Investigating the Effect of Nanoparticle Additives on the Thermal Conductivity and Stability of Phase Change Materials for Solar Energy Storage in Kaduna State

Phase change materials offer a promising thermal energy storage solution for solar energy applications in Kaduna State, North West Nigeria, where high solar irradiation and periodic electricity outages create demand for reliable off-grid thermal storage systems. This study investigates the effect of incorporating aluminium oxide, titanium dioxide, and multi-walled carbon nanotube nanoparticles at concentrations of 0.5, 1.0, and 2.0 weight percent into palmitic acid as a phase change material on thermal conductivity, thermal stability, and latent heat storage capacity. Nanoparticles were functionalised by acid treatment and dispersed by ultrasonication. Thermal conductivity was measured by the transient hot-wire method, latent heat and melting temperature by differential scanning calorimetry, thermal cycling stability by repeated DSC over 200 melt-freeze cycles, and nanoparticle dispersion stability by transmission electron microscopy. Aluminium oxide nanocomposites at 2.0 wt% achieved the highest thermal conductivity enhancement of 28.4% relative to pure palmitic acid without significant latent heat reduction. Multi-walled carbon nanotubes at 1.0 wt% provided a 19.2% conductivity enhancement but reduced latent heat by 7.1% at 2.0 wt% loading due to particle agglomeration. Thermal cycling stability over 200 cycles showed less than 3% variation in latent heat for aluminium oxide nanocomposites, confirming long-term applicability. The study identifies aluminium oxide-palmitic acid nanocomposite as the most suitable formulation for solar thermal storage in Kaduna State contexts. Keywords: phase change material, nanoparticle, thermal conductivity, solar energy storage, Kaduna State