Peltier Junctions for Rabbit cooling

[TMTex]

I've been thinking of using Peltier Junctions to cool rabbits ever since I read about giving frozen bottles to them during the heat.

At first, I thought of building a cooling wall area out of aluminum that was attached to the cooling side of the peltiers and using computer heat sinks with fans to draw the heat off of the hot side. It would take 2 or 3 peltiers to cool a rabbit sized wall.

paradox's idea of the coolers made me think again. I could put a single peltier in a cooler with a heat sink on the inside and a heatsink and fan on the outside. The cooler will make the whole thing much more efficient. Venting the heat would be no problem, since the hot side would be on the outside of the cooler.

An abbreviated background - I buy cabinet coolers for industrial electronics for the company I work for. Some of these are hardened air conditioners and some are peltier systems. The peltier systems use much less electricity and have no moving parts other than the cooling fans. They run on 12 or 24 Volts DC. They cost $1230.57 each plus whatever the power supply costs, plus labor to install. You or I can build them from scrap for less than $10.00 each.

So here I go.

I bought the peltiers from Hong Kong through ebay. There were various sellers involved and my average cost with shipping was just under $4.00 each.

The power supply will be solar eventually, but for now, I have a UPS (battery backup) that has bad batteries. I'll pull the regulator out of it and discard the inverter. I only need the 12V side.

I have some heat sinks from CPUs in old computers that people have discarded. I'll use a plain heat sink on the inside of the cooler and a 12 Volt fan powered one on the outside. They'll be held to the peltier with thermal epoxy that I bought from Newegg. The epoxy was $6.00 each and I figured 2 would more than complete the rabbitry needs. So about $1.00 each.

I'll need an insulating wall to mount the peltier to the cooler. I haven't come up with that yet, but I'll post plans and pics as the project progresses. Hopefully, it'll be in time to keep the bunnies cool before the 100 degree temps become typical.

 

[paradox]

Genius! Cant wait for pics and a report on how well it works! I feel a revamp coming on for our caves!

 

[Marinea]

TMTex, any chance of reposting...in English? I read and reread and can't make heads or tails out of what you said. I know it's me, not you.

Would you try a "Cooling Rabbits for Dummies" version please?

 

[Jack]

pictures man, or at least an explanation article that is written to the 6th grade level with lots of pointy arrows and pictures to show what's happening

 

[TMTex]

I'm sorry Marinea and Jack. Sometimes I just type like I talk. I think it'll become clearer when I post the pics and plans.

Essentially, there are ceramic electronic devices that are flat and square that you can use to heat or cool something in contact with it. They don't take much energy. One side will get hot and the other side will get cold when you apply power. Basically, the device pulls heat from one side and sends it to the other.

If you reverse the voltage, the hot and cold sides will switch. It can be used as a heater too.

There are several things to keep in mind when using them. The cold side can/will freeze and will drop below the dew point. This will cause water to condensate. You need something to drain the water on the inside of the cooler. I'd say just remove the built in drain plug.

The hot side will get hot enough to burn the device up. The heat sinks are the fins you see on radiators and such. Putting one on the cold side will spread the coolness around. The heat sink on the hot side will keep the device from burning up. It'll also pull heat away from the device, allowing more cooling to the inside. The fan makes it work better, but if push comes to shove, you can do it without a fan.

 

[paradox]

That is better TMTex. I got the gist of what you were saying because I speak a little techno geek, but I am far from fluent - LOL.

 

[AmysMacdog]

:lol: :lol: Oh good! I'm not the only one who didn't understand! That sounds interesting! Can't wait for pics.

 

[Secuono]

Yes, we are mainly visual people here! =D


Wait, how do heat sinks help cool a rabbitry? Did I miss something...? Making your own ac or??? :?: :?:
I get how they work on small scale/pcs.

 

[Jack]

I never said didn't know what they were, my understanding is that unless you are running a refrigerant (such as a liquid cooled core) their 'pulling' power is limited
ie. lots of heating/cooling pulled a little ways

You might use it to run chilled waterlines inside the cages, and or chilled water misters.

 

[paradox]

Tried to show this to my hubby and his eyes glazed over. he gets that way when I have put too many projects in his brain. LOL - we just started a fodder experiment so maybe I need to back off a bit.

 

[Marinea]

*waits patiently for pics and plans*

*decides not to even try to work it out til then so my head doesn't explode *

 

[TMTex]

I put the peltier together without the cold side heat sink and the wall that separates the hot and cold sides.

I think this will get the basic idea across. Total cost for this prototype is just under $9.00 so far. I doubt that I'll spend much more on it. I have the cold side heat sink and will find something to act as a wall between the hot and cold sides. The only expense left will be some silicone sealant.

