Energy, exergy and exergo-economic assessment of a geothermal power plant with NCGs reinjection

In this paper, thermodynamic, exergy, and exergo-economic evaluations of a geothermal power plant with reinjection of NCGs are performed. The thermodynamic modeling is conducted in MATLAB software according to the first and second laws of thermodynamic. The Octamethyltrisiloxane (MDM) is considered as ORC working fluid, and the inlet working fluid of the turbine works in supercritical conditions. A sensitivity analysis of the effect of condensation temperature, the inlet pressure of the turbine, NCGs percentage of geothermal fluid, and compressors pressure ratio on exergy and economic performance of the system is done. According to the obtained results, increasing the condensation temperature and compressors' pressure ratio decreases the exergy efficiency and system exergetic performance. Rising the pressure ratio of compressors leads to an increase in specific exergy destruction, power cost, and investment cost. Besides, growing the inlet pressure of the turbine decreases the cycle exergy efficiency and exergetic performance criteria. This trend for total cycle exergy destruction and power cost is converse. Results showed that the presence of NCGs harms exergy efficiency and net power and increases the power cost. The highest exergy destruction is related to main heat exchanger, condenser, and turbine, respectively.