Phase Change Material Enhanced Radiative Cooler for Temperature-Adaptive Thermal Regulation

Abstract

Passive radiative cooling (PRC), as an electricity-free and environmentally friendly cooling strategy, is highly desirable in improving the global energy landscape. Despite numerous efforts, most designs for PRC are so devoted to improving the cooling performance in the daytime that they neglect the triggered overcooling at night. Herein, we approached an effective design for temperature-adaptive thermal management through integrating PRC and temperature control of room-temperature phase change material. Compared with conventional radiative coolers, the developed phase change material-enhanced radiative cooler (PCMRC) can adjust its performance according to the temperature of day and night. The PCMRC achieved an average subambient temperature drop of ∼6.3 °C under direct sunlight and an average temperature rise of ∼2.1 °C above ambient temperature at night, as well as a reduced temperature difference between day and night. The temperature-adaptive PCMRC shows great promise for passive radiative cooling regulation, which can further extend the applications of passive radiative cooling.

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.…”

Phase Change Material-Based Film toward Enhanced Radiative Cooling and Mitigation of Overcooling

“…The thermal properties of SEBS/TiO 2 and SEBS/TiO 2 /SPCM films were characterized by both DSC and thermogravimetric (TG) analyses. As illustrated in Figure B, the melting and crystallization temperatures of the SEBS/TiO 2 /SPCM film are 29.8 and 13.3 °C, respectively, with a latent heat of ∼40 J g –1 , which indicates that the incorporation of the SPCM holds promise in enhancing the radiative cooling efficiency when the temperature reaches ∼29 °C and curbing the risk of overcooling when the temperature drops to ∼13 °C . Besides, no peak appears on the curve of the SEBS/TiO 2 film as it is amorphous and no phase change process occurs.…”

“…With the trend toward global warming, the demand for cooling has been experiencing a notable surge as adequate space cooling is essential for a comfortable living environment. − Conventional cooling techniques, such as mechanical ventilation and air-conditioning systems, usually result in substantial energy consumption and the emission of undesired greenhouse gases that in turn exacerbate global warming. , According to statistics, the usage of cooling systems contributes to ∼15 and ∼10% of the total global electricity consumption and global greenhouse gas emissions, respectively. , Therefore, it is crucial to prioritize the development of energy-free and environmentally friendly cooling technologies. Among many others, radiative cooling is the most promising one as it can spontaneously cool an object without any energy consumption or greenhouse gas emission by radiating heat into the cold outer space (∼3 K). − The idea of radiative cooling was first introduced by Arago in 1828 .…”

“…They fail to adapt to applications in cold environments, such as high-latitude areas, cold nights, or winter, where the ambient temperature is so low that unwanted overcooling may occur. 1,30 Recently, some studies have attempted to address the problem of overcooling in low-temperature environments by adopting materials with temperature-dependent infrared emittance. 8,31,32 However, the designs for these studies are a little complicated and may waste the cold energy from the low-temperature environment, which can be stored first and then released to enhance radiative cooling during hot periods.…”

A Hierarchically Nanofibrous Self-Cleaning Textile for Efficient Personal Thermal Management in Severe Hot and Cold Environments

“…In recent years, radiative thermal management technology, which has the advantages of no energy consumption and zero emissions, has sparked immense attention in many different fields. − Radiative thermal management focuses on the regulation of two types of radiative heat fluxes involving solar radiation from the sun and infrared radiation into the outer space. , Specifically, radiative cooling can be achieved via enhancing the reflectivity in the solar spectrum and increasing the emissivity in the atmospheric window. , Similarly, radiative heating is achieved under the opposite optical conditions . There have been some attempts to investigate the potential of functionalized textiles for personal thermal management, and most research has focused on localized temperature regulation through advanced textiles with single or dual-mode capabilities. − For instance, by adjusting the optical properties based on the surface of the textiles, single temperature-controlled textiles are prepared that can effectively achieve personal radiative cooling or radiative heating performances. − Additionally, dynamic temperature control textiles, such as Janus textiles, and temperature or humidity responsive textiles can meet personal thermal regulation. Nonetheless, these textiles are usually not appropriate for use in severely hot and cold environments owing to their limited temperature regulation capabilities, which could cause heat/cold stress and serious medical emergencies .…”