Sizing of Thermal Storage Under the Eco-Exergetic Operation Optimization for District Energy Networks: Application to a Real Case Study in Italy

District energy networks (DENs) are recognized crucial to contribute to the carbon neutrality target by 2050, thanks to the possibility to integrate renewables at the local level in the heating and cooling sector beyond the electricity one. Thermal energy storage (TES) allows DENs to be more flexible by managing the temporal gap between supply and demand. The identification of the TES size in a DEN is challenging, depending on several variables as energy loads and prices, the coupling of energy processes within the DEN, and the different economic or sustainability priorities. The contribution of this paper is to present an optimization model for sizing TES under the eco-exergetic operation optimization of DENs. The model is based on mixed-integer linear programming and aims to determine the optimal operation strategies of the DEN and the optimal TES capacity with the goal to maximize the economic/exergetic performance of the network. As case study, a real DEN located in Torino is considered. From the comparison with the results obtained with the current case in the absence of the TES, it emerges that the optimization tool brings valuable economic and exergetic benefits to the DEN, thanks to the identification of the optimal TES capacity.