Cold-crystallization of polyelectrolyte absorbed polyol for long-term thermal energy storage

a) Erythritol in cross-linked sodium polyacrylate (PAANa) matrix. b) Typical differential scanning calorimetry (DSC) curves of erythritol-PAANa, and operation of the material as thermal energy storage (TES). Heating and cooling cycles are shown as solid and dashed curves, respectively. The capital letters A-E are the temperatures that correspond to the different heat storage modes of the material. The novel TES is charged by heating the material above 100 °C at which erythritol melts (A → B, seen as peak upwards in the solid DSC heating curve). After melting the material supercools (B→ C, move from right to left along the dashed cooling line), and eventually vitrifies. Thermal energy can be stored long-term in the polyol-PAANa below the cold-crystallization temperature, Tcc. C → D: The material is re-heated to Tcc (solid heating curve). D → E: The material releases the stored thermal energy by cold-crystallization and the temperature rises close to Tm (seen as peak downwards in the solid DSC heating curve).179