Conventional and Advanced Exergy-Based Analysis of Hybrid Geothermal–Solar Power Plant Based on ORC Cycle

Abstract

Today, as fossil fuels are depleted, renewable energy must be used to meet the needs of human beings. One of the renewable energy sources is undoubtedly the solar–geothermal power plant. In this paper, the conventional and advanced, exergo-environmental and exergo-economic analysis of a geothermal–solar hybrid power plant (SGHPP) based on an organic Rankin cycle (ORC) cycle is investigated. In this regard, at first, a conventional analysis was conducted on a standalone geothermal cycle (first mode), as well as a hybrid solar–geothermal cycle (second mode). The results of exergy destruction for simulating the standalone geothermal cycle showed that the ORC turbine with 1050 kW had the highest exergy destruction that was 38% of the total share of destruction. Then, the ORC condenser with 26% of the total share of exergy destruction was in second place. In the hybrid geothermal–solar cycle, the solar panel had the highest environmental impact and about 56% of the total share of exergy destruction. The ORC turbine had about 9% of all exergy destruction. The results of the advanced analysis of exergy in the standalone geothermal cycle showed that the avoidable exergy destruction of the condenser was the highest. In the hybrid geothermal–solar cycle, the solar panel, steam economizer and steam evaporator were ranked first to third from an avoidable exergy destruction perspective. The avoidable exergo-economic destruction of the evaporator and pump were higher than the other components. The hybrid geothermal–solar cycle, steam economizer, solar pane and steam evaporator were ranked first to third, respectively, and they could be modified. The avoidable exergo-environmental destruction of the ORC turbine and the ORC pump were the highest, respectively. In the hybrid geothermal–solar cycle, steam economizers, solar panel and steam evaporators had the highest avoidable exergy destruction, respectively. For the standalone geothermal cycle, the total endogenous exergy destruction and exogenous exergy destruction was 83.61% and 16.39%. Moreover, from an exergo-economic perspective, 89% of the total destruction rate was endogenous and 11% was exogenous. From an exergo-environmental perspective, 88.73% of the destruction rate was endogenous and 11.27% was exogenous. For the hybrid geothermal–solar cycle, the total endogenous and exogenous exergy destruction was 75.08% and 24.92%, respectively. Moreover, 81.82% of the exergo-economic destruction rate was endogenous and 18.82% was exogenous. From an exergo-environmental perspective, 81.19% of the exergy destruction was endogenous and 18.81% was exogenous.

Integrated Geothermal Energy Systems for Small-Scale Combined Heat and Power Production: Energy and Economic Investigation

“…To this purpose, 1 kg/s of geothermal water at 230 • C was considered as energy input [16]. The geofluid was used to drive both the ORC and HEX units depending on the energy request of the investigated users while the minimum reinjection temperature was fixed to 70 • C to prevent scaling and fouling problems within system components and pipes, according to the literature [82,105,106]. The thermal efficiency of the heating process from the geothermal source was fixed to 0.92 [80] and the minimum pinch-point temperature was considered equal to 10 • C [16].…”

4E Assessment of an Organic Rankine Cycle (ORC) Activated with Waste Heat of a Flash–Binary Geothermal Power Plant

“…The environmental impact is mainly a function of the manufacturing materials and the weight of the components [ 20 ]. In this paper, the correlations and values shown in Table 10 have been used.…”

“…To evaluate the environmental impact of the system, the Eco-indicator 99 has been considered; its value represents one-thousandth of the annual environmental impact of an average European inhabitant [ 23 , 65 ]. The environmental impact rate is a function of the useful life of the component and the operating time in hours per year of the components [ 20 , 21 ]: …”

“…In addition to exergetic and exergoeconomic methods, exergoenvironmental analysis, which is a combination of exergetic analysis and life cycle assessment (LCA) concepts, is a recent method for evaluating the environmental impacts of energy conversion systems, such as geothermal power plants with waste heat recovery [ 18 ]. Several authors have investigated this type of systems from this perspective [ 19 , 20 , 21 , 22 , 23 , 24 ]. Table 1 shows previous works focused on evaluations of a low temperature ORC cycle.…”