Exergoeconomic analysis and optimization of an integrated system of supercritical CO2 Brayton cycle and multi-effect desalination

Abstract

A cogeneration system is proposed for power and fresh water production in which the waste heat from a supercritical CO2 recompression Brayton cycle is utilized to power a conventional multi-effect desalination system. Energy, exergy and exergoeconomic analyses are performed for the proposed system and compared to a stand-alone supercritical CO2 recompression Brayton cycle. Under the same operating conditions, the results show that the energy utilization factor and exergy efficiency of the proposed system increase by 6.3% and 0.15%, respectively, compared to the stand-alone supercritical CO2 recompression Brayton cycle. A parametric analysis is conducted to investigate the influence of design parameters on the key performance parameters for the proposed system. Furthermore, single- and multi-objective optimizations are performed to find the optimal design using a genetic algorithm method. The energy utilization factor, exergy efficiency and total product unit cost of the proposed system from exergoeconomic optimization are 54.8%, 67.7% and 7.42 $/GJ, respectively which are 6.2%, 0.52% and 2.1% higher than the corresponding values for a base case. Also, the fresh water and net power productions are increased by 103% and 0.19%, respectively. From exergoeconomic optimization, the water and electricity prices are 0.72 $/m3 and 0.029 $/kWh, respectively.