Geothermal power generation improvement of organic Rankine flash cycle using exergy, advanced exergy and exergoeconomic analyses

Abstract

Replacing fossil energy with geothermal energy can effectively alleviate the energy crisis and many environmental problems. However, the low heat-to-power conversion efficiency of geothermal resources hinders its development and utilization. Therefore, in-depth analysis of the causes of irreversible losses and costs of each component of the geothermal power generation system can provide theoretical support for improving its performance. In this paper, an organic Rankine flash cycle (ORFC) power generation system is analyzed and evaluated based on conventional and advanced exergy/exergoeconomic methods. The results showed that the exergy destruction of each component is mainly caused by its own performance, so the endogenous exergy destruction of all components is higher than the exogenous exergy destruction. The avoidable endogenous exergy destruction/cost of the system accounts for 54.07 % and 48.94 % of the total exergy destruction/cost, respectively. The avoidable endogenous exergy destruction/cost of two turbines accounts for 74.35 % and 86.76 % of the total endogenous exergy destruction/cost, indicating that the turbine has the greatest performance improvement potential and cost saving potential, and the exergy destruction of each component is the main factor affecting the economic benefit of the system. Hence, increasing the isentropic efficiency of the turbines and the working fluid pumps and decreasing the heat transfer temperature difference of the evaporator and the condenser can reduce their own exergy destruction, thereby improving the system performance.