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

Transcription

1 Evaluation of greening scenarios to reduce Paris city vulnerability to future heat waves Cécile de Munck, A Lemonsu, V Masson, M Bonhomme, J Le Bras cecile.demunck@meteo.fr Context & methodology Construction of greening scenarios Benefits for thermal comfort and energy demand in heat wave context Seasonal impacts ICUC9 Toulouse 2015 VegDUD ANR Ville Durable 2009

2 1 Context 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts 2 complementary research projects with similar focus Objectives : VegDUD ANR Ville Durable 2009 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 Viguié et al 20/07 Cassiopée room

3 1 Context 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Recent improvements of Town Energy Balance to address these objectives de Munck et al Le Bras & Masson 2015 Masson 2013 GREENROOF UWG ORIENTATION Atmospheric level ROOF n layers Hamdi & Masson 2008 CANOP URBAN CANOPY u, v, Y T, q, e Thermal mass Air conditioning Heating Bueno et al BEM Internal loads Ti Solar gains Solar protections de Munck 2013 WATERING Infiltration Ventilation Lemonsu et al GARDEN FLOOR n layers WALL n layers

4 1 Context 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Recent improvements of Town Energy Balance to address these objectives de Munck et al Le Bras & Masson 2015 Masson 2013 GREENROOF UWG ORIENTATION Atmospheric level ROOF n layers Hamdi & Masson 2008 CANOP URBAN CANOPY u, v, Y T, q, e Drip irrigation Thermal mass Air conditioning Heating Sprinklers Bueno et al BEM Internal loads Ti Solar gains Solar protections de Munck 2013 WATERING Infiltration Ventilation Lemonsu et al GARDEN Irrig = 25 L m -2 week -1 FLOOR n layers WALL n layers t Irrig = 8 hours at night

5 1 Context 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Recent improvements of Town Energy Balance to address these objectives de Munck et al GREENROOF Le Bras & Masson 2015 UWG Masson 2013 ORIENTATION Atmospheric level ROOF n layers Hamdi & Masson 2008 CANOP URBAN CANOPY u, v, Y T, q, e Thermal mass Air conditioning Heating Pigeon 2011 UTCI Bueno et al BEM Internal loads Ti Solar gains Solar protections de Munck 2013 WATERING Infiltration Ventilation Lemonsu et al GARDEN FLOOR n layers WALL n layers

6 Usage Weather 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts for the evaluation of greening scenarios for Paris city Greening Weather Heat wave 2003 Scenarios

7 Usage Weather 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts for the evaluation of greening scenarios for Paris city Greening Weather Heat wave 2003 Impact of city on atmospheric forcing 2D temperature forcing via UWG Scenarios Urban climate modelling (1km) TEB : Town Energy Balance

8 Usage Weather 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts for the evaluation of greening scenarios for Paris city Greening Weather Heat wave 2003 Impact of city on atmospheric forcing 2D temperature forcing via UWG Indicators Thermal stress/comfort Energy consumption Water ressources Scenarios Urban climate modelling (1km) TEB : Town Energy Balance Evaluation of greening scenarios

9 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Greening Greening of available urban surfaces pavements, squares, roundabouts, car parks, roofs, etc.

10 Green Usage 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Greening of available urban surfaces Low vegetation Low & High vegetation % urban ground available/mesh greened ground VEG

11 Green Usage Usage 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Greening of available urban surfaces Low vegetation Low & High vegetation Green roofs % urban ground available/mesh greened ground VEG roof VEG

12 Usage Usage Green 1 Methodology 2 Greening scenarios 3 Benefits for heat wave Greening of available urban surfaces 3 Heat wave benefits 4 Seasonal impacts Low vegetation Low & High vegetation Green roofs Combination % urban ground available/mesh greened ground VEG roof VEG

13 Green Usage Usage Usage 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Greening of available urban surfaces Low vegetation Low & High vegetation Green roofs Combination % urban ground available/mesh greened ground VEG roof VEG 26 C 19 C «virtuous» target temperatures

14 Green Usage Usage Usage 1 Methodology 2 Greening scenarios 3 Heat wave benefits 4 Seasonal impacts Greening of available urban surfaces LV25 LV50 LV75 LHV25 LHV50 LHV75 GR IGR LHV75-IGR % urban ground available/mesh greened ground VEG roof VEG 26 C 19 C «virtuous» target temperatures

15 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Urban vegetation density / km² REF LV25 LHV25 Greening available urban ground % 50 % 75 % Urban vegetation + 11 % + 22 % + 34 % LV50 LHV50 LV75 LHV75

16 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Urban vegetation density / km² Building types LV50 REF LV25 LHV25 LHV50 LV75 LHV75 GR IGR no GR

17 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impacts on street temperatures at 2m T MAX GR IGR Green roofs do not have an impact on street temperatures unless they are irrigated Their impact remains limited : / C

18 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impacts on daytime street temperatures (2m) T MAX LV25 LV50 LV75 The higher the greening rate, the greater the cooling : between à -2 C

19 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impacts on daytime street temperatures (2m) T MAX LV25 LV50 LV75 LHV25 LHV50 LHV75 The higher the greening rate, the greater the cooling : between à -2 C During the day, the low vegetation is slightly more efficient at cooling than the mixed vegetation.

