Synergetic Effect of Radiative Cooling and Thermal Energy Storage for Advanced Thermal Management

Recent research endeavors strive to develop sustainable thermal management methods to confront the threats posed by extreme weather events and global energy crisis. Thermal energy storage (TES), which harnesses the latent heat of phase change materials (PCMs), is a promising technology that has been extensively explored for thermal management. However, the practical implementation of TES in buildings faces inherent limitations, including issues related to shape stability, supercooling, slow charging/discharging rates, and limited storage capacity. Here we report a shape stabilized PCM composite that overcomes these challenges by exploring the synergetic effect of TES and passive radiative cooling (PRC), which consists of polyethylene glycol (PEG) as PCM and functionalized boron nitride (fBN) particles as solar scatterers. The inclusion of fBN particles induces a Mie-scattering effect and combines with the intrinsic thermal emission of PEG, resulting in an impressive solar reflectivity of 84.5% and a thermal emissivity of 95.0%. Meanwhile, the composite also achieved a latent heat of 97.1 J/g with excellent shape stability promoted by the interaction between fBN with PEG. Compared to traditional TES, this synergetic effect of PRC and TES promises more efficient thermal regulation by (1) effectively charging PCM during nighttime, (2) maximizing daytime cooling capabilities, and (3) mitigating the impact of supercooling effect. Our modeling study showed that the proposed dual-functional composite could extend the effective TES period by over 50% within a 24-hour cycle. The field test also demonstrated a PRC effect of 3.5 °C below ambient during night, which facilitated the charging of PCMs via crystallization. All these benefits are particularly promising for developing sustainable building thermal management.