Comprehensive analysis and multi-objective optimization of power and cooling production system based on a flash-binary geothermal system

Abstract

The sustainable and environmentally-benign nature of geothermal energy motivates the current investigation to design a cogeneration of power and cooling system. The designed system consists of a double-flash binary system with an organic Rankine cycle and ejector refrigeration cycle integration as the waste heat recovery system. The subsystem's performance is enhanced through the zeotropic working fluid implementation. The energy, exergy, and exergo-economic assessments were utilized to compare two zeotropic mixtures' performances and select an appropriate working fluid. This comparison is carried out by comprehensive sensitivity analysis to study their performance under variable operational conditions. The results reveal that the Pentane-Isohexane has higher performance leading to 1.9 MW of net power and 290.15 kW of cooling load generation. Hence, the total exergetic efficiency and payback period are obtained to be 58.33% and 6.70 years. Considering the energy/economic optimization scenario enhances the cooling load generation to 574 kW and reduces the net power to 1.85 kW, while the exergy/economic scenario increases the net power production to 1.99 MW and declines the cooling load. By considering the overall performance indexes, the exergy/economic scenario with 6.56 years payback period provides a higher performance and the best optimization scenario.