Silvia Coccolo

Multi-scale modelling to evaluate building energy consumption at the neighbourhood scale

A new methodology is proposed to couple a meteorological model with a building energy use model. The aim of such a coupling is to improve the boundary conditions of both models with no significant increase in computational time. In the present case, the Canopy Interface Model (CIM) is coupled with CitySim. CitySim provides the geometrical characteristics to CIM, which then calculates a high resolution profile of the meteorological variables. These are in turn used by CitySim to calculate the energy flows in an urban district. We have conducted a series of experiments on the EPFL campus in Lausanne, Switzerland, to show the effectiveness of the coupling strategy. First, measured data from the campus for the year 2015 are used to force CIM and to evaluate its aptitude to reproduce high resolution vertical profiles. Second, we compare the use of local climatic data and data from a meteorological station located outside the urban area, in an evaluation of energy use. In both experiments, we demonstrate the importance of using in building energy software, meteorological variables that account for the urban microclimate. Furthermore, we also show that some building and urban forms are more sensitive to the local environment.

Integration of outdoor human comfort in a building energy simulation database using CityGML Energy Ade

Handling data needed by Building Energy Simulation (BES) tools can be a tedious task, especially at the urban scale. Besides BES, users often have different needs (building energy use, human comfort, integration of renewables, urban planning…) in mind when using simulation tools, but often have access to the same dataset. To simplify and harmonize the process of obtaining a homogeneous dataset, we make use of a PostgreSQL database in the CityGML file format using the Energy Application Domain Extension (ADE), which can be accessed remotely to retrieve data. CityGML with Energy ADE is an open data model with the objective of having a common platform to store and exchange 3D information and energy data between municipalities, professionals and researchers. The structure of the CityGML covers the following modules: geometry, construction, occupancy and energy systems. However, in the CityGML structure an important parameter to describe the city livability is missing: the outdoor human comfort. Considering this, we propose to further develop the database, by adding outdoor human comfort parameters and results. A case study of the Ecole Polytechnique Federale de Lausanne (EPFL) campus will be set-up, stored in the database and simulated with the software CitySim. The resulting human comfort indices will further be sent back to the improved database for an offline analysis with GIS tools. With this new development, the CityGML with Energy ADE can benefit from information on the urban microclimate and its impact on people activities and wellbeing.

Multi-scale modelling to assess human comfort in urban canyons

As the impact of climate change progresses, heat waves are expected to increase significantly in the future. Coupled with the urban heat island effect, this will tend to have a major impact on the comfort of the inhabitants in urban areas. It is thus crucial to adopt the necessary sustainable measures and development scenarios to improve city liveability and human health. The main physical parameters that affect the outdoor human comfort are the air temperature, the relative humidity and the wind speed. Various tools, such as CFD or LES models, have been used in the past to evaluate these variables for the calculation of human comfort indices. These tools however are computationally too expensive and require extensive resources and data. Moreover, in our previous studies on the outdoor human comfort realized with the CitySim software, the meteorological variables were not linked to the urban form, geometry and roughness. To overcome these barriers, the CIM (Canopy Interface Model) was developed to calculate high-resolution vertical profiles of meteorological variables. The CitySim software to perform energy and temperature simulations then used these outputs. In this study, virtual pedestrians were located in two different areas of the EPFL campus, in Lausanne (Switzerland): a natural environment - characterized by clay soil and cherry trees - and an artificial environment, the new asphalt square near the SwissTech Convention Centre. The analysis carried out with the CitySim software compares the outdoor human comfort of pedestrian with the wind data from the traditional Meteonorm dataset, and the new CIM wind simulations. A sensitivity analysis of the results shows the difference between both simulations, quantifying the impact of the new wind model in the calculation of the indices.