Thermo-economic evaluations of dual pressure organic Rankine cycle (DPORC) driven by geothermal heat source

Abstract

The thermo-economic evaluation of the dual pressure organic Rankine cycle system was presented based on the geothermal heat sources ranging from 100 to 180 °C. Two kinds of heat exchangers were selected to form four specific configuration layouts. The comparison between single and dual pressure systems was carried out. Moreover, the influence of economic parameters on cycle performance was analyzed. The electricity production cost (EPC), payback period (ppd), and saving-to-investment ratio are among the crucial considerations when the two stage evaporating pressures and pinch point temperatures are selected as independent variables. The results indicate that the dual pressure system possesses optimal EPC with the variation of low-evaporating pressure and the configuration layouts of type-FF and type-FP perform better. The cost of heat exchangers accounts for the largest proportion in the total cost of the system, followed by the expander. It can also be found that, for R1233zd, the average increasing rate of 20.87% in Wnet brings no economic benefits to the dual pressure system because the EPC also increases 12.98% averagely compared to the single pressure system. In addition, the impact of the annual loan interest rate, on-grid electricity price, and carbon tax of the system economic performance was discussed.