Characterization of Thermoelectric Properties and Power Generation Efficiency of Thermoelectric Materials
1. Characterization of Thermoelectric Properties and
Power Generation Efficiency of Thermoelectric Materials
Andy Muto, D. Kraemer, Q. Hao
Gang Chen’s Group
Dept. of Mechanical Engineering
Massachusetts Institute of Technology
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
2. Where are Thermoelectrics Today
Portable refrigerators Personal temperature control in vehicles
Its hard to justify all the research in thermoelectrics by these niche markets alone
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3. Industrial Waste Heat Solar Thermo
THINK BIG
Vehicle Waste Heat HVAC in Buildings
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4. Introduction to Thermoelectrics
Hot Side
electron holes
Current by N type P type -Individual property measurements can
diffusion
accumulate large uncertainties
Cold Side
Power Generation
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
5. Introduction to Thermoelectrics
Hot Side
electron holes
-High resolution efficiency measurement
Current by N type P type
0.048
Conversion Efficiency
diffusion
0.047
Cold Side 0.046
0.045
Power Generation 0.044
0.043
0.25 0.35 0.45 0.55
Current [A]
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6. Thermocouple Energy Balance
QHOT=IVHEATER
IVTE IVTE
QH QC IVTE
P-type N-type
I VTE I
QCOLD
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7. Actual Measurement and Thermal Losses
QLOSS
QHOT=IVHEATER
P-type N-type
VTE
I I
QLOSS QLOSS
QCOLD
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
8. Actual Measurement and Thermal Losses
Darken color
QLOSS
QHOT=IVHEATER
P-type N-type
VTE
I I
QLOSS QLOSS
QCOLD
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
9. Actual Measurement
Heater calibrated for heat loss, measuring QHOT
THOT
VTE
Cryostat cold finger
maintained at ambient
under vacuum
TCOLD
Current wires
calibrated for
heat loss
Heat flux sensor measuring QCOLD TE cooler maintaining TCOLD at ambient
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10. Calibration of losses
Suspended Heater Calibration
QLOSS IVHEATER
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11. Calibration of losses
Current Leads Calibration
QLEADS QLEADS
QCOLD TCOLD
Cooler Module
TAMBIENT
C LEADS QLEADS
14% 2%
CTOTAL QTOTAL
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
12. Load Matching with Current Source
Variable Load Resistance
IV- IV+
RLOAD
Typical ZT derivation uses a
variable load resistance to reach
optimal current
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
13. Load Matching with Current Source
Variable Load Resistance Equivalent to using a CURRENT SOURCE
IV- IV+ IV- IV+
RLOAD
Advantages:
Typical ZT derivation uses a -control and stability
variable load resistance to reach -in situ AC electrical resistance
optimal current measurements
-can even test in refrigeration or heat
pump regime!
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14. Effective ZT Modeling
0.048 Qcold Efficiency
Qhot Efficiency
ZT=0.76
Conversion Efficiency
0.047
0.046
IVTE
ƞQH =
QH
0.045
IVTE
ƞQC =
QC+IVTE
0.044
0.043
0.25 0.35 0.45 0.55
Current [A]
THOT= 150 [C] , TCOLD=23 [C]
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
15. Effective ZT
0.06
0.68
0.76
Conversion Efficiency
0.05
0.04 0.66
0.74
0.03 0.89
0.02
0.80
After High Temp Exposure
0.01
Before High Temp Exposure
0
75 100 125 150 175 200 225
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THOT [C]
WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
16. Summary
Measured the power conversion efficiency of a unicouple
Both QHOT and QCOLD are measured directly, and calibrated for thermal losses
Load matching controlled by current source
Total energy balance QHOT QCOLD IVTE within 1%
Effective ZT model works
Acknowledgements:
D. Kraemer, Q. Hao
Advisor: Gang Chen
Support from: Masdar, NSF
NanoEngineering Group WARREN M. ROHSENOW HEAT AND MASS TRANSFER LABORATORY @ MIT
