Controllable Supercooling in Phase Change Materials-Advances in Triggering Methods, Lab-Scale Investigations, and Prototype Demonstrations

Supercooled Phase Change Materials (PCMs) offer significant advantages for thermal energy storage by enabling latent heat retention over extended periods with minimal loss. However, controlling crystallization in supercooled states remains a critical challenge for practical applications. This review provides a comprehensive analysis of lab-scale experimental studies on controllable supercooling in PCMs, categorized by triggering methods such as local cooling, mechanical agitation, bubble injection, electric and ultrasonic fields, mechanical shock, and cold crystallisation. Furthermore, the transition of these control techniques into physical prototypes is discussed, highlighting operational challenges and integration issues observed in heat pads, thermal batteries, battery preheating systems, and long-term thermal energy storage units. Despite substantial progress, scaling up supercooled PCM systems introduces new barriers, including premature crystallization, inconsistent triggering, and material degradation. Addressing these challenges through prototype-scale research is critical to achieving reliable, cost-effective thermal energy storage solutions utilising supercooled PCMs as controllable thermal energy storage.