Bioclimatic Design of Sustainable Campuses using Advanced Optimisation Methods

Cities occupy 0.5% of the earth surface, but they consume 75% of worldwide energy, and they are responsible of 50% to 80% of CO2 emissions. Cities are directly responsible for the climate change. However, they are the key for providing solutions to this problem. More specifically, a city comprises a very large number of microclimates, according to their urban and environmental design. A sustainable and liveable urban planning could well improve the urban environmental conditions by mitigating the energy fluxes of the city. The objective of this thesis is to address the energy fluxes within the urban environment, in time and space. The study focuses on the improvement of the energy demand of buildings as well as the outdoor human comfort. To do so, we try to establish a new bridge between the biometeorology and the architecture and to find a simplified approach to bring this research into practice. More specifically, the human comfort is well addressed in the research domain but, due to its complexity, it is quite difficult to use it in the real practice. In order to overcome this problem, we introduce three new modules in the software CitySim Pro. CitySim is an urban energy modelling tool which is able to quantify, dynamically, the energy demand from a building scale to the city scale. A first module, developed in this doctoral thesis, focuses on the quantification of the outdoor human comfort by the Index of Thermal Stress (ITS) and the COMFA* budget. The second module aims to understand the radiative environment by the calculation of the Mean Radiant Temperature (MRT). The third module focuses on the cooling potential of the vegetation and evaluates the shadings and the evapotranspiration provided by greenings. Based on the modules, Comfort Maps are designed, representing an important instrument to bring the research into practice: these maps are proposed as an effective way to share information between architects and municipalities, providing indications on the urban microclimatic conditions. Finally, the developed modules are used to optimize, using the hybrid CMA-ES/HDE evolutionary algorithm, the energy demand and the outdoor human comfort of two campuses: EPFL campus in Lausanne (Switzerland), and the Swiss International School (SISD) campus in Dubai (United Arab Emirates). On site monitoring, realized in the SISD campus, underlined the impact of the built environment, as well as the shadowing strategies, by punctual monitoring in five locations of the campus. The results show that i) we should not limit an architectural design to a single building, but it is important to think and design at the district/ city scale. There is ii) a strong relationship between the energy demand of buildings and the outdoor human comfort, consequently both of them should be jointly addressed by architects and urban planners, focusing on the building and the "space between buildings" design. Finally, iii) a sound urban design should derive from the bioclimatology, transforming the climatic adversities into design opportunities. Finally, a list of practical recommendations is defined, providing a support for a sound architectural design in time, and space

CitySim Guide : Urban Energy Modelling

The proposed work is a dynamic guide, particularly designed for students, researchers and planners, to the tool CitySim. CitySim is an urban energy modelling tool, which belongs to the energy simulation software family. Its peculiar feature is to consider the simulation scene as a complex urban environment, where the energy fluxes interact with each other. Currently, several works (peer reviewed journals and conferences articles) were already performed in order to present the main features of the tool, as well as the physical model behind it, but a complete guide, able to fully describe the tool, is currently missed. Due to the rising interest on the urban energy modelling domain, and its enormous potential as political instrument to manage the energy fluxes within the urban environment, the proposed work represents an essential instrument of support for researchers, students and planners. The proposed book, named “CitySim Guide. Urban energy modelling” is a guide to the software CitySim, able to explain, step by step, how to use this software. The guide presents both the software CitySim, as well as the user graphical interface CitySim Pro. This work is subdivided into three main parts: i) an introduction, with the input data and tools required to create the CitySim model, ii) the physical models behind the tool, the graphical user interface, and iii) a real case study in the city of Torino (Italy). In the introduction, all the required input data to create the CitySim model are presented, as well as the software tools that will be used, showing their role and the way they are integrated within the CitySim features. When introducing the tools, the downloading and installation procedure will be also shown. In the second part, the description of core of the tool are explained, from the buildings features (e.g. the physical properties of the envelope, the renewable energy systems, the occupants behaviors, etc.) to the outdoor surfaces properties (e.g. albedo, thermal conductivity, evapotranspiration, etc.). In the end, a detailed description of the results is reported. In the third part, the case study of a district in the city of Turin (Italy) is described from the processing of input data, to the final phase of the results. The last part is quite important in order to understand the tool: the set-up of the model, as well as the results are presented in detail, providing an important instrument to the users, which are able to reproduce the exercise. The proposed work is an important instrument for the teaching activities: it will be used both in the Politecnico of Torino, as well as in the EPFL of Lausanne, as support to the courses in the Bachelor and Master level of Architecture, Civil and Environmental Engineering, Territorial, Urban, Environmental and Landscape Planning, as well as for the Master Thesis and the semester projects. Additionally, as evident from the references provided in the end of the work, CitySim is an important instrument, well used in the academic world. Consequently, the guide has a strong potential to be used worldwide, by researchers in the field of the urban energy modelling

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

The EPFL campus in Lausanne: new energy strategies for 2050

The increase of the urban population and the climate change are issues that scientists and stakeholders are facing nowadays; in this optic a sustainable design should address buildings, and all the physical phenomena that interact with them, from the urban to the district scale. The Swiss Federal Institute of Technology in Lausanne (EPFL) located in Switzerland is now facing this problematic, and its sustainable strategy "Energy Concept 2015-2045" aims to reduce the energy demand per person by 30%, and the CO2 emissions by 50% in 2035. The university campus is growing-the energy reference area has increased by 25% from 2001, and is expected to continue in the next years- and the actual district heating system (two heat pumps with a combined heat and power facility installed in the early 70s) is facing peak power limitations nowadays. Looking for an answer for this issue, a new concept called Energy Hub is sought for the campus: an intelligent unit able to stock and redistribute energy with different carriers. This paper presents the pre-requisite for a potential energy hub on the site of the EPFL campus in Lausanne: the validation of a dynamic heating energy demand model (correlation factor R2=0.89 compared to monitoring) and a BiPV power plant model for the solar electricity produced on the EPFL buildings roofs (correlation factor R2=0.93 compared to monitoring). Finally, two hypothetical refurbishment of the site, according to the Swiss Minergie and Minergie-P labels, are proposed; they reduce the heating demand of buildings by 38% and 44% respectively. Refurbishments are analysed using actual weather data (average data from the last ten years), as well as future scenarios for 2050, showing the impact of climate change on the building thermal behaviour. © 2015 The Authors

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