scholarly journals Passive Cooling of Surfaces

2018 ◽  
Vol 2 (1) ◽  
pp. 10-15
Author(s):  
Imtiaz Ahmad ◽  
E. E. Khawaja
Keyword(s):  
Ambient Temperature ◽  
Spectral Region ◽  
Film Surface ◽  
Silicon Monoxide ◽  
Suitable Condition ◽  
Passive Cooling ◽  
Radiative Cooling ◽  
Thin Film Surface ◽  
Infrared Transmittance ◽  
Atmospheric Window

Radiative cooling of surfaces without applying an energy source has been suggested in the literature. The basis for radiative cooling is the infrared transmittance of the atmosphere. The spectral transparency (i.e. low absorption) of the atmosphere in the wavelength range of 8 to 13 μm is generally termed the atmospheric window. If the humidity and cloudiness are low, then the downward thermal radiation from the atmosphere in the spectral region of the atmospheric window are expected to be low. A temperature between 15 oC and 25 oC below ambient temperature has been achieved as a result of radiative cooling.Spectrally selective radiating material, which is defined as a material with high emittance in the spectral region of the atmospheric window and high reflectance in the rest of the spectral range, can be used as an essential means in a sky radiator for passive cooling of the material. Silicon monoxide film on highly reflective substrate (aluminum coated glass) was used in the present work. It was found that the temperature of the thin film surface was about 12 oC lower than that of ambient temperature under suitable condition of radiative cooling. Cooling is expected to be more efficient in performance if it is carried out in desert places.

Potential for Passive Radiative Cooling by PDMS Selective Emitters

2017 ◽  
Author(s):  
Braden Czapla ◽  
Arvind Srinivasan ◽  
Qingtian Yin ◽  
Arvind Narayanaswamy
Keyword(s):  
Thin Films ◽  
Ambient Temperature ◽  
Passive Cooling ◽  
Radiative Cooling ◽  
Polydimethyl Siloxane ◽  
Selective Emitter ◽  
The Cost ◽  
Aluminum Substrates ◽  
Selective Emitters ◽  
Fabrication Costs

The scalability and implementation of selective emitters in passive radiative cooling applications are limited by the high fabrication costs due to the complexity of these structures. The usage of commercially available polymers in selective emitters holds potential in lowering the cost of radiative cooling solutions. In this work, we demonstrate that thin films of polydimethyl-siloxane (PDMS) on aluminum substrates act as radiative coolers by selectively emitting in the wavelength range of 8 μm to 13 μm, where the Earth’s atmosphere is highly transparent. We also show that our device can achieve passive cooling up to 12 °C below the ambient temperature under the night sky. This suggests that PDMS, especially due to its ease of deposition, may be a viable selective emitter in passive radiative cooling applications.

scholarly journals High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel

2019 ◽  
Vol 5 (10) ◽  
pp. eaat9480 ◽  
Author(s):  
A. Leroy ◽  
B. Bhatia ◽  
C. C. Kelsall ◽  
A. Castillejo-Cuberos ◽  
M. Di Capua H. ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Air Conditioning ◽  
High Performance ◽  
Recent Progress ◽  
Passive Cooling ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Direct Sunlight ◽  
Solar Absorption ◽  
Solar Noon

Recent progress in passive radiative cooling technologies has substantially improved cooling performance under direct sunlight. Yet, experimental demonstrations of daytime radiative cooling still severely underperform in comparison with the theoretical potential due to considerable solar absorption and poor thermal insulation at the emitter. In this work, we developed polyethylene aerogel (PEA)—a solar-reflecting (92.2% solar weighted reflectance at 6 mm thick), infrared-transparent (79.9% transmittance between 8 and 13 μm at 6 mm thick), and low-thermal-conductivity (kPEA = 28 mW/mK) material that can be integrated with existing emitters to address these challenges. Using an experimental setup that includes the custom-fabricated PEA, we demonstrate a daytime ambient temperature cooling power of 96 W/m2 and passive cooling up to 13°C below ambient temperature around solar noon. This work could greatly improve the performance of existing passive radiative coolers for air conditioning and portable refrigeration applications.

Stoichiometric composition of thin-film surface structures and its influence on the functional characteristics as regards gyroscopic devices

2020 ◽  
pp. 78-90
Author(s):  
M. A. Tit ◽  
S. N. Belyaev
Keyword(s):  
Thin Film ◽  
Titanium Nitride ◽  
Niobium Carbide ◽  
Structural Phase ◽  
Stoichiometric Composition ◽  
Film Surface ◽  
Surface Structures ◽  
Functional Surface ◽  
Base Surface ◽  
Thin Film Surface

This article considers the research results of the effect of stoichiometry on the properties of titanium nitride thin-film coatings of the float and electrostatic gyroscopes. It presents the results of tests of such mechanical and optical characteristics of titanium nitride thin-film structures as microhardness, resistance to wear and friction, and image contrast determined by the reflection coefficients of a titanium nitride base surface and a raster pattern formed by local laser oxidation. When making a rotor of a cryogenic gyroscope, the prospects of use and technological methods for the formation of functional surface structures of niobium carbide and nitride are considered. It is shown that during the formation of coatings of the required composition, the most important is the thermodynamic estimation of possible interactions. These interactions allow us to accomplish the structural-phase modification of the material, which is determined by the complex of possible topochemical reactions leading to the formation of compounds, including non-stoichiometric composition.

