Theoretical analysis of solar thermal desalination performance limitation

Solar thermal desalination systems utilize concentrated or non-concentrated sunlight to produce heat to drive a phase change separation process and produce freshwater. It could be an effective solution for increasingly scarce freshwater resources and energy shortages across the globe. In order to explore the performance limits and operating parameters that affect specific water production (SWP), this paper proposes a thermodynamic model of the ideal solar-driven thermal desalination process. The model compares two different heating configurations of solar collector system and considers surface temperature of solar collector, concentration ratio, recovery ratio and inlet saline water salinity to find maximum specific water production. The results show that under reversible condition, a flat plate collector with inlet saline water salinity of 35 g/kg will experience an increase in SWP from 29.9 gs-1m-2 to 52.7 gs-1m-2 if the recovery ratio decrease from 70% to 10%. For a system with concentration ratio of 10, when the surface temperature of solar collector is 507K, the maximum specific water production can reach 166.3 gs-1m-2 as the recovery ratio approaches zero. Reduction in incoming fluid salinity can further increase these performance limitations. The work fundamentally demonstrates the thermodynamic process of solar thermal desalination, and proposes a method to evaluate the performance limitation.