A comparative study of various fatty acids as phase change material to enhance the freshwater productivity of solar still

The scarcity of potable water due to rapid growth in population, industrialization, and the continuous extraction of groundwater has led to an impending crisis. Researchers have invented numerous techniques to obtain freshwater in order to fulfill the increased requirements, and solar desalination using a solar still is one of the low-cost methods to generate freshwater. In a solar still, the usage of PCM (Phase Change Material) storage under the absorber plate enhances the productivity during the nighttime so that the still continues to generate freshwater even in the absence of solar energy. The present study undertakes the experimental, energy, exergy and economic analysis for a conventional solar still and solar stills using different types of fatty acids as PCM storage along with pin fins for enhanced heat transfer. For a comparative study of different organic fatty acids as PCM storage materials-lauric acid, palmitic acid and stearic acid were used along with high-conductive aluminum pin fins which were inserted in the PCM storage to enhance the rate of heat conduction. The results obtained using the PCM along with pin fins were compared with the output from the conventional solar still (CSS). Thus, four different cases were considered for the current study, namely: the conventional solar still (CSS); the solar still with lauric acid and pin fins (SSLA); the solar still with palmitic acid and pin fins (SSPA), and, the solar still with stearic acid and pin fins (SSSA). The experiments were performed in the months of January (representing the winter season) and May (representing the summer season), at the location Gandhinagar, Gujarat (23.22 degrees N 72.650 degrees E), India, with variation in the depth of water (1 cm, 2 cm and 3 cm) in the basin of solar still. The accumulated productivity, energy efficiency, and exergy efficiency were observed as 4.43 L/m(2), 47.9% and 2.23% for SSLA in January, which was the maximum amongst all cases in January. The accumulated productivity, energy efficiency and exergy efficiency were 5.74 L/m(2), 56.2% and 2.96% for the case of SSSA in the month of May, which was the maximum amongst all the cases. The SSSA was the economical solar still amongst all cases; the payback period and cost per liter of SSSA were 72 days and 0.016 $/L/m(2), respectively.