An investigation of the effect of supercooling on the performance of erythritol as a phase change material

Erythritol, an organic phase change material (PCM), has been identified as a suitable phase change material (PCM) to be used in latent heat thermal energy storage (LHTES) systems for medium temperature applications. Thermal energy storage systems have the advantage of storing solar thermal energy for later use, in a move to alleviate the global energy crisis as well as to reduce the environmental impact of contemporary energy use. The quasi-isothermal behaviour of the storage/release of latent thermal energy of PCMs makes LHTES systems attractive for constant-temperature applications. However, unlike most classes of organic PCMs, erythritol suffers from supercooling which has been identified to contribute to low efficiency of the LHTES system in which it is utilized. While some studies have investigated means of overcoming/suppressing supercooling in erythritol and some other organic PCMs, no study has studied quantitatively the effect of supercooling of erythritol in terms of entropy generation in a practical thermal energy storage scenario. This study uses the temperature history of erythritol in a spherical macro-capsule, during charging and subsequent discharging cycles to quantify the effect of supercooling on the PCM. Supercooling increases entropy change in erythritol whose degree increases with the rate of heat retrieval from the PCM. To utilize erythritol in a LHTES system, high rate of heat transfer and low rate of heat retrieval will minimize entropy generation and ensure high efficiency of such system.