53: Planning for a sustainable city
Professor Manuela Sechilariu, has been director of the UTC Avenues research unit since 2016. She is also Deputy Director of SEEDS, a CNRS research group (GDR) since 2018 and the initiator and leader until 2018, within SEEDS, of the Micro-networks Working Group (MnWG) at the national level in France.
“We focus our research on urban systems and, more specifically, multi-scale modelling of urban systems. That is to say, starting from the building, continuing through the neighbourhood, then the city and finally the surronding territory. The whole being in interaction with the human residents who occupy a central place”, explains Manuela Sechilariu.
A particularity that sheds light on Avenue’s work, combining engineering sciences with those of the human and social sciences, carried out by the research team. In short, a systemic integration of the various disciplinary approaches whose object of study is the urban system. What is the key objective? “To study upstream urban systems, considered as complex dynamic systems which form a system of systems given the multitude of subsystems generated. We are mainly interested in the urban dynamics generated by the diversity of the systems involved and the interaction between these systems and human actors”, she stresses. Hence the importance given to multi-scale modelling within Avenues around five themes.
“These themes — micro networks, transport, hydrological risk, digital models or urban planning and policies, for example — are by no means a catalogue of subjects. Our research focuses on the interrelationship of each theme with the others and the precise links between them, both at the level of of a given building, district, town or territory. They also deal with their interaction with contemporary societal tensions, such as the energy transition, the environmental transition, the digital transition and finally the urban transition”, she says.
Skills that are recognised at national, European and international level. As proof? The projects underway at the national level. “For example, I could mention Mobel_City, which we won in 2017 following a call for projects financed by ADEME and for which we are the coordinators. It concerns the implementation of smart micro-grids and urban implementation for electric mobility in cities. A project that illustrates both the skills accumulated within the unit and the interdisciplinarity that reigns there, since it is at the crossroads of the fields of transport — electric mobility, renewable energies, urban planning and sustainable territory. We are supported by an industrial partner, SYSTRA, who specialise in transport issues on a national scale, but also in the Compiègne Agglomeration (ARC)”, Manuela Sechilariu explains. But also international projects such as COST, a European project, and, most recently, the PVPS-T17¹ project initiated by the International Energy Agency (IEA) on the possible contributions of photovoltaic technologies to transport.
“COST, where UTC-Avenues is vice-president through its Chair of Intelligent Mobility and Territorial Dynamics, is a European project that aims to study the impact of future autonomous and connected vehicles on urban and peri-urban mobility. Within the framework of the PVPS programme, we are coordinators, at the national level, of the PV2E_Mobility project, which represents the French contribution to “task 17”, while at the international level, we are responsible for “sub-task 2”. PV2E_Mobility, a 4‑year project funded by ADEME, focuses on the use of photovoltaic energy in transport. This may concern both on-board photovoltaic sources in vehicles and stationary photovoltaic sources for recharging vehicles. Here again, we have industrial partners such as Enedis, Tecsol, SAP Lab, Polymage and the CEA. Subtask 2″, which we coordinate, concerns stationary photovoltaic sources for recharging electric vehicles with partners such as China, Japan, South Korea, Australia, the Netherlands, Spain, Austria, Germany, etc.”
1 Photovoltaic Power Systems Programme
Geographer by training Nathalie Molines added two strings to her bow during two post-docs: the first at the Faculty of Forestry — Québec on “the contribution of geomatics and cartographic tools in decision support for the concerted management of forest heritage”, the second at the Nantes School of Architecture on “The contribution of spatial analysis tools for the co-building of sustainable neighbourhoods”. So, what is her interest in the issue of sustainable cities? “This notion comes from the theories of sustainable development put forward in the Brundtland report¹, published in 1987. It states, among other things, that “sustainable development is a mode of development that meets the needs of present generations without compromising the ability of future generations to meet their own needs”. A mode of development that is based on three pillars. The economic pillar, the environmental pillar and finally the social pillar. “This applies perfectly to the concept of the sustainable city in the sense that it is a question of finding the right balance between the economic, environmental and social aspects attached to an urban territory. But this balance is difficult to achieve and territorial decision support provides decision-makers with the elements to make informed choices,” she explains.
Her main areas of research? “The first concerns the issues of regulatory urban planning and sustainable cities. The second concerns the impacts of climate change and the third, the issues related to the energy transition of the territories. The three are interlinked,” she says. The first concerns the development of models to evaluate, upstream, the effectiveness of a local urban development plan (PLU), a strategic document defining orientations on the evolution cities over the next 10 to 15 years. A research theme that leads, among other things, to practical applications. “For example, in the framework of a Cifre thesis with the Toulouse Urban Area that I supervised at the UTC, we started from three main themes: urban density, amenities or level of services offered on the territory and the aeration of plots. From there, we reviewed the regulations, in short what was authorised or not, in order to see if the project responded to the issues defined upstream by the politicians “, assures Nathalie Molines.
