Thermo-economic analysis and optimization selection of ORC system configurations for low temperature binary-cycle geothermal plant

Multi-objective programming is used to analyze the performance of different organic Rankine cycle (ORC) plant layouts with different working fluids for low temperature binary-cycle geothermal plant. The studied results show that for the considered ORC plant layouts, the optimal overall performance indices increase with the geothermal temperature increasing. For a specific working fluid, the optimal ORC system for overall performance always remains unchanged despite the increase in the geothermal temperature. The optimal schemes of ORC systems vary with the performance indices of ORC system. The optimal scheme for comprehensive performance index is simple cycle with R123 when the geothermal temperature increases from 80 °C to 95 °C. The optimal scheme for thermal efficiency is regenerative cycle with R123, while the optimal scheme for capital cost is superheated cycle with R123. For the work output and exergy efficiency, the optimal scheme is superheated cycle with R152a when the geothermal temperature varies from 80 °C to 85 °C, while the scheme of superheated cycle with R134a is better for work output and exergy efficiency when the geothermal temperature is greater than 90 °C. This study provides useful references for the researchers selecting the optimal configuration of ORC system for low temperature binary-cycle geothermal plant.