EFFECT OF DIFFERENT ROOF CONFIGURATIONS ON THERMAL PERFORMANCE OF SOLAR STILLS

The goal of this study was to evaluate the thermal performance of four identical solar stills with different roof shapes. Four solar stills with similar basin area with different roof glass cover configurations were designed, installed and tested at the Agricultural Engineering Department, Faculty of Agriculture, Suez Canal University, Ismailia Governorate, Egypt (latitude angle of 30.62ºN, Longitude angle of 32.27ºE, and mean altitude above the sea level of 5 m). The solar stills had four different roofs, single slope, downward slanting cover, double slope, and pyramidal shape. The basin of each solar still made of galvanized iron sheet, with a net upper surface area of 0.42 m^2. It was painted with matt black paint to absorb the maximum possible amount of solar radiation incident on it. In the bottom and sides of the basin, 0.03 m of Styrofoam insulation was placed to reduce the heat losses. The obtained results indicated that the productivity of four solar stills was 116, 107, 84 and 72 ml/hr with average thermal efficiency of 33.7, 31.0, 24.7 and 21.2% for the single slope, downward slanting, double slope, and pyramidal roofs, respectively.