Evaluating the effects of sugarcane juice-mediated ZnO nanofluids on solar light activation for enhancing double-slope solar still performance

•Double-slope solar stills (DS) use SZNs for enhanced absorption properties.•SZNs provide DS with high-yield drinking water, improving efficiency of energy storage.•High-temperature SZNs at 30% concentration accelerate the DS reaction.•During the process, the output reaches 4.5 kg/m² at 30% SZNs concentration.•Daily heat transfer coefficients increase by 37.20% with SZNs at 30% concentration. The investigation evaluates the operational efficacy of double-slope solar stills (DS) integrated with ZnO nanofluids synthesized via sugarcane juice (SZN) using the spray pyrolysis method, emphasizing their potential in advancing sustainable water desalination technologies. Key performance metrics examined include freshwater yield, thermal efficiency, and thermal gradient within the DS system. The incorporation of ZnO nanofluids was found to significantly augment the thermal performance of the DS due to their high thermal conductivity and superior solar radiation absorption characteristics. This enhancement facilitated more efficient heat transfer, promoting accelerated evaporation rates and resulting in increased freshwater productivity compared to conventional DS systems. The experimental setup was deployed in Vijayawada, India (16°31′N, 80°37′E), under varying meteorological conditions. Results demonstrated that the DS system employing SZN achieved a peak temperature of 72.6 °C, substantially higher than the maximum temperature of 62.6 °C observed in the system without SZN. Moreover, the integration of SZN improved system efficiency, achieving peak values of 22.53%, 36.43%, 25.24%, and 29.50% for SZN concentrations of 10%, 20%, 30%, and 40%, respectively, under optimized water depths of 0.5 cm. The sustained thermal performance of SZN-enhanced systems ensured consistent freshwater yield even under variable solar flux conditions. The synthesis of SZN as a reducing agent presents an environmentally sustainable and economically feasible method. This approach employs naturally derived, biodegradable materials, thereby reducing the ecological impact compared to conventional chemical synthesis techniques. ZnO nanofluids synthesized through this method demonstrated excellent thermal performance, scalability, and potential for integration into large-scale applications. This study highlights the capability of SZN-enhanced DS systems to address water scarcity, particularly in rural and coastal regions, by improving thermal conductivity and overall system efficiency. The eco