Synergies between buildings retrofit and district heating. The role of DH in a decarbonized scenario for the city of Milano

The goal of this work is to present challenges and opportunities for the development of 4th generation district heating in future decarbonized scenarios for the Italian city of Milano. The work has been developed in the framework of a Climate-KIC project to support Milano municipality in developing decarbonization measures. The first part of the work consists in the evaluation of a geographical distribution of the civil sector heat demand according to a bottom-up approach based on open data. Thanks to this statistical tool, also buildings retrofit can be analysed. Three retrofit scenarios are simulated according to policy goals for 2030 and 2050, foreseeing a retrofit priority of worst energy performances buildings, resulting in 8.8TWh, for the first two scenarios, and 9.4TWh for the last one. The areas characterized by the majority of retrofit can be identified as the most suitable for low temperature district heating development. Renewables and low temperature waste heat sources are also assessed, resulting in 9.8TWh of available heat. The application of district heating in combination with the identified renewables is assessed in these scenarios with a clustering approach. The evaluation of potential diffusion of 4GDH is based on the comparison between the overall cost of district heating and the competing individual systems costs: district heating is considered feasible only in retrofitted buildings where district heating cost is lower than individual systems cost (about 0.7TWh in each scenarios). The retrofitting scenarios combined with the diffusion of renewable based 4GDH are assessed also in terms of environmental impact. The current greenhouse gas emissions related to the actual heating systems, evaluated through the Thermal Systems Regional Cadastre database, is compared to the district heating development scenarios and to individual heat pump system scenarios. The results show the highest reduction of emission in the district heating scenarios (65%).