Entropy, exergy, and cost analyses of solar driven cogeneration systems using supercritical CO2 Brayton cycles and MEE-TVC desalination system

Abstract

In this study, performance and cost analyses are conducted for a solar power tower integrated with supercritical CO2 (sCO2) Brayton cycles for power production and a multiple effect evaporation with a thermal vapor compression (MEE-TVC) desalination system for water production. The study is performed for two configurations based on two different supercritical cycles: the regeneration and recompression sCO2 Brayton cycles. A two-tank molten salt storage is utilized to ensure a uniform operation throughout the day. From the entropy analysis, it was shown that the solar tower is the largest contributor to entropy generation in both configurations, reaching almost 80% from the total entropy generation, followed by the MEE-TVC desalination system, and the sCO2 power cycle. The entropy generation in the two-tank thermal storage is negligible, around 0.3% from the total generation. In the MEE-TVC system the highest contributing component is the steam jet ejector, which is varying between 50% and 60% for different number of effects. The specific entropy generation in the MEE-TVC decreases as the fraction of the input heat to the desalination system decreases; while the specific entropy generation of the sCO2 cycle remains constant. The cost analysis performed for different regions in Saudi Arabia and the findings reveal that the regions characterized by the highest average solar irradiation throughout the year have the lowest LCOE and LCOW values. The region achieving the lowest cost is Yanbu, followed by Khabt Al-Ghusn in the second place, and the rest are as follows, Jabal Al-Rughamah, Jizan, Al-Khafji, and Dhahran. The LCOE of Yanbu at a fraction of 0.5 for the regeneration and recompression solar cogeneration cycles are 0.0915$/kWh and 0.0826$/kWh, respectively.