Performance and economic analyses of a geothermal reservoir model coupled with a flash-binary cycle model

A reservoir model was coupled with a flash-binary cycle model to investigate the performance and economics of a geothermal system. The production temperature Tpro of the reservoir decreased with an increase in the operation time, which affected the net output power of the system; thus, a method for calculating the electricity production cost (EPCM) and payback period (PBPM) was developed. The net output power decreased with an increase in the operation time because of the effect of Tpro. This decrease resulted from the combined effect of a considerable decline and marginal increase in the net output power of a single-flash cycle (decline of 1278.86 kW) and an organic Rankine cycle (increase of 68.6 kW), respectively, with an increase in the operation time. For high flash pressure, the decreases in the output power, firs- and second-law efficiencies of the system (Wtot,net, eta tot,I, and eta tot,II, respectively) from the 1st to the 30th year of operation were 52.08 %, 34.53 %, and 24.53 %, respectively, with the percentage decrease in Wtot,net being greater than those in eta tot,I and eta tot,II. The system with a flash pressure of 800 kPa was discovered to achieve the best EPCM and PBPM values of 0.129 USD/kWh and 12.503 years, respectively.