Tetraethylammonium chloride as a novel eutectic partner for sodium acetate trihydrate-tailored phase change materials for efficient solar heat pump systems

Abstract

Sodium acetate trihydrate (SAT) is a promising phase change material for thermal energy storage, but its application is limited by its phase change temperature, subcooling, phase separation, and leakage. In this study, we successfully addressed these challenges by forming a binary eutectic with tetraethylammonium chloride (TEAC) and incorporating additives and a support material. The addition of 15 wt% TEAC reduced the phase change temperature to 49.2 °C while maintaining a high latent heat of 184.9 J/g. Further improvements were achieved by adding 1 wt% sodium tetraborate decahydrate (STD) as a nucleating agent to reduce subcooling and 1 wt% carboxymethyl cellulose (CMC) as a thickener to prevent phase separation. The issue of leakage was resolved by adsorbing the eutectic salt onto silicon dioxide (SiO₂), resulting in a shape-stable composite with minimal leakage. The optimized SAT-TEAC/SiO₂ composite phase change material demonstrated excellent thermal stability and retained its phase change properties even after 1000 thermal cycles. This new composite material shows great promise for thermal energy storage and solar heat pump systems due to its enhanced performance and stability.