DIY Thermoelectric Temperature Control

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Dude and I have been talking about this for a while. I finally got around to giving it a try. Part of this was sparked by some of Dude's suggestions, and part of it was from a brainstorm I had when I caught a glance inside one of those travel coolers that runs on car cigarette lighter power. It turns out that they're nothing more than Peltier coolers, and they contain many of the parts required to adapt the same principle to a fermenter. Here are some pictures and further explanation:

Here you can see some of the inner workings. I sandwiched a second 40mm/113W Peltier device (eBay) between a 1/2" aluminum plate and the guts of the travel cooler. The devices work as heat pumps if you stack them on top of each other (with sufficient power and heat sink capability). The threaded aluminum bar is intended to extend inside the keg (like an aquarium cooler) and seals with an o-ring.
4688-peltierpieces.JPG


Here's another view with the threaded piece attached. You can see how one of the Peltier devices is sandwiched between the aluminum pieces. The other one is insulated with a foam square from the travel cooler.
4688-peltieroutsidekeg.JPG


Here's what it looks like inside the keg:
4688-peltierinsidekeg.JPG


Here's a picture of my first test run. It's plugged into a 12VDC/6A power supply. The keg is a 7 gallon corny I welded up today. I'm monitoring the temperature with the digital thermometer on top. It'll probably be a few hours before I notice any temperature changes.
4688-peltiertest.JPG
 
Yuri looks great, do you have any pictures of the components?

Also do you have any results yet?

I think I remember that if you reverse the current these will heat right? so can this be setup to heat and cool?
 
I'll take some more pictures the next time I dismantle the system.

Results so far are rather inconclusive. I think I need to insulate the keg - it only maintains a degree or two below room temperature. I'll get it sorted out and post more when I have the info.

You're correct, Todd - if you reverse the polarity, the unit will begin heating. My wiring is very simple so far, but I could include a polarity switching circuit if that becomes desirable.

I should take a picture of the power supply also - it's DIY as well (and somewhat laughable the way it looks at the moment). Just a 120V/12V@6A transformer, a big bridge rectifier, and a smoothing capacitor.
 
Yuri_Rage said:
I'll take some more pictures the next time I dismantle the system.

Results so far are rather inconclusive. I think I need to insulate the keg - it only maintains a degree or two below room temperature. I'll get it sorted out and post more when I have the info.

You're correct, Todd - if you reverse the polarity, the unit will begin heating. My wiring is very simple so far, but I could include a polarity switching circuit if that becomes desirable.

I should take a picture of the power supply also - it's DIY as well (and somewhat laughable the way it looks at the moment). Just a 120V/12V@6A transformer, a big bridge rectifier, and a smoothing capacitor.


I'd like more details as you go. I've looked at this some but not sure I really follow it that well.
 
Man... I can see some killer applications here. If insulated I wonder what the temperature change range would be. In a 100 degree garage could it keep a well insulated keg, or conical fermenter, at 65 degrees? or the flipside... reverse the polarity and keep it at 65 degrees when it's 35 degrees in the garage? If insulated properly you wouldn't have to rip apart a clunky BIG chest freezer to lager. You could do it on a shelf in the garage!!! Maybe use 2 of these units at the same time? Man, my beer closet only holds 4 carboys empty and 2 carboys now with 6 cases of beer... If I could ferment in the garage I could use that closet for a storage closet instead of an everything closet. It would DOUBLE my beer bottle/keg conditioning room!!!
 
So far the results are less than optimal - I don't think my heat sink is big enough to handle the power from the beefed up Peltier device(s). I've got a few BIG heat sinks in the mail that I think will make all the difference. More to come as I tweak this project.
 
I used to use Pelts to cool my CPU chips when I was way into computer tweaking. You need a very large heat sink, and a big fan in order to disipate the heat effectively. Using a copper heat sink and water cooling I was able to keep my CPU around freezing by using one, and a CPU puts out a tremendous amount of heat. Should not be all that hard when your only dealing with room temps, and cooling.
 
Meyer817 said:
Using a copper heat sink and water cooling I was able to keep my CPU around freezing by using one, and a CPU puts out a tremendous amount of heat.
If I were to use water cooling, I'd avoid the Peltier device completely and invest in some recirculating pumps and a refrigerator. The point is less moving parts with effective temperature control.

Meyer817 said:
Should not be all that hard when your only dealing with room temps, and cooling.
Except instead of dealing with large temperature changes, I'm dealing with large volumes - which wind up being somewhat equivalent in terms of energy transfer.

