Introduction to Thermoelectric Effects
And Their Applications in
Energy and Environment
Shang-Fen Ren
Department of Physics, Illinois State University
Normal, IL 61790-4560
ren@phy.ilstu.edu
Research Supported by
National Science Foundation,
Research Corporation,
and Caterpillar, Inc
Main Research Collaborators
Wei Cheng (Beijing Normal University)
Gang Chen (MIT)
Walter Harrison (Stanford)
Peter Yu and Sam Mao (UC-Berkeley)
Andrew McGilvray, Bo Shi, and Mahmoud Taher (Caterpillar)
Research Students (1994-present)
David Rosenberg, Latanya Molone, Garnet Erdakos, Heather Dowd, Jason
Stanford, Maria A. Alejandra, Chad Johnson, Kim Goodwin, Joel Heidman,
Paul Peng, Josh Matsko, Brian Mavity, Rory Davis, Nathan Tovo,
Victor Nkonga, Shelley Dexter, Scott Gay, Tim Hughes, Gabriel Altay, Louis Little,
Victor Nkonka, Benjamin Thompson, Jonathan Andreason, Zoe Paukstys,
Colin Connolly, Marcus Woo, Courtney Pinard, Danthu H.Vu,
Valerie Hackstadt, Derek Wissmiller, Scott Whitney, Chris S. Kopec,
Erika Roesler, Elizabeth Williams,Trina Karim, Mike Morrissey, Nick Jurasek,
Nathan Bogue, Mid-hat Abdulrhman, Maggie Hansen, Jade Exley
Outline
Thermoelectric Effect
What is Thermoelectric Effect (TE)
Potential Applications of TE
TE and Nanotechnology
TE Applications in Energy and Environment
Research Collaboration on TE with Caterpillar
Thermoelectric Effects
Discovered in 1821 by Thomas Johann Seebeck: observed a compass needle to move
when placed in the vicinity of a closed loop of two dissimilar metal conductors joined together at the
ends to make a circuit, when the junctions were maintained at different temperatures.
Introduction to Thermoelectrics
Heat in
Thermoelectric
Couple
Thermoelectric
elements (legs)
Th
N
P
Tc
-
+
Current out
Two legs of a thermocouple.
The magnitude of the thermoelectric
voltage is proportional to the difference
of two temperatures.
Most materials with good thermoelectricity efficient
are semiconductors. Two legs are made by
N-type and P-type of semiconductors respectively.
Thermoelectrics Nomenclature
Thermoelectric Device
(Module)
+
-
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Thermoelectrics Nomenclature
Thermoelectric System/Application
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Commercial Bulk TE Modules
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Thermoelectrics Power Generation (Seebeck Effect)
Thermal Power in
Qh
-
Electric Power out
Po
Th
+
Tc
Carnot Efficiency
 max
Th  Tc

Th
1  ZTav  1
Po

Tc Qh
1  ZTav 
Th
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Thermoelectrics Cooling (Peltier Effect)
Peltier Effects was discovered 13 years later.
Th
-
Electric Power in
Pin
+
Tc
Thermal Power Out
Qc
COPmax
Tc

Th  Tc
1  ZTav
Th

Tc
1  ZTav
Qc

Pin
1
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Applications of Thermoelectrics (I)
TE Power Generation (Seebeck)
Power generation for special applications
Space
Military
Waste heat to energy (green energy)
Applications of Thermoelectrics (II)
TE Cooling (Peltier)
High accuracy thermometer
Environmentally-friendly refrigerator
New air-conditioning
Cooling for electronics
Simple system, small volume,
high accuracy, high sensitivity, highly reliable,
long lifetime, environmentally friendly
Thermoelectric Efficient
Figure of Merit ZT

