Introduction to Thermoelectric Effects And Their Applications in Energy and Environment Shang-Fen Ren Department of Physics, Illinois State University

Introduction to Thermoelectric Effects

And Their Applications in Energy and Environment

Shang-Fen Ren Department of Physics, Illinois State University

Normal, IL 61790-4560

[email protected]

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

Current out+-

TThh

TTcc

NN PP

Thermoelectric Couple Thermoelectric

elements (legs)

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.

Introduction to TE and Their Applications in Energy and Environment By Shang-Fen Ren

Thermoelectrics Nomenclature

+

-

Thermoelectric Device

(Module)


Thermoelectrics Nomenclature

Thermoelectric System/Application


Commercial Bulk TE Modules


Thermoelectrics Power Generation (Seebeck Effect)

+

-

+

-Electric Power out

Po

Thermal Power in

QhTThh

TTcc

h

o

h

cav

av

h

ch

Q

P

T

TZT

ZT

T

TT

1

11max

Carnot Efficiency


Thermoelectrics Cooling (Peltier Effect)

in

c

av

c

hav

ch

c

P

Q

ZT

T

TZT

TT

TCOP

11

1

max

+

-

+

-Electric Power in

Pin

Thermal Power Out

Qc

TThh

TTcc

Peltier Effects was discovered 13 years later.

Applications of Thermoelectrics (I)

TE Power Generation (Seebeck)

Power generation for special applications

SpaceMilitary

Waste heat to energy (green energy)

Applications of Thermoelectrics (II)

TE Cooling (Peltier)High accuracy thermometer Environmentally-friendly refrigeratorNew air-conditioningCooling for electronics

Simple system, small volume, high accuracy, high sensitivity, highly reliable, long lifetime, environmentally friendly

Thermoelectric Efficient

ZT=

T 2

Figure of Merit Figure of Merit ZTZT

α is the Seebeck coefficient of the material (V/K)is the Seebeck coefficient of the material (V/K) is the electrical resistivity of the material (Ωm)is the electrical resistivity of the material (Ωm) is the thermal conductivity of the material (W/mK)is the thermal conductivity of the material (W/mK)

The heart of the research is to look for materials that conduct electricity well but conduct heat poorly (phonon glass and electron crystal (PGEC)).

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

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

Night visionNight vision

Radioisotope thermoelectric Radioisotope thermoelectric generatorgenerator

Electronics CoolingElectronics Cooling AutomobileAutomobilePortable FridgePortable Fridge DehumidifierDehumidifier

Offshore power generationOffshore power generationChillerChiller

In high end cars (GM, Ford, Toyota, Nissan, Lexus, etc) .

Huge market!!! Over 4 million units sold so far.

Climate Control Seat (CCS) System Vehicle Application

Solid state refrigerators may replace traditional compressor refrigerators in the future

Progress in Thermoelectric Efficiency ZT

0

0.5

1

1.5

2

2.5

3

3.5

4

1940 1960 1980 2000 2020

YEAR

FIG

UR

E O

F M

ER

IT (

ZT

) max

Bi2Te3 alloyPbTe alloy

Si0.8Ge0.2 alloy

Skutterudites(Fleurial)

PbSeTe/PbTeQuantum-dotSuperlattices(Lincoln Lab)

Bi2Te3/Sb2Te3

Superlattices(RTI)

Dresselhaus

(MichiganState)

Figu

re o

f Mer

it (

ZT)

max

Year

0

0.5

1

1.5

2

2.5

3

3.5

4

1940 1960 1980 2000 2020

YEAR

FIG

UR

E O

F M

ER

IT (

ZT

) max

Bi2Te3 alloyPbTe alloy

Si0.8Ge0.2 alloy

Skutterudites(Fleurial)

PbSeTe/PbTeQuantum-dotSuperlattices(Lincoln Lab)

Bi2Te3/Sb2Te3

Superlattices(RTI)

Dresselhaus

(MichiganState)

Figu

re o

f Mer

it (

ZT)

max

Year


Thermoelectrics Materials: Bulk and Nano-Scale

Less than 5% conversion efficiency

BulkBulk

• More than 40 years

• Niche applications

• Well established product

Nano-ScaleNano-ScalePredicted 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


A World from Macro to Nanoscale

1 nm = 10-9

m


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.

These materials also have tunable properties that makes them valuable for many different real world applications.

Why nano?The nanoworld provides scientists with a rich set of materials that can be useful of probing the fundamental nature of matter.


Examples of Nanostructures

Carbon Nanotubes (Ren, et al., Stanford Science, 1998)

Chemical Etching of Porous Silicon

by Thomas Research Group

C60 discovered by Kroto in 1985

Self-assembled Ge pyramid 10nm

(www.nano.gov)

48 Fe atoms on Cu (111) surface, Quantum Corral, by

D. Eigler,IBM


Properties of Nanostructures: Electron Density of States as a Function of Dimensionality

Quantum wires(QWR)

1-D

Quantum well (QW) 2-D

Quantum Dots (QD) 0-D


Properties of Nanoscale Materials: CdSe Quantum Dots


Properties of Nanoscale Materials: Size and Band Gap

Electrons: Blue shift of the electronic band gap

Uncertainty

Principle

US Energy Flow Trend (2002)

Massive Quantity of “Waste” Energy

97% Oil Dependent

Imported Oil

Massive Quantity of “Waste” Energy

97% Oil Dependent

Imported Oil

Unit: quads, (1quads =1 quadrillion BTU, 1

BTU=1055J)

Opportunities for Recovery of Waste Heat in Transportation

Co

mb

us

tio

n

30% Engine

100

%

40% Exhaust

Gas

30%Coolant

5% Friction & Radiated

25Mobility &

Accessories

Gas

olin

e

Gas

olin

e

Co

mb

us

tio

n

30% Engine

100

%

40% Exhaust

Gas

30%Coolant

5% Friction & Radiated

25Mobility &

Accessories

Gas

olin

e

Gas

olin

e

Gas

olin

eG

asol

ine

Gas

olin

eG

asol

ine

Distribution of Fuel Energy in Passenger Vehicles


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

Synthesis &Processing

Evaluation

Computation(Modeling & Simulation)

Characterization

New Materials

Synthesis &Processing

Evaluation

Computation(Modeling & Simulation)

Characterization

New Materials

Materials Technology Flow for Solid State Waste Heat Energy Recovery

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.

Collaboration with Caterpillar

Potential Location for TE Generator


Caterpillar’s 550 HP Heavy Truck Equipped with TEG

TE Generator for Light Vehicles


TE Materials for Applications in Energy and Environment

Documents

Introduction to Thermoelectric Effects And Their Applications in Energy and Environment Shang-Fen Ren Department of Physics, Illinois State University