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tag Thermodynamic optimization of a double-pressure Organic Rankine Cycle driven by geothermal heat source
Qingxuan Sun, Yaxiong Wang, Ziyang Cheng, Jiangfeng Wang, Pan Zhao, Yiping Dai
Session: Poster session & Welcome drinks
Session starts: Wednesday 13 September, 17:30



Qingxuan Sun ()
Yaxiong Wang ()
Ziyang Cheng ()
Jiangfeng Wang ()
Pan Zhao ()
Yiping Dai ()


Abstract:
Geothermal energy, as a typical low-temperature heat source, has been exploited for decades to generate electricity. Organic Rankine cycle (ORC) system has a high energy conversion efficiency due to the good performance of organic fluids under the geothermal water temperature. In this study, a double-pressure organic Rankine cycle system driven by geothermal heat source is used to generate electricity. The double-pressure system achieves the cascaded utilization of energy, which can improve the efficiency of energy conversion. Mathematical model has been established based on thermodynamic laws, and the overall system performance has been evaluated. A parametric analysis is conducted to examine the effects of some key thermodynamic parameters, namely turbine high-level inlet pressure, low-level inlet pressure, high level inlet temperature, on the system performance. Parametric optimization is conducted by means of genetic algorithm (GA) to find the maximum system performance. At the same time, performances of several organic working fluids are examined. Results indicate that R245fa has a better performance among several organic fluids. The system overall exergy efficiency exceeds 5.8% under the supply water of 120°C, and it produce more than 800kW electricity with the hot water mass flow rate of 250t/h. It is also found that the turbine high level inlet pressure and low level inlet pressure has peak values on the effect of system efficiency. At the same time, the increasing turbine high level inlet temperature brings a positive effect to the system performance. Exergy analysis is also conducted and the result shows that the main exergy loss occurs in evaporator. The simulation result shows that the double-pressure organic Rankine cycle has a better performance in utilizing geothermal energy than single-pressure system.