Energy Analysis of a Small Geothermal District Heating System in Southern Italy

Small and medium size district heating networks have seen some spread over the last two decades, especially in cities which are not supplied by natural gas grids. In this paper, the authors investigate the energetic feasibility of a small district heating network feeding two schools in a city of Southern Italy (Mondragone). In particular, the district heating is powered by a low-temperature geothermal fluid pumped from a well located 2.1 km away from the city center. Geothermal fluid has a temperature of 34 degrees C and a flow rate of 6 l/s. The buildings have been rehabilitated by an energy point of view and are equipped of low-temperature fan-coils in order to ensure their compatibility with the 4th generation district heating system. Energy analysis were conducted through the implementation of transient simulation model in TRNSYS environment. The feasibility of two configurations of the system is compared: the first, with one heat pump installed nearby the geothermal well feeding the grid, and the second one with the heat pumps installed in each building substation. Transient simulations results show that the first configuration is energetically less efficient than the second one due to the high thermal losses (55% of the total consumption) of the district supply pipes.