A material that can be used to convert thermal energy into electric energy or provide refrigeration directly from electric energy

1. Thermoelectric Materials
&
Applications
1
E.A.N.S.Edirisingha

2. Content
 Thermoelectric Materials
 History of Thermoelectric effect
 Seebeck Effect & Peltier Effect
 Materials selection criteria
 Thermoelectric power generation
 Thermoelectric (TE) Cooling
 Advantages & Disadvantages
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3. 3
Waste Heat to Electricity
Thermoelectric

4. Thermoelectric Materials
A material that can be used to convert
thermal energy into electric energy or provide
refrigeration directly from electric energy.
Eg :
Bismuth chalcogenides (Bi2Te3 & Bi2Se3 )
Lead telluride (PbTe)
4http://www.sigmaaldrich.com/materials-science/metal-and-ceramic-science/thermoelectrics.html
Access on 26.07.2014

5. History Of Thermoelectric effect
• Seebeck found that a circuit made from two
dissimilar metals, with junctions at different
temperatures would deflect a compass
magnet
• Peltier found that an electrical current would
produce heating or cooling at the junction of
two dissimilar metals.
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6. Seebeck Effect
An electric current would flow continuously in a
closed circuit made up of two dissimilar metals, if
the junctions of the metals were maintained at
two different temperatures.
𝐒 =
∆𝑽
∆𝑻
Where;
𝐒 – Seebeck Coefficient
∆𝑽 – Voltage Difference
∆𝑻 – Temperature Gradient
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7. Peltier Effect
An electrical current would produce a
temperature gradient at the junction of two
dissimilar metals.
7http://www.thermoelectrics.caltech.edu/thermoelectrics/history.html
Access on 26.7.2014

8. Materials selection criteria
1.Figure Of Merit
The potential of a material for thermoelectric
applications is determined in large part to a
measure of the material’s dimensionless figure of
merit,
ZT =
S 𝟐
𝝈𝑻
𝒌
ZT =
S 𝟐
𝑻
𝝆𝒌
𝒌 = 𝒌e + 𝒌g
8

9. where,
S - Seebeck Coefficient
ρ - Electrical Resistivity
k - Thermal Conductivity
ke - Electronic Conductivity
kg - Lattice Conductivity
Note:
 Low electrical resistivity and thermal conductivity
are required for high figure of merit.
 These values are temperature dependent
therefore, the figure of merit is temperature
dependent.
 p and n type material have different figures of merit
and are averaged to determine a materials overall
quality.
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10. 2. Power Factor
Under a given temperature difference, the ability of
a material to produce useful electrical power is
quantified by its power factor,
Power Factor = σS2
3. Device efficiency
The efficiency of a thermoelectric device for
electricity generation is given by ɳ.
ɳ =
𝑬𝒏𝒆𝒓𝒈𝒚 𝒑𝒓𝒐𝒗𝒊𝒅𝒆𝒅 𝒕𝒐 𝒕𝒉𝒆 𝒍𝒐𝒂𝒅
𝑯𝒆𝒂𝒕 𝒆𝒏𝒆𝒓𝒈𝒚 𝒂𝒃𝒔𝒐𝒓𝒃𝒆𝒅 𝒂𝒕 𝒉𝒐𝒕 𝒋𝒖𝒏𝒄𝒕𝒊𝒐𝒏
10http://www .sigmaaldrich.com/materials-science/metal-and-ceramic-science/thermoelectrics.html
Access on 26.07.2014

11. Thermoelectric power generation
 A thermoelectric power generator is a solid state
device that provides direct energy conversion from
thermal energy into electrical energy.
 Principle of operation is “Seebeck Effect”.
 Thermoelectric generators contain no moving
parts and completely silent.
 Thermoelectric generators have been used
reliably for over 30 years of maintenance-free
operation
11http://www.electrochem.org/dl/interface/fal/fal08/fal08_p54-56.pdf
Access on 26.7.2014

12. 12http://isen.northwestern.edu/news_media/articles/2014/04/21april2014_waste_heat_material.html
Access on 4.8.2014
Thermoelectric Module
Electric Insulators

13. Uses Of Thermoelectric Generators
1. Harvesting automobiles produce waste heat
energy
2. Industrial processes waste heat reused to
generate electricity
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14. 3. Used as power sources in satellites, space probes
(Radioisotope thermoelectric generator)
3. For small portable applications,
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15. Thermoelectric (TE) Cooling
 Thermoelectric cooling uses the “Peltier effect” to
create a heat flux between the junction of two
different types of materials.
 The amount of heat that can be absorbed is
proportional to the current and time.
15
W = PIt
http://www.tec-microsystems.com/EN/Intro_Thermoelectric_Coolers.htm
Access on 26.7.2014

16. Basic Principles
 For n type TE materials
 For p type TE materials
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17. 17
 The most efficient
configuration of producing
TEC
 One side is attached to a
heat source and the other a
heat sink that remove the
heat away.
 The electrical insulator must
have a high thermal
conductivity
 Ceramics like alumina are
generally used as a insulator

18. Which Industries Use TE Cooling?
1. Electronic
2. Medical
3. Aerospace
4. Telecommunications
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19. Uses Of Thermoelectric Cooling
1. Laser diodes Cooling
2. Laboratory sample cooling
19
TE
Si bench

20. 3. Medical Sample cooling
4. Portable beverage coolers
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21. 5. Climate-controlled jackets
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22. Advantages of TE
 Environmentally friendly
 No moving parts so maintenance is required less
frequently
 No chlorofluorocarbons
 Reliable source of energy
 Recycles wasted heat energy
 Has a long life, with mean time between failures
(MTBF) exceeding 100,000 hours
 Scalability, meaning that the device can be applied
to any size heat source from a water heater to a
manufacturers equipment
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23. Disadvantages Of TE
 Slow technology Progression
 Requires relatively constant heat source
 Low energy conversion efficiency rate
 Lack of customer/ industry education about
thermoelectric generators
 Able to dissipate limited amount of heat flux.
 Lower coefficient of performance than vapor-
compression systems.
 Relegated to low heat flux applications.
23http://thermoelectricgeneratorgeneration.blogspot.com/2010/06/thermoelectric-generators-advantages.html
Access on 26.7.2014

24. References
 http://isen.northwestern.edu/news_media/articles/2
014/04/21april2014_waste_heat_material.html
 http://www.electrochem.org/dl/interface/fal/fal08/fal0
8_p54-56.pdf
 http://www.rsc.org/education/eic/issues/2012March/
thermoelectric-materials-nanoparticles.asp
 http://www.tec-microsystems.com/
EN/Intro_Thermoelectric_Coolers.htm
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