Thermodynamic analysis and optimization of quality-improving heat pumps coupled with organic Rankine cycle for mid-low temperature geothermal power generation

In order to achieve efficient utilization of mid-low temperature geothermal resources, three different types of quality-improving heat pumps coupled with organic Rankine cycle for mid-low temperature geothermal power generation system are designed and discussed. Initially, mathematical models of each system as well as a thermodynamic evaluation system are developed. Secondly, by optimizing the operating parameters with the optimization goal of maximum overall exergy efficiency, the optimal operation states for each system are obtained. Finally, thermodynamic performance parameters of each system are compared and appropriate application scenarios for both systems are discussed. The results reveal that the optimal operating conditions for AHT-ORC-A, AHT-ORC-B, and CHP-ORC are achieved when the heat pumps elevate the temperatures to 117.0 °C, 104.8 °C, and 115.0 °C respectively. Meanwhile, their overall exergy efficiencies are 38.93%, 53.07%, and 35.40% respectively. AHT-ORCA boasts the highest output power density, while CHPORC has the lowest power density. Therefore, from the perspective thermodynamic performance, AHT-ORC outperforms CHP-ORC. Furthermore, when the condensation heat from AHT is utilized to meet the heating demands of users, a more efficient utilization of energy can be achieved.