Increasing the productivity and the thermal efficiency of conventional solar stills using a new rotating discs mechanism

Modified solar stills with rotating metallic discs were presented as new distillation mechanism to enhance conventional system productivity. To improve the system water’s evaporative surface and solar radiation exposure, six rotating discs fixed on two vertical shafts were inserted in the modified distiller. The discs were powered by a DC-motor using a photovoltaic system. Another modification was carried out using fixed rods on the discs to enhance the turbulence effect. The impact of varying the rotational discs velocities (from 0.025 to 4 rpm) on the productivity of the two modified solar stills were investigated. The results demonstrated that the distillate yield increased considerably. The rotating discs with rods system at 0.5 rpm achieved the best production, with an increase from 63.22 to 94.82%. The Modified solar still with rotating discs and the Modified solar still with rotating discs and rods have maximum thermal efficiencies of 24.5 and 29.8% at 0.15 and 0.5 rpm, respectively. While the efficiency of conventional solar still was only 15%. An economic analysis was carried out to confirm the profitability of the two modified distillers. The estimated price of distilled water using the conventional system was 0.057 $/L, whereas for the two modified systems it was 0.056 and 0.054 $/L, respectively.