Activity report Simulation survey (Villaggio Artigiano)

Transcription

1 Activity report Simulation survey (Villaggio Artigiano) Component: 5 - Pilot testing of the methodology, evaluation and capitalization Corresponding phase: 5.3 Computer simulations and analysis of questionnaires Axe2: Protection of the environment and promotion of a sustainable territorial development Objective 2.2: Promotion and renewable energy and improvement of energy efficiency Authors: Fondazione Democenter Staff Ingegneri Riuniti Spa Minicipality of Modena, Filippo Bonazzi Submission date: 25/05/2015 Status: Final [25/05/2015]

2 1. Purpose of the activity In activity 5.3 the purpose was to provide possible urban refurbishment to contrast the Urban Heat Island effect. The hypothesis planned in Urban Space Audit (D.5.1) have been implemented: Rigging, flower beds, self-locking with green areas, urban design that allows the increase of albedo (i.e. infrared emission). Cold asphalt or cold paving called cool Materials, road surfaces with high values of solar reflection and high infrared emission. The goal of this simulation is to evaluate the benefits arising from cool surfaces and vegetation application in the pilot area (square/parking area) situated in the Villaggio Artigiano in Modena. The aim was to quantify the difference in temperature between two scenarios: 1. the first one corresponding to the current situation 2. the second one corresponding to the hypothetical presence of vegetation and cool pavement and, therefore, to understand and quantify the impact on the Urban Heat Island (UHI). Aerial view of the pilot area in Via Nobili, Villaggio Artigiano (Modena) and possible scenario of refurbishment [Google Maps]

3 2. Methodology followed to conduct the survey To assess the Urban Heat Island on the pilot site, the software ENVI-met was used as basis; then a second simulation on the same perimeter has been implemented with the Modena Model in order to compare the two approaches (see Section 1 and 2 of D. 5.3). ENVI-met is a three-dimensional non-hydrostatic microclimate software developed by Prof. Michael Bruse, University of Mainz (Germany). It is designed to simulate the surface-plant-air interactions in urban European environment thanks to the presence of different submodels which include soil, vegetation and atmosphere databases. It is an open software downloadable directly from the site and, even if since 1th November 2014 it is available version 4, version 3.1 beta 4 was used for this study. The Modena Model is an experimental model created by the city of Modena with the contribution of the Engineering Faculty of the University of Modena and Reggio Emilia, in the framework of the European project "UHI Project". Within the model it was developed an index, called OUTLOAD, which estimates the thermal load generated by all surfaces of a lot (courtyard area, vertical walls and roofs). The urban heat island effect calculation assumes, as a first approximation, that the phenomenon is a function of the fraction of solar radiation absorbed by the constructed surfaces, which results in overheating of the surfaces themselves and the air in contact with them. In other words, it is assumed that radiation reflected off the surfaces into the upper atmosphere, infrared energy radiated into the upper atmosphere, and heat dispersed by transpiration and evaporation in green areas do not contribute to the effect. The parameters are developed on the basis of UNI technical rules (UNI/TS or UNI EN ISO for calculation of building thermal behavior, and UNI for standard athmospheric data). 1 1 Bonazzi F., M. Capucci, A. Muscio, C. Rizzo. "Creation of experimental urban indices in order to estimate the environmental performance of urban/building regenerations". Geographia Polonica (2014) vol. 87, iss. 4/2014, pp , ISSN

4 The pilot area The pilot area a parking area and the surrounding buildings in Villaggio Artigiano - in Modena is 70 m x 100 m, the buildings are 7 8 m height and the presence of vegetation is limited to a few trees and a grass areas. The buildings façades are made of bricks and concrete, while the roofs are covered with bituminous sheats or with brick roof tiles. 100 m 70 m Aerial view of the pilot area in Via Nobili, Villaggio Artigiano (Modena) [Google Maps] According to the Modena s weather web-site (Il clima di Modena. Modena Meteo. [Online] [Riportato: ] it was possible to collect the information about the following parameters: 1) Temperature 2) Relative humidity (%) 3) Wind speed and direction ENVI-met 1st Simulation Current situation The model domain was created on a scale of 1:200 and its grid is 35 (x) x 50 (y) x 10 (z) m. Moreover, it was rotated of 63 not to cut the main white building.

