Thermodynamic Analysis on the Performance of a Low-Enthalpy Geothermal Field Using a CO 2 Supercritical Binary Cycle

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The exploitation of geothermal energy can play a significant role for providing clean and renewable energy, especially when environmentally-friendly working fluids are used for power production. Along these lines, in the present work a thorough analysis is attempted on the thermodynamic performance and the power production potential of a binary cycle, using supercritical carbon dioxide (sCO2) as working fluid, for the exploitation of a low-enthalpy geothermal field, located in Sidirokastron, Greece. As regards the associated analysis, simplified thermodynamic models of the sCO2 cycle were developed, attempting to incorporate the binary-cycle main components performance characteristics, based on the literature-available data of similar applications. For further improvement of the thermodynamic cycle performance, the use of preheating of the working fluid after the condenser, with the use of solar power, was also considered. The effect of cycle heat-addition pressure and heat-rejection temperature conditions were assessed through parametric studies, taking into consideration the annual regional variations. Furthermore, the effect of the technology level of the critical cycle components, such as the heat exchangers, on the thermodynamic cycle performance was considered. The results were compared to similar, low-enthalpy configurations described in literature. The aforementioned analysis clearly reveals the effect of cycle-operating conditions on the thermodynamic performance of the binary cycle and the high potential of using sCO2 as working fluid, for the exploitation of low-enthalpy geothermal fields, in the pursue of an environmentally-friendly power production.