Thermo-economic evaluation and optimization of a regenerative orc cycle utilizing geothermal energy

Thermo-Economic analysis was applied for the Regenerative Organic Rankine Cycle utilizing geothermal fluid as a heat source. The considered cycle works with n-Pentane (R601) as a working fluid and uses geofluid at temperature and mass flow rate of 165° C and 100 kg/s, respectively. In order to optimize the cycle in terms of thermodynamics and economics, the important operation parameters such as evaporator pressure, condenser temperature, mass flow rate of geofluid and also pinch point temperature difference were considered. Moreover, the optimum values of parameters were calculated to maximize the thermodynamic efficiencies and minimize the production cost. The optimization process was carried out by direct method in EES (Engineering Equation Solver) to determine the optimum values of mentioned parameters as restriction criteria. The results showed that the cycle gives the highest energy and exergy efficiency of 19.93% and 60.98%, respectively. While the maximum energy output of 3,860 kW was obtained from optimized cycles based on economic considerations. Also, the maximum and minimum cost rate of 28.4 $/GJ and 25.1 $/GJ was estimated for the optimized cycle based on energy efficiency and economic, respectively.