Investigation of the thermoeconomic improvement of integrating enhanced geothermal single flash with transcritical organic Rankine cycle

Abstract

In this research, the integration of an enhanced single flash geothermal cycle with a transcritical organic Rankine cycle (TORC) is proposed. To discover the feasibility and thermoeconomic improvement, the proposed system is investigated and compared thermoeconomically with a subcritical ORC integrated to single flash geothermal. Thermoeconomic evaluation is conducted with consideration Pseudo-critical point effect in supercritical condition as well as Bauman rule in geofluid turbine. The considered key parameters to conduct a parametric study are heat source temperature, separator pressure, and geofluid condenser pressure. To perform the thermoeconomic analysis, the heat transfer areas, as well as overall heat transfer coefficients of all heat exchangers, are calculated. Moreover, the total cost rate and levelized cost of energy for the considered systems are obtained. The results reveal that the heat source temperature plays an important role in the power production variation, while the separator and flash condenser pressures are kept constant. An increment of 20 °C in the heat source temperature leads to an increase of up to 22% in generated power for both considered systems. Also, based on the comparative study, a combination of the flash-transcritical ORC cycle has 7.2% higher power production compared to the combination of flash-subcritical one. A multi-objective optimization based on the genetic algorithm method is performed. The optimization results show that the energy and exergy efficiencies, exergy destruction rate, and total cost rate is well improved in single flash-TORC compared to the subcritical one.