Optically Triggered Synchronous Heat Release of Phase‐Change Enthalpy and Photo‐Thermal Energy in Phase‐Change Materials at Low Temperatures

Abstract

Abstract Phase‐change materials (PCMs) are used in several energy recycling utilization systems due to their latent‐heat‐storage and ‐release ability. However, the inability of PCMs to release heat at temperatures below their freezing point limits their application in distributed energy utilization systems. This paper reports optically‐triggered low‐temperature heat release in PCMs based on a solid–liquid phase change (PC) controlled by the trans – cis ( E – Z ) photo‐isomerization of azobenzene. To achieve this, a photo‐responsive alkyl‐grafted Azo is incorporated into tetradecane (Ted) to create a photo‐sensitive energy barrier for the PC. The Azo/Ted composite exhibits controllable supercooling (4.04–8.80 °C) for heat storage and achieves synchronous heat release of PC enthalpy and photo‐thermal energy. In addition, the Azo reduces the crystallization of Ted by intercalating into its molecular alignment. Furthermore, under light illumination, the Azo/Ted composite releases considerable heat (207.5 J g −1 ) at relatively low temperatures (−1.96 to −6.71 °C). The temperature of the annular device fabricated for energy utilization increases by 4 °C in a low‐temperature environment (−5 °C). This study will pave the way for the design of advanced distributed energy systems that operate by controlling the energy storage/release of PCMs over a wide range of temperatures.