LAUSR

Abstract The bi-layered structure has drawn a wide interest due to its good performance in solar steam generation. In this work, we firstly developed a calculation model which could capture experiment data well. Then, this model was applied to numerically study the effects of the depth of the bulk water, the temperature of the ambient air, the temperature of the bulk water, the porosity and the thermal conductivity of the second-layer porous material on the evaporation efficiency. Results show that when the depth of the bulk water is large enough, the thermal insulation at the bottom of the bulk water is unnecessary. There is a linear dependence of the evaporation efficiency on the temperature of the ambient air or/and the temperature of the bulk water, and an equation has been given to describe this phenomenon in the text. Compared to the temperature of the ambient air, the temperature of the bulk water has a much larger effect on the evaporation efficiency. The effective thermal conductivity of the second layer, which could impose important effect on the evaporation efficiency, mainly depends on the porosity rather than the thermal conductivity of the second-layer porous material. Thus, when selecting second-layer materials, the thermal conductivity is not an important factor for consideration. This study is expected to provide some information for designing a high-evaporation-performance bi-layered system.