Exergy Evaluation of Desalination Processes

Abstract

Desalination of sea or brackish water sources to provide clean water supplies has now become a feasible option around the world. Escalating global populations have caused the surge of desalination applications. Desalination processes are energy intensive which results in a significant energy portfolio and associated environmental pollution for many communities. Both electrical and heat energy required for desalination processes have been reduced significantly over the recent years. However, the energy demands are still high and are expected to grow sharply with increasing population. Desalination technologies utilize various forms of energy to produce freshwater. While the process efficiency can be reported by the first law of thermodynamic analysis, this is not a true measure of the process performance as it does not account for all losses of energy. Accordingly, the second law of thermodynamics has been more useful to evaluate the performance of desalination systems. The second law of thermodynamics (exergy analysis) accounts for the available forms of energy in the process streams and energy sources with a reference environment and identifies the major losses of exergy destruction. This aids in developing efficient desalination processes by eliminating the hidden losses. This paper elaborates on exergy analysis of desalination processes to evaluate the thermodynamic efficiency of major components and process streams and identifies suitable operating conditions to minimize exergy destruction. Well-established MSF, MED, MED-TVC, RO, solar distillation, and membrane distillation technologies were discussed with case studies to illustrate the exergy performances.

Ionic liquid enables highly efficient low temperature desalination by directional solvent extraction

“…The ability to operate a DSE process at the relatively mild temperatures shown with [emim][Tf 2 N] (e.g., 45 °C) constitutes a significant advantage wherein waste heat is a viable source of operating power. Exergy is the maximum amount of extractable work from a heat source with Carnot efficiency, and is a useful measure of the overall system efficiency when comparing different desalination technologies 6 , 21 . As shown in Fig.…”

Drivers, challenges, and emerging technologies for desalination of high-salinity brines: A critical review

“…Alternative energy metrics have been proposed, including 1stlaw efficiency, 2nd-law efficiency, exergy destruction, and the standard primary energy used for Fig. 3B [103,439,[443][444][445][446], and efforts should continue to introduce additional complementing standards. Metrics that incorporate the grade and carbon intensity of energy utilized will become increasingly essential as renewable sources continue to replace fossil fuels in electricity generation [447][448][449][450][451][452][453][454][455][456].…”

Life Cycle Assessment for Tertiary Wastewater Treatment and Reuse versus Seawater Desalination

“…Gude [59] and Ihm, et al [60]. The types and amounts of chemical additives per cubic meter of desalinated water were obtained from local desalination plants [61] and from Al-Shayji and Aleisa [56].…”