Productivity amelioration of stepped solar still using phase change material and evacuated tube collector

Abstract

This study investigates the individual and cumulative effects of phase change material (PCM) and evacuated tube collector (ETC) on the performance of a stepped solar still (SSS). Experiments have been performed on SSS, SSS loaded with PCM (SSS‐PCM), SSS coupled with ETC (SSS‐ETC), and SSS loaded with PCM and coupled with ETC (SSS‐PCM‐ETC). An innovative way of loading paraffin wax as PCM is introduced to utilize solar energy efficiently for the distillation process during off‐sunshine hours. ETC is used to provide pre‐heated RO wastewater to the distillation unit. The distillate output was observed maximum for SSS‐PCM‐ETC (4.97 kg/m2 day) which is 99% more than that of the SSS unit. The PCM and ETC individually with SSS unit increases the distillate output by 31% and 24%, respectively. The working time of the distillation unit was observed to be increased by 3 h by the use of PCM. The total heat transfer coefficient was evaluated at the maximum for SSS‐PCM‐ETC and was observed in the range of 16.94–167.04 W/m2 °C. The thermal energy efficiencies of SSS, SSS‐ETC, SSS‐PCM, and SSS‐PCM‐ETC were evaluated as 28.65%, 35.59%, 43.88%, and 44.04%, respectively. SSS‐PCM‐ETC is found to be the most economic with the best environmental conservation having maximum values of daily productive cost ($0.69) and carbon credits earned ($184.8).