Multi-objective optimization and exergoeconomic analysis of solar and geothermal-based power and cooling system using zeotropic mixtures as the working fluid

Abstract

The current paper proposes a double-flash geothermal system with a dual-pressure organic Rankine cycle binary system. To improve the system’s performance, the inlet geofluid is preheated via an indirect mode of a solar system, and an Ejector Refrigeration Cycle system is installed to the geofluid’s brine line to produce cooling capacity. Comprehensive investigations are performed to select the Dual-pressure Organic Rankine Cycle s working fluid among various pure substances and zeotropic mixtures that refer to choosing the R245ca/R142b. The system presents 12.12 MW net power at the base mode with a 1.87 MW cooling load and 4.88 years payback period. Some main parameters’ change effect on the system is studied. The low-pressure steam turbine’s exit pressure influences the cooling load and energetic efficiency. The high-pressure turbine’s input pressure affects the total exergy destruction and net power higher than the other. The optimum state of the system is obtained through two energy-economic and exergy-economic assessments. The energy-economic assessment provides a higher cooling load of about 5.7 MW and a lower net power of about 10.8 MW with 4.59 years payback period. The exergy-economic assessment represents 12.22 MW net power and a cooling load of about 1.97 MW with 4.77 years payback period.