---

Here are the components with a quarter to show size. I added an extra peltier device for the added cooling potential in case I need it. It doesn't add to the energy consumption unless I call for more cooling. The "cold" side of the peltiers have the part numbers stamped on them. If you wire it with the red to positive and black to negative, this side will cool and the other side will heat. If you reverse the wiring, the "cold" side will heat and the "hot" side will cool.

The temperature probe is in the top right of the pic, but is only a tool used for this demo.




This is a computer I'm building for a user that needs to use an older Operating System. This is likely the type that you'll find being discarded. The front of the computer is to the right and the top is on top. I have the side panel removed. The CPU Cooler is circled to show which component you need to borrow to make the cooler.




This is an old CPU Cooler that I'll use as a heat sink for this prototype. I cleaned it with alcohol and a paper towel. It's upside down in this pic.




This is the Thermal Epoxy. You use equal parts and mix it like regular epoxy. As you can see, a little dab will do you.



I've applied the epoxy to the hot side of the peltier on the right. The left one is still dry in this pic. It takes a very thin coat. Too much will degrade the thermal efficiency.




The "hot" sides of the peltiers are glued on to the heat sink.




Once glued, I put a couple of books on top to press the peltiers down onto the heat sink. Cure time is rumored to be 2 hours. (Yeah, try to find a decent set of instructions for this stuff. Good luck with that.)




To shorten the cure time of the epoxy, I could have applied heat with a heat gun. Being that the hot side of the peltiers will do the same thing, I just applied limited power to warm them up. This is the power supply and it shows 0.99 amps at 3.4 volts. This comes out to about 3.4 watts of power. The cure time was about 1 hour.




These thermometers show the room temperature and the hot side of the heat sink with the 3.4 watts applied. As you can see, there's a temperature differential of 34.4 degrees F.




After one hour of cure time, I turned power off, let the temperature stabilize and removed the weight. I hooked the fan up and turned power back on. Keeping the cool side above freezing, 27.7 watts were being used. The cold side of the peltier was 34.9 degrees F. The room temp was 75.2 and the peltier hot side was 101.4 degrees F with the fan running. The nominal power draw for the pair is 120 Watts and they can be overdriven to 180 watts. So I'm using about 23% of the nominal capacity and 15.4% of the full capacity for this test.

Once the cold side heat sink is installed, the cooled air will sink and hot air will rise to be cooled. The cooler should be mounted mid level to high on a side wall. A fan on the inside of the rabbit enclosure won't be needed.




Even though the shop is air conditioned, it didn't take long for condensation to build up on the peltiers. This condensation will be on the cold side heat sink when it's attached. That's why you need to have some way of draining the water.

 

[Demamma]

Thanks for the pictures. opcorn: I think I will need to reread it a few hundred times to understand. :-? So glad there are technical people who can do stuff like this. :-D I think I will go back to my cave and think about ice bottles. :wink:

 

[MamaSheepdog]

I think I will go back to my cave and think about ice bottles. :wink:

:rotfl:

But, but... Demamma...

... if you have a cave, why not just put the buns in there?

 

[Demamma]

Great idea MSD. I can have cave bunnies.

 

[Demamma]

Great idea MSD. I can have cave bunnies.

__________ Wed Jun 12, 2013 3:23 pm __________

 

[TMTex]

Hmm...I figured these would be a good DIY project. Once I get the pattern down and any bugs worked out, maybe I should help build these for folks. It didn't take me long to do the prototype.

Of course, my work and the cute bunnies take a lot of my time. Maybe some of us can get together and help those who don't want to tackle it by themselves. My only requirement would be that we don't charge for our time since this is for the public domain.

 

[MamaSheepdog]

Sorry for not mentioning earlier, Tex, but what an excellent tutorial!

:judges:

Great idea MSD. I can have cave bunnies.

Thank you. I have my moments.

But... too many generations of cave bunnies will likely cause them all to become blind albinos.

Perhaps not such a bad thing on freezer camp day because...

wait for it...

They'll never see it coming!!! :mrgreen:

(I slay myself. Just sayin'.)

 

[grumpy]

:x :x :x :x :x :x :x

You're far beyond my expertise my friend!!

:lol: I thought I was doin' good with the water cooler. :lol:

It sounds very intriguing. But how will it be applicable?
How 'large' will the unit/units be?

Keep us posted on your progress...you may be developing
a completely new type of cooling for rabbitry's on a large scale.

grumpy.

 

[MamaSheepdog]

My only requirement would be that we don't charge for our time since this is for the public domain.

What a generous offer!

But, as they say, time is money. I see no reason why you shouldn't make a bit of profit for your work.

Long live the free market! :hobbyhors