Temperature-adaptive porous polymer radiative cooling coatings for all-season thermal management and annual energy-saving

Traditionally, the passive radiative cooling materials (PRCMs) researches focus on optimizing the cooling power by spontaneously increasing sunlight reflectivity and infrared emissivity. However, the resultant overcooling in winter will increase the construction heating costs. Here, temperature-adaptive porous polymer radiative cooling coatings (TA-PRCMs) were developed from an all-season thermal management perspective, which can adaptively adjust the sunlight reflectivity according to ambient temperature. The fabricated porous polymer coatings switch from the colorless phase to the colored phase, when the ambient temperature is lower than the transition temperature, with the solar reflectance of black, rose red, orange, violet, blue and yellow coatings changed from 0.85, 0.9, 0.92, 0.9, 0.75 and 0.9 to 0.6, 0.7, 0.73, 0.67, 0.62, and 0.86, respectively. The outdoor temperature tests show that the average and maximum daily surface temperatures of the black sample are up to 2.7 ℃ and 4.7 ℃ higher than superior performance hierarchically porous radiative cooling (HPRC) film on a winter day. Energy consumption simulations show that the energy-saving performance of TA-PRCMs coatings outperforms the HPRC film in most cities of China with various climates. Such as in Lhasa, China, the black color coating can save up to 5000∼6000 kWh for a two-story office building.