Mix wettability surface on solar still cover for freshwater productivity enhancement

Abstract

Water purification using renewable energy sources is prevalent to produce clean water for human consumption and sanitation. Solar still is a water distillation method that uses solar energy as a heat source to produce fresh water. Selection of a solar still condensing cover material remains a challenge, particularly for enhancing the condensate formation and collection. Therefore, the application of a mixed wettability surface on the solar still condensing cover is examined and investigated. A commercial water-based silicone coating is used on a glass cover with different surface areas. The contact angle and surface profile for both coated area and uncoated area of the surface was examined to measure the wettability of the surfaces. The freshwater output was observed for the solar still at a steady-state condition in a laboratory experiment. The addition of coating showed improvement to the solar still productivity with the highest freshwater output at 30% coated surface area. However, by increasing the coating surface area above 50%, the inner cover temperature increased due to the increase in thermal resistance from the coating layer. A coating surface area of below 50% showed to be more cost-effective compared to a bare glass cover.