Develop Thermoelectric TechnologyDevelop Thermoelectric Technology for Automotive Waste Heat Recoveryfor Automotive Waste Heat Recovery
Sponsored by
US Department of Energy
Energy Efficiency Renewable Energy (EERE) DE-FC26-04NT42278
Outline � Background
− Objective, partnering, … − Motivation: fuel economy
� Technology Development Jihui Yang − Subsystem modeling
GM Research & Development Center − Cost − Cost-effective materials
� Summary
1
DOE Program ObjectiveDOE Program Objective
Demonstrate a 10% fuel economy improvement using thermoelectric waste heat recovery technology, without increased emissions and at a cost-effective way.
2
PartneringPartnering• GM
– Materials Research – Subsystem design, integration, modeling, and validation
• GE – TE module design and construction – Subsystem design and construction
• Oak Ridge National Lab – High temperature materials properties measurement
• RTI – Superlattice-base materials and modules
• University of South Florida – bulk materials development: clathrates, nano-grain PbTe, …
• University of Michigan – Bulk materials development, skutterudites, nano-composites,…
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Accessories2.2 (1.5)%
Accessories2.2 (1.5)%
Energy Distribution –Energy Distribution –Typical Mid-Size Vehicle on Federal Test Procedure (FTypical Mid-Size Vehicle on Federal Test Procedure (F-- Urban (Highway) % energy usUrban (Highway) % energy use
4
Standby/Idle 17.2 (3.6)%
Engine Losses 62.4 (69.2)%
Driveline Losses 5.6 (5.4)%
Aero 2.6 (10.9)%
Rolling 4.2 (7.1)%
Kinetic
Braking 5.8 (2.2)%
Engine 100% 18.2%
(25.6%) D/L 12.6% (20.2%)
PNGV source
Standby/Idle 17.2 (3.6)%
Engine Losses62.4 (69.2)%
Driveline Losses5.6 (5.4)%
Aero2.6 (10.9)%
Rolling4.2 (7.1)%
Kinetic
Braking5.8 (2.2)%
Engine100% 18.2%
(25.6%) D/L 12.6%(20.2%)
PNGV source
Example of an Energy RecoveryExample of an Energy RecoverySystemSystem
TransmissionEngine
Catalyst ERS
Radiator
Alternate: make the radiator into an energy recovery device.
(smaller ΔT)5
Exhaust as Potential TE Heat SourceExhaust as Potential TE Heat Source
kW
Exhaust Heat
80
70
60
50
40
30
20
10
0
0 500 1000 1500 2000 2500
Test Time (s)
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Thermoelectric Energy ConversionThermoelectric Energy Conversion
4.0 room temperature
3.5 PbSexTe1-x/PbTe quantum dots
3.0 Bi2Te3/Sb2Te3 superlattices
2.5
2.0
CeyCoxFe4-xSb121.5 Yb0.19Co4Sb12 Ba0.3Co3.95Ni0.05Sb12Bi2Te3 La CoFe3Sb121.0
0.9 SiGe PbTe
Efficiency: ε = THT
− TC 1 + ZT − T 1 C
0.5
H 1 + ZT + 0.0 TH
0 200 400 600 800 1000 1200 1400 T (K)
ZT
7
8
IC Engine
Electrical Storage Transmission
Electric Power
Controls
Powertrain Control
Electronics
Catalytic Converter Heat Collector
Thermoelectric Device
Cooling
Exhaust
Vehicle Electrical System
Alternator
Generic Concept for a Thermoelectric Energy Recovery Augmented Electrical System
Generic Concept for a Thermoelectric Energy Recovery Augmented Electrical System
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TE Module ModelingTE Module Modeling
n p
metal
metalmetal
metal
conductor
Contact Resistances
conductor conductor
insulator
insulator
Hot side heat exchanger
Cold side heat exchanger
thermal
thermal
Electrical & thermal
thermal
thermal
volume resistivity
Electrical & thermal
Thermal shunt path
Joule & Peltier terms
Joule heating from all electrical contacts are accounted for.
