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.

scholarly journals A Pragmatic Bilayer Selective Emitter for Efficient Radiative Cooling under Direct Sunlight

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1208 ◽  
Author(s):  
Liu ◽  
Bai ◽  
Fang ◽  
Ni ◽  
Lu ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Ambient Temperature ◽  
High Efficiency ◽  
Volume Fraction ◽  
Ambient Air ◽  
Radiative Cooling ◽  
Direct Sunlight ◽  
Cooling Performance ◽  
Selective Emitter ◽  
Functional Nanoparticles

Radiative cooling can make the selective emitter cool below ambient temperature without any external energy. Recent advances in photonic crystal and metamaterial technology made a high-efficiency selective emitter achievable by precisely controlling the emitter’s Infrared emission spectrum. However, the high cost of the photonic crystals and meta-materials limit their application. Herein, an efficient bilayer selective emitter is prepared based on the molecular vibrations of functional nanoparticles. By optimizing the volume fraction of the functional nanoparticles, the bilayer selective emitter can theoretically cool 36.7 °C and 25.5 °C below the ambient temperature in the nighttime and daytime, respectively. Such an efficient cooling performance is comparable with the published photonic crystal and metamaterial selective emitters. The rooftop measurements show that the bilayer selective emitter is effective in the ambient air even under direct sunlight. The relatively low cost and excellent cooling performance enable the bilayer selective emitter to have great potential for a practical purpose.

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.

Phase configuration, nanostructure, and mechanical behaviors in Ti-B-C-N thin films

2009 ◽  
Vol 24 (8) ◽  
pp. 2520-2527 ◽  
Author(s):  
Yonghao Lu ◽  
Junping Wang ◽  
Yaogen Shen ◽  
Dongbai Sun
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Solid Solution Hardening ◽  
Mechanical Behaviors ◽  
Additional Increase ◽  
N Content ◽  
X Ray ◽  
Nanocomposite Thin Films ◽  
The Cost ◽  
Nano Grains

A series of Ti-B-C-N thin films were deposited on Si (100) at 500 °C by incorporation of different amounts of N into Ti-B-C using reactive unbalanced dc magnetron sputtering in an Ar-N2 gas mixture. The effect of N content on phase configuration, nanostructure evolution, and mechanical behaviors was studied by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and microindentation. It was found that the pure Ti-B-C was two-phased quasi-amorphous thin films comprising TiCx and TiB2. Incorporation of a small amount of N not only dissolved into TiCx but also promoted growth of TiCx nano-grains. As a result, nanocomposite thin films of nanocrystalline (nc-) TiCx(Ny) (x + y < 1) embedded into amorphous (a-) TiB2 were observed until nitrogen fully filled all carbon vacancy lattice (at that time x + y = 1). Additional increase of N content promoted formation of a-BN at the cost of TiB2, which produced nanocomposite thin films of nc-Ti(Cx,N1-x) embedded into a-(TiB2, BN). Formation of BN also decreased nanocrystalline size. Both microhardness and elastic modulus values were increased with an increase of N content and got their maximums at nanocomposite thin films consisting of nc-Ti(Cx,N1-x) and a-TiB2. Both values were decreased after formation of BN. Residual compressive stress value was successively decreased with an increase of N content. Enhancement of hardness was attributed to formation of nanocomposite structure and solid solution hardening.

Growth of InN thin films on different Si substrates at ambient temperature

2013 ◽  
Vol 30 (2) ◽  
pp. 63-67 ◽  
Author(s):  
Maryam Amirhoseiny ◽  
Zainuriah Hassan ◽  
Sha Shiong Ng
Keyword(s):  
Thin Films ◽  
Ambient Temperature ◽  
Si Substrates

scholarly journals Electrodeposition of Vanadium Oxide/Manganese Oxide Hybrid Thin Films on Nanostructured Aluminum Substrates

2014 ◽  
Vol 161 (10) ◽  
pp. D515-D521 ◽  
Author(s):  
David Rehnlund ◽  
Mario Valvo ◽  
Kristina Edström ◽  
Leif Nyholm
Keyword(s):  
Thin Films ◽  
Vanadium Oxide ◽  
Manganese Oxide ◽  
Hybrid Thin Films ◽  
Aluminum Substrates

scholarly journals SERS on Bimetallic Nanostructured thin films

2021 ◽  
Author(s):  
revathy m s ◽  
D Murugesan ◽  
Naidu Dhanpal Jayram
Keyword(s):  
Thin Films ◽  
Thermal Evaporation ◽  
Low Cost ◽  
Active Surface ◽  
Surface Enhanced Raman Spectroscopy ◽  
Nanostructured Film ◽  
Sers Substrates ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
The Cost

