Low-carbon local energy system models: technical and economic fundamentals, institutional conditions for implementation and consequences for lifestyles.

Summary The development of the district as a scale of a more sustainable urban development is part of a period of awareness related to climate change for which the European Union has set up an energy transition policy. Currently, eco-districts are structured around two key points at the energy level: energy efficiency and energy supply. Energy efficiency, which encompasses the energy performance of buildings and the control of energy demand, is the spearhead of existing local energy transition policies. In contrast, low-carbon energy supply does not yet seem to have reached sufficient maturity to be fully realized at the neighborhood scale. Nevertheless, the analysis of eco-neighborhood projects shows a growing interest in creating a low-carbon energy supply using local resources. This interest reflects, in particular, the desire of certain local actors to achieve a certain degree of energy autonomy. In order to consider the neighborhood as a relevant scale for low-carbon energy supply, it is necessary to analyze the technical-economic and institutional conditions to be implemented. It reveals the need for a paradigm shift in the structuring of energy systems from centralized to decentralized systems. However, this new paradigm is conditioned by the technical and economic maturity of the infrastructures that can be installed in the district and by the ability to find a viable business model that will make the investment profitable at this scale. From an institutional point of view, it causes a modification of the relations between the actors using the energy vectors studied (electricity and heat). The rise of new production profiles with the development of renewable energies and the emergence of new consumer profiles becoming producers modifies the energy value chain and obliges to guarantee the flexibility of energy systems to ensure their proper functioning. To try to shed light on the possible forms that these relationships could take, a methodological approach based on the construction of ideal-types has been carried out. It reveals the need for a new actor, the energy manager, to guarantee the proper functioning of the energy systems installed in the districts.