Efficiency improvement of solar stills through wettability alteration of the condensation surface: An experimental study

Abstract

The condensation process is of great importance in many heat transfer devices in which a large amount of energy must be transferred. Furthermore, condensation is a crucial part of energy conversion and affects the energy efficiency of thermal desalination plants and solar stills. During the condensation process in solar stills, an essential part of the energy is transferred through the condensation surface to produce fresh water. Therefore, the condensation surface plays a significant role in the working efficiency of solar stills. The wettability of the condensation surface influences the condensation mechanism, which, in turn, affects the efficiency of solar stills. This study aims to improve the efficiency of solar stills through wettability alteration of the condensation surface by utilizing nanoparticles. To this end, the condensation surfaces of various materials were selected and coated with titanium dioxide and silicon nanoparticles (which have different wetting properties) to increase and/or decrease the surface wettability. Outdoor and indoor experiments were conducted to evaluate the productivity of solar stills with regard to utilizing clean and nano-coated condensation surfaces. Furthermore, scanning electron microscopy and atomic force microscopy analyses were utilized to examine the deposition of nanoparticles on the condensation surfaces. The experimental results indicated that nano-coated condensation surfaces significantly improved the efficiency of solar stills. For instance, silicone coating caused an increase in the productivity of solar still by 20% for the glass condensation cover.