PERFORMANCE ASSESSMENT OF SMART DISTRICT HEATING NETWORKS: THE INFLUENCE OF DISTRIBUTED (CO)GENERATION ON THE NETWORK PRIMARY ENERGY CONSUMPTION

The European and US strategies - providing for energy efficiency increase, pollutant emissions reduction and fossil fuel consumption reduction - leads to an increasing attention on the concept of complex energy networks and/or smart cities. In this scenario, an innovative approach in the heat sector is the integration between District Heating Networks and distributed generation systems, such as solar thermal panels or micro-combined heat and power generators. This approach allows to realize a bidirectional thermal energy exchange at the final users and, consequently, the development of the so-called Smart District Heating in which one or more of the thermal users are converted into prosumers. The aim of this paper is - starting from the thermo-hydraulic analysis of an existing network located in the North of Italy which is set as case study - the evaluation of the influence on the network energy performance of the thermal prosumers location and distributed generation system typology, in order to optimize the network smart transformation and operation. Based on the optimization analysis, two smart configurations are proposed (respectively considering the transformation of one and two traditional users into smart ones) and analyzed for a whole year of operation. The analysis allowed to appropriately design the distributed cogeneration systems and to quantify the annual obtainable reduction in the electrical consumption for the pumping station, network thermal losses and primary energy consumption. The results show that the conversion of a traditional District Heating Network into a smart one with Combined Heat and Power generators allows an increase in efficiency and goes towards the rational use of fossil fuels, increasing the fuel utilization factor of the whole system. This study also shows how the choice of the optimal smart users should be developed with reference to the introduction of two bidirectional substations in the same network.