Thermal energy storage mitigates nighttime heating penalty, condensation and frosting risk for passive daytime radiative coolers

• Latent and sensible thermal mass-enhanced radiative coolers are proposed. • The nighttime heating penalty was reduced by 50% in winter. • The condensation period was shortened by 7.5 h on a cold winter night. • Condensation and frosting on radiative coolers worsen winter overcooling. • The daytime cooling capacity was enhanced by 240% in summer. Passive Daytime Radiative Coolers (PDRCs) may deliver superior performance for passive cooling in buildings and for mitigating urban overheating when installed on flat roofs. However, PDRCs may suffer from overcooling and associated heating penalty in winter, particularly at night. Further, the effects of condensation and frosting on PDRCs’ performance remain largely unexplored. Here, we provide a solution that combines sensible and latent thermal energy storage (TES) to mitigate the overcooling, condensation, and frosting of PDRCs on winter nights while simultaneously enhancing cooling performance during summer days. A 15-mm layer of phase change materials (PCMs) with phase change temperatures of 8 ℃ for winter and 24 ℃ for summer, and a 50-mm layer of concrete are integrated under PDRCs as TES. Outdoor experimental measurements were conducted over three consecutive days in both summer and winter in Western Sydney. For PDRCs, nighttime condensation and potential frosting induce an early-morning heating penalty lasting over 2 h in winter but provide additional cooling for 2–3 h in summer. Compared with conventional PDRCs, the proposed thermal mass enhanced radiative cooler (TMRC) can increase the surface temperature by up to 8 ℃, prolong the non-condensation period by 7.5 h, and reduce the nighttime heating penalty by 50% on a cold winter night, while reducing the peak temperature by up to 7.1 ℃ and increasing the daytime cooling capacity by 240% on a hot summer day. This work offers a promising strategy for environmentally adaptive and year-round passive radiative cooling.