# The Peltier Effect by MJJKZn

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```									   The Peltier Effect
Jacob McKenzie, Ty Nowotny, Colin Neunuebel
SRJC Engr45 - Fall 2005
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
existed within the bar.
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
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.
What is a Peltier Cooler?

Thermoelectric heat pumps that will produce a
temperature gradient that is proportional to an applied
current.
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.
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
other and deliver it to where
they meet.
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.
Our Peltier:
Change in Temperature @ 12v
Temperature and Temperature Difference
as a Function of Time
160.00

140.00

120.00
Temperature (¡F)

100.00
Hot Side
80.00
Cold Side
60.00
Temp
Difference
40.00

20.00

0.00
0       200      400       600   800
Time (s)
our peltier:
Temperature Gradient as a Function of Voltage
Carnot Efficiency
70.00

60.00
Nc @ 12v:
50.00                                                                        =1-Tc/Th
Voltage vs
=1-283.6/342.3
Temperature, ¡C

Temp Diff
40.00
Cold vs V    =17.1%
30.00                                                           Hot vs V

20.00

10.00

0.00
0.00      2.00   4.00     6.00       8.00   10.00   12.00
Voltage, V
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
Generator (RTG)
Pros and Cons

Pros

Solid state (no moving parts)

No maintenance

Cons

Large electrical power requirements

Inefficient compared to phase change cooling
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

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