A novel solar absorber using activated carbon nanoparticles synthesized from bio-waste for the performance improvement of solar desalination unit

Enhancing the efficiency of low-cost solar-powered desalination technologies such as solar stills (SS) is essential to ensuring sustained access to potable water in water-stressed areas. In the present work, the potential enhancement of SS performance through the addition of different concentrations of activated carbon nanoparticles (ACNPs) to the standard black paint used to coat the absorber plate was explored. SSs were fabricated with absorber coated using black paint doped with 0, 5, 10 and 15 wt% ACNPs (denoted as CSS, MSS-5, MSS-10 and MSS-15, respectively) and the effect on water temperature and distillation efficiency determined. ACNPs were synthesized by crushing dead Kigelia Africana leaves and pyrolysis of the leaf powder in a muffle furnace at 500 °C. Absorber surface roughness analysis illustrated increasing roughness with increasing the loading of ACNPs in the nano-paint, leading to significant increase in heat transfer. Significant improvement in average water temperature (12.5%) and absorber (14.5%) was noted in the modified SS coated with 15 wt% ACNP over the CSS. The augmented temperature of this still enhanced the peak hourly and full-day water yield of MSS-15 by ⁓39.3%, compared to the conventional SS. The water quality analysis shows that the distilled water is appropriate for drinking. In conclusion, the synergetic effect of the high thermal conductivity and excellent solar absorption of the ACNP-based solar absorber improves the performance of the SS unit.