My existing heat sink gets VERY hot, and that heat winds up finding its way back to the cold side of the Peltier. That's why I'm getting larger heat sinks.
 
With a large heatsink and a large fan I think the project will work fine. Too many homebrews are affecting my ability to communicate. I was just relaying my positive experience using Peltiers.
 
Meyer817 said:
With a large heatsink and a large fan I think the project will work fine. Too many homebrews are affecting my ability to communicate. I was just relaying my positive experience using Peltiers.
Cool. I was being a little abrasive. It's all good.
 
I have thought about making my own cooled fermentor for years, and yours is what I initially started thinking about Yuri. Now I have moved up to 16 gallon batches and can't afford one of the big conicals with cooling I am really starting to look for ways to not have to build a cooler room for two or three bathes of lager fermenting around the same time (future thinking, I just brew ales right now in a basement). I am interested in hearing how the peltier's work when you get insulated or larger heatsinks. I plan on running everything through the lid down into the fermentor so I would make an extra long cold probe for the conical hopper I have now so it wouldn't collect yeast. I don't want any extra holes or welds on my coni exept the opening at the bottom. Can't wait to hear more Yuri, you have really given me lots of extra thinking about a lot of ideas I have had in the past but never had the "balls"/cash to go for. I finally have access to a machine shop again so hopefully the combination of your projects and my ideas for my setup will finally start coming together for me. You guys are all so great and I am loving the fact that there are so many adventurers into beer gadgetry on here. I usually get asked why I don't do something the old way when I go to other sites and ask questions about potentially cool ideas I have. They push me down and reading you guys stuff brings me back up, so I thank you. :mug:
 
Alright, commence round two of testing the thermoelectric chiller. The UPS guy just dropped off my eBay find - five relatively giant aluminum heat sinks. I swapped the old one (shown on the left) for a new one, and I have the chiller powered up again. The water is at 70 degrees F, and the cold side of the chiller is at 52. Hopefully I'll see a temperature change this time. I still don't have the fermenter insulated, but that'll be next.

4688-heatsinkdifference.JPG
 
It's working! The ambient temperature in my house is 72 degrees F. The water started at 70. It's down to 68 after 4 hours. That may not seem like much, but the fermenter isn't insulated, and there is a lot of metal surface area working against me at the moment. Also, this is a pretty low energy system. It should probably take overnight to stabilize at its lowest temperature even when it's insulated. You may not be encouraged by my results at this point, but I sure am! I think this thing is going to work!
 
If you have time could you take temperature readings at the connection to the keg, junction between peltier modules, and heat sink. Now the big question how many modules would it take for a 10 gallon batch in a conical fermentor with your system.
 
Yuri_Rage said:
It's working! The ambient temperature in my house is 72 degrees F. The water started at 70. It's down to 68 after 4 hours. That may not seem like much, but the fermenter isn't insulated, and there is a lot of metal surface area working against me at the moment. Also, this is a pretty low energy system. It should probably take overnight to stabilize at its lowest temperature even when it's insulated. You may not be encouraged by my results at this point, but I sure am! I think this thing is going to work!


Great job. I was wondering would you see better results if you made your cooling rod look more like these heat sinks? Perhaps you could cut grooves in it or somethign to increase the surface area?
 
Todd said:
Great job. I was wondering would you see better results if you made your cooling rod look more like these heat sinks? Perhaps you could cut grooves in it or somethign to increase the surface area?
Funny, I was considering that as well! I may have to try it now.
 
Yuri_Rage said:
Funny, I was considering that as well! I may have to try it now.

This all sounds random, I'm just throwing ideas out.

yeah it was just a thought. I suppose the question to ask first is how efficient is the cold transfer into the rod vs into the beer?

I think what I mean is, how cold is the plate vs the end of the rod? You could probably test it in the open air to see how long it takes for the two to equalize. Perhaps more contact area between the two would help.

How hard would it be to use some of that 1/2" plate you have and weld it to the rod end. Then have that sit against the petier device. This would give you a much larger area for heat transfer.

While we are talking about this can you show details of how it all connects to the keg? is the threaded rod the only part transfering heat?
 
I've gone to a single Peltier device. Running two of them in parallel was too big a current draw on my power supply, and running them in series is less efficient than just running one. I used the aftermarket one, which is a little more powerful than the one I scavenged from the travel cooler (the aftermarket one is advertised at 113W).

