Bubble-injection-enabled significant reduction of supercooling and controllable triggering of crystallization of erythritol for medium-temperature thermal energy storage

Erythritol, having a nominal melting point of ∼118 °C, has been considered a candidate phase change material (PCM) for medium-temperature thermal energy storage (TES) due to its large latent heat of fusion (∼330 kJ/kg). However, it suffers from severe supercooling effect, up to several tens of degrees Celsius, upon crystallization by cooling, which remains to be a critical issue for its application. Here we propose a novel method of injection of gas bubbles into subcooled liquid erythritol to facilitate the nucleation of erythritol crystals, so as to reduce its degree of supercooling. Using this method, we obtained successfully an unprecedented reduction of the degree of supercooling of erythritol down to only 5 °C, which is much lower than those achieved by other conventional methods like adding a nucleating agent or ultrasonication. As a bonus, the latent heat of crystallization was found to be greatly increased by nearly 50%, from 218.2 kJ/kg to 322.3 kJ/kg. The injection of bubbles also enables an effective way for actively triggering the crystallization of erythritol in a controllable manner. Our results showed that by changing the injecting timing of bubbles, crystallization can always be triggered immediately with only the crystallization point being varied over a wide range. The injection of bubbles is thus deemed to be a highly-efficient, cost-effective, and scalable method for addressing the supercooling issue of erythritol, and other similar PCMs with deep supercooling, making it more promising for TES applications.