scholarly journals Performance simulation of polymer-based nanoparticle and void dispersed photonic structures for radiative cooling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jay Prakash Bijarniya ◽  
Jahar Sarkar ◽  
Pralay Maiti
Keyword(s):  
Fdtd Method ◽  
Solar Spectrum ◽  
Thermal Infrared ◽  
Performance Estimation ◽  
Radiative Cooling ◽  
Slab Thickness ◽  
Slight Variation ◽  
Performance Simulation ◽  
Atmospheric Window ◽  
Substrate Independent

AbstractPassive radiative cooling is an emerging field and needs further development of material. Hence, the computational approach needs to establish for effective metamaterial design before fabrication. The finite difference time domain (FDTD) method is a promising numerical strategy to study electromagnetic interaction with the material. Here, we simulate using the FDTD method and report the behavior of various nanoparticles (SiO2, TiO2, Si3N4) and void dispersed polymers for the solar and thermal infrared spectrums. We propose the algorithm to simulate the surface emissive properties of various material nanostructures in both solar and thermal infrared spectrums, followed by cooling performance estimation. It is indeed found out that staggered and randomly distributed nanoparticle reflects efficiently in the solar radiation spectrum, become highly reflective for thin slab and emits efficiently in the atmospheric window (8–13 µm) over the parallel arrangement with slight variation. Higher slab thickness and concentration yield better reflectivity in the solar spectrum. SiO2-nanopores in a polymer, Si3N4 and TiO2 with/without voids in polymer efficiently achieve above 97% reflection in the solar spectrum and exhibits substrate independent radiative cooling properties. SiO2 and polymer combination alone is unable to reflect as desired in the solar spectrum and need a highly reflective substrate like silver.

Bio-skin inspired 3D porous cellulose/AlPO4 nano-laminated film with structure-enhanced selective emission for all-day non-power cooling

2021 ◽  
Author(s):  
Shuangjiang Feng ◽  
Yuming Zhou ◽  
Xi Chen ◽  
Shengnan Shi ◽  
Chenghuan Liu ◽  
...  
Keyword(s):  
Radiative Cooling ◽  
Preparation Technology ◽  
Cellulose Films ◽  
Highly Efficient ◽  
Atmospheric Window ◽  
Complex Preparation

Porous cellulose films have been reported as sustainable and highly-efficient non-power radiative cooling (PRC) materials but still challenged by their insufficient atmospheric window (AM) emissivity and complex preparation technology. Herein,...

Microarray of neuroblastoma cells on the selectively functionalized nanocrystalline diamond thin film surface

2016 ◽  
Vol 361 ◽  
pp. 269-276 ◽  
Author(s):  
Young-Sang Park ◽  
Hyeong-Guk Son ◽  
Dae-Hoon Kim ◽  
Hong-Gi Oh ◽  
Da-Som Lee ◽  
...  
Keyword(s):  
Thin Film ◽  
Neuroblastoma Cells ◽  
Film Surface ◽  
Nanocrystalline Diamond ◽  
Thin Film Surface ◽  
Diamond Thin Film

Thin Film Surface Resistance Measurements For Superconducting Cavity Applications

1991 ◽  
pp. 155-160
Author(s):  
A. Andreone ◽  
C. Attanasio ◽  
A. Di Chiara ◽  
L. Maritato ◽  
A. Nigro ◽  
...  
Keyword(s):  
Thin Film ◽  
Surface Resistance ◽  
Film Surface ◽  
Superconducting Cavity ◽  
Thin Film Surface

scholarly journals SYNTHESIS OF THIN FILM OF TiO2 ON GRAPHITE SUBSTRATE BY CHEMICAL BATH DEPOSITION

2010 ◽  
Vol 6 (2) ◽  
pp. 121-126 ◽  
Author(s):  
Fitria Rahmawati ◽  
Sayekti Wahyuningsih ◽  
Pamularsih A.W
Keyword(s):  
Thin Film ◽  
Chemical Bath Deposition ◽  
Surfactant Concentration ◽  
High Efficiency ◽  
Anatase Phase ◽  
Film Surface ◽  
Optical Microscope ◽  
Graphite Substrate ◽  
Thin Film Surface ◽  
Photon Conversion

Thin film of TiO2 on graphite substrat has been prepared by means of chemical bath deposition. Cetyltrimethylammonium Bromide served  as linking agent of synthesized TiO2 to graphite substrate.The optical microscope and Scanning Electron Microscope (SEM) indicate that surfactant concentration affects the pore morphology of thin film Surface Area Analysis (SAA) of thin film indicated that the pore of thin film included in mesopore category. The anatase phase of TiO2 quantity arised as the surfactant concentration increase, gave high efficiency of induced photon conversion to current efficiency (% IPCE).   Keywords: thin film, TiO2, deposition, graphite

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