Evaluation of thermal energy storage for medium-low temperature applications: Comparison of commercial solutions with a xylitol-based prototype

In recent years, thermal energy storage (TES) has become a promising and popular technology for energy storage. Among the different technologies, this work focuses on latent heat thermal energy storage (LHTES) system, specifically it assesses the potential of xylitol as phase change material (PCM) in TES systems for low-medium temperature applications. Xylitol, a sugar alcohol with stable supercooling, has a high latent heat (240 J/g), high energy storage density (1.45 kg/l), and a melting temperature of 92 °C. However, stable supercooling and low crystallization rate limits its practical application. Therefore, a laboratory-scale prototype working in the 70-100 °C range has been proposed and experimentally characterised that uses a seeding and shearing technique to mitigate this supercooling and accelerate crystallization, thereby increasing the thermal energy discharge power. The study compares this lab-scale prototype with four leading commercial solutions in terms of both materials and systems. Moreover, the methodology developed in the framework of IEA SHC Task 58 for TES system comparison in terms of energy density and power is applied. The results show the xylitol prototype has higher normalized power values than other experimental systems analysed in the framework of IEA SHC Task 58, reaching energy densities of up to 40.8 kWh/m3 system-wise in an optimized configuration. The study concludes that stirred TES prototype with xylitol is a competitive alternative to current commercial solutions.