The threaded end of the "cooling rod" is 1/2" in diameter. I racked my brain as to how to make the contact area between the chiller plate and rod larger, but my lathe sucks at threading operations (it's a great hobby-style lathe, but it has its limitations), I don't have the lathe tooling to thread a bore, and the biggest tap/die set I have is 1/2". So, this is the design I settled on for now.

Below you can see how the device is situated against the outside of the keg. The fan is mounted somewhat temporarily, but it works just fine. I have two options for improving this portion. The more difficult option is to contour the chiller plate to the outside of the keg. I'll explain the other option later, since it ties into some other improvements I may make.

4688-chilleroutsidekeg.JPG


Here, you can see how the entire assembly goes together:

4688-chillerassembly.JPG


And here is a disassembled view. From left to right:
Fan (detached and almost out of view)
Heat sink
Peltier device and foam insulation (still stuck to the heat sink)
Chiller plate (screws into the heat sink to sandwich the Peltier - the screws are insulated with some plastic washers so that they don't transfer heat to the chiller plate)
Threaded rod (seals from the inside of the keg with an o-ring)

4688-chillerexploded.JPG


Here's how I'm thinking of improving this thing:
Cut a flat piece of stainless sheet the size of the chiller plate and weld a couple of threaded studs to it.
Cut a rectangular hole in the side of the keg and weld the flat piece to it.
Cut a hole in the now flat keg side to allow the rod to pass through it.
Weld the rod to the chiller plate.
Attach the chiller assembly to the side of the keg using the threaded studs.

I'm sure that's a little tough to imagine, but I'll post pictures if/when I decide to make the modifications.
 
Thanks yuri your photos help my thought process a lot.

Your idea with the flat plate is actually something I was thinking as well.

What I was thinking is.

Make the flat spot on the keg side and on the outside things would look the same (setup wise) as now.

On the inside make another aluminum plate with a 1/2" hole, sandwich this between the keg inside and the rod.

This would allow the plate on the outside to cool a larger area on the keg and hopefully transfer more of that into the inside because of the aluminum block in the keg. What I'm not sure about is how to seal everything without losing the metal to metal contact. is there a seal that will transfer heat? Could something like aluminum foil work as a gasket?



Yuri_Rage said:
I've gone to a single Peltier device. Running two of them in parallel was too big a current draw on my power supply, and running them in series is less efficient than just running one. I used the aftermarket one, which is a little more powerful than the one I scavenged from the travel cooler (the aftermarket one is advertised at 113W).

The threaded end of the "cooling rod" is 1/2" in diameter. I racked my brain as to how to make the contact area between the chiller plate and rod larger, but my lathe sucks at threading operations (it's a great hobby-style lathe, but it has its limitations), I don't have the lathe tooling to thread a bore, and the biggest tap/die set I have is 1/2". So, this is the design I settled on for now.

Below you can see how the device is situated against the outside of the keg. The fan is mounted somewhat temporarily, but it works just fine. I have two options for improving this portion. The more difficult option is to contour the chiller plate to the outside of the keg. I'll explain the other option later, since it ties into some other improvements I may make.

4688-chilleroutsidekeg.JPG


Here, you can see how the entire assembly goes together:

4688-chillerassembly.JPG


And here is a disassembled view. From left to right:
Fan (detached and almost out of view)
Heat sink
Peltier device and foam insulation (still stuck to the heat sink)
Chiller plate (screws into the heat sink to sandwich the Peltier - the screws are insulated with some plastic washers so that they don't transfer heat to the chiller plate)
Threaded rod (seals from the inside of the keg with an o-ring)

4688-chillerexploded.JPG


Here's how I'm thinking of improving this thing:
Cut a flat piece of stainless sheet the size of the chiller plate and weld a couple of threaded studs to it.
Cut a rectangular hole in the side of the keg and weld the flat piece to it.
Cut a hole in the now flat keg side to allow the rod to pass through it.
Weld the rod to the chiller plate.
Attach the chiller assembly to the side of the keg using the threaded studs.

I'm sure that's a little tough to imagine, but I'll post pictures if/when I decide to make the modifications.
 
Todd said:
What I'm not sure about is how to seal everything without losing the metal to metal contact. is there a seal that will transfer heat? Could something like aluminum foil work as a gasket?
I thought about this for a while after posting my idea above. I think I have it figured out. I'll machine a relief into the aluminum for an o-ring. If I leave the relief depth just a bit more shallow than the o-ring thickness, I can tighten the pieces together enough to smash the o-ring for a seal, but still achieve metal to metal contact. Make sense?
 