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0
1
2
3 4n4p
5p 5n
6n6p
7n7p 8
9
10
11
Preliminary Temperature ProfilePreliminary Temperature Profile
0 100 200 300 400 500 600 700 800 900
0 1 2 3 4 5 6 7 8 9 10 11
Tem
pera
ture
(K)
20% 15% 5%
ΔTE ΔHX
Position in TE device (node)
60 kW exhaust flow
Validation of GE’s subsystem ModelValidation of GE’s subsystem Model with GEN I TE Generatorwith GEN I TE Generator
Experiment Model Output Power 109W 121W Vload 16.5V 17.4V Current, I 6.6A 7.0A Hot side temperature 183C 189C Cold side temperature 35C 35C
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On the Cost of Fuel EconomyOn the Cost of Fuel Economy
2000
1800 $2/gallon$3/gallon1600 � Cost of fuel economy - $/Δmpg$4/gallon
1400 •This kind of calculation can be used to balance technology options1200
1000
� $/Δmpg ≤ Savings/Δmpg is necessary800
to provide consumer value600
400
200
00 10 20 30 40 50 60 70
FE (mpg)
Consumer Fuel Savings/Δmpg ≈ $300-400/Δmpg (15000 mile/yr., 3yrs., 18-20 mpg)
3 Y
ear F
uel S
avin
g pe
r 1m
pg F
E im
prov
emen
t
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Skutterudites Nano-101Skutterudites Nano-101 � CoAs3 -based minerals found in region
of Skutterud, Norway � Compounds with the same crystal
structure are known as “skutterudites” � Filled skutterudites are electron-crystal-
phonon-glass materials
2 2
( )T L e
S SZ κ ρ κ κ ρ
= = +
Co Sb
�2Co4Sb12
Filler atoms
Filled skutterudites as CandidateFilled skutterudites as Candidate Materials for Exhaust Heat RecoveryMaterials for Exhaust Heat Recovery
ZT
1.5 room temperature CeyCoxFe4-xSb12 (p-type)
� High ZT values near the exhaustYb0.19Co4Sb12(n-type) Ba0.3Co3.95Ni0.05Sb12
(n-type) temperature1.0
La CoFe3Sb12 (p-type)0.9
� Both high performance n- and p-typeBi2Te3 SiGe PbTe exist – suitable for TE module
0.5
0.0 0 200 400 600 800 1000 1200 1400
T (K)
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MischmetalMischmetal �Mischmetal: from German - “mixed metals”; a
naturally occurring alloy of rare earth elements � Composition (wt%):
Ce : 50-55 La : 30-35 Nd : 5-10 Pr : 5-10 � Cost Comparison*:
Mischmetal (99.0%): $0.19/g Cerium rod (99.9%): $8.37/g Lanthanum rod (99.9%): $6.40/g
* source: Alfa Aesar
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Mischmetal Starting MaterialMischmetal Starting Material
Element Wt.%
Ce 52.4 La 23.5 Nd 17.1 Pr 5.9 Si 0.6 Fe 0.3 Al 0.1
Sum 99.9
electron probemicroanalysis
wet chemistry Element Ce La Nd Pr Sample
%
53 23 18 5
17
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Electron Probe Microanalysis of Mischmetal-filled Skutterudites Electron Probe Microanalysis of Mischmetal-filled Skutterudites
9.1433(2)Mm0.88Fe4Sb12.06MmFe4Sb12 *
9.1294(2)Mm0.82Fe3.51Co0.49Sb11.99Mm0.93Fe3.5Co0.5Sb12 *
9.146(1)Mm0.82Fe4Sb11.96MmFe4Sb12
9.126(1)Mm0.72Fe3.43Co0.57Sb11.97Mm0.93Fe3.5Co0.5Sb12
9.117(1)Mm0.65Fe2.92Co1.08Sb11.98Mm0.82Fe3CoSb12
9.109(1)Mm0.55Fe2.44Co1.56Sb11.96Mm0.71Fe2.5Co1.5Sb12
Room temperature lattice parameter (Å)Actual compositionNominal composition
� nominal comp. chosen according to the optimal filled skutterudites CeyFe4-xCoxSb12 ~ PRL 80, 3551 (1998)
� Mm actual concentration < nominal due to high Mm vapor pressure
� all samples are nearly phase pure � typical secondary phase:
MnSb2 or CoSb2 < 1 vol. %
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Isotropic Atomic Displacement Parameter – Evidence of Rattling Isotropic Atomic Displacement Parameter – Evidence of Rattling
U is
o (Å
2 ) 0.000
0.005
0.010
0.015
0.020
0.025
T (K) 0 50 100 150 200 250 300
U is
o (Å
2 )
0.000
0.005
0.010
0.015
0.020
Mm0.82Fe3.51Co0.49Sb11.99
Mm0.88Fe4Sb12.06
Mm
Fe/Co
Sb
Mm
Fe
Sb
� low T intercepts of Uiso represent a combination of zero-point vibration and static disorder at the corresponding crystallographic sites
� zero-point vibration ∝ 1/M, expected contribution ~ Mn < Sb < Fe Æstatic disorder at the Sb sites, more so at the Mn sites (Mn vs. �)
� θE ~ 71.5 K ( La: 80 K, Ce: 78 K, Eu: 83 K, and Yb: 65 K)
Room Temperature PropertiesRoom Temperature Properties ComparisonComparison
100 1.2
Ce Fe4-xCo Sb12y x
MmyFe4-xCoxSb12
La0.9Fe3CoSb12
10 Ce0.9Fe3CoSb12
1
Latti
ce th
erm
al re
sist
ivity
(m K
/W)
1.0
0.8
0.6
0.4
0.2
S2 /ρ
(μW
/cm
K2 )
0.1 0.01 10 100 1000 10000 0.0 0.2 0.4 0.6 0.8 1.0 p (1018 cm-3) y
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Summary of Challenges for Automotive TE Waste Heat Recovery Summary of Challenges for Automotive TE Waste Heat Recovery
Outline � Background
− Objective, partnering, … − Motivation: fuel economy
� Technology Development − Subsystem modeling − Cost − Cost-effective materials
� Summary
Need better materials, heat exchanger, contact joining, thermal & mechanical stability, …
Consumer focus: consider $/Δmpg (also valuable for balancing tech. options)
Low cost materials is a must
Thank you ! Questions ?