Experimental evaluation and thermodynamic Gibbs free energy analysis of a double-slope U-shaped stepped basin solar still using activated carbon with ZnO nanoparticles

Abstract

Solar distillation methods require expensive energy storage in the basin area to enhance productivity, confirming the cost-effectiveness of natural green dyes as an appealing process. The present study investigated the potential for enhancing productivity of a double-sloped U-shaped stepped basin solar still (DUSS) by covering its sides with matte black paint (BP) mixed with different concentrations of activated carbon nanoparticles (ACNPs). It was prepared from ACNP using Mangifera Indica (M) with Celostia Argentea (C), which consists of carbon powder with doped ZnO nanoparticles (Z) and discussed in the samples. In this case, a U-shaped stepped basin (USB) surface was coated with BP doping with different ratios of 5, 10, 15, 20, and 25 wt% for the ACNP. The USB coated with BP with ZMC was subjected to a thermodynamic study to calculate the entropy change using Gibbs free energy equation. Silver-colored steel balls (SBs) were used to increase convective heat transfer as they could absorb incident solar radiation and transfer it into the BP-ACNP and affect the thermal performance of the DUSS. It was found that ZMC leads to higher heat transfer with a potential of DUSS containing the BPACNP, resulting in an enrichment increase of 20% by weight and an average water temperature of 25%. The performance enhancement of the DUSS with USB-coated BPACNP integrated with SBs was 16.91% compared to the conventional double U-shaped stepped basin solar still (CDUSS). The proposed new design could increase the water temperature of the DUSS and enhance the performance to 14.92 l/m2day with an average daily efficiency of 38.73%. The results of the water quality analysis indicated that the produced distilled water is suitable for drinking. The theoretical and experimental results obtained for the BPACNP-SB integrated with the DUSS indicated an increased thermal conductivity.