20191027 Wang Seminar at NTHU (Radiative Thermal Control).pdf
1. Spectral Control of Infrared Emission
for Passive and Active Radiative Thermal Management
Research Seminar at National Tsing Hua University
Hsinchu, Taiwan, October 28, 2019
Liping Wang, Ph.D.
Associate Professor in Mechanical and Aerospace Engineering
Director of Nano-Engineered Thermal Radiation Laboratory
School for Engineering of Matter, Transport & Energy
Arizona State University, Tempe, AZ USA
http://faculty.engineering.asu.edu/lpwang
Email: liping.wang@asu.edu
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Nano-Engineered Thermal Radiation Group
Phoenix, AZ
² 5th largest city in US with population ~1.7 million (2018)
² Abundant solar radiation: ~300 days sunshine /year
² Average temp.: summer >35degC, winter ~10degC
² < 5 hr driving to Los Angeles, San Diego, Las Vegas
² 5 hr driving to Grand Canyon and other national parks
² 2 hr driving to Flagstaff AZ (Ski resort, Indian habitat)
² ASU is Located in Tempe, Arizona, USA, southeast in the
Phoenix Metro Area with Intel, Freescale, etc
o Phoenix, AZ
ASU
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Nano-Engineered Thermal Radiation Group
ASU’s strong commitment to solar energy
Total Solar Generation Capacity: 24.1 MW (50% ASU daytime peak load)
(PV: 21.8 MW; Solar thermal: 13,908 MMBTUs = 2.3 MW equivalent)
Total Solar Systems: 89
Total Number of PV Panels Installed: 81,424
Total Number of CPV Modules Installed: 8,652
Total Number of Solar Collectors Installed: 9,280
Total Number of Shaded Parking Spaces: 5,952
http://about.asu.edu, https://cfo.asu.edu/solar
² Established in 1885
² #1 in the US for Innovation by US News & World Reports
(#2 Stanford, #3 MIT)
² #1 student enrollment (~100,000) in US universities (2018)
² #1 public university chosen by international students
² Top 1% of world’s most prestigious universities
² Top 10 in total research expenditures among US universities
without medical school
² #42 Graduate program in Engineering by US News
² One of the greenest universities in USA
ISTB4
May 2012
300K sq. ft
Old Main
built in 1898
A New American University
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Nano-Engineered Thermal Radiation Group
Outline
1. Background and Motivation
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
• SiC metasurface with coherent thermal emission
• Bulk LiF for sub-ambient daytime radiative cooling
• Outdoor radiative cooling test
3. Active Heat Control with Tunable Thermal Emission
• VO2 metamaterial emitter
• VO2 metafilm emitter
• Vacuum thermal test
4. Summary and Acknowledgments
6. Nano-Engineered Thermal Radiation Group
1. Background and Motivation
What is radiative cooling?
Zhao et al., Appl. Energ. 236, 489-513 (2019)
• Solar radiation, qsun
• Self emission, qrad
• Atmospheric radiation, qsky
• Low solar absorption
• High emission at the window
• Low emission out the window
Radiative cooling requirements
Ø Atmospheric window (8-13 µm), where the ambient does not emit/absorb radiation
6
7. 7
Nano-Engineered Thermal Radiation Group
Active radiative thermal control
Building Cooling Space Cooling
Challenge: dynamic control of surface emissivity
due to changing environment
1. Background and Motivation
8. Nano-Engineered Thermal Radiation Group
Micro/nanostructured selective surfaces
SiC grating
• Surface phonon polariton
Greffet et al., Nature 416, 61-64 (2002)
SiC slit
SiC grating
• Magnetic polariton
Wang et al., Opt. Express 19, A126-A135 (2011)
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
8
a-quartz PhC
• Photonic crystal
Rephaeli et al., Nano Lett. 13, 1457-1461 (2013)
9. Nano-Engineered Thermal Radiation Group
SiC metasurface – FIB fabrication
Yang, Taylor, Alshehri, Wang, APL 111, 051904 (2017) 9
