ENERGY NANOTECHNOLOGY
--- A Few Examples
Gang Chen
Nanoengineering Group
Rohsenow Heat and Mass Transfer Laboratory
Massachusetts Institute of Technology
Cambridge, MA 02139
Email: [email protected]
http://web.mit.edu/nanoengineering
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Thermal-Electrical Energy Conversion
Temperature (K)
50 100 150 200 250 300500
REFRIGERATION
8
6
1000
1500
0.8
0.6
Power Plant
0.4
ThermoPV
0.2
Auto
0
Environmentally
Benign Refrigeration
6000
1
IMIT
L
C
I
M
ODYNA
M
R
E
H
T
4
2
5500
POWER GENERATION
Household
Refrigerator
Thermoelectrics
2000 5000
2500
Energy Efficiency
Waste Heat Recovery
Solar PV
0
Renewable
Energy
Grand Challenges: Efficiency and cost effective mass production
NanoEngineering Group
EFFICIENCY
COEFFICIENT OF PERFORMANCE
0
10
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Nano for Energy
• Increased surface area
• Interface and size effects
Molecules
Λ = 1−100 nm
λ=1 nm
Λ---Mean
free path
λ---wavelength
Electrons
Λ=10-100 nm
λ=10-50 nm
NanoEngineering Group
• Thermodynamics
• Kinetics
Photons
Λ > 10 nm
λ=0.1-10 µm
Phonons
Λ=10-100 nm
λ=1 nm
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Phonon and Electron Engineering
for
Thermoelectric Materials
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Thermoelectric Devices
COLD SIDE
COLD SIDE
-
I
N
+
P
HOT SIDE
HOT SIDE
Nondimensional Figure of Merit
Joule
Heating
Seebeck Coeff.
Electron Cooling
σS2T
ZT =
k
GPHS Radioisotope
Thermoelectric Generator
NanoEngineering Group
Reverse Heat Leakage
Through Heat Conduction
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
State-of-the-Art in Thermoelectrics
4
3.5
FIG U R E O F M ER IT (ZT)max
PbTe/PbSeTe Nano
PbSeTe/PbTe
Quantum-dot
Superlattices
(Lincoln Lab)
3
2.5
S2σ (µW/cmK2)
k (W/mK)
ZT (T=300K)
(Michigan
State)
1.5
1
Skutterudites
(Fleurial)
Bi2Te3 alloy
PbTe alloy
0.5
0
1940
Si0.8Ge0.2 alloy
1960
NanoEngineering Group
28
2.5
0.3
Harman et al., Science, 2003
Bi2Te3/Sb2Te3
Superlattices
(RTI)
2
32
0.6
1.6
Bulk
1980
YEAR
Dresselhaus
2000
Bi2Te3/Sb2Te3 Nano
Bulk
S2σ (µW/cmK2)
k (W/mK)
ZT (T=300K)
50.9
1.45
1.0
40
0.6
2.4
Venkatasubramanian et al.,
Nature, 2002.
2020
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Layer B
Layer A
Unit Cell of Superlattice
Heat Conduction Mechanisms
Unit Cell of B Layer
A New Crystal?
NanoEngineering Group
Inhomogeneous Multilayers?
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Heat Conduction Mechanisms in Superlattices
LD
BULK
In-Plane
60
40
In-P
lane
LD
SPECULAR (p=1)
Cross-Plane
Major Conclusions:
p=0.95
T=300K
AlAs/GaAs
20 -1
10
Yao 1987
DIFFUSE
(p=0)
p=0.8
0 1
10
1
10
ne
Ideal Superlattices
Yu et al. 1995
Capinski et al. 1999
Yao (1987)
Capinski et al. 1999
10
2
C ro
ssPla
Normalized
Thermal(W/mK)
Conductivity
THERMAL CONDUCTIVITY
0
80
10
Yu et al. (1995)
4
2 3
10 3
10 10
10
Period Thickness (Å)
• Ideal superlattices do not cut off all
phonons due to pass-bands
• Individual interface reflection is
more effective
• Diffuse phonon interface scattering
is crucial
LAYER THICKNESS (Å)
Coherent Structures Are Not Necessary, Nor Optimal!
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Photon Engineering:
Thermophovoltaics
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
4
10
2
EMISSIVE POWER (W/cm µm)
Photovoltaic Cells
Filter
Heat Source
Thermophotovoltaics
Useful Useless
3
10
2
5600 K
10
2800 K
1
10
1500 K
0
10
800 K
10
-1
0
•
•
•
•
•
NanoEngineering Group
2
EG
4
6
WAVELENGTH (µm)
8
Frequency Selective Emitter
Frequency Selective Filters
Photon Recycling Structures
Evanescent Wave Structures
High Efficiency PV Cells
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
10
Surface Waves and Near Surface
Energy Density
Wavelength (µm)
5
5
10
15
20
25
d = 10 nm
3
10
-3
-1
Energy Density (Jm eV )
10
ω
Free Space
1
10
d = 100 nm
d = 1 µm
-1
10
-3
10
d = 10 mm
-5
Surface
Modes
kx
blackbody
10
0.1
0.2
0.3
0.4
0.5
0.6
Energy (eV)
Energy density in the vicinity of a
half-plane of BN.
High Energy Density, Monochromatic EM Fields Exists Near Surfaces
When ε is Equal but of Opposite Signs. But They Are Non-Emitting!
