Impact of Exergy Analysis on the Operation Planning of Multi-Energy Systems: Application to an Italian District Energy Network

The integration of multi-energy systems (MESs) for the energy supply of buildings is constantly growing, thanks to the support policies adopted at European level, which recognize in distributed generation a promising alternative to conventional energy supply. The main benefit of MESs lies in the possibility of integrating different energy sources and to exploit the flexibility coming from the interplay of multiple energy carriers. The operational planning of MESs is crucial for achieving these objectives, and the application of exergy analysis based on the balancing of exergy levels between supply and demand, may further increase their sustainability. In this paper, a multi-objective optimization model is proposed to determine the optimal hourly operating strategies of an MES serving a district energy network (DEN) on the Pareto frontier, considering economic and exergetic objectives. The optimization model has been implemented by considering a real DEN in Italy, using experimental data. Results show that under the economic optimization, the DEN operation strategies are sensitive to the variation of energy prices, whereas under the case of exergetic optimization, the users’ electrical load is mainly satisfied by the cogeneration system. Furthermore, it emerges that the economic/exergy performances of the network with optimized operation significantly improve in the range 13-43% as compared to the current operation mode, demonstrating the effectiveness of the proposed optimization model.