This study concerns a thermodynamic analysis of Organic Rankine Cycles for energy conversion from geothermal resources. A
numerical flow-chart tool based on a lumped parameters approach is adopted to compute values of thermodynamic variables
during each transformation composing the cycle. The equation of state is expressed by the Peng-Robinson formulation. The
different plant components are outlined by single blocks, linked each other by connections through balance equations. Analyses
are carried-out considering two working fluids (isopentane and isobutane). Results are obtained for several sets of operating
parameters, such as the evaporation and condensation pressure for the working fluid, the mass flow rate of the geothermal fluid
and the cooling water temperature. From results, thermodynamic cycles are built-up in the T-s plan, allowing to quantify
effectiveness and energy benefit related to the investigated functional scenarios.