Among renewable resources, geothermal energy is one of the most promising for its independence on weather conditions. However, design and installation of borehole heat exchangers on low enthalpy regions must consider numerous influencing factors. Here, we focus on the efficiency improvement in hot water production and heating and cooling of buildings of a pilot geothermal plant, which was implemented as part of a hybrid system within the frame of a research project at the University of Camerino (Italy). The aims of the geothermal plant were to study the subsoil thermal properties and monitoring the parameters of the system during operation. As an important application for the design and sizing of low enthalpy geothermal systems, we propose a mathematical model to study the heat transfer between the fluid circulating in the pipes and the underground, where the mutual influence between the soil and the exchanger is considered. We present results of these approximated solutions based on experimental measurements acquired in the actual geothermal exchangers. Laboratory and in situ tests were also carried out to investigate the underground thermal properties and thermal regime of the heterogeneous soil sedimentary succession.
borehole heat exchanger, geothermal energy, heat transfer modeling, thermal conductivity
This work has benefited from the contribution of Unicam FAR 2014-15, PI Invernizzi. The authors are particularly grateful to Stefano Calabrò for suggestions, assistance and scientific contribution to the MATREND project, and to Sara Ciattoni for re-processing of data within her bachelor thesis project.
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