Exergy analysis of thermal desalination processes: a review

This study reviews the efforts made regarding thermal desalination systems, focusing on the exergetic aspect. Each plant has a component, which limits the magnitude of thermal energy improvement; however, the target should be an effort to minimize the exergy destruction. It was found that all stand-alone systems required modification or integration with other desalination plants due to their low exergy efficiency. Furthermore, the exergy-destructive components in humidification-dehumidification (HDH) systems as a domestic desalination process, in poly-generation systems by the ability of freshwater production and energy generation, and in combined cooling-heating-power (e.g., MEE-CCPP) cycles as the recent desalination technologies were introduced. The exergy efficiency of a desalination plant increased by coupling to a solid oxide fuel cell or heat pump, using surplus low-pressure or makeup steam and optimization of the effect and stage numbers. Designing a poly-generation system capable of producing power, desalinated water, as well as liquefied natural gas heating/cooling could improve the system exergetically. Desalination systems were found to benefit from increasing the evaporation temperature caused by a Rankine cycle. Coupling the HDH system to a reverse osmosis unit or thermo-compressor vapor compression-reverse osmosis plant was found to improve the system performance exergetically. [GRAPHICS] .