Thermal performance enhancement of tubular solar distiller using bees wax, nanoenhanced beeswax and paraffin as thermal energy storage in waste soda cans

Freshwater shortage and very low productivity of solar stills require effective thermal enhancement techniques at lower costs for solar desalination. The present study analyzes thermal performance enhancement and fresh water collection from a tubular solar still (TSS) using beeswax, reduced graphene oxide (rGO)-doped beeswax, and paraffin wax stored in aluminum cans as thermal energy storage and compares the results against the conventional TSS. Due to high thermal conductivity and enhanced solar absorption capability, the incorporation of rGO contributes to improved heat transfer and latent heat storage characteristics of beeswax, resulting in better thermal stability and longer evaporation time. The thermal, optical, and structural properties of beeswax and rGO-doped beeswax are analyzed using FTIR, UV-DRS, and DSC characterization. FTIR results confirm that the chemical structure remains the same when rGO is added to beeswax. In contrast, diffuse reflectance using UV-DRS shows a reduction in reflectance from 47.8% to 9.4%, which reflects the improved absorption. Results from DSC revealed that the melting temperature of rGO-doped beeswax increases to 50.6^∘C. In comparison to beeswax, the latent heat of fusion of rGO-doped beeswax improved by 7.7%, demonstrating an excellent material for storing heat with improved thermal stability. The tubular solar still with different configurations is tested under the climatic conditions of Dhahran, Saudi Arabia, to analyze the variance in the temperature, fresh water collection, thermal, and exergy efficiency. The results demonstrated that the daily fresh water collection is higher in the case of rGO-doped beeswax in aluminum cans, which also demonstrated a higher water temperature inside the absorber. Similarly, the average thermal efficiency using the proposed method is found as 51.66%, which is higher compared to the conventional TSS, with beeswax and paraffin wax. The exergy efficiency of the rGO–beeswax system (3.14%) surpassed those of paraffin wax (2.48%), beeswax (2.08%), and conventional TSS (1.25%). Economically, the rGO–beeswax configuration exhibited the lowest distilled water cost ($0.011/L) and the shortest payback period (5.6 months). These findings demonstrate that integrating nano-enhanced PCMs within waste metal encapsulations provides an efficient, sustainable, and low-cost route to significantly enhance the thermal and economic performance of solar desalination systems.