Theoretical study of the aspect ratio of a solar still with double slopes

Madhlopa, Amos and Clarke, Joseph Andrew (2011) Theoretical study of the aspect ratio of a solar still with double slopes. In: World Renewable Congress, WREC 2011, 2011-05-08 - 2011-05-13.

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Clean water is essential for good health which influences the social and economic development of any nation. However, there is limited access to safe water on a global scale. This challenge can be overcome through a multi-faceted approach, including the development of appropriate technologies for water treatment and decision-making tools. Solar distillation is one of the commonest non-conventional methods for improving the quality of water. In this vein, the most widely-exploited solar distillation system is a conventional solar still, which has a thin layer of saline water in a shallow basin with a transparent cover over the water and one or two slopes. The productivity of a solar distillation system is influenced by design, climatic and operational factors, with solar radiation being the most influential meteorological parameter. It is therefore necessary to optimize solar radiation that effectively reaches the base of the solar still. Previous attempts have sought to improve the design characteristics of conventional solar stills through the consideration of system geometry and optical properties of construction materials. One of the important geometric parameters is the ratio (R) of length to width (aspect ratio) of the still base. For a single-slope solar still (SSS), R has been examined in preceding studies. Nevertheless, there is a paucity of information on the aspect ratio of a double-slope solar still. In this study, a state-of-the-art software (ESP-r) was used to simulate the variation of effective insolation with R for a double-slope solar still (DSS) in the east-west and north-south orientations and a SSS facing south. Meteorological data captured at the University of Strathclyde and Guantanamo Bay was employed in this analysis. Simulation results show that the optical performance of a DSS was lower (in both orientations) than that of a SSS at both sites. The DSS collected more solar energy in the east-west orientation than north-south orientation, for a given value of R. In addition, effective insolation increased with R to an optimum level for both the DSS and SSS. Approximate optimum values of R were 3.0 and 2.0 for the University of Strathclyde and Guantanamo Bay respectively. However, the optimum value of R was not sensitive to the orientation of the DSS at the two sitesFurther, the DSS and SSS exhibited the same optimal value of R at a specific site. . It appears that R significantly affects solar collection in DSS.


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