Study on Methodology about Environmentally Friendly Urban …icuc7/extended_abstracts/pdf/... · 2009-08-26 · Study on Methodology about Environmentally Friendly Urban Development

Study on Methodology about Environmentally Friendly Urban Development forCreating Cool Spots and Reducing CO2 Emissions in Urban Area

Shinji Yamamura*, Osamu Nagase***NIKKEN SEKKEI Research Institute, Tokyo, Japan, **NIKKEN SEKKEI, Tokyo, Japan

Abstract

The urban heat island phenomenon and increase in CO2 emissions from buildings have usually beendiscussed as separate problem. However, these problems are significantly related to each other. Forinstance, the energy consumption in buildings, which generates CO2 emissions as well as heatexhaust from buildings, causes consequential impact on the outdoor thermal environment. In order toimprove urban area more environmentally friendly, the balanced developing method is necessary forboth creating “Cool Spots” in urban area and reducing CO2 emissions. This paper shows the feasibilityof environmentally friendly urban development in existing urban area, Tokyo, Japan and studies aboutthe effectiveness of integrated-rebuilding and planting tall trees along the street, etc.

Key words: Environmentally Friendly Urban Development, Cool Spots, CO2 emissions

1. INTRODUCTION

Under the environmentally friendly urban planning, CO2 savings (energy savings) and heat islandmitigation measures have been discussed as separate problem1), 2). However, in urban area, theseproblems are related to each other. Furthermore, in practical urban development, supportive approachis required for determining effectiveness of variety of measures and its feasibility comprehensively andpromptly under the constraint of construction investment costs. In this paper, it assumes mixed-usehigh density district based on an existing district in Tokyo, in order to examine the feasibility ofenvironmentally friendly development method applying outdoor thermal environmental improvementand CO2 savings measures in an integrated manner.

2. OUTLINE OF ANALYSIS

2.1 Study district and appraisal model

In this study, Ikebukuro district of Toshima, Tokyo is selected as a study area referring to the plan‘Ikebukuro subcenter gland vision 2008’ 3) proposed by ward of Toshima. This district is mixed-usehigh density area. Most of buildings are old detached houses built over 40 years ago, and for someother reasons, these buildings are desired to be rebuilt or renovated. Since there are a number ofdevelopment plans such as proposal for new Toshima-ward government building plan and streetsidedevelopment plan, Ikebukuro district has high potential to undertake outdoor thermal environmentalimprovement and CO2 savings measures in an integrated manner. It assumes two model districts, oneis the district before development and other is the district after the development in an environmentallyfriendly way (Figure 1, 2). The district before the development is designed based on the buildingvolume, allocation and land use in existing Ikebukuro district. The model district after the developmentis designed based on the each development plans proposed in Ikebukuro district mentioned earlier.

This study covers the district area of 290m×260m (Figure 1). In the district, redevelopment is proposedin area [A] where the maximum permitted floor area ratio increases from 500% to 800%. Therefore,the total floor area increases 22% (Fifure 2) in the district. On the other hand, integrated-rebuildingarea (area [B]) is set along the main street extending across the district from south to north, where itsfloor area ratio remains the same. In this integrated-rebuilding area (area [B]), small-scale buildingsare required to jointly rebuilt to the corporative buildings with setback for producing open space.Streetside tall trees and water volatile pavement are treated in the open space. Buildings are rebuilt inan environmentally friendly way with high efficient building services, thick insulation, Low-e glass andreflective paint on the roof. The development of area [B] is implemented as a trigger for rebuilding inentire district. It supposes that high efficient building services are also installed to the existing buildingsoutside of the development areas. Also, tall trees and water volatile pavement are treated in entiredistrict.

The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan

Table 1 shows the comparison between specifications of building services before and after thedevelopment. Table 2 shows the comparison between specifications of the external facing before andafter the integrated-rebuilding. Table 3 shows menus of outdoor thermal environmental improvementmeasures.

64

34

20

29

33

32

2

2

0 50 100 150

After

Before

OFFICE COMMERCIAL RESIDENCE CULTURE

Total Floor( ×103 m2 )

22％UP

Fig. 2 Total Floor Area in Entire District (Before & After development)

Table 1 Specifications of Building Services ( Before & After development )

Table 3 Menus for Thermal ImprovementMeasuresTable 2 Specifications of Buildings ( Before & After development )

Before After Before After Before After Before After Before AfterExisting : HP typeRebuilding : Gas(Latentheat recovery)

