The need for more efficient and less pollutant energy systems can be satisfied only through the deployment of proper optimization tools, capable to improve environmental, economic, and social sustainability. In this master thesis are illustrated some procedures aimed at including new functionalities to an optimization tool. XEMS13, the tool under consideration, can be used to optimize the operation of polygeneration systems. In this case, it is able to optimize the production of thermal and electrical energy of a group of selected components, to satisfy the energy demands of a district heating network. The work is divided into two main topics. The first part regards the analysis of the input data of XEMS13.