Energy, exergy, economic and environmental (4E) analyses of a geothermal power plant with NCGs reinjection

In this study, a conceptual geothermal power plant with Non-Condensable Gases (NCGs) reinjection is analyzed from energy, exergy, exergo-economic, and environmental perspectives. The cycle is evaluated in considering both subcritical and supercritical working conditions. A sensitivity analysis comprising the variation of condensing temperature, turbine inlet pressure, and amount of NCGs within the geofluid is performed to assess the system performance from the thermodynamic, economic, and environmental points of view. The exergy efficiency results for the supercritical and the subcritical cycles are 52% and 50.5%, respectively. Results showed increasing the condensing temperature decreases exergy efficiency, net power, and exergetic performance parameters and increases total exergy destruction, exergo-destruction impact, and specific power cost in both working cases. According to the obtained results, an increase in the inlet pressure of the turbine in the supercritical case study reduces exergy efficiency and exergetic performance and increases the exergo-destruction impact factor. However, it increases the cycle exergy efficiency and exergetic performance criteria first and then decreases in a subcritical case. The LCOE for the supercritical cycle is 6.96 (c€/kWh) and for the subcritical is 5.52 (c€/kWh). The highest exergy destruction rates are related to the main heat exchanger, condenser, and turbine, respectively.