OFFICEMulti-type packagedair conditioner

Multi-type packagedair conditioner

2.64 3.3 20 15(Hf) Gas Gas

COMMERCIALMulti-type packagedair conditioner

Multi-type packagedair conditioner

2.64 3.3 30 15(Hf) Gas Gas

CULTURE Room air conditioner Room air conditioner 2.72 3.4 15 15 GasGas(Latent heat

recovery)Area [A] HP Chiller(CWV） HP Chiller(VWV） 2.64 4.5 20 15(Hf) Gas Gas CAV VAV, THX(60％)

* HP:Heat Pump, CWV:Constant water volume, VWV:Variable water volume, CAV:Constant air volume, VAV:Variable air volume, THX:Total heat exchanger

Building type

3.4 15 15 GasRESIDENCE Room air conditioner Room air conditioner

Hot Water Supply Unit Air Handling Unit

2.72

Heating/Cooling Plant COP Lighting(VA/m2)

Type Part Before After ( & Rebuilding )

WallNo insulation, Wooden,Mortar

RoofNo insulation, Wooden,Slate

Window Float glass with CurtainWall Insulation :15mm, RC Insulation :35mm, RC

Roof Insulation :20mm, RCInsulation :35mm, RC,Reflective paint (Roof)

Window(C) Float glass with Curtain Pair glass with CurtainWindow(O) Float glass with Blind Low-e grass with Blind

DETACHEDHOUSE

APARTMENTCOMMERCIAL(C)

OFFICE(O)

integrating detachedhouses to anApartment

Before After

Sidewalk Tile pavementWater volatilepavement

Building site ConcreteWater volatilepavement

Railway Gravel TurfSidewalk inArea B

−Two roadside treelines on each side

Sidewalk inArea A

−One roadside treeline on each side

Rooftop inArea A

− Tall tree

Place

Groundcover

Tree

(2)After development★： Integrated-rebuilding

★★

★

★★

★

★

★

★

★

★★

★

★

★★

★★

★

★

★

Asfhalt Concrete Pavement Soil(dry) Gravel Water volatile pavement Turf

■Ground cover type(except rooftop） ■Building typeOffice

Commercial Residence Culture

Redevelopment area( Area [A] )Maximum permitted floor area ratio : 800％(Ratio of total floor area within district : 45％）

Fig. 1 Evaluation Case

(1)Before development

park Redevelopment Areaalong Main Street（ Area [B] ）

Redevelopment area( Area [A] )Maximum permitted floor area ratio : 500％（ Ratio of total floor area within district : 32％）

Railway

The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan

2.2 Outline of evaluation

Each case shown in figure 1 is evaluated its performance byfollowing methods. ① Applying comprehensive simulationmethod to evaluate thermal radiation environment in outdoorspace and energy consumption in buildings4), distribution ofsurface temperature within the district, energy consumptionin buildings and sensible heat load are calculated in everyhour. ②Predicting airflow and air temperature distribution bythe standard k-ε turbulent model of computer fluid dynamics(CFD) based on the solid surface boundary condition (givensurface temperature at noon calculated above). Table 4shows the calculation condition of CFD.

3. RESULT OF EVALUATION

3.1 Distribution of surface temperature

Figure 2 shows distribution of surface temperature at noon in midsummer (August) before and afterthe development. In area [A] and area [B], streetside tall trees shade and water volatile pavement onthe sidewalk contribute to lower surface temperature by 10 degree to15 degree in over 60% ofstreetside area. Coating the high reflective paint on the roof, surface temperature results in lower.These efforts tend to be shown between at noon to 17:00PM, and can be concluded that thesetreatment is capable to improve thermal radiation environment in wide area of the district and over aprolonged period of time.

3.2 Distribution of outdoor air temperature

Air flow and air temperature distribution are analyzed under the condition of surface temperaturedistribution at noon and exhaust heat from buildings. In area [A] and area [B], since streetside talltrees and water volatile pavement are treated, corridors of cool wind remaining 2 degree lower thanthat before the development is emerged. In the outside of the redevelopment area, to vegetate alongthe railway road and continuously link the line of streetside tall trees to existing large-scale green area,it contributes to allow cool air in the large-scale green area inflow to downward wide area of the district.In addition, since exhaust heat from buildings decreases by the integrated-rebuilding, air temperaturetend to decrease in wide area not only in the redevelopment area but also in entire district (figure 3). 3.3 Sensible heat load to atmosphere

Figure 4 shows sensible heat to atmosphere in the district. The sensible heat from building decreasesby 17% at 13:00PM after the development. The sensible heat from land surface also decreases by28% at 17:00PM. The total becomes 22% reduction compared to that before the development, theseefforts can be determined that these treatment done by the development can contribute to heat islandmitigation.

