Multi-scale experimental characterization and management of supercooling of isosorbide, a phase-change material for thermal energy storage

Isosorbide, with a melting temperature about 60–65 °C, is an interesting bio-based material for use in Phase-Change Material (PCM) Thermal Energy Storage (TES) systems. It is suitable for low- to moderate-temperature applications, based on its safety characteristics and phase-change enthalpy. However, Isosorbide is known to exhibit moderate to significant overcooling, which may be an issue in TES applications. This study experimentally investigates the overcooling characteristics of Isosorbide and how to manage them. Tests were performed at three distinct scales: material-scale (about 10.3 mg sample), lab-scale (400 mL), and TES prototype-scale (37 kg). At all three scales, extensive supercooling is observed. At the material-scale, Isosorbide solidifies at temperatures below 5 °C, whereas melting occurs in the range 60–65 °C. At beaker-scale, an overcooling rate exceeding 30 °C is observed. Seeding and N2 bubbling trigger crystallization, with bubbling providing clearly higher efficiency. At TES-scale, overcooling remains stochastic, limiting experimental reproducibility. The addition of bubbling during discharge triggers crystallization, making it an effective means to manage supercooling. However, this approach also leads to temperature homogenization in the PCM volume. Tests at prototype-scale reveal that this homogenization is not an issue for TES performance as it allows energy to be recovered at higher temperatures during discharge. • Isosorbide is considered as storage material in PCM TES. • Experimental characterization of the thermal behavior of isosorbide has been made from material to TES prototype scales. • Significant supercooling has been observed at all scales. • Bubbling allows to significantly reduce supercooling and its stochastic behavior. • Bubbling induces global axial homogenization of the temperature at TES prototype scale.