Radiative cooling of TiO2 white paint

Harrison, A. W.; Walton, Matthew

doi:10.1016/0038-092x(78)90195-0

Cited by 207 publications

(107 citation statements)

References 3 publications

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“…In previous studies, polyethylene fi lms with a high IR transmittance were used as a front cover by placing it on top of the radiator with suffi cient gap which can drastically minimize the natural convective and conductive processes. [2][3][4]8,11 ] In reference, [ 4 ] the use of an IR transparent low-density polyethylene fi lm, as a wind shielding front cover, resulted in a practical combined convective and conductive heat-coeffi cient, Q = 6.9 W m −2 K −1 . We consider the impact of the nonradiative processes on the cooling performance of the CMM structure with Q values of 1, 3, and 6.9 W m −2 K −1 .…”

Section: Communicationmentioning

confidence: 99%

“…[1][2][3][4] However, the realization of such ideal emitters for effective radiative cooling has always been a challenge. [2][3][4][5][6][7][8] In this paper, we propose the use of a strictly selective yet broadband metamaterial emitter toward highly effi cient radiative cooling. We demonstrate an anisotropic and conical-shaped metamaterial structure, to facilitate the polarization insensitive, highly enhanced, and broadband infrared (IR) emission, selectively spanning over the entire atmospheric transparency window.…”

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confidence: 99%

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A Metamaterial Emitter for Highly Efficient Radiative Cooling

Hossain

Jia

2015

Advanced Optical Materials

521

232

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COMMUNICATIONTo demonstrate effi cient radiative coolers, selective IR emitters have been extensively studied. [1][2][3][4][5][6][7][8][9][10][11] In particular, composite materials, [ 2,9 ] white pigmented paints, [ 5,8 ] SiO fi lms, [ 6,7,10 ] and polymeric materials [ 3,11 ] are demonstrated to possess IR emission within the atmospheric transparency window. However, almost all of these materials either lack near-unity emission or broadband emission within the entire 8-13 μm window. [ 1,2,[5][6][7][8][9][10] In addition, signifi cant IR absorption outside the transparency window, where the atmosphere is highly emissive, also restricts the materials to cool down well below the ambient temperature. [2][3][4][5]11 ] On the other hand, artifi cial metallic nanostructures, such as, plasmonic nanostructures, [12][13][14][15][16][17][18] and metallic photonic crystals [19][20][21][22] possess highly selective IR optical absorptions. However, in most cases, their absorption spectra are diffi cult to optimize for wide-band absorption. Metamaterials, on the contrary, can provide both selective and broadband IR absorption. [23][24][25][26][27] Recently, multilayer metal-dielectric anisotropic metamaterials have been demonstrated to possess intriguing optical properties. [ 25,[28][29][30] By employing dispersive properties and anisotropy, ultra-broadband, spectrally selective and polarization sensitive absorption was achieved in the visible to microwave frequencies. Here, for the fi rst time, we propose the use of anisotropic metamaterials toward the application of highly effi cient radiative cooling. To achieve an ideal thermal emitter, we design and demonstrate a microstructure consisted of an array of symmetrically shaped conical metamaterial (CMM) pillars leading to a near unity absorption of unpolarized light. By selectively matching the thermal emission (absorption) to the entire 8-13 μm atmospheric transparency window, the CMM structure can possess a practical radiative cooling power of 116.6 W m −2 .Our design concept of an elementary metal-dielectric CMM pillar consists of alternating layers of aluminum and germanium as depicted in Figure 1 a. Each of the metal and dielectric layers maintains the circular symmetry along the vertical axis and the diameters of the layers decrease gradually from bottom to top which gives the structure a conical shape. The thickness of the aluminum layer is 30 nm and the thickness of the germanium layer is 110 nm. The top and bottom diameters of the CMM pillars are defi ned t and b . The substrate of the CMM structure is set to 150 nm thick aluminum which is optically thick enough to diminish any IR transmission through the substrate. The dispersive permittivity of aluminum is defi ned from reference [ 31 ] and the permittivity of germanium is 16. The periodicity of the CMM pillars, p is set to 1.3 times b , providing a suffi cient gap between the adjacent CMM pillars to avoid any proximity effects. [ 29 ] The aspect ratio, s , of t and b is optimized to 0.6 and seven periods of metal...

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Section: Communicationmentioning

confidence: 99%

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confidence: 99%

A Metamaterial Emitter for Highly Efficient Radiative Cooling

Hossain

Jia

2015

Advanced Optical Materials

521

232

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“…Fortunately, emittance properties approaching these ideals can be found in bulk materials suitable for massive production. They have been extensively studied in pioneering works of the 1970s and 1980s [1,2,5,6,10,11,42,[51][52][53][54][55][56][57]. Similar to bulk materials, gaseous materials such as ethylene and ammonia have also been proposed to be radiative coolers [56,58,59].…”

Section: Radiative Cooling Materials and Structuresmentioning

confidence: 99%

Radiative sky cooling: fundamental physics, materials, structures, and applications

et al. 2017

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Radiative sky cooling reduces the temperature of a system by promoting heat exchange with the sky; its key advantage is that no input energy is required. We will review the origins of radiative sky cooling from ancient times to the modern day, and illustrate how the fundamental physics of radiative cooling calls for a combination of properties that may not occur in bulk materials. A detailed comparison with recent modeling and experiments on nanophotonic structures will then illustrate the advantages of this recently emerging approach. Potential applications of these radiative cooling materials to a variety of temperature-sensitive optoelectronic devices, such as photovoltaics, thermophotovoltaics, rectennas, and infrared detectors, will then be discussed. This review will conclude by forecasting the prospects for the field as a whole in both terrestrial and space-based systems.

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“…Note that there is no pigment for "whiteness." Indeed, structural whiteness is technologically important in systems ranging from power-efficient computer displays, to sensors, to energy-efficient buildings, windows, and vehicles (22)(23)(24).…”

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confidence: 99%

Varying and unchanging whiteness on the wings of dusk-active and shade-inhabiting Carystoides escalantei butterflies

Yang

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Whiteness, although frequently apparent on the wings, legs, antennae, or bodies of many species of moths and butterflies, along with other colors and shades, has often escaped our attention. Here, we investigate the nanostructure and microstructure of white spots on the wings of Carystoides escalantei, a dusk-active and shadeinhabiting Costa Rican rain forest butterfly (Hesperiidae). On both males and females, two types of whiteness occur: angle dependent (dull or bright) and angle independent, which differ in the microstructure, orientation, and associated properties of their scales. Some spots on the male wings are absent from the female wings. Whether the angle-dependent whiteness is bright or dull depends on the observation directions. The angle-dependent scales also show enhanced retro-reflection. We speculate that the biological functions and evolution of Carystoides spot patterns, scale structures, and their varying whiteness are adaptations to butterfly's low light habitat and to airflow experienced on the wing base vs. wing tip.butterfly wings | whiteness | angle dependent | retro-reflection |

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Radiative cooling of TiO2 white paint

Cited by 207 publications

References 3 publications

A Metamaterial Emitter for Highly Efficient Radiative Cooling

A Metamaterial Emitter for Highly Efficient Radiative Cooling

Radiative sky cooling: fundamental physics, materials, structures, and applications

Varying and unchanging whiteness on the wings of dusk-active and shade-inhabiting Carystoides escalantei butterflies

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