Impact of blending of phase change material for performance enhancement of solar energy storage

Abstract

The contemporary challenge of energy scarcity underscores the vital necessity for effective energy storage solutions. Addressing this concern becomes particularly crucial given the abundance of solar energy available for harnessing. Thermal energy storage emerges as a pivotal approach in this context, with phase change materials serving as valuable components due to their affordability and widespread accessibility. Specifically, various inorganic salts find application as phase change materials, contributing to the development of cost-effective and readily available solutions for storing the ample energy derived from solar sources. This research assesses the impact of varying Sodium chloride (NaCl) proportions on the thermophysical properties of nitrate-based salts, specifically Sodium nitrate (NaNO3) and Potassium Nitrate (KNO3). The investigation reveals significant influences on latent heat, specific heat, and thermal conductivity. High levels of NaCl adversely impact the thermal properties, leading to a decrease in the latent heat of NaNO3 and KNO3 by 7.3 % and 4.4 %, respectively. This reduction resulted due to the disruption of the crystal structure caused by blending, which results in the initiation of melting at lower energy levels. Conversely, lower NaCl quantities, particularly 7.5 %, positively influence latent heat for both salts. Thermal conductivity and specific heat show enhancement with 7.5 % and 10 % NaCl, but further increases mitigate these properties. Microstructure analysis indicates that limited NaCl promotes a compact structure with strong bonding forces, while exceeding a threshold increases lattice vibration frequency. A network structure between NaNO3 and NaCl forms, becoming more compact and complex with increased NaCl content, impacting melting and solidification points. X-ray diffraction (XRD) analysis confirms the stability of both mixtures. The NaNO3–NaCl combination exhibits superior thermophysical properties compared to KNO3–NaCl, underscoring the importance of fine-tuning NaCl proportions for optimal performance in these salt mixtures.