Thermal endurance of xylitol as a phase change material for thermal energy storage applications

Xylitol shares the good thermophysical properties of other sugar alcohols that are candidates for thermal storage purposes, with one singularity: it shows noticeable supercooling coupled with a low crystallization rate. This makes it a suitable material for long-term heat storage applications based on supercooled PCMs, but its thermal endurance for TES purposes remains unknown. Accordingly, a stability test was performed, which consisted of placing several tubes with fresh xylitol inside a heating cabinet, where they remained under isothermal conditions for periods of up to 150 days. Both open and closed (tight) tubes were employed under various test temperatures. Samples were afterwards analyzed by differential scanning calorimetry, X-ray diffraction and high performance liquid chromatography. The thermal properties and structure of the material remained stable during the 150 days of the test at 10 °C above its melting point, while at higher temperatures degradation was observed in the material over shorter periods. The behavior is noticeably better than the thermal endurance of other sugar alcohols reported in the literature, such as mannitol, dulcitol, erythritol and inositol.