Integrated radiative and evaporative cooling beyond daytime passive cooling power limit

Abstract

Radiative cooling technologies can passively gain lower temperature than that of ambient surroundings without consuming electricity, which has emerged as potential alternatives to traditional cooling methods. However, the limitations in daytime radiation intensity with a net cooling power of less than 150 W•m −2 have hindered progress toward commercial practicality. Here, we report an integrated radiative and evaporative chiller (IREC) based on polyacrylamide hydrogels combined with an upper layer of breathable poly(vinylidene fluoride-co-trifluoroethylene) fibers, which achieves a record high practical average daytime cooling power of 710 W•m −2 . The breathable fiber layer has an average emissivity of over 76% in the atmospheric window, while reflecting 90% of visible light. This IREC possesses effective daytime radiative cooling while simultaneously ensuring evaporative cooling capability, enhancing daytime passive cooling effectively. As a result, IREC presents the practicability for both personal cooling managements and industrial auxiliary cooling applications. An IRECbased patch can assist in cooling human body by 13 °C low for a long term and biocompatible use, and IREC can maintain the temperature of industrial storage facilities such as oil tanks at room temperature even under strong sunlight irradiation. This work delivers the highest performance daytime passive cooling by simultaneous infrared radiation and water evaporation, and provides a new perspective for developing highly efficient, scalable, and affordable passive cooling strategy.

Ultrahigh Passive Cooling Power in Hydrogel with Rationally Designed Optofluidic Properties

“…As such, the IPC automatically tunes the contributions of evaporative cooling to maintain a stable temperature, leading to adaptive passive cooling under various conditions regardless of the varying weather or indoor/outdoor conditions. In comparison with recent reported works, we experimentally achieved a record-high cooling power of approximately 350 W/m 2 on a typical sunny day, which is superior to those of state-of-the -art passive coolers with various designs (Figure h,i). ,− In comparison with the reported multilayer structure, direct optical modification of the hydrogel matrix ensured mechanical stability since a interfacial adhesion problem between the radiative and evaporative layers may occur when the hydrogel matrix suffers great water loss. The higher cooling power of IPC-2 is attributed to a larger evaporative surface without covering a layer of a radiative cooler.…”

Skin‐Inspired Ultrafast Self‐Healing Wearable Patch with Hybrid Cooling for Comfortable and Durable Electromyographic Monitoring

“…[ 19 ] As a result, hybrid cooling can effectively surpass single radiative or evaporation cooling. [ 26 ]…”

Passive Photovoltaic Cooling: Advances Toward Low‐Temperature Operation

“…During the past few years, passive evaporative cooling has witnessed great advances with the progress of water-rich materials, especially for hydrogels. [44,[59][60][61][62] The high enthalpy of water evaporation (over 2200 kJ kg −1 ) can enable the great cooling potential for heat dissipation. Generally, evaporative cooling power mainly depends on water evaporation rate, which can be quantitatively depicted in Figure 2b.…”