Enhancing Solar Water Heating Performance with Stabilized Recycled Aluminum-Stearic Acid Composite Phase Change Materials

This work reports the formulation and performance assessment of composite phase change materials (C-PCMs) for solar thermal energy storage, comprising stearic acid (SA), recycled aluminum (Al) powder (5–25 wt %), and sodium dodecyl sulfate (SDS, 0–2.5 wt %). The approach addresses SA’s low thermal conductivity and dispersion instability. Optimal performance was achieved with 15 wt % Al and 1.5 wt % SDS, yielding a 29% reduction in heating time and 43% increase in discharge duration (T > 45°C) relative to pure SA. SDS minimized sedimentation, improved UV–Visible absorption, and enhanced collector efficiency to 54.5%. However, additives reduced latent heat by 32.9%. Characterization via FTIR, DSC, TGA, and UV–Vis confirmed physical interactions, improved stability, homogeneity, and photothermal properties. Using recycled Al promotes sustainability and cost-effectiveness. These C-PCMs offer a viable solution for efficient solar water heating, balancing enhanced heat transfer and optical properties against latent heat trade-offs.