Thermodynamic assessment of hybrid solar-geothermal organic Rankine cycle: An exergy and energy-based analysis

This study presents a comprehensive analysis of an organic Rankine cycle (ORC) integrated with a hybrid solar-geothermal energy system. The research aims to evaluate the thermodynamic performance and exergy efficiency of the hybrid system and compare it with a standalone solar ORC. The problem is approached by analyzing exergy destruction within key components, using the entropy method, and evaluating the impact of different working fluids. For the standalone solar ORC with a 1 MW turbine, the turbine and condenser were identified as the main sources of exergy destruction, contributing 40% and 25%, respectively. In the hybrid solar-geothermal ORC, the solar collectors were the dominant source of exergy destruction, contributing 58%, while the turbine's share was reduced to 10%. The use of R245fa improved the overall efficiency by up to 3%. A validated Simulink model was developed, confirming the reliability of the simulation results. The findings highlight the potential of hybrid systems in improving energy efficiency for small- to medium-scale combined heat and power applications, with future work focusing on optimizing operational parameters and exploring additional working fluids.