A strategy of hierarchical particle sizes in nanoparticle composite for enhancing solar reflection

Pang

et al. 2021

EcoMat

Passive daytime radiative cooling (PDRC) dissipates terrestrial heat to the extremely cold outer space without using any energy input or producing pollution. It has the potential to simultaneously alleviate the two major problems of energy crisis and global warming. In this review, we summarize general strategies implemented for achieving PDRC and various applications of PDRC technologies. We first introduce heat transfer processes involved in PDRC, including radiative and nonradiative heat transfer processes, to evaluate the PDRC performance. Subsequently, we summarize the general material designs used for controlling PDRC performance, such as tuning the thermal mid-infrared emittance and solar reflectance. Finally, we discuss the diverse applications of PDRC technologies to overcome problems in space cooling, solar cell cooling, water harvesting, and electricity generation.

Section: Solar Reflectancementioning

confidence: 99%

“…69 (D) Polymer microsphere coating. Source: Reproduced with permission: Copyright 2021 and 2019, Elsevier, 21,79 and Reproduced with permission: Copyright 2021, Spring. 43 (E) Porous polymer coating (such as: P(VdF-HFP), PDMS, and PMMA).…”

Section: Colored Pdrc Coatingmentioning

confidence: 99%

Passive daytime radiative cooling: Fundamentals, material designs, and applications

Pang

et al. 2021

EcoMat

“…In order to optimize the bionic performance, a reflectance predicting model was constructed with the four-flux theory, and the influences of particle volume fraction and water content on the reflection characteristics were analyzed, respectively. However, the absorption and scattering characteristics of the particles are the key factors affecting the reflection properties of the translucent biomimetic materials [15,16] and have not been investigated from the essential properties of the particles, such as optical parameters and size. Therefore, it is vital to provide insights into the absorption and scattering mechanisms of the biomimetic materials containing particles.…”

Section: Introductionmentioning

confidence: 99%

Preparation and optimization of biomimetic materials simulating solar spectrum reflection characteristics of natural leaves

2020

J Mater Sci

Solar spectrum reflection characteristics of natural leaves are caused by the absorption and scattering processes of incident radiation in the leaves. To realize hyperspectral camouflage in the background of vegetation, two types of biomimetic materials are prepared. One type utilizes Cr 2 O 3 particles to simultaneously simulate the absorption characteristics in the visible light band and the scattering characteristics in the solar spectrum band and is named as COG-BM. The other type contains chlorophyll and TiO 2 particles to simulate the absorption and scattering characteristics in the above two bands, respectively, and is named as CH/TD-BM. The measured results show that both can simulate the solar spectrum reflection characteristics of the leaves approximately. In order to optimize the bionic performance, the reflectance predicting model was constructed with Lorenz-Mie scattering and four-flux theories. The simulation results show that with the increase in particle volume fraction, the reflectance of COG-BM in the visible light band is maintained at almost the same level as that of the leaves because of the simultaneous increase in absorption and scattering coefficients. Nevertheless, the reflectance of CH/TD-BM increases significantly, because the absorption coefficient of CH/TD-BM is constant with the increase in the particle volume fraction, and the scattering coefficient enhances remarkably. More interestingly, with the increase in particle size, the near-infrared plateau of COG-BM and CH/TD-BM is closer to horizontal, exhibiting greater similarity to the natural leaves. Moreover, the water absorption characteristics at 1450 and 1940 nm become more significant with the increase in water content.

“…Then the surface temperature can be decreased below the ambient. Therefore, certain natural materials, such as polymeric materials, 15,16 titanium dioxide, [17][18][19] silicon nitrides, 20 and silicon-monoxide (SiO), 21 have potential for limited selectivity. But it is difficult to find out a simple bulk material with high emissivity and high reflectivity in the desirable spectrum range simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Recent advances and progresses in photonic devices for passive radiative cooling application: a review

Goyal

Kumar

2020

J. Nanophoton.

This review covers the recent progress made in the nanophotonic devices-based daytime passive radiative coolers. The radiative cooling capabilities along with the structural description of various natural species are discussed. The design principle along with key characteristics of the omnidirectional solar reflectors as well as thermal adiators is discussed in detail. Several analogues planner one-dimensional and two-dimensional photonic nanostructures and their current state-of-the-art techniques have been discussed. For each kind of the photonic structure, the novelty, measurement principle, and their respective daytime radiative cooling capability are presented. The reported works and the corresponding results predict the possibility to realize an efficient and commercially viable radiator for passive radiative cooling applications.