5 3D view of model domain for the 1 st simulation Panoramic aereal view [Bing] As in this area there is not a weather station, the input data required to start the simulation were deducted in different ways: 1) Wind speed in 10 m above the ground [m/s] 2) Wind direction 3) Initial atmospheric temperature 4) Specific Humidity at 2500 m height 5) Relative Humidity at 2 m height Moreover, in ENVI-met model it was possible to specify the following building characteristics: 1) The inside temperature was supposed to be around 20 C, so 293 K. 2) As there are no available data to evaluate the heat transmission of roofs and walls, these data were not changed from the default ones. 3) The walls albedo was chosen to be 0.27 (brown walls). 4) The roof albedo was chosen to be 0.30 (concrete). 2nd Simulation Hypothetical presence of vegetation and cool pavement The difference between the previous one and this new scenario consists in the insertion of some cool asphalt (indicated with the abbreviation cp in red) in the area corresponding to the parking spaces and some 10-m tall trees (indicated with the abbreviation ds in green) (Figure 1 - Figure 2). The cool asphalt material has been defined in the PROFILS.DAT database of ENVI-met, creating a new one characterized by a short-wave albedo of 0.70 and an emissivity of The Configuration file is the same as the first simulation.

6 Modena Model 1st Simulation Current situation The model domain is not rotated, its grid is 116 (x) x 116 (y) x m. The trees 2 have been reduced to a single typical form, with oval in shape, 5 metres tall, with the crown at 4m off the ground and of radius 1.5m. The solar reflectance of surfaces was chosen to be: 0,25 (gardens/trees), 0,1 (asphalt), 0,3 (light colour roof), 0,1 (dark colour roof). 2 file Solar radiation.pdf

7 2nd Simulation Hypothetical presence of vegetation and cool pavement The difference between the previous one and this new scenario consists in the insertion of some cool asphalt (characterized by a solar reflectance of 0,40) and some trees and gardens.

8 3. Major conclusions obtained ENVI-met The main differences in temperature may be seen in the early hours of the afternoon. It is possible to appreciate a mean cooling effect from 1.5 to 2.0 K at pedestrian level (Figure 3-9) depending on the hour considered. This solution lowers the temperature of the whole parking area, but also that of the surrounding buildings surfaces. The cooling effect is tied to the wind intensity and direction. Figure 1: top view corresponding to the 1 st scenario (current situation) Figure 2: top view corresponding to the 2 nd scenario (hypothetical presence of vegetation and cool asphalt)

9 Figure 3: comparison between the 1 st (left) and 2 nd scenario (right) at 13:00, horizontal section made at 1.60 m from ground level (max T = 2.00 C) Figure 4: comparison between the 1 st (left) and 2 nd scenario (right) at 14:00, horizontal section made at 1.60 m from ground level (max T = 2.00 C)

10 Figure 5: comparison between the 1 st (left) and 2 nd scenario (right) at 15:00, horizontal section made at 1.60 m from ground level (max T = 1.60 C) The change in pavement (from a dark asphalt to a ligther one) and the insertion of some 10-m tall trees entail a significant decrease in temperature at pedestrian level during the hotter hours of the afternoon (around 2 C). Even if the areas considered is small, the simulation highlights how a little change in urban practices can positively affect pedestrian comfort. Modena Model To allow comparison with Envi-met model, the thermal Energy absorbed in a July day from all surfaces of each scenario has been calculated. The inclusion of trees on 2 nd scenario reduces the incident solar radiation on parking area surfaces (in figures: incident solar radiation on horizontal surfaces, roofs and areas at pedestrian level).

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12 In the 2nd scenario, thanks to the presence of trees and cool asphalt, the thermal load of the parking area (thermal energy absorbed) appears significantly reduced (in figures: thermal load on horizontal surfaces, roofs and areas at pedestrian level).

13 The average thermal load values of the parking area are 2,67 kwh/m 2 (1 st simulation), 1,99 kwh/m 2 (2 nd simulation, at pedestrian level), 2,38 kwh/m 2 (2 nd simulation, also connsidering trees). Based on an estimate of the average sol-air temperature, the difference between scenarios is about 1.8 C (considering only surfaces at pedestrian level), and about 0,8 C (also considering trees). 4. Cost/Benefit Analysis In order to evaluate the the strengths and weaknesses of the intervention, both its economic sustainability (project and annunal maintenance costs) and the impact of the deriving benefits were assessed. The evaluation was realized a mixed approach quantitative for the costs, qualitative for the benefits. The results of the cost analysis is reported in the following table: Project costs Annual Maintenance Costs 29,775 3,875 As shown in the table reported below, the improvement in human comfort obtained with the intervention is not negligible. Benefits Lowered air temperature Reduced energy use

14 Better air quality and lower greenhouse gas emissions Better water quality and stormwater runoff Increased pavement life Table 1. Qualitative benefits analysis. Low increase Good increase High increase