Abstract Thin films and Surface Enhanced Raman spectroscopy have a strong bonding towards development of Sensors. From last 4 decades SERS has been used as effective tool for detection of toxic dyes, in food industry and agriculture world. To minimize the cost and fabrication over large surface is the most challenging task in substrate fabrication. In the present work an attempt has been made towards dual coatings, which could act as an effective SERS Substrates. An effective and facile approach of low cost bi-metallic Nanostructured film has been fabricated using thermal evaporation. Using the standard characterization techniques such as FE-SEM and XRD, the obtained films were Rhodamine 6G was used as an analyte for the SERS studies. The detection of R6G was up to 10− 10mol l− 1solution.The present bi-metallic coating can be serves as an excellent SERS active surface and provides a versatile pathway to fabricate anisotropic nanostructure on a glass film.

High-Temperature PbTe Thin Films for Use in Cascade Thermoelectric Power Generation

2003 ◽  
Vol 793 ◽  
Author(s):  
J.B. Posthill ◽  
J.C. Caylor ◽  
P.D. Crocco ◽  
T.S. Colpitts ◽  
R. Venkatasubramanian
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Power Generation ◽  
High Temperature ◽  
Ambient Temperature ◽  
Thermoelectric Power ◽  
Thermal Evaporation ◽  
Potential Candidate ◽  
Substrate Orientation ◽  
Subtle Effect

ABSTRACTPbTe-based thin films were deposited by thermal evaporation at temperatures ranging from ambient temperature to 430°C on different vicinal GaAs (100) substrates and BaF2 (111). This materials system is being evaluated as a potential candidate thermoelectric material for a mid-temperature stage in a cascade power generation module. Pure PbTe, PbSe, and multilayer PbTe/PbSe films were investigated. All films deposited on different vicinal GaAs (100) substrates were found to be polycrystalline when deposited at 250°C or lower. A subtle effect of substrate orientation and multilayer periodicity appears to contribute to the more randomly oriented polycrystallinity, which also lowers the thermal conductivity. These results are compared with PbTe epitaxial results on BaF2 (111).

Performance Improvement of Gas Turbine Power Plant by Intake Air Passive Cooling Using Phase Change Material Based Heat Exchanger

2017 ◽  
Author(s):  
Devendra Dandotiya ◽  
Nitin D. Banker
Keyword(s):  
Heat Exchanger ◽  
Ambient Temperature ◽  
Phase Change ◽  
Gas Turbine ◽  
Air Temperature ◽  
Power Output ◽  
Ambient Air ◽  
Passive Cooling ◽  
Air Intake ◽  
Change Material

The power output of a gas turbine plant decreases with the increase in ambient temperature. Moreover, the ambient temperature fluctuates about 15–20°C in a day. Hence, cooling of intake air makes a noticeable improvement to the gas turbine performance. In this regard, various active cooling techniques such as vapor compression refrigeration, vapor absorption refrigeration, vapor adsorption refrigeration and evaporative cooling are applied for the cooling of intake air. This paper presents a new passive cooling technique where the intake air temperature is reduced by incorporating phase change material (PCM) based heat exchanger parallel to conventional air intake line. During the daytime, the air is passed through the PCM which has melting temperature lower than the peak ambient temperature. This will reduce the ambient air temperature before taking to the compressor. Once the PCM melts completely, the required ambient air would be drawn from the ambient through conventional air intake arrangement. During the night, when there is lower ambient temperature, PCM converts from liquid to solid. The selected PCM has a melting temperature less than the peak ambient temperature and higher than the minimum ambient temperature. It is observed from the numerical modeling of the PCM that about four hours are required for the melting of PCM and within this time, the intake air can also be cooled by 5°C. The thermodynamic analysis of the results showed about 5.2% and 5.2% improvement in net power output and thermal efficiency, respectively for four hours at an ambient temperature of 45°C.

Sign in / Sign up

Export Citation Format

Share Document