3.4 CO2 emissions（caused by energy consumption in buildings）

In area [B] where the floor area ratio remains the same as that before the development, due to theimprovement of specification of the external facing and building services, amount of integral CO2emissions per day is reduced by 36% in August. In area [A] where increases the floor area up to 70%,CO2 emissions from air-conditioning is reduced by 5.0% and, in entire district it stays 4.3% increase.Overall, it is verified from the study that in spite of the fact that the total floor area increases by 22%within the district, CO2 emissions is reduced by 4.9% (figure 5). This effort tends to be remarkable inwinter. The reduction of air-conditioning load by installing thick insulation substantially influences tothe amount of integral CO2 emissions per day in midwinter (February). It is reduced by over 45% inarea [B] and over 23% in entire district (figure 6). It verifies that applying development method like thisproposed development in this study, in spite of over 20% increase in floor area, it is possible to reduceannual amount of CO2 emissions in entire district.

Table 4 CFD ConditionParameter Condition

Distribution at 12:00,（Log-law on solid surface)

Evaluationarea size

800ｍ×900ｍ×500ｍ

Outdoor airtemperature

34℃

Inlet Wind1.5m/s at 10ｍ Height、(1/4 Power law profile）Drag coefficient:0.8, leaf areadensity of tree canopy:1.17Evaporative cooling :− 68W/m3

Heat exhaustfrom building

1.5m/s (vertical direction from theRooftop)

Turbulentmodel

Standard ｋ-εmodel

Tree Crown

Surfacetemperature

The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan

4. CONCLUSION

This paper examines the feasibility of introduction of comprehensive method, as an environmentallyfriendly development method, to improve outdoor thermal environment and reduce CO2 emissions andits effects. As exploiting opportunities of redevelopment and streetside development, it allowsintegrated-rebuilding with setback and continuous tree line along the street, water volatile paving andinstallation of high reflective materials in large area. Moreover, to promote rebuilding of old buildingsand renewing conventional building services to improve the external facing and building servicesperformance in outside of the development areas, it makes possible to improve thermal environmentin outdoor space and effectively reduce CO2 emissions.

Further study should focus on the effectiveness of comprehensive environmental and energy savingsmeasures considering not only enhancement of building services efficiency but also conversion fromsensible exhaust heat to latent exhaust and photovoltaic generation. Notes:Following value were used as CO2 emission coeffisient ;0.339[kg-CO2/kWh] for Electric, 0.0509[kg-CO2/MJ] for Gas.

References1) Masahiko Kaneda, Daisuke Narumi, Yoshiyuki Shimoda : A

Basic Study on the Impact of Building Shape Differences onOutdoor Thermal Environment and Energy Consumption for AirConditioning, Annual meeting of SHASE of Japan, 1205-1208,2008

2) Hong Chen, Ryuzo Ohoka, et al : Study on RelaxationMeasures of Outdoor Thermal Environment on Present UrbanBlocks Using Coupled Simulation of Convection, Radiation andConduction (Part 1, 2), Annual meeting of AIJ, 805-808, 2007

3) Toshima ward Homepage, http://www.city.toshima.lg.jp/ , 20084) Takashi Asawa, Shinji Yamamura, Akira Hoyano : Prediction

system of thermal environment and energy consumption ofurban blocks; Part 1, Annual meeting of AIJ, 2009

Fig. 2 Distribution of Surface Temperature（12:00）(1)Before (2)After

Fig. 4 Sensible Heat Load to Atmosphere(August）

0

10

20

30

40

0時 4時 8時 12時 16時 20時

Sensi

ble H

eat

Loa

d （ M

W ） -22％

-17％

Before: Building Before: Surface & Building After : Building After : Surface & Building

0:00 4:00 8:00 12:00 16:00 20:00

沿道整備エリアCO2排出量（夏）

0 1 2 3 4

After

Before

再開発エリアCO2排出量（夏）

0 5 10 15

After

Before

0 10 20 30

After

Before

Fig. 5 CO2 Emissions per day(August)

(b) Area [A]

+4.3%

(c) Total Area

-4.9%

(a) Area [B]

-36.8%(ｔ -CO2/day）

0102030 Air Conditioning Lighting Others

(ｔ -CO2/day）

(ｔ -CO2/day）

沿道整備エリアCO2排出量（冬）

0 1 2 3 4

After

Before

再開発エリアCO2排出量（冬）

0 5 10 15

After

Before

0 10 20 30

After

Before

-23.6%

-21%

-45.5%

Fig. 6 CO2 Emissions per day(Februray)

(b) Area [A]

(c) Total Area

(a) Area [B]

(ｔ -CO2/day）

0102030 Air Conditioning Lighting Others

(ｔ -CO2/day）

(ｔ -CO2/day）

(1)Before (2)After

Fig. 3 Disutribution of Air Temperature ( 12:00, GL+1.5m )

(℃)

Wind

(1)Before ( a-a section ) (2)After ( b-b section )

a

a

b

b

Wind

The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan