Combining the exergy and energy analysis for the assessment of district heating powered by renewable sources

During the last few years, European Union has supported many energy projects to enhance the role of renewables in the European Countries, in order to reduce the energy consumption and CO2 emissions of the residential sectors. In this context, the implementation of the cogeneration plant and district heating seems to be a good solution, especially thanks to the possibility of coupling those systems with renewable sources. In literature, the development of a district heating supplied by Renewable Energy Sources (RES) was investigated by several researches. However, traditional energy indices, normally used for assessing the performance of the systems are not suitable for the efficiency evaluation of generation system powered by RES. The aim of this work is to combine the energy index with an exergy index, for assessing the performance of a District Heating network, modeled with Matlab Simulink. The proposed models simulate the behavior of a microgrid connected to residential, commercial and office buildings. Those simulations have been developed for three Italian cities, located in three different climatic zones (Milan, Rome, and Palermo). The results showed the positive impact of the exergy index for the assessment of a real district heating powered by RES.