI

Pigeon 2011


GREENROOF

Masson 2013

ORIENTATION


UWG

Hamdi & Masson 2008

URBAN CANOPY

ICUC9-TLSE2015

for the evaluation of greening scenarios for Paris city

1 – Methodology 2 – Greening scenarios 3 – Benefits for heat wave 4 – Seasonal impacts

Scenarios

Weath

er

Heat wave 2003

Gre

enin

g

Weath

er 1999-2008

Usa

ge

Urban climate modelling (1km)

Impact of city on atmospheric forcing

2D temperature forcing via UWG



Scenarios

Weath

er

Heat wave 2003

Gre

enin

g

Weath

er 1999-2008

TEB : Town Energy Balance ICUC9-TLSE2015

Usa

ge

Evaluation of greening scenarios

Indicators

Energy consumption

Thermal stress/comfort

Water ressources

Urban climate modelling (1km)

Impact of city on atmospheric forcing

2D temperature forcing via UWG



Scenarios

Weath

er

Heat wave 2003

Gre

enin

g

Weath

er 1999-2008

TEB : Town Energy Balance ICUC9-TLSE2015

Usa

ge


Greening of available urban surfaces

ICUC9-TLSE2015

Gre

enin

g

pavements, squares, roundabouts, car parks, roofs , etc.



Gre

en

Usa

ge

ground VEG

% urban ground available/mesh greened

25 25 50 50

75 75

Low vegetation Low & High vegetation

ICUC9-TLSE2015



Gre

en

Usa

ge

ground VEG

roof VEG U

sage

25 25 50 50

75 75

Low vegetation Green roofs Low & High vegetation

ICUC9-TLSE2015


1 – Methodology 2 – Greening scenarios 3 – Benefits for heat wave

3 – Heat wave benefits

4 – Seasonal impacts


Gre

en

Usa

ge

ground VEG

roof VEG U

sage

25 25 50 50

75 75 75

Low vegetation Green roofs Combination Low & High vegetation

ICUC9-TLSE2015




Gre

en

Usa

ge

ground VEG

Usa

ge

roof VEG U

sage

25 25 50 50

75 75 75

Low vegetation Green roofs Combination Low & High vegetation

ICUC9-TLSE2015


26 °C 19 °C « virtuous » target temperatures

1 – Methodology 2 – Greening scenarios 3 – Heat wave benefits 4 – Seasonal impacts


Gre

en

Usa

ge

ground VEG

26 °C

Usa

ge

roof VEG U

sage

19 °C « virtuous » target temperatures

LV25 LV50 LV75 LHV25 LHV50 LHV75

GR IGR LHV75-IGR

25 25 50 50

75 75 75

ICUC9-TLSE2015



Urban vegetation density / km²

LV25 LHV25

LV75 LHV75 LV50 LHV50

REF

Greening available

urban ground

+ + +

Urban vegetation

+ 11 % + 22 % + 34 %

25 % 50 % 75 %

ICUC9-TLSE2015


Urban vegetation density / km²

LV25 LHV25

LV75 LHV75 LV50 LHV50

REF

GR IGR

Building types

no GR ICUC9-TLSE2015

Impacts on street temperatures at 2m T MAX

Green roofs do not have an impact on street temperatures unless they are irrigated

Their impact remains limited : - 0.25 / - 0.5 °C

1 – Methodology 2 – Greening scenarios

3 – Benefits for heat wave 4 – Seasonal impacts

GR IGR

ICUC9-TLSE2015

Impacts on daytime street temperatures (2m) T MAX



LV25 LV50 LV75

The higher the greening rate, the greater the cooling : between - 0.25 à -2 °C

ICUC9-TLSE2015

During the day, the low vegetation is slightly more efficient at cooling than the mixed vegetation.

Impacts on daytime street temperatures (2m) T MAX



LV25 LV50 LV75

LHV25 LHV50 LHV75

The higher the greening rate, the greater the cooling : between - 0.25 à -2 °C

ICUC9-TLSE2015

At night, the mixed vegetation is far more efficient than the low one (due to watering schedule and system)

LV25 LV50 LV75

LHV25 LHV50 LHV75

Impacts on nighttime street temperatures (2m ) T MIN



ICUC9-TLSE2015

Impact on UHI



5°C

28

27

26

25

24

23

22

21

2m

nig

htt

ime

tem

per

atu

res

(°C

)

20 0 40 60 80 100

Distance (km)

ICUC9-TLSE2015

Impact on UHI



28

27

26

25

24

23

22

21

2m

nig

htt

ime

tem

per

atu

res

(°C

)

20 0 40 60 80 100

Distance (km)

- 0.3 °C

5°C

ICUC9-TLSE2015

Impact on UHI



28

27

26

25

24

23

22

21

20 0 40 60 80 100

Distance (km)

2m

nig

htt

ime

tem

per

atu

res

(°C

)

- 0.3 °C

- 1.2 °C

5°C

ICUC9-TLSE2015

The mixed wooded vegetation can reduce nighttime UHI amplitude further than low vegetation.

