Energetic and exergetic performance assessment of the inclusion of phase change materials (PCM) in a solar distillation system

Abstract

In this experimental work, the energetic and exergetic performance enhancement of solar distillation system (solar still incorporated with PCM storage unit) is performed by using two techniques. First, pin fins heat sink (PF) is embedded inside the PCM to act as a thermal conductivity enhancer. Second, black steel mesh fibers (SWF) are employed in the solar still basin with PCM. In this regard, four cases of the solar stills are studied and compared conventional still: conventional solar still (without PCM), still with PCM (With PCM), still with PCM and pin fins heat sink embedded in the PCM (With PCM-PF) and still with PCM and SWF in the basin (With PCM-SWF). The energetic and exergetic performance of the four cases is evaluated and compared under the meteorological conditions of New Borg El-Arab City, Egypt. The results show that the total daily cumulative yield of distilled water of still with PCM, still with PCM-PF, and still with PCM-SWF are greater than of conventional still by 9.5%, 16.8%, and 13%, respectively. Additionally, the inclusion of the fins heat sink in the PCM increases the average daily energy and exergy efficiencies by 17.9, and 13.2%, respectively compared to conventional one. Likewise, the energy and exergy efficiencies of still with PCM-PF are higher than those of solar still with PCM by 7.7 and, 6.8%, respectively. Furthermore, placing SWF in the basin of still with PCM significantly enhances the daytime energy and exergy efficiencies with a considerable reduction of these values in the nighttime. The total daily evaporative exergy for still with PCM-SWF is greater than those of conventional still, still with PCM, and still with PCM-PF by 13, 8, and 2%, respectively. Also, still with PCM, still with PCM-PF, and still with PCM-SWF exhibit an increment of the daily exergy efficiency 5.9, 13.2, and 17.3%, respectively compared to still without PCM. Still with PCM-PF achieved the highest accumulated daily water productivity and energy efficiency but still with PCM-SWF attained the highest daily exergy efficiency with nearly no additional cost.