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.

A transdisciplinary approach to understand, compute and visualize the city interface

Silvia Coccolo, Jing Gong, André Gabriel Kostro, Dasaraden Mauree, Amarasinghage Tharindu Dasun Perera, Jean-Louis Scartezzini, Andreas Schueler

In order to face the climate change and to improve the sustainability of our cities, architects and urban planners focus on an efficient urban design, improving the energy fluxes within the built environment. But frequently, due to the complexity of the urban metabolism, the impact of the buildings on the urban climatic conditions, as well as on the outdoor thermal and visual conditions is left behind. Indeed, several famous buildings, due to their form and reflectivity, are examples for the uncomfortable conditions created by their facades [1]. The main problem during the design phase, is that, up to now it is quite difficult to compute all the energy fluxes animating the city, and no tool is available to completely support architects and urban planners. In order to overcome this problem, we propose the development of a digital framework [2] to compute and digitalize the urban environmental conditions, and their variation as function of the city interface. In the present work, the city interface is defined as the space in-between the indoor and the outdoor environment, i.e. the building envelopes. The present study focuses on the impact of the city interface on the urban microclimate and the outdoor thermal comfort of pedestrians. An interdisciplinary approach (architecture, bioclimatology, engineering and physics) trying to fill a gap of knowledge within the urban simulations and design will be applied. Firstly, we modelled three urban canyons (East-West and North-South oriented) with a height-width ratio included between 0.5 to 3. Then, with the urban energy tool CitySim, we computed the outdoor thermal comfort perceived by the pedestrians, by the means of the comfort energy model COMFA* budget. In order to understand the impact of the buildings envelope with an advanced glazing system [3], the glazing percentage and glazing interface properties (e.g. the specular and diffuse reflectivity from glazing to the outdoor environment) are varied. The effect of the city interface on the urban microclimatic conditions (outdoor air temperature and wind speed) is investigated by the simulation. The results underline the importance of the city interface on the thermal comfort of pedestrians, being highly responsible, as function of the canyon geometry, the glazing properties and the climatic conditions, for the discomfortable hours during the daytime. Finally, thanks to the proposed methodology, all the energy fluxes affecting the pedestrian’s thermal sensation are quantified (short and longwave radiation, evaporation, convection and metabolic activity) and visualized. A future development of this study is presented, focusing on the computation of the city interface on the energy demands of buildings and on the energy systems optimization.

2018

Modeling the effects of future urban planning scenarios on the Urban Heat Island in a complex region

Sylvain Labedens, Dasaraden Mauree, Jean-Louis Scartezzini

Because of the global warming, urban planning strategies must be investigated to reduce the building energy consumption and increase the thermal comfort in cities. In the framework of Energy Strategy 2050 of Switzerland, this research aim to highlight the impact of future climate change on urban planning and proposes strategies to help urban planners and policymakers face this new challenge particularly in a future where heat waves are going to become common at mid-latitudes. However, to do so in the best possible way, the models currently used have to be robust enough in complex regions (with lakes and mountains) to evaluate future planning scenarios. First, this study proposes a methodology to cluster buildings in urban areas and use it in a mesoscale numerical weather prediction system to evaluate the urban heat island and its impact on the energy demand for cooling at the city scale. Second, this research proposes urban planning strategies to reduce building energy consumption due to the urban heat island phenomenon in the city of Lausanne. The model has been validated with six different weather stations. It emphasizes the presence of the urban heat island in the Lemanic region which lead to the increase of air temperatures in Geneva and Lausanne by 2°C during the day and by up 4°C during the night compared to the surrounding areas. The presence of multiple cities around the lake lead to the creation of the urban heat archipelago. We demonstrate with these simulations that the performance of the WRF model is very heterogeneous in this complex setting. In the evaluation of the future urban densification scenario, we noted that there will be an increase in temperature caused by the UHI phenomenon by up 0.6°C. The increase of albedo of roofs and walls and the use of greenings are good mitigation solutions, with a most significant impact for the albedo. In addition to the climatic impact, the model highlights that the densification scenario has a significant impact on the peak cooling demand.

2018

A review of assessment methods for the urban environment and its energy sustainability to guarantee climate adaptation of future cities

Silvia Coccolo, Dasaraden Mauree, Vahid Moussavi Nik, Emanuele Naboni, Amarasinghage Tharindu Dasun Perera, Jean-Louis Scartezzini

The current climate change is calling for a drastic reduction of energy demand as well as of greenhouse gases. Besides this, cities also need to adapt to face the challenges related to climate change. Cities, with their complex urban texture and fabric, can be represented as a diverse ecosystem that does not have a clear and defined boundary. Multiple software tools that have been developed, in recent years, for assessment of urban climate, building energy demand, the outdoor thermal comfort and the energy systems. In this review, we, however, noted that these tools often address only one or two of these urban planning aspects. There is nonetheless an intricate link between them. For instance, the outdoor comfort assessment has shown that there is a strong link between biometeorology and architecture and urban climate. Additionally, to address the challenges of the energy transition, there will be a convergence of the energy needs in the future with an energy nexus regrouping the energy demand of urban areas. It is also highlighted that the uncertainty related to future climatic data makes urban adaptation and mitigation strategies complex to implement and to design given the lack of a comprehensive framework. We thus conclude by suggesting the need for a holistic interface to take into account this multi-dimensional problem. With the help of such a platform, a positive loop in urban design can be initiated leading to the development of low carbon cities and/or with the use of blue and green infrastructure to have a positive impact on the mitigation and adaptation strategies.

PERGAMON-ELSEVIER SCIENCE LTD2019

A transdisciplinary approach to understand, compute and visualize the city interface

Silvia Coccolo, Jing Gong, André Gabriel Kostro, Dasaraden Mauree, Amarasinghage Tharindu Dasun Perera, Jean-Louis Scartezzini, Andreas Schueler

2018

Modeling the effects of future urban planning scenarios on the Urban Heat Island in a complex region

Sylvain Labedens, Dasaraden Mauree, Jean-Louis Scartezzini

2018