Enhanced performance buildings connected to district heating systems: multi-objective optimization analysis

This paper aims to define the energy and economic performance of a district heating (i.e., DH) considering the impact of cost-optimal refurbishment solutions of the connected buildings. The possibility to shift to a lowtemperature DH is considered a feasible solution to reduce thermal losses and hence increasing the network efficiency that is connected with a systematic approach to the refurbishment of the connected buildings. For this purpose, an integrated model has been developed. The energy performance of the coupled DH buildings system has been assessed taking into account different measures for the improvement of the existing buildings considering different refurbishment levels of the building stock, i.e. 30 %, 60 % and 100 % of refurbished buildings. The considered improvements involve building envelope. A multi-objective optimization has been carried out to reduce the energy needs while minimizing the Net Present Value (NPV) for the final user. The minimum distribution temperatures that satisfy the requirements of the buildings are used to compute the network distribution temperature along the year. Finally, NPV, primary energy (EP), distribution efficiency and generation-distribution efficiency are evaluated for the whole DH system to investigate the energy and economic performance. The results highlight how the cost-optimal building refurbishments, from a user perspective, influence NPV, EP, distribution efficiency and generation-distribution efficiency of the whole DH system.