2. Introduction
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”.
3. Seebeck Effect
• Thermoelectric power generation is based on a
phenomenon called “Seebeck effect” discovered by
Thomas Seebeck in 1821.
• When a temperature difference is established
between the hot and cold junctions of two
dissimilar materials (metals or semiconductors) a
voltage is generated, i.e., Seebeck voltage.
4. Q(h)= high temperature
heat transfer
T(h)=high temperature
Q(l)=low temperature heat
transfer
T(l)=low temperature
W(e)= output energy
W(e)=Q(h)-Q(l)
5. Specification
•Sizes of conventional
thermoelectric devices vary
from 3 mm2 by 4 mm thick to
75 mm2 by 5 mm thick.
•50 mm in length.
•Height of modules vary from
1mm to 5mm.
•Modules contain 3 to 127
thermocouples.
•There are multistage
thermoelectric modules of
height 20 mm.
• Below is a 3 stage module.
•
Schematic diagram showing components and
arrangement of a typical single-stage
thermoelectric power generator.
6. Performance of Thermoelectric Power
Generator
Performance of thermoelectric materials
can be expressed as:
• Z= a^(2)/kr
where,
Z is thermoelectric material
figure-of-merit
a is Seebeck coefficient
k is the total thermal
conductivity
R is the electric resistivity
• ZT = a T / kR
where,
T=T(h)+T(l)/2
• Carnot efficiency
n = 1- T(l)/T(h)
7. Conversion efficiency as
a function of temperature
and module material
figure-of-merit.
With the increase in the
value of T(h) conversion
efficiency increases.
But with the increase in
the value of Z has an
opposite effect on the
conversion efficiency.
8. Materials Used
• Ceramic plates usually made from alumina.
• Semiconductor thermoelements usually SiGe.
• The hot and cold plates are usually connected
using highly conductive material like copper.
• Foe Power Generators these are further
categorized as :
Conventional and Novel
9. Conventional Material
• Alloys based on Bismuth (Bi) in combinations
with Antimony (An), Tellurium (Te) or
Selenium (Se) are referred to as low
temperature materials and can be used at
temperatures up to around 450K.
• The intermediate temperature range - up to
around 850K is the regime of materials based
on alloys of Lead (Pb)
10. • Thermoelements employed at the highest
temperatures are fabricated from SiGe alloys
and operate up to 1300K.
• Although these materials provide a limited
efficiency.
• These are a cornerstone in practical and
commercial application.
11. New or Novel Materials
• Promising candidate to fill the temperature
range in the ZT spectrum between those
based on Bi2Te3 and PbTe is the
semiconductor compound ß-Zn4Sb3.
• Possesses an exceptionally low thermal
conductivity and exhibits a maximum ZT of 1.3
at a temperature of 670K.
12. • Apart from this a thin thermo electric
generator film made from semiconductors are
also synthesized.
• Their primary focus is not only on figure of
merit (Z) but to improve thermal contact.
13. Stirling Engine
•A Stirling engine is a heat
engine operating by cyclic
compression and
expansion of air or other
gas, the working fluid, at
different temperature
levels such that there is a
net conversion
of heat energy to
mechanical work.
•Noted for its high
efficiency compared to
steam engines.
14. Automotive thermoelectric generator
• An automotive thermoelectric
generator (ATEG) is a device that
converts waste heat in an internal combustion
engine (IC) into electricity.
• The thermoelectric materials are made up of
p-type and n-type semiconductors, while the
heat exchangers are metal plates with
high thermal conductivity.
16. Industrial Waste Heat Applications
• Most of the recent research activities on applications
of thermoelectric power generation have been
directed towards utilisation of industrial waste heat.
• This can revolutionize the energy crisis as well as the
environmental effects.
17. Photograph of a
thermoelectric power
generator produced
power for cathode
protection of the well
and gas line, which
used the temperature
difference between
hot and cold legs of
glycol natural gas
dehydrator cycle.