Time of day (UTC)

Day

of

hea

t w

ave

00 03 06 09 12 15 18 21 00

1 2 3 4 5 6


3 – Benefits for heat wave


Impact of greening on outdoor thermal comfort

Thermal comfort / stress indicator : UTCI (°C)

ICUC9-TLSE2015

Glossary of terms for Thermal

Physiology (2003)

Time of day (UTC)

Day

of

hea

t w

ave

00 03 06 09 12 15 18 21 00

1 2 3 4 5 6 Integration

over time 06:00 – 22:00

Mea

n t

ime

spen

t in

th

erm

al h

eat

stre

ss (

h)

REF - shade





Thermal comfort / stress indicator : UTCI (°C)

16

14

12

10

8

6

4

2

0

ICUC9-TLSE2015

Glossary of terms for Thermal

Physiology (2003)





Person in the shade – Dense collective housing

Tim

e sp

ent

in t

her

mal

str

ess

(h)

16

14

12

10

8

6

4

2

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

0

ICUC9-TLSE2015






Tim

e sp

ent

in t

her

mal

str

ess

(h)

16

14

12

10

8

6

4

2

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

0

- 0:12

ICUC9-TLSE2015

Green roofs have a very limited effect on outdoor thermal comfort






Tim

e sp

ent

in t

her

mal

str

ess

(h)

16

14

12

10

8

6

4

2

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

0

ICUC9-TLSE2015

- 0:26 - 1:10

- 0:49

- 1:12

Ground vegetation allows for the time spent in heat stress to be reduced

The greater the greening rate, the lower the time spent in heat stress







Tim

e sp

ent

in t

her

mal

str

ess

(h)

16

14

12

10

8

6

4

2

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

0

ICUC9-TLSE2015

Ground vegetation allows for the time spent in heat stress to be reduced

The greater the greening rate, the lower the time spent in heat stress


Cumulative effect for the maximum combination of vegetation

- 0:12 - 1:12

- 1:24

Impact of greening on energy consumption for air conditioning

% reduction / REF

0

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

Ene

rgy

con

sum

pti

on

(G

W h

)

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12



ICUC9-TLSE2015

GR are good performers only if they are irrigated




% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015

The higher the ground greening rate, the greater the reduction of energy consumption

Greater reduction with a mixed wooded vegetation

GR are good performers only if they are irrigated




% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015

Irrigated green roofs are as efficient as the greatest mixed wooded scenario




% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015





+ 25% of mixed wooded vegetation allows for an energy reduction equivalent to + 75% of low vegetation

% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015





+ 25% of mixed wooded vegetation allows for an energy reduction equivalent to + 75% of low vegetation

Cumulative effect for the maximum combination of vegetation

% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600 - 25

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015

Consequences of greening on water consumption for watering urban vegetation



% reduction / REF

Ene

rgy

con

sum

pti

on

(G

W h

)

0

200

400

600

- 5 - 7 - 8 - 10 - 13

- 4 - 2 759 800

- 12

- 25

Wat

er

con

sum

pti

on

(M

m3)

18

20

22

24

26

28

30

69 % V Seine

53 % V Seine

59 % V Seine

65 % V Seine

71 % V Seine

87 % V Seine

LV2

5

LV5

0

LV7

5

GR

IGR

REF

LHV

75

-IG

R

LHV

75

LHV

25

LHV

50

ICUC9-TLSE2015

- 4.5 %

- 8 %

Based on 10-year simulations (1999-2008)

- 0.3 % - 23 % - 28 %

- 7.2 %

- 7.7 % - 7.5 %

- 0.2 %

Impact of greening on heating and air conditioning energy consumption

EFcum (GW h)

in summer, all greening strategies diminish energy consumption

green roofs perform well all year round (insulators)

outside summer, the wooded mixed vegetation result in a greater energy consumption



ICUC9-TLSE2015

(M m3) REF GR IGR LV25

LHV25 LV50

LHV50 LV75

LHV75

Summer watering

282 282 362 314 346 378

Surface runoff 426 370 410 39 332 286

Impact on water ressources management

comparison of volumes of water devoted to summer watering & annual surface runoff



ICUC9-TLSE2015

(M m3) REF GR IGR LV25

LHV25 LV50

LHV50 LV75

LHV75

Summer watering

282 282 362 314 346 378

Annual surface runoff

426 370 410 39 332 286

Can surface runoff compensates for vegetation irrigation ?

x x

comparison of volumes of water devoted to summer watering & annual surface runoff

Impact on water ressources management



ICUC9-TLSE2015

Outdoor comfort

from - 0.5 to - 2 °C

Summary

Energy consumption

AC demand can be reduced by greening and is explained :

• for ground vegetation : by street cooling • for green roofs : mainly by their insulating capacity

Green roofs appear more efficient than ground vegetation all year round

- 7 %

heat wave 2003

summer

year

- 28 %

- 12 %

Sustainable managnement of water ressources

Urban vegetation allows annual urban surface runoff to be massively reduced, by 10 % in the case of green roofs.

Vegetation irrigation in summer could be fully or partially provided by the collection & storage of the town annual surface run off.

Green roofs have nearly no impact on street level air temperatures.

With ground vegetation the higher the cooling effect : the greater the proportion of trees the greater the vegetation cover

Increasing wooded vegetation may increase demand for heating (present climate).

ICUC9-TLSE2015

green roofs (evapotranspiration) – project TERRACES

street trees (shading) – ongoing PhD work

evaluate alternative watering strategies

study strategies combining urban vegetation and sustainable water management (TEB-HYDRO)

Main perspectives

Redon et al 21/07 St Exupéry amphitheater

Chancibault et al 24/07 Caravelle room

Daniel et al 23/07 Cassiopée room

Claverie et al 24/07 St Exupéry amphitheater

Towards estimating city carbon balance

Carbon sources : building energy consumption, traffic, etc.

Carbon sinks : vegetation (TEB-ISBA-Ags)

Improve vegetation description in TEB

ICUC9-TLSE2015

Thank you for your attention

This research was funded by two projects from the French National Research Agency : MUSCADE and VegDUD VegDUD

ANR Ville Durable 2009

evaluation of greening scenarios to reduce paris city ... · cécile de munck, a lemonsu, v masson,...

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