A research axis that also translates into academic partnerships. “I work with the Water and Environment Laboratory of the Gustave- Eiffel University, which is a specialist unit in the hydrological modelling of rainwater. The aim is to combine our two areas of expertise in order to verify the extent to which urban planning documents make it possible to imagine cities capable of limiting the impacts of climate change, in particular rainwater management by facilitating groundwater infiltration and reducing the risk of flooding. A thesis, co-directed by our two laboratories and devoted to urban climate, in particular the limitation of “hot spots” and rainwater infiltration, will be launched next autumn,” she points out.
Are there projects on the impacts of climate change? “A first project with the Water and Environment laboratory focused on the prospective analysis, with a 20/30 year horizon, of how land use in the Lyon region, including urban sprawl, and how climate change might impact the territories. We worked on different scenarios integrating both land use and climate change hypotheses. Very recently, we submitted a project, as part of the State-Region plan contracts, which deals with the impacts of environmental changes on air and water quality as well as on health and biodiversity in the region Hauts-de-France,” she explains.
The last axis relates to energy transition of the territories. “Using a spatial approach, I am working both on electric mobility and on the energy efficiency of buildings. If we take, for example, the optimisation of the installation of recharging stations, this presupposes a detailed knowledge of uses and attractor, high density zones. In other words, commercial areas, work areas or even living areas. Another aspect concerns the energy of buildings,” concludes Nathalie Molines.
Justin Emery — a geographe by trainingsees himself as an “urban quantitative geographer”. His PhD thesis was awarded in 2016 are the University of Bourgogne. The theme of the PhD? “I developed a simulation model for urban road traffic to better measure automotive air pollution. A model based on data, in particular road counts at given spot,” he explains.
Since then, he has been particularly interested in urban geography and the problems of transport and mobility, integrating a quantitative approach. “These are all the methods that make it possible to measure the relationship between human actors and the environment to the urban space in a “normative” way. This requires the use of data. In the case of my thesis, for example, they were derived from road counts. In my current work, I sometimes use surveys; other times I use spatial data. For data analysis, I rely in particular on geo-computation, i.e., the use of digital tools in the representation of space such as geographic information systems (GIS) or multi-agent systems (MAS) or data processing tools,” he adds.
His research focuses therefore on the transport/ environment duo. “I started with the theoretical frameworks of complex systems via multi-agent simulation. They have also been used, for the last ten years or so, in social sciences, where social systems are analysed as complex systems,” explains Justin Emery.
What is meant by a complex system? “By analogy, the city functions de facto like an anthill. If you look at it, you realise that an ant on its own is not significant, but that all the ants together form a complex system, the anthill colony. The city is made up of interacting individuals who move around, who move between different amenities (home and work) and thus form an urban system. It is therefore a question of including the city in its spatial dynamics, which means that the issue of transport and mobility must be taken into account”, he stresses.
One major axis of his research? “I am trying to deepen the theoretical framework of complex systems for the study and visualisation of spatial dynamics, particularly in the field of transport and road traffic. This framework is fundamentally interdisciplinary, since it is a question of articulating the different scales of the city, running individuals to buildings and infrastructures and up to the city. In short, it is a multi-scalar vision,” he says.
A theoretical framework that allows Justin Emery to test practical applications. “Using modelling approaches, it is a question of testing operational capacities and seeing how they can help decisionmaking on the scale of an urban space. In addition to this, all the approaches of territory surveys are being tested. The aim is to gain a better understanding of transport demand, then how transport functions and finally the factors that influence transport demand, such as the need to travel to work, for example. It is also about better understanding how these factors influence demand, how the territory functions. Especially since we know that a territory functions through mobility and transport. However, there is often a lack of “normative” data. Specific tools must therefore be put in place and ad hoc surveys must be developed to better understand how people move around. These surveys will enable the construction of evaluation tools adapted to transport systems and the movements of inhabitants. We are thus moving from a classic logic of “first we build an infrastructure and then we see if people use it” to a logic of “how to make mobility as fluid as possible and adapt transport to mobility”, he says.
It also applies this approach to the city/climate problem. “Having worked with climatologists during my doctorate, I had to use geographical information systems, tools that enabled me to identify the link between urban layout, urban planning and their impact on the environment. This is, for example, the case of the study of the urban heat island (hot-spots), or how urban form impacts heat in the city”, he concludes.
What exactly is a micro-network? “An electric micro-grid is made up of a set of energy sources, both renewable and traditional sources for the local supply of loads, such as buildings or electric vehicles. Thus, concerning renewables, this raises the question of the intermittent nature of this form of energy and therefore its storage and/or connection to the public grid,” she explains.
What is the key idea in micro-networks? “It is a question, through micro-grids, of integrating renewable energies as best possible, as quickly as possible and on a massive scale with the help of local regulation in order to relieve the network from its regulation at the national level and to maintain the balance between production and consumption”, she emphasises.
