Inducing and controlling supercooling in industrial-grade sodium acetate trihydrate for long-term PCM based thermal energy storage system

Phase change material (PCM) based energy storage systems are a promising solution to ensure a continuous energy supply from intermittent renewable sources for long-term applications. This study explores the potential of economical, industrial-grade sodium acetate trihydrate (SAT) for thermal energy storage, as pure SAT is expensive. Unlike conventional approaches to mitigate supercooling, this research induces controlled supercooling for long-term usage of latent heat activation. Composites, including Tween 80, coconut oil, and ethylene glycol, were incorporated into industrial-grade SAT to analyze their effects on supercooling behavior. The morphological and thermophysical properties of composite PCMs (CPCMs) were analyzed. PCM samples with 30g were heated to 65 °C, 80 °C, and 95 °C, then cooled naturally, with crystallization triggered using a heterogeneous seeding technique. The influence of composites at varying concentrations, with mass ratios of 1/2 and 1/3, was evaluated for their effects on the crystallization temperature and supercooling degree. Additionally, the behavior of copper particles submerged in supercooled SAT and air-surface interactions was examined. The experimental results revealed that Tween 80-based CPCMs exhibited the highest degree of supercooling across all conditions, while coconut oil-based CPCMs showed an interesting trend at higher initial temperatures of 95 °C, where the degree of supercooling increased, a behavior not observed at lower temperatures. Conversely, ethylene glycol-based CPCMs exhibited poor crystallization kinetics, tailoring the maximum heat release temperature from 58 °C to 40 °C, which makes them suitable for specific thermal applications. In all CPCMs, higher composite concentrations increased supercooling, highlighting the need to optimize composite levels for desired thermal performance.