Performance Evaluation of a Conventional Solar Still with Different Types and layouts of Wick Materials

Abstract

Solar distillation is regarded by many investigators as one of the important methods of utilizing solar energy to solve water scarcity problems. A solar still is a simple device which can be effectively used to convert saline water into fresh water. The enhancement of solar stills performance and improving their production capacity of distilled water are the main goals of the investigators in recent years.  In this research, three identical conventional basin type solar stills were designed and constructed in order to experimentally investigate the affect of using different wick materials in two different layout arrangements. The first solar still was used as a reference still for comparison. The second solar still was used for uniformly spreading the wick material sheets in the saline water. In this case, the wick materials sheets were completely immersed in the saline water covering the total still basin area. The third solar still had a specially designed set up of steel mesh wires.  In this case, the wick materials were partially immersed in the saline. The net basin horizontal effective area of each solar still was 1 m², and the glass cover's tilted angle was fixed at 32.5º.  Five types of wick materials in the form of material sheets were used. They were light black cotton fabric, light jute fabric, black velvet fabric, black sheer mesh fabric, and a 4 mm thick sponge sheet. Spreading the wick material sheet to cover the basin area had the effect of preventing the sunrays from reaching the still basin and consequently absorbed by the saline water and the wick material resulting in enhancing the yields of solar stills. The aim of adding mesh wire layout arrangement is to have the additional effect of increase the surface area of evaporation relaying on capillary effect to raise the saline water to the non-immersed part of the materials. It has been found that the solar still with only wick materials and no special arrangement performed much better than the other two solar stills. In both layout arrangements, it has been found that the light black cotton fabric was the most effective material in enhancing the still productivity in with 36.9% and 26.3% respectively. The sponge sheet was found the less effective material in enhancing the still productivity with 11.5% and 9.9% respectively.

Keywords: Productivity; Solar stills; Water desalination; Wick materials; Wire mesh