Subambient Cooling of Water: Toward Real-World Applications of Daytime Radiative Cooling

Real-world applications of radiative sky cooling require thoughtful design of the system, along with clear understanding of weather effects on system performance. This work explores application of radiative sky cooling based upon a low-cost radiative cooling metamaterial that can be scalably manufactured. A radiative cooled-cold collection (RadiCold) module is developed to cool water to 10.6°C below ambient at noon under stationary conditions. The effects of different weather conditions (wind speed, precipitable water, and cloud cover) on the performance of radiative cooling have been investigated. A kilowatt (kW)-scale RadiCold system with 13.5 m2 radiative cooling surface area is then built and demonstrated to provide a maximum cooling power of 1,296 W at night, and an average cooling power of 607 W at noon (12–2 p.m.) under 952 W/m2 average solar irradiance at 26.5 L/(h⋅m2) volumetric flow rate. A building-integrated RadiCold system is proposed to provide continuous day-and-night cooling.