Energetic Investigation of Organic Rankine Cycles (ORCs) for the Exploitation of Low-Temperature Geothermal Sources – A possible application in Slovakia

The paper aims at analysing the energetic performances of Organic Rankine Cycles (ORCs) for the exploitation of low temperature heat sources. Specifically, the attention has been focused on low-enthalpy geothermal energy for small-scale applications. To this purpose a thermodynamic model has been developed and a parametric investigation has been performed considering different organic fluids (isobutane, isopentane, and R245ca). Saturated conditions at the expander inlet have been adopted and the effect of the internal regenerator on the system performances has been evaluated. The investigation highlights the large impact of the evaporation temperature on the ORC behaviour and the positive influence of the internal regenerator at the highest temperatures. Conversely, the effect of the internal heat exchanger reduces when the evaporation temperature decreases. Furthermore, a possible application in the Kosice Basin (Slovakia) has been analysed. The investigation demonstrates that the organic Rankine cycle represents an interesting option for efficient valorisation of low-enthalpy geothermal resources and electricity production in small-scale applications.