Environmental impact assessment of a real geothermal driven power plant with two-stage ORC using enhanced exergo-environmental analysis

Abstract

Geothermal driven power plants (GPPs) with two-stage ORC are mostly used in low-temperature geothermal fields around the World. The environmental impacts of these GPPs create a gap in the literature. In this study, enhanced exergo-environmental analysis for the GPP and its components is conducted as a case study. With the analysis, the component-related, exergy degradation-related, and pollution formation-related environmental impacts (EIs) are separated endogenous/exogenous and avoidable/unavoidable parts. In this way, detailed information about the interaction and improvement potential between components is acquired by using the recommended performance indicators. The results of the study show that for the enhanced exergo-environmental analysis, EI related to exergy destruction of components is predominated. In the traditional exergo-environmental analysis the total amount of EI is condenser with 1.386 Pt/h while in the enhanced one the highest avoidable-endogenous exergy destruction is condenser with 716 Pt/h. The value of EI which is caused by electricity generation is 0.108 Pts/kWh. The EI value of geothermal fluid is 11.8 Pt/GJ. The EI value of the plant's avoidable-endogenous pollution formation is 8 Pt/h. As the reason for this, the mass flow rate of the geothermal fluid steam and the amount of NCG gas in it are effective. Eventually, if the plant could be operated under enhanced analysis' operation conditions, the EI of released CO2 value can be reduced by 8.4% by carbon capture and storage. Thus, the details of the analyzes performed for the plant are expected to guide the researchers.