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

Abstract

A reservoir model was coupled with a flash–binary cycle model to investigate the performance and economics of a geothermal system. The production temperature T_pro 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 (EPC_M) and payback period (PBP_M) was developed. The net output power decreased with an increase in the operation time because of the effect of T_pro. 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 ($W_{tot,net}$, ${\eta }_{tot,I}$, 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 $W_{tot,net}$ 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 EPC_M and PBP_M values of 0.129 USD/kWh and 12.503 years, respectively.