SIMULATION OF A DISTRICT HEATING CASE STUDY IN AALBORG

District heating and cooling (DHC) networks play a fundamental role in the transition towards a sustainable supply of heating and cooling, due to their ability to integrate any available source of thermal energy and to distribute it to the buildings. The possibility of recovering waste and renewable heat in urban areas has made district heating networks one of the key infrastructures for decarbonising the heating sector in Europe. An example of such systems is presented in this paper: part of a network located in Aalborg (Denmark), that mainly recovers waste heat from a cement factory has been analysed with the simulation tool NeMo, a steady state hydraulic and transient thermal model, developed by the University of Padua, which predicts the behaviour of district heating networks. Before tackling the simulation of this real case, the accuracy of the tool has been examined by means of an ideal simplified case study consisting of three pre-insulated single pipes, comparing the results with a MATLAB-based theoretical solution, and with another simulation tool developed by Eurac Research, highlighting the differences among them. The analysis of the Aalborg network has then been carried out based on load estimated through the EUReCA tool. Thermal losses and return temperature have been assessed. Moreover, a clustering work has been completed for the considered network, composed of 158 nodes and 157 branches, reducing the number of elements by about 15%. This cut contributes to reduce the computational effort of such models, in order to decrease the simulation time, as in this case, from 27 to 20 minutes. The clustering method used in this work is based on the Danish Method, taken from the literature, which allows to conserve the same features of the original network such as thermal power, mass flow rate, water volume and heat losses, without conserving the length of the pipes in the equivalent one, by using two steps, implemented in MATLAB as functions. This work will contribute to part of the project LIFE4HeatRecovery, contract nr. LIFE17_CCM/IT/000085, a European project funded by the LIFE Programme and focused on low-temperature waste heat recovery in district heating and cooling networks.