Dynamically Tunable Solid-State Thermal Energy Storage

Thermal energy storage (TES) utilizing phase-change materials (PCMs) holds substantial promise in various applications, such as climate control in buildings and thermal management for batteries and electronics. A critical challenge in PCM-based TES applications is the limited tunability of the operating temperature, especially for the near-ambient applications, as the PCM has a fixed transition temperature as designed. or instance, within buildings, the required operating temperature can significantly fluctuate between summer and winter, and even exhibit notable diurnal variations. This results in suboptimal PCM utilization, often leading to incomplete melting or no phase transition at all. Recent efforts have aimed to enhance the tunability of thermal materials and devices, enabling dynamic changes in their properties and performance. However, most of these endeavors have primarily concentrated on modifying thermal transport properties, such as thermal conductivity, while neglecting thermodynamic characteristics, specifically the transition temperature of materials. Changing the transition temperature using external stimuli like pressure, electric fields, or magnetic fields presents a non-trivial task, as the required magnitude of the stimulus to achieve a sizable change in Tm is typically large, and the enthalpy change at Tm is only moderate for thermal storage applications. Additionally, handling the liquid phase of PCMs during phase transitions (melting) has hindered practical TES implementation. To address these challenges, this work reports a solid-state, tunable TES utilizing shape stabilized PCMs. This innovative tunable TES achieves an impressive dynamic transition temperature tunability of up to 10°C and enables outstanding shape stability over a month without leakage during melting. Such advancements offer the potential for simplified and safer TES device and system designs. Furthermore, the tunable TES exhibits exceptional cyclability, maintaining TES capacity across more than 100 cycles, thus presenting a promising avenue for practical applications.