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

Abstract

Radiative sky cooling of large thermal mass water to 10.6 C below the ambient temperature is demonstrated around noon under direct sunlight by using polymerbased low-cost radiative cooling metamaterial. Subambient cool-water production at various constant temperatures is experimentally demonstrated. The parasitic effects of different weather conditions (local wind speed, precipitable water, and cloud cover) on the performance of sky radiative cooling have been investigated, which is critical for developing operation strategies for real-world applications.

Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling

“…), humidity, and wind speed have been investigated and these could strongly affect the cooling performance. 33,34 Our outdoor experimental data have shown that the cooling performance varied on different days even for the same apparatus and the same samples 187-190 (1982). Figure S1.…”

Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

“…The concept of radiative cooling is that a substance (referred as radiator) on earth could spontaneously reduce its temperature without any energy input, by sending excessive heat to outer space in the form of infrared thermal radiation through the atmospheric window (8–13 µm) . This environmentally‐friendly technology could be put into practical applications via two ways: 1) directly attach radiators on the surfaces of objects (e.g., building rooftop) which need to be cooled; 2) Use radiators to cool heat‐transfer (e.g., water) fluid which could be integrated into other thermal systems (e.g., air conditioner or condensers) . Particularly, daytime radiative cooling has attracted intense interest in recent years.…”

“…Particularly, daytime radiative cooling has attracted intense interest in recent years. To realize daytime cooling, a radiator must satisfy two criteria: high visible—near infrared solar reflectance to minimize absorbed solar energy and strong mid‐infrared (MIR) emissivity to maximize emitted thermal energy . Pioneered by Fan and co‐workers making multilayer photonic structures to realize 4.9 °C daytime radiative cooling, many designed radiators with precise and complex photonic structures, such as metamaterials, photonic crystals, and multilayer stacks, have been reported.…”

“…Pioneered by Fan and co‐workers making multilayer photonic structures to realize 4.9 °C daytime radiative cooling, many designed radiators with precise and complex photonic structures, such as metamaterials, photonic crystals, and multilayer stacks, have been reported. However, these photonic radiators generally require stringent and nanoscale‐precision fabrication including electron beam lithography, vacuum deposition, and so forth. Such sophisticated and expensive fabrication techniques greatly restrict the mass production of the radiators and render them implausible to meet the large‐area demands of the residential and commercial applications that can benefit most from radiative cooling.…”

Broadband Radiative Cooling and Decoration for Passively Dissipated Portable Electronic Devices by Aperiodic Photonic Multilayers

“…Later, several novel materials have been studied and implemented in radiative cooling, such as nanoparticle‐embedded double layer [ 14 ] and phase‐change material, [ 15 ] as well as new design methods like memetic algorithm. [ 16 ] Subsequently, radiative cooling has been applied on solar cells, [ 17–20 ] continuous thermal sources, [ 21 ] spacecrafts, [ 22,23 ] and water [ 24 ] with different requirements and mechanisms.…”