A Comprehensive Thermodynamic Evaluation of a Geothermal Power Plant Coupled with Organic Rankine Cycles at Full and Part Loads

A geothermal power plant coupled with a two-stage organic Rankine cycle has been studied using energy and exergy analysis. For the first time, the refrigeration load needed to provide the coolant for the condensers of the Rankine cycles has been considered for analysis. Also, for the first time, a part load performance study has been carried out. It has been found that the refrigeration load of the condensers’ coolant has a significant influence on the net power produced as the coolant is required at very low temperatures. The coolant refrigeration load caused a drop of 6.2% points of energy efficiency and 11.9% points of exergy efficiency. At part load (80%), the energy and exergy efficiencies have dropped by 3% points and 2% points, respectively. From the present study, it could be concluded that it is prudent to consider the coolant load for a realistic performance analysis based both on energy and exergy. From the study, it turns out that the organic Rankine cycles are parasitical in nature and actually consume the power produced by the main geothermal plant turbine.