Thermal Conductivity Enhancement of Quaternary Nitrate Salt Mixtures for Thermal Energy Storage with Al₂O₃ Nanoparticle Doping

Abstract

Effective thermal energy storage (TES) is essential for concentrated solar power (CSP) plants, driving the need to explore advanced heat transfer fluids with improved thermal conductivity. Traditional binary nitrate salt mixtures face limitations in thermal performance, leading to increased research into quaternary mixtures and the incorporation of nanoparticle additives. This study investigates thermal conductivity enhancement in quaternary nitrate salt mixtures for thermal energy storage (TES) in concentrated solar power (CSP) systems, focusing on Al₂O₃ nanoparticle doping effects. Seven quaternary mixtures of KNO₃, LiNO₃, Ca(NO₃)₂, and NH₄NO₃ were prepared with varying compositions. Thermal conductivity was measured for undoped and 5 wt% Al₂O₃-doped samples using differential scanning calorimetry (DSC) from 290-350K. Results show significant composition-dependent thermal conductivity, ranging from 0.2173 to 0.4687 W·m⁻¹·K⁻¹ for undoped samples. Al₂O₃ doping led to diverse outcomes: a 49.11% increase in Sample 5 but decreases of 16.53% and 11.41% in Samples 2 and 4, respectively. DSC analysis revealed well-defined phase transitions with melting points suitable for CSP applications. These findings demonstrate the potential for enhancing TES material performance through compositional optimization and nanoparticle doping, while highlighting the complex salt-nanoparticle interactions. This research contributes to the development of advanced TES materials for more efficient CSP systems.