The energy efficiency of interfacial solar desalination

Solar-thermal evaporation, a traditional steam generation method for solar desalination, has received numerous attentions in recent years due to the significant increase in efficiency by adopting interfacial evaporation. While most of the previous studies focus on improving the evaporation efficiency by materials innovation and system design, the underlying mechanisms of its energy efficiency improvement are less explored, leading to many confusions and misunderstandings. Herein, we investigate the mechanisms of interfacial solar desalination with a detailed heat and mass transfer model. Using this model, we elucidate the advantages of interfacial evaporation over the traditional evaporation method. Furthermore, we clarify the role of tuning the solar flux and surface area on the evaporation efficiency. Moreover, we quantitatively prove that the influence of environmental conditions on evaporation efficiency could not be eliminated by subtracting the dark evaporation rate from evaporation rate under solar. We also find that interfacial evaporation in a solar still does not have the high overall solar desalination efficiency as expected, but further improvement is possible from the system design. Our analysis gains insights to the thermal processes involved in interfacial solar evaporation and offers important perspectives to the further development of interfacial solar desalination technology.