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Re: Peltier element in space ?



MERRETT, David wrote (in part):

>As bob suggests, If you already intend on using sun light as the power
>source, solar cells are much more efficient.
>(Although Possibly an advantage of peltier is their reliability? - I dont
>know).
>  
>
Not based on my experience!  I have a small peltier based refrigerator 
in my office (holds about a 12 pack of soda).  The pelteir is in the 
lid.  I started out with 2 of them, but only used one.  After not all 
that many months, the lid I was using had failed so I switched to the 
other lid.  After a while the second one had failed as well.  I bought a 
replacement peltier, and installed it.  It's failing now as well.  Each 
one has lasted about a year.
The way these are built is an array 40mm square with dozens of peltier 
junctions between 2 plates (each junction looks like a small chip 
capacitor).  When the unit was new it would draw about 5 amps from an 
Astron 12V power supply.  As more and more of the individual junctions 
fail, the current draw is dropping.  It's now down to about 3 amps and 
about the best the refrigerator ever does is temperature down to about 
41 degrees F (it used to be able to frost up).
Based on my experience, I would not want to use a peltier on a satellite 
(a little hard to fix)

 
73
-------------------------------------
Jim Walls - K6CCC
k6ccc@amsat.org
Ofc:  626-302-8515
http://home.earthlink.net/~k6ccc
AMSAT Member 32537 - WSWSS Member 395


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