scholarly journals Analysis of Sustainable Materials for Radiative Cooling Potential of Building Surfaces

2018 ◽  
Vol 10 (9) ◽  
pp. 3049 ◽  
Author(s):  
Roxana Family ◽  
M. Mengüç
Keyword(s):  
Heat Transfer ◽  
Emission Spectra ◽  
Spectral Emissivity ◽  
Volumetric Analysis ◽  
Solar Heating ◽  
Heat Transfer Analysis ◽  
Surface Phenomenon ◽  
Radiative Cooling ◽  
Atmospheric Window ◽  
Building Surfaces

The main goal of this paper is to explore the radiative cooling and solar heating potential of several materials for the built environment, based on their spectrally-selective properties. A material for solar heating, should have high spectral emissivity/absorptivity in the solar radiation band (within the wavelength range of 0.2–2 μm), and low emissivity/absorptivity at longer wavelengths. Radiative cooling applications require high spectral emissivity/absorptivity, within the atmospheric window band (8–13 μm), and a low emissivity/absorptivity in other bands. UV-Vis spectrophotometer and FTIR spectroscopy, are used to measure, the spectral absorption/emission spectra of six different types of materials. To evaluate the radiative cooling potential of the samples, the power of cooling is calculated. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis is used. Results are discussed for the selection of the best materials, for different applications on building surfaces.

scholarly journals Continuously variable emission for mechanical deformation induced radiative cooling

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Xiaojie Liu ◽  
Yanpei Tian ◽  
Fangqi Chen ◽  
Alok Ghanekar ◽  
Mauro Antezza ◽  
...  
Keyword(s):  
Effective Medium Theory ◽  
Outer Space ◽  
Emission Spectra ◽  
Radiative Cooling ◽  
Medium Theory ◽  
Dynamic Tuning ◽  
The Past ◽  
Atmospheric Window ◽  
Human Need ◽  
Different Strains

AbstractPassive radiative cooling, drawing heat energy of objects to the cold outer space through the atmospheric transparent window, is significant for reducing the energy consumption of buildings. Daytime and nighttime radiative cooling have been extensively investigated in the past. However, radiative cooling which can continuously regulate its cooling temperature, like a valve, according to human need is rarely reported. In this study, we propose a reconfigurable photonic structure, based on the effective medium theory and semi-analytical calculations, for the adaptive radiative cooling by continuous variation of the emission spectra in the atmospheric window. This is realized by the deformation of a one-dimensional polydimethylsiloxane (PDMS) grating and nanoparticle-embedded PDMS thin film when subjected to mechanical stress/strain. The proposed structure reaches different stagnation temperatures under certain strains. A dynamic tuning in emissivity under different strains results in a continuously variable “ON”/“OFF” mode in a particular atmospheric window that corresponds to the deformation-induced fluctuation of the operating temperatures of the reconfigurable nanophotonic structure.

scholarly journals Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Mingke Hu ◽  
Gang Pei ◽  
Lei Li ◽  
Renchun Zheng ◽  
Junfei Li ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Heating Surface ◽  
Solar Heating ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Relative Temperature ◽  
Composite Surface ◽  
Spectral Selectivity ◽  
Atmospheric Window ◽  
Inclination Angles

A spectral selectivity surface for both solar heating and radiative cooling was proposed. It has a high spectral absorptivity (emissivity) in the solar radiation band and atmospheric window band (i.e., 0.2~3 μm and 8~13 μm), as well as a low absorptivity (emissivity) in other bands aside from the solar radiation and atmospheric window wavelengths (i.e., 3~8 μm or above 13 μm). A type of composite surface sample was trial-manufactured combining titanium-based solar selective absorbing coating with polyethylene terephthalate (TPET). Sample tests showed that the TPET composite surface has clear spectral selectivity in the spectra of solar heating and radiation cooling wavelengths. The equilibrium temperatures of the TPET surface under different sky conditions or different inclination angles of surface were tested at both day and night. Numerical analysis and comparisons among the TPET composite surface and three other typical surfaces were also performed. These comparisons indicated that the TPET composite surface had a relative heat efficiency of 76.8% of that of the conventional solar heating surface and a relative temperature difference of 75.0% of that of the conventional radiative cooling surface, with little difference in cooling power.

scholarly journals Radiative Heat Transfer Analysis within Three-Dimensional Clouds Subjected to Solar and Sky Irradiation

2004 ◽  
Vol 61 (24) ◽  
pp. 3125-3133 ◽  
Author(s):  
Toru Nishikawa ◽  
Shigenao Maruyama ◽  
Seigo Sakai
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Three Dimensional ◽  
Anisotropic Scattering ◽  
Heat Transfer Analysis ◽  
Radiative Cooling ◽  
Emission Model ◽  
Fair Weather ◽  
Convex Shape

Abstract A three-dimensional radiative heat transfer analysis of an arbitrary-shaped modeled cloud subjected to solar and sky irradiation has been performed. The Radiation Element Method by Ray Emission Model (REM2) was used for numerical simulation. Nongray, anisotropic scattering, absorbing, and emitting are taken into account in calculating the three-dimensional cloud. The modeled cloud is considered to be a low-level fair-weather cumulus in a tropical atmosphere. The cloud is modeled by unstructured mesh elements in order to investigate the curvature of cloud shape. Radiative cooling occurs in the thin layer below the cloud surface, and the thickness is approximately 20–40 m. Radiative cooling is enhanced at the swelled top of the cloud with a convex shape, which can cause a downward forcing and enhance the entrainment instability. On the other hand, radiative cooling close to the root of the swelled top is relatively weak. The solar heating does not affect the temperature change in the cloud compared with radiative heat transfer by longwave infrared radiation.

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