Considering Micro/nanostructures at the Surface of Photothermal Materials: A Game Changer in Correct Estimation of Evaporation Rate and Energy Conversion Efficiency in Interfacial Solar Vapor Generation Systems

Interfacial solar evaporator generation (ISVG) is a new, cost-effective, and eco-friendly emerging method for water desalination. Two main criteria for evaluating ISVG performance are evaporation rate (<i>ṁ</i>) and solar-to-vapor conversion efficiency (η). The main challenge of the previously presented models for the estimation of <i>ṁ</i> and η in 2D systems is that in most cases the calculated values are beyond the theoretical limits, <i>ṁ</i> > 1.47 kg m^-2 h^-1 and η > 100%, both of which are not acceptable from the thermodynamics viewpoint. Also, the recently presented strategy of reduced vaporization enthalpy for obtaining η < 100% is unacceptable from the thermodynamics approach for ISVG as a two-step continuous process. Therefore, this work aims to present a model and consequently new equations for the correct estimation of evaporation rate and energy conversion efficiency in two-dimensional (2D)-ISVG systems, which are consistent with their corresponding theoretical limits. The basis of the present model is discrimination between the projection area and evaporation area by considering the micro/nanostructures on the surface of interfacial support (photothermal material). This leads to the presentation of new equations for <i>ṁ</i> and η having consistency with thermodynamics laws. The presence of micro/nanostructures on the surface of photothermal material provides a higher evaporation area which is not considered in the previous models and led to theoretically inconsistent results. The results of the present study provide a theoretical basis for the correct estimation of the evaporation rate and energy conversion efficiency in 2D-ISVG systems in future works.