Clean Water Production Through Tubular Solar Still Using Carbonized Cashew Nut Shells as Biowaste Thermal Storage Material

ABSTRACT The solar still (SS) desalination using a tubular design is the latest trend in SS. Due to increasing freshwater demand, the yield of the tubular SS (TSS) should be enhanced using a heat energy storage material (HESM). The novelty of this research is that it experimentally examines the impact of carbonized cashew nut shell powder as HESM in a TSS. Two types of TSS were fabricated: one with carbonized cashew nut shells powder in the basin and the other conventional TSS (CTSS). The outcomes revealed that using carbonized cashew nut shell powder increased output by 91.63% compared to CTSS. The production of TSS using carbonized cashew nut shell powder was 4.81 kg, but for CTSS, it was 2.51 kg. The thermal and second law efficiencies for TSS using carbonized cashew nut shell powder and CTSS were 39.38%, 2.3%, 18.86%, and 1.8%, respectively. Using carbonized cashew nut shell powder in the TSS improves thermal and second law efficiencies by 108.84% and 69.1%, respectively, compared to the CTSS. Additionally, economic and environmental analyses have been conducted. The results indicate that the payback period for TSS using carbonized cashew nut shell powder is 0.2 years, whereas that for CTSS is 0.4 years.