  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 are less explored, leading to many confusions and misunderstandings.
Herein, we clarify these mechanisms with a detailed thermal analysis 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 part. Our analysis gains insights to the thermal processes
involved in interfacial solar evaporation and offers perspectives to the
further development of interfacial solar desalination technology.
