Enhancing the performance of a single-basin single-slope solar still by using Fresnel lens: Experimental study

A refraction-based methodology for concentrating sunlight is proposed to augment the pure water production of a conventional solar still. The Fresnel lens (FRL) was integrated with a single-basin, single-slope solar still to refract the incident sunlight to a focal point that was constantly located on the basin bottom. Due to the introduction of the FRL, two major impressive findings were observed. The first observation was a high hourly productivity window (HHPW), during which the proposed system produced fresh water at a relatively high and stable rate. The second one was the occurrence of nucleate boiling phenomenon, which is believed to significantly increase the heat transfer coefficient for the phase change process of the basin water. Consequently, with the increased heat input and the high heat transfer rate, the utilization of FRL achieved a significant pure water production enhancement (L/m(2)/day) of about 467%, as well as a significant daily efficiency (eta) improvement of about 84.7%, compared to a conventional system without FRL. A series of tests were conducted to study the impact of the operational parameters on the system performance. The system daily output demonstrated a linear and negative correlation with water depth (d(w)) in the basin. The introduction of forced air cooling showed a positive impact on system performance and enhanced the distillate yield. It was also found that increasing d(w) or/and applying forced air cooling effect could benefit from increasing eta. (C) 2019 Elsevier Ltd. All rights reserved.