Exergoeconomic optimization of a new double-flash geothermal-based combined cooling and power (CCP) system at two different cooling temperatures assisted by boosters

Abstract

A new cooling/power cogeneration system applicable to double-flash geothermal power plants is devised which provides cooling load at two different adjustable cooling temperatures. To further increase efficiency of the set-up, two boosters are employed to boost pressure of the secondary flow of each ejector due to the considerable drop of pressure of the geofluid through the steam turbines as well as the throttling valves. A comprehensive modeling of the proposed system is achieved from thermodynamics laws as well as economic perspectives and the results are elaborated with more details. In comparison with the previous integrated systems based on the flash geothermal power plants, the present system produces around 47.8% more cooling load and 38.9% more electricity. Also, the results of multi-objective optimization revealed that the net electrical power and exergetic efficiency can be increased approximately 20.59% and 68.11%, respectively. However, the unit cost of power and cooling (UCPC) is decreased around 36.3%. Meantime, the total exergy destruction rate is decreased after optimization. Among all elements, the highest exergy destruction occurred in the condenser by 2570 kW out of 7609 kW (in base mode) and 2333 kW out of 6836 kW (in optimum mode). Also, it is found that the energy efficiency of the proposed system can be increased by increasing turbines outlet pressure, boosters pressure ratio, and separator 1 pressure or decreasing separator 2 pressure.