Microscopic Modeling

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Introduction to Thermoelectric Effects And Their
Applications in Energy and Environment Shang-Fe
n Ren  Department of Physics, Illinois State
University Normal, IL 61790-4560 ren_at_phy.ilstu.ed
u

 Research Supported by National Science
Foundation, Research Corporation, and
Caterpillar, Inc
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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

 
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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


 
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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.
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Introduction to Thermoelectrics 

 
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.
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Thermoelectrics Nomenclature
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Thermoelectrics Nomenclature
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Commercial Bulk TE Modules
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Thermoelectrics Power Generation (Seebeck Effect)
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Thermoelectrics Cooling (Peltier Effect)
Peltier Effects was discovered 13 years later.
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Applications of Thermoelectrics (I) TE Power
Generation (Seebeck) Power generation for
special applications Space Military
 

Waste heat to energy (green energy)
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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
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Thermoelectric Efficient 
Figure of Merit ZT
ZT
a is the Seebeck coefficient of the material
(V/K) is the electrical resistivity of the
material (Om) 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)).
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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.
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Coefficient of Performance for Thermoelectric
Cooling as Function of ZT 
 
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Figure of Merit Bulk
 
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Bulk Module Markets
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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.
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Solid state refrigerators may replace traditional
compressor refrigerators in the future

 
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Progress in Thermoelectric Efficiency ZT 
 
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Thermoelectrics Materials Bulk and Nano-Scale
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A World from Macro to Nanoscale
1 nm 10-9 m
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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.

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Examples of Nanostructures
48 Fe atoms on Cu (111) surface, Quantum Corral,
by D. Eigler,IBM
Self-assembled Ge pyramid 10nm (www.nano.gov)
Chemical Etching of Porous Silicon by Thomas
Research Group
Carbon Nanotubes (Ren, et al., Stanford Science,
1998)
C60 discovered by Kroto in 1985
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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
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Properties of Nanoscale Materials CdSe Quantum
Dots
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Properties of Nanoscale Materials Size and Band
Gap
Electrons Blue shift of the electronic band gap

Uncertainty Principle
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US Energy Flow Trend (2002) 
 
Unit quads, (1quads 1 quadrillion BTU, 1
BTU1055J)
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Opportunities for Recovery of Waste Heat in
Transportation
 
Distribution of Fuel Energy in Passenger Vehicles
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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

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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

 
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Science-based Approach for TE material Discovery 
 
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Materials Technology Flow for Solid State Waste
Heat Energy Recovery 
 
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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.
 
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Potential Location for TE Generator

 
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Caterpillars 550 HP Heavy Truck Equipped with TEG
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TE Generator for Light Vehicles  

 
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TE Materials for Applications in Energy and
Environment
Thank you!