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1. The Peltier Effect
Jacob McKenzie, Ty Nowotny, Colin Neunuebel
SRJC Engr45 - Fall 2005

2. History of the Seebeck effect
Discovered by Thomas Johann Seebeck
in 1821.
He accidentally found that a voltage
existed between two ends of a metal
bar when a temperature gradient
existed within the bar.

3. The Seebeck Effect
A temperature difference causes diffusion of
electrons from the hot side to the cold side of a
conductor.
The motion of electrons creates an electrical
current.
The voltage is proportional to the temperature
difference as governed by:
V=α(Th-Tc)
where α is the Seebeck coefficient of the couple

4. History of Peltier devices
The Peltier effect is named after Jean Charles Peltier (1785-
1845) who first observed it in 1834.
The Peltier effect had no practical use for over 100 years until
dissimilar metal devices were replaced with semiconductor
Peltiers which could produce much larger thermal gradients.

5. What is a Peltier Cooler?
Thermoelectric heat pumps that will produce a
temperature gradient that is proportional to an applied
current.

6. Peltier Effect With Dissimilar
Metals
At the junction of two dissimilar metals the energy level of
conducting electrons is forced to increase or decrease.
A decrease in the energy level emits thermal energy, while an
increase will absorb thermal energy from its surroundings.
The temperature gradient for dissimilar metals is very small.
The figure of merit is a measure of
thermoelectric efficiency.

7. Semiconductor Peltier
Bismuth-Telluride n and p
blocks
An electric current forces
electrons in n type and holes in
p type away from each other on
the cold side and towards each
other on the hot side.
The holes and electrons pull
thermal energy from where
they are heading away from
each other and deliver it to
where they meet.

8. Device Construction
Individual couples are
connected in series
electrically and in parallel
thermally.
Couples are thermally
connected by a ceramic that
has high electrical resistivity
and high thermal
conductivity.

9. Our Peltier:
Change in Temperature @ 12v
Temperature and Temperature Difference
as a Function of Time
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
0 200 400 600 800
Time (s)
Temperature (°F)
Hot Side
Cold Side
Temp
Difference

10. our peltier:
Temperature Gradient
Temperature Gradient as a Function of Voltage
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Voltage, V
Temperature, °C
Voltage vs
Temp Diff
Cold vs V
Hot vs V
Carnot Efficiency
Nc @ 12v:
=1-Tc/Th
=1-283.6/342.3
=17.1%

11. Applications
Deep space probes
Microprocessor cooling
Laser diode temperature stabilization
Temperature regulated flight suits
Air conditioning in submarines
Portable DC refrigerators
Automotive seat cooling/heating
Radioisotopic Thermoelectric
Generator (RTG)

12. Pros and Cons
Pros
Solid state (no moving parts)
No maintenance
Long service lifetime
Cons
Large electrical power requirements
Inefficient compared to phase change cooling

13. References
http://www.its.caltech.edu/~jsnyder/thermoelectrics/history_page.htm
http://www.tellurex.com/12most.html
http://www.thermoelectrics.com/introduction.htm, Thermoelectric Materials
http://www.digit-life.com/articles/peltiercoolers/
http://www.heatsink-guide.com/content.php?content=peltierinfo.shtml, THE
HEATSINK GUIDE: Peltier Guide, Part 1
http://saturn.jpl.nasa.gov/index.cfm