Performance investigation of new design of single and double axis passive tracking solar still

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The problem of low freshwater production of the solar still (SS) is studied in this paper experimentally using two new designs of single and double axis tracking SSs and their performance is compared with the convection solar still (CSS). The first tracked still is single axis tracking solar still (SATSS) around the vertical axis, and the second tracked is a double axis tracking solar still (DATSS) rotating around vertical and horizontal axes. The optimum daily tilt angle of the DATSS and SATSS is estimated during mathematical modeling and adjusted manually during the experimental measurements. The study is performed under the climate conditions of Assiut city, Egypt, on winter, spring, and summer days. The results show that the best tilt angle of the DATSS and SATSS is in winter, spring, and summer, respectively. DATSS has the maximum daily freshwater production and efficiency, followed by SATSS, and CSS has the lowest. The total daily freshwater yield of CSS, SATSS, and DATSS is about 2.3, 4.5, and 5.5 kg/m 2 .day, respectively, in winter, 3.6, 3.973, and 6.13 kg/m 2 .day, respectively, in spring, and 4.43, 6.65, and 8.9 kg/m 2 .day, respectively, in summer. The average daily CSS, SATSS, and DATSS efficiencies are about 23.6, 41, and 44.9%, respectively, in winter, 31, 34.7, and 46.3%, respectively, in spring, and 38.5, 53.5, and 60.2%, respectively, in summer. The tracking system rises maximumly the freshwater production by more than 130% and SS efficiency by about 90%.