Optically triggered cascade heat releasing from leakage-proof hydrate salt for intelligent thermal energy storage

Abstract

Hydrate salts are promising phase change materials for energy storage and conversion due to their safety, large latent heat and low cost. However, leakage during melting and supercooling in solidification are two main obstacles limiting their practical application. Herein, sodium sulfate decahydrate (SSD) was encapsulated with silica shell and further modified to be highly hydrophobic thus to achieve leakage-proof. Furthermore, azobenzene was introduced with delicate design to conduct isomerization under light illumination, the heat of which triggered solidification of supercooled SSD thus forming a cascade heat release process. The encapsulated SSD possesses high latent heat (123 J/g) and energy storage efficiency (80 %), and maintains shape-stable at 25 °C above SSD's m.p. More importantly, introduction of Azo can release heat stored in SSD promptly with temperature increased by 12 °C. This study paves the way for designing an intelligent thermal energy storage method by optically triggering cascade heat releasing from a stably stored phase change materials composite.