Optimizing solar still design and developing cost-effective and evaporating bio-materials are critical to improving freshwater production. This study experimentally investigates the performance enhancement of a tubular solar still (TSS) through three innovative scenarios incorporating biomaterials. The first scenario involves coating the absorber plate with carbon quantum dots (CQDs) and graphite nanoparticles (GNPs). The second scenario incorporates natural porous materials: sponge and loofah on the absorber plate. The third scenario combines CQDs and sponges and compares them with conventional black paint. Performance evaluations were conducted based on hourly and cumulative water productivity and thermal efficiency. The experimental results reveal that the CQDs and sponge combination achieved the highest cumulative water productivity of 3.66 L/m2 and the highest thermal efficiency of 57.28%, outperforming black paint by 28.8% and conventional sponges by 3.7%. This improvement is attributed to the synergistic effect of the high heat absorption of CQDs and the porous sponge structure, which improves energy distribution and water evaporation. These results provide valuable insights for developing solar-powered desalination technologies to sustainably and efficiently produce freshwater.
El-Fakharany et al. (2026) studied this question.