1. Introduction to Thermoelectric Effects And Their Applications in
Energy and Environment
Shang-Fen Ren
 Department of Physics, Illinois State University
Normal, IL
 Research Supported by
National Science Foundation,
Research Corporation,
and Caterpillar, Inc

2. Main Research Collaborators Research Students (1994-present)
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

3. 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

4. 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.

5. Introduction to Thermoelectrics
Heat in
Current out + -
Thermoelectric Couple
Thermoelectric elements (legs) Th Tc N P
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.

6. Thermoelectrics Nomenclature
Thermoelectric Device
(Module) + -

7. Thermoelectrics Nomenclature
Thermoelectric System/Application

8. Commercial Bulk TE Modules

9. Thermoelectrics Power Generation (Seebeck Effect)+ -
Electric Power out Po
Thermal Power in Qh Th Tc
Carnot Efficiency

10. Thermoelectrics Cooling (Peltier Effect)
Peltier Effects was discovered 13 years later. + -
Electric Power in
Pin
Thermal Power Out Qc Th Tc

11. Applications of Thermoelectrics (I)
TE Power Generation (Seebeck)
Power generation for special applications
Space
Military
Waste heat to energy (green energy)

12. 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

13. Thermoelectric Efficient
Figure of Merit ZT
ZT=
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)).

14. 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.

15. Coefficient of Performance for Thermoelectric Cooling
as Function of ZT 

16. Figure of Merit – Bulk

17. Offshore power generation
Bulk Module Markets
Portable Fridge
Dehumidifier
Electronics Cooling
Automobile
Offshore power generation
Chiller
Night vision
Radioisotope thermoelectric generator

18. 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.

19. Solid state refrigerators may replace traditional compressor refrigerators in the future

20. Progress in Thermoelectric Efficiency ZT

21. Thermoelectrics Materials: Bulk and Nano-Scale
Less than 5% conversion efficiency
Bulk
More than 40 years
Niche applications
Well established product
Nano-Scale
Predicted with 30% conversion efficiency
Less than 10 years
Potential for a wide variety of applications
Still being incubated at small companies, universities and national labs
Just like thermocouples, where are a pair of dissimilar metals connected together at a junction is exposed to a temperature difference is

22. A World from Macro to Nanoscale
1 nm = 10-9 m

23. Introduction: Nanoscience and Nanotechnology
What is a Nanostructure?
The word “nano” means 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.

24. Examples of Nanostructures
48 Fe atoms on Cu (111) surface, Quantum Corral, by D. Eigler,IBM
Self-assembled Ge pyramid 10nm (
Chemical Etching of Porous Silicon
by Thomas Research Group
Carbon Nanotubes (Ren, et al., Stanford Science, 1998)
C60 discovered by Kroto in 1985

25. Properties of Nanostructures: Electron Density of States as a Function of Dimensionality
Quantum well (QW) D
Quantum wires(QWR) 1-D
Quantum Dots (QD) D

26. Properties of Nanoscale Materials: CdSe Quantum Dots

27. Properties of Nanoscale Materials: Size and Band Gap
Electrons: Blue shift of the electronic band gap
Uncertainty Principle

28. US Energy Flow Trend (2002) 
Unit: quads, (1quads =1 quadrillion BTU, 1 BTU=1055J)

29. Opportunities for Recovery of Waste Heat in Transportation
Distribution of Fuel Energy in Passenger Vehicles

31. 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
Program Goals
Research Goals:
By 2012, achieve at least 21% efficiency in cost effective thermoelectric devices for waste heat recovery in transportation applications.
This is the goal from the DOE OFCVT 5-year plan for waste heat rejection in cars and trucks
Is this too conservative for our program?

32. 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

33. Science-based Approach for TE material Discovery

34. Materials Technology Flow for Solid State Waste Heat Energy Recovery

35. 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 high-efficiency TE applications.

36. Potential Location for TE Generator

37. Caterpillar’s 550 HP Heavy Truck Equipped with TEG

39. TE Generator for Light Vehicles

40. TE Materials for Applications in Energy and Environment
Thank you!