[Noisebridge-discuss] N00b question - changing power supply voltage

Sean Cusack sean.p.cusack at gmail.com
Tue Jul 6 16:35:52 UTC 2010


Oh yes...I know they are terrible at efficiency...but they are also the only
thing that I know of that can get you to sub-ambient temperatures without
using a (comparatively) giant refrigeration system.

I'm planning on using these to cool a few pieces of lab equipment.
Typically, to get to sub ambient conditions, you have to use ice/water (gets
you to 0C), or dry ice/acetone (gets you to -78C), or full on Liquid N2
which gets you too cold for most practical applications. It would be
*awesome* to hit like -20 or -10 or even 5C repeatedly and controllably for
a million and one different chemical reactions.

There is equipment that allows you to do this now, but pretty much its a
standalone refrigeration system that pumps cooled silicon based oil through
your reaction mixture. It takes up a ton of room on my bench, and since
those refrigerators are on the order of $7k a pop, its tough to convince my
boss to allow me to buy more than about 2 of them. In other words, longer
hours for Sean in the lab = teh sux.

So, I'm trying to use these doodads as a way to run a bunch of reactions at
a controllably cold temperature. I agree there's problems, but given the
application, it may just work!

Sean

On Tue, Jul 6, 2010 at 8:44 AM, Jonathan Foote <jtfoote at ieee.org> wrote:

> On Tue, Jul 6, 2010 at 4:17 AM, Corey McGuire <coreyfro at coreyfro.com>
> wrote:
>
> > Messy, messy stuff.  TEJ's are not efficient.  This is fine by
> themselves.  When you stage them, their inefficiencies > become readily
> apparent as they begin to compound.
> >
> > May I ask what you intend to do with them?
>
> Yeah, also curious. Corey is absolutely right: TEJs have terrible
> Carnot efficiency --  way less than 10%. This means to move (not
> remove) 5 watts of heat you have to put in 50+ watts of power, which
> turns into heat you ALSO need to remove.
>
> So they are only useful in a few applications where the small temp
> difference over a tiny scale is worth the waste. If they really were
> the magic refrigerators people think they are, they would be in every
> PC and laptop. And note that if you are trying to keep things cool,
> there may be far better solutions.
>
> "In this house we obey the laws of thermodynamics!"
>
> -J
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