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This work aims at developing a methodology for the assessment of district heating (DH) potential through the mapping of energy demand and waste heat sources. The presented method is then applied to the Metropolitan City of Milano as a case study in order to investigate the current and, especially, the future sustainability of DH with the foreseen building refurbishment and consequent heat demand reduction. The first step is the identification of the areas the most interesting from a heat density and an economic point of view through a clustering algorithm, in which lies the main novelty of the work. The potential is then assessed by investigating their synergy with the available heat sources, which are mapped and analyzed in terms of recoverable thermal energy and costs. In future scenarios with foreseen heat demand reduction, low-temperature networks and excess heat sources are considered, such as metro stations and datacenters, together with the conventional sources, such as thermoelectric plants. The outcomes prove that lower heat demand corresponds to higher network costs with consequently reduced district heating potential but also prove that the properties of low-temperature district heating can potentially compensate for the drop in its cost-effectiveness. Another interesting finding is that the renovation of buildings in an area should be not performed evenly but with criteria; for instance, in synergy with DH diffusion. © 2021 by the authors. Licensee MDPI, Basel, Switzerland., Funding Agency:Italian district heating association, AIRUItalian association of multiutilities, UTILITALIA, in the framework of the project "Valutazione del potenziale di diffusione del teleriscaldamento efficiente su territorio nazionale"EIT Climate-KIC in the framework of the project "Deep Demonstration: Milan" (DDMI)Project "Analysis on new models for 4GDH in Italy: an innovative tool for the fast integration of RES sources?"

The evaluation of the district heating network investment costs requires the knowledge of its topology. However, when assessing district heating potential, the topology is not known a priori and a simulation is required. One method for modelling future heat networks involves the use of Minimum Spanning Tree, from the graph theory. In this work, the MST is used together with real networks lengths to elaborate an updated equation describing the effective width in correlation with the number of building ratio instead of plot ratio. The reason motivating the use of simulated networks lies in the goal of analysing sparse areas where there’s a general lack of data. In this study, the census cells vertexes and local roads layout are used as inputs for the application of the MST in order to simulate DH network layouts in areas where DH is not present. The method has been validated by running simulations in areas where DH is already present, allowing the comparison of the respective lengths. The validation shows a variable but systematic overestimation of the simulated lengths. The study of the error has brought to the definition of a correlation between accuracy of results and the share of buildings with centralized heating systems suitable for DH connection. The updated version of the effective width confirms the exponential tendency and gives higher results for Italian cities then for Scandinavian ones, showing an important impact of the city structure in the curve. The city of Milano is finally used as a case study to show the effects of using the updated effective width curve.

This work aims at showing the unexploited potential of waste and renewable heat in Italy through detailed mapping of these sources. The ambition is to highlight the areas with an important heat recovery potential that could be exploited through DH expansion. The recoverable heat sources have been analysed in terms of geographical location, and recovery aspects with a special focus on temperature levels and technological implications for temperature upgrades. The methodology presented in this work addresses not only the theoretical potential of waste heat and renewable heat use in DH, but also several technical aspects to get a result as closer as possible to the realistic potential at national level. Two different approaches have been used to map potential heat: one to quantify existing waste heat recovery from industrial processes, waste to energy plants, wastewater treatment plants and one to estimate the energy coming from potential new plants based on biomass, geothermal energy and solar thermal. Results shows that for a total heat demand for the civil sector of 329 TWh, out of which 114 TWh come out being suitable for a DH connection, the national available waste and renewable heat that could be integrated in DH amounts to 156 TWh. These results show the significant unexpressed potential of waste heat use in Italy and how its mapping is essential to properly estimate the utilization potential. This work has been commissioned by AIRU, Italian DH association. Copyright © 2021 Elsevier Ltd., Funding: AIRU the Italian District Heating Association and Utilitalia the Italian association of multiutilities, Valutazione del potenziale di diffusione del teleriscaldamento efficiente su territorio nazionale