Thermal performance of radiative cooling panels

Berdahl, Paul; Martin, M.; Sakkal, F.

doi:10.1016/s0017-9310(83)80111-2

Cited by 150 publications

(61 citation statements)

References 18 publications

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“…However, to estimate the practical cooling effi ciency of the radiative cooler, we need to consider the effect of the nonradiative (i.e., conductive + convective) heat exchange processes. The nonradiative heat exchange processes in a system can be stated as [ 1,4,34,35 ] …”

Section: Communicationmentioning

confidence: 99%

A Metamaterial Emitter for Highly Efficient Radiative Cooling

Hossain

Jia

2015

Advanced Optical Materials

543

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%

A Metamaterial Emitter for Highly Efficient Radiative Cooling

Hossain

Jia

2015

Advanced Optical Materials

543

232

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“…incident solar power, convective, and conductive heat transfer), the maximum cooling power determines the lowest temperature achievable. Initially, nighttime radiative cooling appeared much more promising thanks to the absence of solar irradiance, and constituted the focus of the early work [42][43][44][45][46]. Enabled by recent advances in photonic design, daytime radiative cooling below ambient temperature has been demonstrated by Rephaeli et al [16].…”

Section: Principle Of Coolingmentioning

confidence: 99%

“…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%

“…Polyvinyl chloride (PVC) [5], polyvinyl fluoride (PVF) [1,6,42,53,54], and polymethylpentene (TPX) [52] were shown to have high emittance in the atmospheric window. Most plastic coolers reported in the literature were aluminized at the back to block transmission without adding significant absorption outside the atmospheric window.…”

Section: Bulk and Gaseous Materials Radiative Coolersmentioning

confidence: 99%

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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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“…Whereas historically radiative cooling was largely developed for night-time applications (1)(2)(3)(4)(5)(6)(9)(10)(11)(12)(13), recent works have achieved daytime radiative cooling (7,14). In particular, it was shown that the radiative cooling to below ambient air temperature can be achieved (7), with a photonic structure that reflects almost all incident sunlight and simultaneously emits significant thermal radiation in the midinfrared.…”

mentioning

confidence: 99%

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Zhu

Raman

Fan

2015

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

525

351

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A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13°C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.radiative cooling | thermal radiation | photonic crystal | solar absorber T he universe, at a temperature of 3 K, represents a significant renewable thermodynamic resource: it is the ultimate heat sink. Over midinfrared wavelengths, in particular between 8 and 13 μm, Earth's atmosphere is remarkably transparent to electromagnetic radiation. This wavelength range coincides with the peak wavelength of thermal radiation from terrestrial structures at typical ambient temperatures. Thus, a sky-facing terrestrial object can have radiative access to the universe. Exploiting this radiative access has led to the demonstration of radiative cooling (1-7), as well as proposals for direct electric power generation from thermal radiation of terrestrial objects (8).Whereas historically radiative cooling was largely developed for night-time applications (1-6, 9-13), recent works have achieved daytime radiative cooling (7,14). In particular, it was shown that the radiative cooling to below ambient air temperature can be achieved (7), with a photonic structure that reflects almost all incident sunlight and simultaneously emits significant thermal radiation in the midinfrared. Such a structure, being a near-perfect solar reflector, makes no use of incident sunlight. On the other hand, in many applications, including solar cells (15) and outdoor structures (16), the utilization of sunlight through absorption is intrinsic for either operational or aesthetic considerations, but the heating associated with sunlight absorption is undesirable. For these applications, lowering operating temperatures via radiative cooling is only viable if one can simultaneously preserve the absorption of sunlight.Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal, using a thermophotonic approach (17-30). When placed on a silicon absorber under sunlight, such a blackbody preserves and even slightly enhances sunlight absorption, but reduces the temperature of the silicon absorber by as m...

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Thermal performance of radiative cooling panels

Cited by 150 publications

References 18 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

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

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