How do smart-grids or smart grids work? “Let’s take the French national electricity grid, for example. If we superimpose on this network communication means and message transmission that allow us to manage, in real time, the balance between production and consumption, then we can speak of a “smartgrid”. The information exchanged in real time between the producer and the consumer on the one hand and the consumer, who can also be a “conso-actor”, i.e., an energy producer, and the producer on the other hand, helps to optimise energy management for network operators of the transmission grid and also at local distribution network level », details Manuela Sechilariu. What are the objectives of these micronetworks? “Firstly, we seek to optimise the use of the various sources, including storage, and secondly, to be able to supply loads — buildings and vehicles, for example — as efficiently as possible. All this at the lowest possible energy cost. This implies being able to increase the share of renewables consumed while minimising the negative impact on the national grid. These objectives are achieved thanks to algorithms that allow consumption optimisation by taking into account production and consumption forecasts at time t. Algorithms capable of analysing data from the smart grid, data from the various players and finally metadata such as weather data, for example,” she says.
Several hurdles still need to be passed. “The first concerns the control of uncertainties that relate to the control of production, for example, since renewable sources are, by nature, dependent on the weather, or those surrounding the level of consumption. The second, technological hurdle, relates to communicating interfaces at various scales, since an intelligent network integrated into a building must necessarily communicate with the public network but also, in the case of an electric vehicle recharging installation, with the drivers in order to optimise the operation of the electric power supply station. Finally, the last point concerns social acceptability. This is a primordial condition to be able to develop services that are subsequently used by users”, explains Manuela Sechilariu.
Micro-networks which, as we can see, interact strongly with the theme of mobility, but also with the theme of regulatory relevance and urban policy. “The installation of photovoltaic sources such as micro-grids or storage must therefore be consistent with the planning of a district, a city or a territory. We are dealing with issues that concern buildings and territory with positive energy bills”, she specifies.
What are hydrological risks? “These are all the natural risks related to water. These are, for example, floods, torrential rain, rising water tables or avalanches. I am mainly interested in modelling floods due to rain, rising rivers or rising sea levels. This requires knowledge of the functioning of the water cycle in order to model it, but also knowledge of statistics and probabilities. In fact, as soon as we are interested in the risk, we have to integrate the probability that this risk will or will not occur,” she explains.
Her specific research field? “I’m very interested in the urban environment, because that’s where the vulnerability of a territory lies. In the past, urban planning was essentially based on aesthetic and functional criteria. Today, we are trying to integrate environmental criteria into urban planning upstream, for example: taking into account the flood risk and the means of “minimising” it,” she stresses.
Among the tools used? “Modelling enables a hydrological phenomenon to be understood and simulated using mathematical equations. In the case of flood risks, for example, it is based on historical rainfall and flow rate data. This allows us to create hydro-meteorological scenarios and to see the impact of each scenario on the territory concerned. It also allows us to make long-term projections. Finally, flood modelling enables us to understand how the territory functions in relation to this risk and to build solutions to protect. Thus, if we take a disaster scenario, in hydrometeorological terms, we will be able, among other things, to analyse its impact on the road network or evaluate optimal routes for the delivery of relief supplies… In short, it’s a question of preventing the risk in order to better manage it,” explains Nassima Voyneau.
An example of recent research work? “A thesis, presented in December 2019, which I cosupervised with Philippe Sergent du Cerema. It deals with the modelling of flood risk in the city of Le Havre. With one particularity: it involved modelling floods generated by the conjunction of two phenomena. Namely the rise in sea level combined with heavy rainfall. The uncertainties linked to climate change have also been taken into account,” she explains.
Some concrete projects? “As part of the Sao Polo project, carried out in partnership with other laboratories (CETMEF, EDF, University of Le Havre, etc.), we have worked in particular on the adaptation of coastal cities, including Bordeaux, Le Havre and Saint-Malo, to flooding. The questions at stake are: should this adaptation be carried out by raising the existing dikes or by removing houses from the shore line, for example? Of course, as each city has its own characteristics, the scenarios created are different and the solutions proposed are differentiated. We have also worked on a CIFRE thesis with the RATP, on the modelling of the risk of seeing the Paris Métro network flooded, as happened in 1910. It was necessary to identify the areas impacted, the stations and lines that would need to be to be closed, etc.”, she explains.
It is clear that the theme of flooding is strongly connected with the theme of urban development. “We know that urbanisation will impact the water cycle by reducing the infiltration capacity of the soil by “bitumising” it. This creates abundant surface runoff and favours flooding. Today, both planners and public authorities prefer to integrate the risk upstream, as early as the design phase of an urban development project, so as to propose developments that do not modify the water cycle. This is known as ‘managing rainfall at source’. Thus, we see the appearance of some engineering offices that do not propose solutions to fight against floods but urban developments that integrate infiltration zones. These offer two advantages: they feed the water table while reducing surface runoff, which often causes flooding,” she concludes