20 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impacts on nighttime street temperatures (2m ) T MIN LV25 LV50 LV75 LHV25 LHV50 LHV75 At night, the mixed vegetation is far more efficient than the low one (due to watering schedule and system)

21 2m nighttime temperatures ( C) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact on UHI C Distance (km)

22 2m nighttime temperatures ( C) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact on UHI C C Distance (km)

23 2m nighttime temperatures ( C) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact on UHI C C C Distance (km) The mixed wooded vegetation can reduce nighttime UHI amplitude further than low vegetation.

24 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Day of heat wave Impact of greening on outdoor thermal comfort Thermal comfort / stress indicator : UTCI ( C) Time of day (UTC) Glossary of terms for Thermal Physiology (2003)

25 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Day of heat wave Mean time spent in thermal heat stress (h) Impact of greening on outdoor thermal comfort Thermal comfort / stress indicator : UTCI ( C) 6 Integration 5 over time :00 22: Time of day (UTC) Glossary of terms for Thermal Physiology (2003) REF - shade

26 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Time spent in thermal stress (h) REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on outdoor thermal comfort Person in the shade Dense collective housing

27 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Time spent in thermal stress (h) REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on outdoor thermal comfort Person in the shade Dense collective housing :12 Green roofs have a very limited effect on outdoor thermal comfort

28 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Time spent in thermal stress (h) REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on outdoor thermal comfort Person in the shade Dense collective housing :49-0:26-1:10-1:12 Green roofs have a very limited effect on outdoor thermal comfort 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

29 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Time spent in thermal stress (h) REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on outdoor thermal comfort Person in the shade Dense collective housing :24-0:12-1:12 Green roofs have a very limited effect on outdoor thermal comfort 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

30 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF

31 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF GR are good performers only if they are irrigated

32 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF GR are good performers only if they are irrigated The higher the ground greening rate, the greater the reduction of energy consumption Greater reduction with a mixed wooded vegetation 0

33 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF Irrigated green roofs are as efficient as the greatest mixed wooded scenario

34 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF Irrigated green roofs are as efficient as the greatest mixed wooded scenario + 25% of mixed wooded vegetation allows for an energy reduction equivalent to + 75% of low vegetation 200 0

35 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Impact of greening on energy consumption for air conditioning % reduction / REF Irrigated green roofs are as efficient as the greatest mixed wooded scenario + 25% of mixed wooded vegetation allows for an energy reduction equivalent to + 75% of low vegetation 200 Cumulative effect for the maximum combination of vegetation 0

36 Energy consumption (GW h) 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts REF GR IGR LV25 LV50 LV75 LHV25 LHV50 LHV75 LHV75-IGR Water consumption (M m 3 ) Consequences of greening on water consumption for watering urban vegetation % reduction / REF % V Seine % V Seine 71 % V Seine % V Seine % V Seine 53 % V Seine

37 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact of greening on heating and air conditioning energy consumption EF cum (GW h) Based on 10-year simulations ( ) % - 23 % - 28 % % % - 8 % % % % 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

38 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact on water ressources management comparison of volumes of water devoted to summer watering & annual surface runoff (M m 3 ) REF GR IGR LV25 LHV25 LV50 LHV50 LV75 LHV75 Summer watering Surface runoff

39 1 Methodology 2 Greening scenarios 3 Benefits for heat wave 4 Seasonal impacts Impact on water ressources management comparison of volumes of water devoted to summer watering & annual surface runoff (M m 3 ) REF GR IGR LV25 LHV25 LV50 LHV50 LV75 LHV75 Summer watering Annual surface runoff Can surface runoff compensates for vegetation irrigation? x x

40 Summary Outdoor comfort Green roofs have nearly no impact on street level air temperatures. the greater the vegetation cover With ground vegetation the greater the proportion of trees the higher the cooling effect : from to - 2 C 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 heat wave 2003 summer year Increasing wooded vegetation may increase demand for heating (present climate) % - 28 % - 7 % 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.

41 Main perspectives Improve vegetation description in TEB 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) Claverie et al 24/07 St Exupéry amphitheater Redon et al 21/07 St Exupéry amphitheater Daniel et al 23/07 Cassiopée room Chancibault et al 24/07 Caravelle room Towards estimating city carbon balance Carbon sources : building energy consumption, traffic, etc. Carbon sinks : vegetation (TEB-ISBA-Ags)

42 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