Surface Plasmons and Surface Phonon Polaritons
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Near Field Energy Conversion
89
1.2 10
Wavelength (µm)
8.75
8.5
8.25
8
SiC
Source (BN, SiC) PV material
3
Power absorbed (Wcm-2)
10
2
10
Power absorbed
7
8 10
d = 1 nm
d = 0 nm
d = 10 nm
4 107
Blackbody
101
0
0.14
100
10-1
0
Flux (Wm-2eV-1)
d = 5 nm
100
200
Vacuum gap (nm)
NanoEngineering Group
0.145 0.15 0.155
Frequency (eV)
0.16
300
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Coupled Conduction and Radiation
Nonequilibrium Thermoelectric Devices
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Nonequilibrium Transport
Conventional TE Cooler
Conventional Micro TE Cooler
Electron
Temperature
T2
T1
Cooling
Target
T1
Cooling
Target Thermoelectric Element
Phonon
Temperature
T2
Thermoelectric Element
Battery
Battery
Proposed Nonequilibrium Thermoelectric Devices
¾ Explore nonequilibrium between
electrons and phonons
¾ couple the cooling target with
thermoelectric element without
direct lattice contact
ZT =
NanoEngineering Group
σS 2T
ke +X
kp
Vacuum
Gap
Electron
Temperature, Te
Phonon
Temperature, Tp
T2
T1
Cooling
Target
Battery
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Surface Plasmon Coupling of Electrons
Model Based on Fluctuation-Dissipation Theorem
d
d=10 nm
Macroscale
gap
T1
Far-Field
Nanoscale
gap
T1
Surface Waves
NanoEngineering Group
Three orders of magnitude increase in energy
transfer flux due to surface plasmon resonance
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Surface-Plasmon Enabled Nonequilibrium
Thermoelectric Refrigerators
260
1
Cooling Load q = 50 W/cm2
240
10
0.8
220
G
200
180
160
0.6
InSb
ke/k=0.1
Z=0.002K-1
TH=300K
8
3
140
3
G = 10 W/(m K)
12
3
G = 10 W/(m K)
Conventional
ke/k = 0.1
Z = 0.002K-1
TH = 300K
0.4
3
G=10 W/(m K)
10
COP
COLD END TEMPERATURE (K)
8
G = 10 W/(m K)
3
G=10 W/(m K)
12
3
G=10 W/(m K)
Conventional
120 0
1
2
3
4
10
10
10
10
10
THERMOELECTRIC ELEMENT LENGTH (µm)
0.2
0
1
10
100
THERMOELECTRIC ELEMENT LENGTH (µm)
• Performance is determined by the doping concentration and operation temperature.
• Principle works for both refrigerators and power generators.
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
Key Points
• Nanoscale effects are enabling breakthroughs in
energy technologies.
• Need cost-effective and mass producible
nanotechnology for energy applications.
• Fundamental understanding leads to new
manufacturing paradigms.
• Fundamental research problems exist in both
individual
nanostructures
and
mesoscopic
nanostructures.
• Multidisciplinary research and interdisciplinary
researchers are needed.
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY
ACKNOWLEDGMENTS
• Current Members
• Collaborators
H. Asegun (Molecular Dynamics)
M.S. & G. Dresselhaus (MIT, NW&CNT, Theory)
V. Berube (hydrogen storage)
J.-P. Fleurial (JPL, Thermoelectric Devices)
Z. Chen (Metamaterials, TPV)
J. Joannopoulos (MIT, Photonic Crystals)
S. Goh (polymers)
Z.F. Ren (BC, Thermoelectric Materials, CNT)
T. Harris (Thermoelectrics&Nanomaterials)
X. Zhang (Berkeley, Metamaterials)
Q. Hao (Thermoelectrics)
D. Kramer (Solar thermoelectrics)
• Past Members (Partial List)
H. Lee (Thermoelectric Materials)
Prof. C. Dames (Nanowires, UC Riverside)
H. Lu (TPV and PV)
Prof. D. Borca-Tasciuc (Nanowires, RPI)
A. Minnich (thermoelectrics)
Prof. T. Borca-Tasciuc (Thermoelectrics,RPI)
A. Muto (nanowires and thermoelectrics)
Dr. F. Hashemi (Nano-Device Fabrication)
S. Nakamura (nanowires and thermoelectrics)
Dr. A. Jacquot (TE Device Fabrication)
A. Narayanaswamy (Metamaterials, TPV)
Dr. M.S. Jeng (Nanocomposites, ITRI)
G. Radtke (hydrogen storage)
Dr. R. Kumar (Thermoelectric Device Modeling)
A. Schmidt (ps pump-and-probe)
Dr. W.L. Liu (superlattice)
E. Skow (polymers)
Dr. D. Song (TE and Monte Carlo, Intel)
S. Shen (lubrication, rarefied gas dynamics)
Dr. S.G. Volz (MD, Ecole Centrale de Paris)
Dr. M. Chieso (nanofluids)
Prof. B. Yang (TE and Phonons, U. Maryland)
Dr. X. Chen (thermoelectrics, Pump-and-Probe)
Prof. R.G. Yang (Nanocomposites, U. Colorado)
Dr. D. Vashee (thermoelectrics)
Prof. D.-J. Yao (TE Devices, Tsinghua Univ.)
Prof. Y.T. Kang (nanofluids)
Prof. T. Zeng (Thermionics, NCSU)
Sponsors: ARO, DOE, NASA, NSF, ONR, Industries
NanoEngineering Group
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY