Ultraviolet Resistant Colored Radiative Cooling Paints for Robust Outdoor Performance

Abstract

Abstract. Radiative cooling (RC) paint provides passive cooling by reflecting sunlight and emitting thermal radiation through the sky window to deep space. To maximize solar reflectance, radiative cooling paints are often white; however, colored paints are also necessary for aesthetic, safety, antiglare, and color-coding purposes. Here, we demonstrate single-layer green and blue colored radiative cooling paint with a 26.9 and 13.7 percentage point enhancement, respectively, over commercial paints of a similar color. The enhanced solar reflectance is achieved by increasing the UV and NIR reflectance through a narrow band absorption color pigment, a low absorption binder, and a high volume fraction of BaSO4 pigment. Additionally, accelerated UV weathering tests show this paint retains high UV-resistance. This is attributed to the use of inorganic pigment instead of dyes or organic pigment which are commonly used in colored radiative cooling paints. Field tests further confirm these results with our colored radiative cooling paints showing up to 6.3 °C (11.3 °F) and 3.2 °C (5.8 °F) lower temperatures than the commercial counterparts under direct sunlight. Overall, our work realizes single-layer, scalable, and cost effective colored radiative cooling paints that allow a surface to stay cooler, thereby reducing energy demand for buildings, vehicles, and outdoor equipment while retaining high UV-resistance.