
Peltier Application Note – Thermoelectric Cooling [pdf] - dragontamer
https://www.cui.com/catalog/resource/peltier-app-note.pdf
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dragontamer
I was nerdsniped by a coworker, who was talking about personal projects. She
was working on an wine-rack / cabinet that held a specific temperature. Key to
the design is a Peltier module to pump the temperature to the ideal for wine
storage.

CUI's application note on Peltier modules was very well written and a joy to
read. I've barely touched on the physics of this subject, but it was so
clearly written that I was able to understand the overall design process to
use this kind of device.

Overall, Peltier modules are far less efficient than classic "compressor"
refrigeration units. But Peltier modules are far smaller and far simpler to
operate: just apply voltage, and away you go. As such, Peltier modules are the
ideal easy-to-use tool for hobbyists, even if its not quite as efficient as
what the professional HVAC people use.

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mdorazio
Just to build on your comment so other hobbyists don't get the wrong idea,
Peltier modules are _significantly_ less efficient than compressor-based
coolers. To the tune of 30% or more efficiency drop depending on ambient
conditions and your heatsink setup. It's also important to note that the
overall setup for a Peltier system ends up being a lot bulkier than most
people expect when they start. You need a really beefy hot side radiator and
fan to get any significant cooling potential out of the system - think large
CPU heatsink + fan size and you're close. If it's humid you'll also have to
deal with condensation on the cold side so you don't accidentally get water
dripping on your electronics.

~~~
mgamache
I agree. Peltier fits a narrow niche. If you want a small temperature drop and
can dissipate the heat on the hot side and are okay with the inefficiency it's
for you. I tried to create a Peltier cooling system for a wearable device. It
was a miserable failure. WIthout a way to dissipate the heat (your CPU
heatsink + fan comment) it resulted in a net heat gain.

~~~
std_throwawayay
Forgetting about the enormous heat sink is a typical rookie mistake. Those
things produce lots of heat when you try to cool something. They are much
better suited for heating something to a specific temperature than cooling.

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charliemil4
Would an aerogel-like material suffice as an 'enormous heat sink'? Has anyone
tried this?

Edit: would a metal aerogel not count? (Definitely not maker ready though, I
assume)

[http://www.aerogel.org/?p=932](http://www.aerogel.org/?p=932)

~~~
velosol
A metal aerogel would have very high surface area (much like adsorption
humidity control crystals) but that's not really helpful when you then need to
move the fluid touching all that surface area in order to remove the heat.

Typically the fluid will be air which sucks at moving heat (hence why aerogels
are great insulators as they hold a lot of air).

I'm not positive but I suspect that an aerogel in a higher specific heat fluid
wouldn't do any better as the flow volume through the aerogel would be quite
low bounded by the volume of the aerogel.

If you want to cool the hotside of a TEC you need to push a lot of watts per
unit area. The best things for that are high specific heat fluids which are
often used in compressor systems and then they're termed refrigerants so
you're back to traditional air conditioning. The other option is very cold
fluids (liquid nitrogen) but at that point you may be better off bringing the
LN2 into more direct contact with whatever you're trying to cool.

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Liveanimalcams
I've been working on solar powered Peltier AC for my home. This past summer it
was able to keep my living room (250sqft) at a comfortable 72F - 75F even when
the outside temp was over 95F. It is crazy power hungry, using 12v 5A, but
with solar its fine. The hard part as people have said is the heat dissipation
and dealing with high ambient temperatures.

My newest design incorporates a few new upgrades. 1) geothermal cooling to
dissipate the heat. As the ground temperature stays consistent at ~65F.
Allowing me to not worry about the ambient temperature anymore 2) I moved to a
24V 6amp peltier which has a larger delta from the hot to cold side. 3) I now
use a 24v ~7.6amp solar panel to power it. 4) I added a 15 Amp high-power
motor driver so I can switch between producing cold and hot air. So now it
will be viable in all weather conditions.

A core idea is to keep costs cheap which is why I have not added a battery to
the mix. Although it would be nice as some nights are quite hot. I got the 24v
panel used at $50 and the peltiers are super cheap (3 for ~15). The motor-
controller/h-bridge was ~$40, but I didn't want to cheap out on that though
and start a fire.

Its quiet unless I turn the fans up and doesn't cost anything to run after
initial setup costs, due to the solar. My future plans for making it even
better are to use multi-stage peltiers and try to leverage the hot side to
produce more power. Also to add raspberry pi so I can control it remotely.

~~~
skyde
How do you use geothermal? Do you have a diagram or picture of your setup? I
would love to build something like this

~~~
Liveanimalcams
I use geothermal as a way to absorb/dissipate the heat. I got the idea from
here: [https://forums.overclockers.com.au/threads/concrete-slab-
wat...](https://forums.overclockers.com.au/threads/concrete-slab-water-cooler-
loop-hooked-up.800958/) Instead though I dug a trench outside that was 4ft
deep 20ft long and then buried some pex pipe. As the water flows into the
aluminum block attached to the peltier it absorbs the heat and then as it
enters the ground it dissipates so when it comes out of the ground of its back
at 55F. The water is moved with a 12v pump. The longer the run the better as
the ground is not efficient in energy transfer. If its to short it wont cool
down all the way.

I thought of trying to use copper pipe with round engine heat sinks attached
to it, to increase the energy transfer rate. However it didn't seem like the
copper would last long before potentially reacting with the ground.

Simple diagram: [https://www.ernstheating.com/wp-
content/uploads/2018/01/Erns...](https://www.ernstheating.com/wp-
content/uploads/2018/01/Ernst-geothermal-heating-768x768.jpg)

~~~
skyde
Thanks a lot. I agree copper will probably not last long but maybe some HDPE
flexible pipe would work.

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layoric
Peltiers are a fascinating piece of tech, I remembering hacking together a
cooling system for a high school project (20 years ago now..) to show people
and have had a fascination ever since. Problem is they just aren't that useful
due to their large inefficiencies. Situations where power consumption, heat
removal and humidity aren't a problem are pretty rare at any scale. Saying
that, if a situation where heat removal is straight forward due to other
factors, space is abundant with solar generation (that's not needed/can't be
used for anything else) and humidity is benefit, peltiers size and simplicity
can be leveraged nicely.

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bacon_waffle
Free product idea: Here in NZ, and I suspect other places with lower quality
housing, lots of people use electric resistance heaters, and also have
problems with damp air and/or dehumidifiers.

How about a solid state dehumidifier+heater using peltlier elements?

A dehumidifier is basically an air/air heat pump, with the cold side optimised
for water condensation without freezing, and one issue with them is the noise
from the compressor...

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r3drock
A neat application with peltiers for CPU cooling:
[https://www.youtube.com/watch?v=GZ3SwM2-rD4](https://www.youtube.com/watch?v=GZ3SwM2-rD4)

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stcredzero
Tech Ingredients: DIY Peltier fridge

[https://www.youtube.com/watch?v=YWUhwmmZa7A](https://www.youtube.com/watch?v=YWUhwmmZa7A)