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
10. Nano-Engineered Thermal Radiation Group
Spectral emittance by FTIR Microscope
Yang, Taylor, Alshehri, Wang, APL 111, 051904 (2017) 10
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
11. Nano-Engineered Thermal Radiation Group
Definition of ideal radiative cooler
Zhao et al., Appl. Energ. 236, 489-513 (2019)
Ø Selective ideal emitter A:
unity emittance among 8-13 µm
Ø Broadband ideal emitter B:
unity emittance among 4-30 µm
Ø Selective ideal emitter:
Advantage: To achieve an ultra-low
stagnation temperature
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
11
12. Nano-Engineered Thermal Radiation Group
Proposed bulk LiF based selective emitter
1-mm-thick LiF crystal w/o or w/ Ag coating
• LiF crystallized from melted powder, then polished
• Ag coating deposited by electron beam evaporation
• LiF with highest transmittance in UV-VIS-NIR spectrum
Yang et al., preprint on arXiv (manuscript under review) 12
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
13. Nano-Engineered Thermal Radiation Group
Bulk LiF - spectral emittance measurement
• A pretty low solar absorptance less than 5%
• Nearly ideal infrared selectivity with high emission only at the window
UV-VIS-NIR spectrophotometer Fourier-transfer infrared spectroscopy
Yang et al., preprint on arXiv (manuscript under review) 13
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
14. Nano-Engineered Thermal Radiation Group
Bulk LiF - outdoor test apparatus
• PE cover, suspended acrylic dish,
wood needles to minimize
convection & conduction loss
• Al foil to minimize side radiation
• Face the sky to consider radiative
transfer between the sample,
sun and atmosphere
( ) ( ) ( ) ( ) ( )
cool s rad s sun atm a conv s a
,
q T q T q G q T q T T
= - - -
Yang et al., preprint on arXiv (manuscript under review) 14
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
15. Nano-Engineered Thermal Radiation Group
Bulk LiF - stagnation temperature measurement
( ) ( ) ( ) ( ) ( )
cool s rad s sun atm a conv s a
cool s
,
0
q T q T q G q T q T T
q T
= - - -
= Þ
Measured in the daytime on Apr. 19 Measured from Apr. 25 to Apr. 28
• Sub-ambient cooling effect demonstrated with 5 ℃ during the daytime and
10 ℃ during the nighttime below the ambient
Yang et al., preprint on arXiv (manuscript under review) 15
2. Selective Infrared Thermal Emission for Passive Radiative Cooling
16. Nano-Engineered Thermal Radiation Group 16
L = 1 µm, w = 0.5 µm
h = 80 nm, d = 80 nm
Wang, Yang and Wang, APL 105, 071907 (2014)
FDTD simulation
VO2 metamaterial emitter – initial design
3. Active Heat Control with Tunable Thermal Emission
17. Nano-Engineered Thermal Radiation Group 17
VO2 thin film - fabrication process
Electron Beam Evaporation:
• Deposit V thin film
Tube Furnace Oxidation:
• Oxidize V thin film to VO2
What furnace conditions do we control?
• Temperature
• Time
• O2 flow rate
• N2 flow rate
Taylor, Long, Wang, Thin Solid Films, Vol. 682, pp. 29-36 (2019)
3. Active Heat Control with Tunable Thermal Emission
18. Nano-Engineered Thermal Radiation Group 18
VO2 thin film - composition
• XRD peaks at 38.5, 44.7, and 65 degrees are consistent with published
patterns for VO2
• Raman spectrum peaks are likewise consistent with established VO2 spectra
VO2 (021)
VO2 (401)
VO2 (013)
146
194
223
304
391
441
521
614
821
Taylor, Long, Wang, Thin Solid Films, Vol. 682, pp. 29-36 (2019)
3. Active Heat Control with Tunable Thermal Emission
19. Nano-Engineered Thermal Radiation Group 19
VO2 thin film – infrared transmittance vs. temperature
• ~26% change in NIR wavelengths
• ~17% change in MIR wavelengths
• consistent among 3 samples
• 77 K < T < 800 K (LN2 cooled)
• 400 nm < λ < 25 µm
• 10-7 Torr vacuum
