| Abstract |
Water scarcity remains a critical global challenge, particularly in arid and semi-arid regions where access to freshwater is limited. In such contexts, the development of efficient and sustainable methods for freshwater production is of paramount importance to ensure the well-being of communities and the preservation of ecosystems. Concentrated solar stills offer a promising avenue for addressing this challenge by harnessing solar energy to produce distilled water from saline or brackish water sources.
The present study experimentally assessed a novel sun-tracking concentrated solar still within Egyptian climatic conditions during the summer of 2022. The proposed solar still system comprises a 1.2 m diameter parabolic reflector mirror equipped with a dual-axis tracking mechanism, ensuring optimal solar energy capture throughout the day. Coupled with a cylindrical solar still featuring a volume of 0.0037 m3 positioned at the focal point, the system has a concentration ratio of 12.5, maximizing the efficiency of water vaporization and condensation processes.
Two important parameters are explored in this investigation: the salinity of the feed water and the filling ratio of saline water within the solar still. By evaluating three samples of feed water with varying salinity levels (17, 27, and 37 ppt) and four different filling ratios of saline water (26.5%, 39.8%, 53.1%, and 66.3%), insights into the impact of these factors on the system's performance are sought.
While augmenting the salinity of the feed water exhibited negligible impact on solar still productivity, variations in the saline water filling ratio yielded noticeable effects. The study indicated that elevating the filling ratio from 26.5% to 53.1% led to notable enhancement in both daily cumulative productivity and system efficiency by 22.69% and 26.34%, respectively. However, a further increase in the filling ratio to 66.3% resulted in decreased daily cumulative productivity and system efficiency by 7.06% and 6.87%, respectively. Additionally, augmenting the feed water salinity from 17 ppt to 37 ppt led to a reduction in daily cumulative productivity by approximately 5.61% and daily system efficiency by 5.1%.
The daily cumulative productivity of the system was determined to be 6 kg/m2, for an optimal filling ratio of 53.1%, achieving a daily efficiency rate of 42.88%. Additionally, the average cost associated with freshwater production was estimated at 0.0489 $/kg. Notably, the proposed system attained the highest instantaneous efficiency of 61.77% and the maximum distilled water productivity rate of 0.941 kg/hr.m2. |
