An investigation into the effect on the productivity of cascade-type solar distillation systems with varying cover thicknesses and still orientations under tropical Caribbean climatic conditions

Abstract

Previous investigative work related to solar stills focuses mainly on issues relating to the temperature gradient between the brine and the condensing surface. It is common practice when calculating the efficiencies of solar stills to use the temperature of the outer glass as the condensing surface temperature rather than the temperature of the actual condensing surface. This practice is done due to the fact that the outer glass surface temperature is easily measurable and on the assumption that there is little or no drop in temperature across the thickness of the cover. These conventions in turn create room for misleading results owing to temperature losses across the cover thickness. The main objectives of this research work are to investigate the effect of using different glass cover thicknesses and different solar still orientations on the productivity of cascade-type solar stills tested under tropical Caribbean climatic conditions. In the investigation, three identical units fitted with glass covers of thicknesses 3.18, 4.76 and 6.35mm are used. Each unit comprised two identical solar stills: one oriented to face north and the other to face south. Results were gathered at the University of the West Indies in St. Augustine, Trinidad and comparative analyses were conducted. The results indicate that the solar still with the glass cover thickness of 4.76mm facing south produced the highest yield.