Taylor, Long, Wang, Thin Solid Films, Vol. 682, pp. 29-36 (2019)
3. Active Heat Control with Tunable Thermal Emission
20. Nano-Engineered Thermal Radiation Group
VO2 metamaterial emitter - sample fabrication
SEM image
(top view)
20
Long et al., Materials Today Energy, Vol. 13, 214-220 (2019)
Stepper
E-beam deposition
& lift-off
Spin coating
Cleaning E-beam deposition
P = 1.6 µm
d = 0.8 µm
h = 200 nm
t = 100 nm
3. Active Heat Control with Tunable Thermal Emission
21. Nano-Engineered Thermal Radiation Group 21
VO2 metamaterial emitter – FTIR microscopy
5 6 7 8 9
0
20
40
60
80
100
80o
C
90o
C
20o
C
50o
C
Absorptance,
5
C,,
(%)
Wavelength (5m)
Long et al, Materials Today Energy, Vol. 13, 214-220 (2019)
3. Active Heat Control with Tunable Thermal Emission
22. Nano-Engineered Thermal Radiation Group
VO2 metamaterial emitter – numerical modeling
Long et al, Materials Today Energy, Vol. 13, 214-220 (2019)
3. Active Heat Control with Tunable Thermal Emission
23. Nano-Engineered Thermal Radiation Group 23
VO2 metafilm emitter - design
df = 25 nm ds = 730 nm
Taylor, Yang, Wang, JQSRT 197, 76-83 (2017)
3. Active Heat Control with Tunable Thermal Emission
24. Nano-Engineered Thermal Radiation Group 24
Al layer with Electron
Beam Evaporation
Si layer with sputtered
silicon
VO2 layer with EBE +
Furnace Oxidation
Si Wafer
200 nm Al
450 nm Si
55 nm VO2
Si Wafer
200 nm Al
450 nm Si
Si Wafer
200 nm Al
VO2 metafilm emitter - sample fabrication
Taylor et al., manuscript to be submitted
3. Active Heat Control with Tunable Thermal Emission
25. Nano-Engineered Thermal Radiation Group 25
VO2 metafilm emitter – variable emittance vs. temp
Taylor et al., manuscript to be submitted
3. Active Heat Control with Tunable Thermal Emission
26. Nano-Engineered Thermal Radiation Group 26
Vacuum
Spring-Loaded
Needles
Tsample
Thermocouple
Sample
Cu Block
Heater
Al
Foil
Vacuum thermal test – experimental setup
Taylor et al., manuscript to be submitted
3. Active Heat Control with Tunable Thermal Emission
27. Nano-Engineered Thermal Radiation Group Taylor et al., manuscript to be submitted
Vacuum thermal test – VO2 metafilm emitter
3. Active Heat Control with Tunable Thermal Emission
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Nano-Engineered Thermal Radiation Group
Summary
SiC Metasurface for
Coherent Thermal Emission
LiF-based Sub-ambient
Daytime Radiative Cooling
Yang et al., preprint on arXiv
Yang et al., APL 111, 051904 (2017)
5 6 7 8 9
0
20
40
60
80
100
80o
C
90o
C
20o
C
50o
C
Absorptance,
5
C,,
(%)
Wavelength (5m)
Long et al., Materials Today Energy
13, 214-220 (2019)
VO2 Metamaterial for
Tunable Thermal Emission
Taylor et al., manuscript to be submitted
VO2 Metafilm for
Tunable Thermal Emission
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Nano-Engineered Thermal Radiation Group
Acknowledgements
Team Players:
o Dr. Yue Yang (2016-2012, currently Assistant Professor at Harbin Institute of Technology, Shenzhen)
o Dr. Hao Wang (2016-2012, currently postdoc at Lawrence Berkeley National Lab)
o Dr. Jui-Yung Chang (2017-2012, currently Assistant Professor at National Chiao Tung Univ., Taiwan)
o Dr. Hassan Alshehri (2018 – 2014, currently Assistant Professor at King Saud University, Saudi Arab)
o Dr. Linshuang Long (3rd year postdoc, VO2 metamaterial and graphene metasurface)
o Dr. Qing Ni (3rd year postdoc, TPV measurement and ultrathin cells)
o Mr. Payam Sabbaghi (5th year PhD student, near-field TPV and near-field radiation measurement)
o Ms. Sydney Taylor (4th year PhD student, NASA NSTRF Fellow, VO2 fab and metafilm)
o Ms. Xiaoyan Ying (3rd year PhD student, near-field radiation measurement and 2D materials)
o MS and UG students: Ramteja Kondakindi, Ryan McBurney, Lee Lambert, Niko Vlastos, etc