T
ZT=

2
α is the Seebeck coefficient of the material (V/K)
 is the electrical resistivity of the material (Ωm)
 is the thermal conductivity of the material (W/mK)
Most materials have a ZT much less than 1.
Thermoelectric systems in automobiles requires a ZT of about 2.
To substitute conventional refrigerators requires a ZT of about 4
The heart of the research is to look for materials that
conduct electricity well but conduct heat poorly (phonon
glass and electron crystal (PGEC)).
Performance of Thermoelectric Generator as Function of ZT
For above temperatures, the Carnot efficiency is about 61 percent, making the TE generator
to be about 24 to 30 percent efficient with TE materials with ZT between 2 and 3.
Coefficient of Performance for Thermoelectric Cooling
as Function of ZT
Figure of Merit – Bulk
Bulk Module Markets
Portable Fridge
Chiller
Dehumidifier
Electronics Cooling
Automobile
Offshore power generation
Radioisotope thermoelectric
generator
Night vision
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Climate Control Seat (CCS) System Vehicle Application
In high end cars (GM, Ford, Toyota, Nissan, Lexus, etc) .
Huge market!!! Over 4 million units sold so far.
Solid state refrigerators may replace traditional
compressor refrigerators in the future
Progress in Thermoelectric Efficiency ZT
FIGURE
OFofMERIT
Figure
Merit (ZT)
(ZT)max
max
4
PbSeTe/PbTe
Quantum-dot
Superlattices
(Lincoln Lab)
3.5
3
Bi2Te3/Sb2Te3
Superlattices
(RTI)
2.5
(Michigan
State)
2
1.5
1
Skutterudites
(Fleurial)
Bi2Te3 alloy
0.5
PbTe alloy
Si0.8Ge0.2 alloy
Dresselhaus
0
1940
1960
1980
Year YEAR
2000
2020
Thermoelectrics Materials: Bulk and Nano-Scale
Bulk
Less than 5%
conversion efficiency
Nano-Scale
Predicted with 30%
conversion efficiency
• More than 40 years
• Less than 10 years
• Niche applications
• Potential for a wide
variety of applications
• Well established
product
• Still being incubated at
small companies,
universities and national
labs
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
A World from Macro to Nanoscale
1 nm = 10-9 m
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Introduction: Nanoscience and Nanotechnology
What is a Nanostructure?
The word “nano” means 10-9 . So a
nanometer is one billionth of a meter. In
general, nanostructures are objects in the
size range from tens to hundreds of
nanometers.
Nanoscience concerns the study of
objects in this size range, and
nanotechnology is to fabricate and
work on objects in this size range.
Why nano?
The nanoworld provides scientists with a
rich set of materials that can be useful of
probing the fundamental nature of matter.
These materials also have tunable
properties that makes them valuable for
many different real world applications.
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Examples of Nanostructures
48 Fe atoms on Cu (111) surface,
Quantum Corral, by D. Eigler,IBM
Chemical Etching of Porous Silicon
by Thomas Research Group
C60 discovered by Kroto in 1985
Self-assembled Ge pyramid
10nm (www.nano.gov)
Carbon Nanotubes (Ren, et al.,
Stanford Science, 1998)
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Properties of Nanostructures: Electron Density of
States as a Function of Dimensionality
Quantum well (QW)
2-D
Quantum wires(QWR) 1-D
Quantum Dots (QD)
0-D
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Properties of Nanoscale Materials: CdSe Quantum Dots
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Properties of Nanoscale Materials: Size and Band Gap
Electrons: Blue shift of the electronic band gap
Uncertainty Principle
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
US Energy Flow Trend (2002)
Massive Quantity of
“Waste” Energy
Imported Oil
97% Oil
Dependent
Unit: quads, (1quads =1 quadrillion BTU, 1 BTU=1055J)
30%
Engine
Combustion
100%
Gasoline
Gasoline
Opportunities for Recovery of Waste Heat in
Transportation
25
Mobility &
Accessories
5%
Friction &
Radiated
30%
Coolant
40%
Exhaust
Gas
Distribution of Fuel Energy in Passenger Vehicles
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
Goal for TE in Transportation, a Research Roadmap
By 2012, achieve at least 25% efficiency in
advanced thermoelectric devices for waste heat
recovery to potentially increase passenger and
commercial vehicle fuel economy by 10%.
DOE Initiative for a Science-Based Approach to
Development of Thermoelectric Materials for
Transportation Applications, ORNL, Nov. 2007
Technical Barriers
Unusual combination of properties
Matching n- and p- type materials
Performance often dependent on doping
Difficult metrology and lack of standards
Scale up of synthesis and processing of thin-film materials from lab
scale
Cost effective thermoelectric materials and devices
System issues critical to operation of thermoelectric devices
Science-based Approach for TE material Discovery
Computation
(Modeling &
Simulation)
Evaluation
New
Materials
Characterization
Synthesis &
Processing
Materials Technology Flow for Solid State Waste Heat
Energy Recovery
Collaboration with Caterpillar
We have developed a physics-based model that simulates the
structure of multilayered nanostructures.
Our modeling tool is used to predict the TE property of various
multilayered structures with different structural configurations
and doping concentrations.
Our calculations have helped with the understating of the TE
property of nanostructure affected by various conditions, and
the results are used to guide the experimental research in
developing nanostructured thin-film based materials for highefficiency TE applications.
Potential Location for TE Generator
Caterpillar’s 550 HP Heavy Truck Equipped with TEG
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren
TE Generator for Light Vehicles
TE Materials for Applications in Energy and Environment
Introduction to TE and Their Applications in Energy and Environment
By Shang-Fen Ren