Intégration de sources énergétiques non conventionnelles : cas de la Ville de Montréal

In 2013, the City of Montreal identified a number of actions to be taken to reduce greenhouse gas emissions, one of which was to replace its buildings' fossil-fuel systems with a cleaner energy source. In this perspective, the idea of heating and cooling buildings with geothermal energy has been suggested. However, conventional geothermal systems (closed and open loop wells) are neither adapted to the particularly dense urban context nor to the hydrogeological parameters of the island of Montreal. It was therefore proposed to identify different nonconventional energy sources suitable to the specific conditions of the Montreal area. Through an extensive literature review, the selected energy sources were: with wastewater heat exchange; with heat exchange in subway lines; with surface water heat exchange; and standing column wells. The main objective of this research was therefore to characterize and quantify the potential of the non-conventional energy sources identified in the City of Montreal's existing building. However, one aspect that is commonly overlooked in the design of geothermal systems is interference between underground structures. In the long term, interference can lead to a loss of durability and efficiency of systems and very few investigations have been done to quantify the risks. In order to optimize the characterization of the potential, it was required to investigate the long-term influence of the operation of the selected technologies. Thus, the specific objectives of this work were to identify and to characterize the potential buildings, to determine the consequences and the risks of thermal and hydraulic interferences of the exploitation of the selected technologies and, finally, to establish guidelines for the realization of pilot projects. Following the literature review on the proposed technologies, the energetic characteristics of the City of Montreal's building inventory were established. Of all the buildings owned by the municipality, 250 buildings use fossil fuels (natural gas, oil, propane, etc.) and would benefit from a conversion to a cleaner energy source. Based on this identification, an extensive digital map was developed. Among other things, the map includes a number of geological, hydrological and hydrogeological parameters, as well as the energy and geographical characteristics of the buildings identified in the City. The development of this map was intended to identify the potential areas and buildings that are most suitable for energy conversion, in order to quantify their conversion capabilities. Of the different systems studied, the results show that standing column wells are the most readily deployed on the island of Montreal. Proximity to the source and the small space required for their installation greatly increase their potential. Wastewater heat recovery systems also have a good potential for integration into buildings. However, surface water and tunnel energy recovery systems demonstrate a lower potential than the other two technologies, due to the large distances between the buildings and their energy source. Once the mapping was completed, a large three-dimensional finite element model was built with the software Comsol Multiphysics in order to simulate the thermal and hydraulic behaviour of the installation of a standing column wells on a municipal building. The purpose of this process was to characterize the interferences between several systems in order to improve the mapping of this technology. The building chosen was the Centre Père-Marquette, located in the Rosemont-la-Petite-Patrie district, which has a strong potential for energy conversion. Four other systems were added at the same time in order to increase the interference on the surrounding area. In total, five geothermal systems, fourteen standing column wells and five injection wells were modeled. Results indicated the viability of all five systems over ten years of simulation with no significant degradation in thermal performance. They also showed that thermal changes were larger and more significant than hydraulic changes. In addition, building-induced alterations were significantly larger than those from geothermal wells. Furthermore, the results showed that interference between the systems is possible, but remains superficial. However, it would be beneficial to position the injection wells as far away from the PCPs as possible. The analysis also confirmed that the operation of PCP systems in an urban context would be viable in the short and long term. Operating smaller systems, such as residential buildings, results in minimal changes to the thermal and hydraulic regimes. However, deployment of larger systems should be done with more care, which involves effective positioning of wells to reduce the risk of interference. In the end, following the conclusions of the numerical analysis showing that the risk of interference between buildings is low, a final cartography displaying the location of the buildings with the highest potential for each of the technologies studied was produced. It should be noted that the regional mapping established in the context of this work should be completed by precision studies at the local scale.