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Seebeck Coefficients for calculating Voltage

Submitted by Matt on Thu, 2006-04-13 20:05
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Hi, I was wondering if anyone can tell me what the seebeck coefficients are for the pelt pictured in the link below. Its material is Bi2Te3 and I would like to use the equation V=(Sa-Sb)(T2-T1) to calculate the output voltage.

www.frozencpu.com/exp-01.html

Thanks,
Matt

‹ Absolute TEP of Pt The Four Thermoelectric Effects ›

RE: Seebeck Coefficients for calculating Voltage

Submitted by zts-webmaster on Fri, 2006-04-14 01:18.

Matt,

Well, it would take a pretty good eye to figure it out just from a picture! But they give some specs too, so we can estimate it:

Imax = 24 Amps
Qmax = 226.1 Watts

Qmax is the point where exactly 1/2 of the peltier cooling is balanced by joule heating. So,

Qmax = 0.5 * Imax * (Sa-Sb) * T

Using T = 300 K I get
(Sa-Sb) = 0.0628 V/K

That should correspond to the total Seebeck of some number "N" of thermocoules in series, and is the same number that goes into the open-circuit voltage equation you give in your post

V=(Sa-Sb)(T2-T1)

As a sanity check, Bi2Te3 might have a Seebeck of 225 microV/K positive for the p-leg and negative for the n-leg or about 450 microvolts/K for a single couple. Dividing to get "N"

N = 0.0628 / 0.000450 = 139.6

So, there must be something like 140 thermocouples in series in that module. That's a reasonable number of thermocouples and might be good to +/- 10% or so.

Best of luck. I'm guessing you are doing a measurement, so tell us what you get!

- Cronin