Optimisation of single-slope solar still performance using response surface methodology

The increasing demand for low-cost and energy-efficient desalination systems has intensified interest in solar distillation technologies. The optimisation of a single-slope solar still with respect to ambient temperature, wall lining thickness, solar radiation, and wind velocity was carried out in this study using Response Surface Methodology (RSM) based on the Central Composite Design (CCD). A total of thirty experiments were carried out to assess the influence and interactions of the process parameters on freshwater productivity. The highest temperature of the basin, glass, water and vapour was 68.5°C, 63.25°C, 68.0°C and 66.5°C respectively. The productivity of the freshwater in the lined basin was also improved: from 1260 mL/day for the unlined basin to 2230 mL/day and 2330 mL/day for the 4 mm and 8 mm wall lining thicknesses, respectively, with a productivity increase of 77% and 85% respectively. The developed quadratic regression model exhibited excellent predictive accuracy, with an R2 of 0.9926. The optimum conditions resulted in a production of 2330 mL/day under a 1.96% prediction error. The distilled water met the WHO drinking water standards, which is an indicator of the ability of the proposed system to produce freshwater in a sustainable manner.