on the sensitivity of building performance to the urban heat island effect
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”On the sensitivity of Building Performance to the Urban Heat Island Effect”. By Adil Rasheed, Darren Robinson, Alain Clappier. Overview. Problem statement Model Description Case Study Results Conclusion Future Work. Problem Statement.

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on the sensitivity of building performance to the urban heat island effect

”On the sensitivity of Building Performance to the Urban Heat Island Effect”

By

Adil Rasheed, Darren Robinson, Alain Clappier

overview
Overview
  • Problem statement
  • Model Description
  • Case Study
  • Results
  • Conclusion
  • Future Work
problem statement
Problem Statement

Current practice Reality

Weather Station

Building to be simulated

Urban Heat Island : Cities are warmer than its surrouding

Should UHI be considered while conducting building simulations ?

global model
Global Model

Madrid

Measurement data can be fed to a global model

But resolution of a Global Model is of the order of a few hundred Km

mesoscale model
Mesoscale grid

Grid for global models

Mesoscale Model

(Resolution: few meters to Km)

uhi modelling
Mass:

Mom:.

Energy:

Humidity:

TKE

UHI Modelling
  • Governing Equations:

The effects of building is included in the source terms Di

Input to the model: Boundary Conditions, Landuse and Topology data

urban parameterization
Mesoscale Grid

Urban Grid

Urban Parameterization
  • Highlights:
    • City is assumed to be a regular array of buildings with uniform spacing.
    • Impact of horizontal and vertical walls (drag and shear)
    • Accounts for solar radiation
    • Accounts for building density, urban forms and different landuse.
    • Heat conduction through walls, ceilings and ground.

Source

case study madrid s topology
Case Study: Madrid’s topology
  • Location: 40º 23´N and 3º 40´W
  • Mountain peaks surrounding relatively low lying plains
  • Province of Madrid: 8028 sq. m
  • Temperate Mediterranean climate:
    • Cool winters: Below 273 K.
    • Warm summer: Above 303 K
  • Mild nocturnal average temperature during the summer months due to Madrid's high altitude.

Height above sea level: Varies from 400m-2000m

land distribution rural
Land Distribution: % Rural
  • Largest city of Spain
  • Third most populous city in EU
  • Densely urbanized city center: 100% urban area.
  • City surrounded by rural area.
simulation set up
SIMULATION SET UP
  • Domain size: 110km by 110km by 10km (covers the entire troposphere)
  • Horizontal Resolution: 2km
  • Vertical Resolution: 10m – 1 km .
  • Three simulations: Cases 1, 2 and 3.
    • Case 1: Topology as that of Madrid but 100% rural
    • Cases 2 and 3 correspond to the actual land use, but with different thermo-physical properties for the building surfaces.
  • Building Width: 15m, Street Width: 15m.
  • Internal temperature of the buildings: 298 K.
  • Urban Parameterization scheme by Martilli
  • Radiation model by: Schayes and Sasamori
  • Duration of Simulation: 18:00H 13th July to 18:00 14th July
results temperature velocity profiles
RESULTS: Temperature & Velocity profiles

Case 3

18:00

00:00

06:00

13:00

City core is always hotter (Urban Heat Island)

Entrainment of cooler air towards the center

results cooling load
Cooling Load:
    • C is total building conductance (W.K-1)
    • DDc are the cooling degree-days
    • η Boiler Efficiency

Base Temperature: 291 K

RESULTS: Cooling Load

Linear relation between energy demand and cooling load.

results normalized cdd
RESULTS: Normalized CDD

Case 2 Case 3

  • Cooling load increases by a factor of 1.7
  • Changing the thermophysical properties of the built material
  • can alter the cooling demand
  • Contours of urban area doesn’t coincide with the contours of CDD: because of wind
conclusion
Conclusion
  • Urban Heat Island should be considered during Building Energy Analysis
  • Thermophysical and radiometric properties of the built material may play a very important role in designing an energy efficient city.
  • Development of plume: Can be used for “natural scavenging” of the city
future work
Future Work
  • Validation of the basic assumptions in Urban Parameterization.
  • Development of better Urban Canopy Model for better representation of the buildings and canopies.
  • Inclusion of more sophisticated Building Modules in the Mesoscale Model.
  • Finally to study the effects of changing various thermophysical and radiometric properties.
acknowledgement
Acknowledgement
  • The financial support received for this work from national research programme 54 of the Swiss National Science Foundation is gratefully acknowledged.
  • Many thanks also to Alberto Martilli for providing the data required for the simulation.
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