On the use of heat pipe principle for the exploitation of medium–low temperature geothermal resources

In the direct use of geothermal energy without fluid extraction, heat transfer takes place with no alteration of the natural hydrogeological balance of the basin. An interesting solution both for thermal energy and power production could be the application of heat pipe principle, in particular the Closed Loop Two Phase Thermosyphons (CLTPT). In shallow or not much deep geothermal reservoirs with temperature below 100 °C, the two phase closed loop thermosyphon can transfer heat very efficiently. In this case the most important task is the enhancement of the heat transfer mechanism between the heat exchanger and the aquifer. first part of the paper a review of particular applications connected to the geothermal heat pipe applications is proposed, then an analysis of the main technical elements regarding the geothermal aquifer exploitation through two phase thermosyphon systems are given. Some guidelines for power systems sizing are discussed and a proposal for the design of a single borehole heat extraction system with binary cycle utilization is provided.