Yuri_Rage said:
I thought about this for a while after posting my idea above. I think I have it figured out. I'll machine a relief into the aluminum for an o-ring. If I leave the relief depth just a bit more shallow than the o-ring thickness, I can tighten the pieces together enough to smash the o-ring for a seal, but still achieve metal to metal contact. Make sense?


sounds great to me, in fact I was thinking about an inset o ring but I doubted your ability. Silly me.

Are we right that the extra metal to metal contact would greatly increase the heat transfer ability?

Another idea would be puting a small heat exchanger on the inside. Not sure if all the surface area would cause trouble sanitizing or not?
 
Todd said:
Are we right that the extra metal to metal contact would greatly increase the heat transfer ability?

Another idea would be puting a small heat exchanger on the inside. Not sure if all the surface area would cause trouble sanitizing or not?
In my mind, the efficiency of this system is about three things:
Surface area, conductivity (metal to metal contact), and insulation (yet to be addressed). I think I'm going to machine grooves into the rod as you suggested. A bit of math suggests that if I do that, the surface area of the portion inside the fermenter will almost double.

I could use part of the old heat sink inside the fermenter, like you suggest, but I will lose the welded connection between the portion inside the fermenter and the chiller plate outside the fermenter. I can achieve the same surface area by putting grooves into the rod, and I will have a solid aluminum piece that should transfer heat very well.
 
Yuri, how about liquid cooling this?

Couldn't you use the peltier device to somehow cool a liquid cooled blanket that could surround the keg?

I don't know how you'd construct the liquid cooling lines but i'm going to search the subject.

It might be a better alternative to cool more of the metal surrounding the keg-- and increase the surface area.

This is only IF you continue to have insulation issues--but I think you are on the right track. I'm just throwing out suggestions.
 
I know you guys are working with alot of stainless steel... What about copper. I bring this up because back in the 70's my folks were into metal sculpture. Their medium was brass and copper so it's one i have a small understanding of. Isn't copper a better conductor of heat than stainless? Instead of machining down that rod why not machine out a copper rod to attach it to the chiller plate then braise(my spelling sucks, is this right?) some fins onto it? Copper is very easy stuff to work with. Just a suggestion.:)
 
Grimsawyer said:
I know you guys are working with alot of stainless steel... What about copper. I bring this up because back in the 70's my folks were into metal sculpture. Their medium was brass and copper so it's one i have a small understanding of. Isn't copper a better conductor of heat than stainless? Instead of machining down that rod why not machine out a copper rod to attach it to the chiller plate then braise(my spelling sucks, is this right?) some fins onto it? Copper is very easy stuff to work with. Just a suggestion.:)
All of those machined pieces are aluminum...which is only a slightly poorer conductor than copper. If copper weren't so expensive, I'd certainly give it a shot.

As for liquid cooling - I think that might actually reduce the efficiency of the system. Perhaps not. It would certainly increase the complexity quite a bit, and I'm attempting to keep this kinda simple....kinda...

I'm about to break out the welder and finish round 3 of modifications. Pictures and results to follow!
 
Ok, here's the latest...

The parts are very similar, but I made a new chiller plate to fit flat against the side of the keg. The rod still threads into it, but it's got a ton more metal to metal contact. There is no o-ring between the rod and the plate. I machined a few grooves into the rod as well to increase surface area.

4688-newcomponents.JPG


Here's the relief I machined for the o-ring. It allows for metal to metal contact with the chiller plate and keg side while maintaining a seal.

4688-o-ringrelief.JPG


Here's the side of the keg with the flat plate welded in. Geez, corny sides are thin material! The welds turned out a bit erratic because I a had bit of trouble controlling the heat well enough not to burn through. Guess I need a bit of practice on the really thin stuff. I did manage to minimize any warpage on the flat portion.

4688-flatkegside.JPG


Here's the chiller plate bolted on.

4688-flatchillerplate.JPG


I have it powered up again, starting at 73 degrees, crossing my fingers...
 
seanhagerty said:
Thats great for a full keg, what happens when the level gets below the cooling rod on the inside of the keg?
The rod is at the four gallon point. It's for fermenting, not serving. I guess if you made three gallon batches, it wouldn't work so well.
 
This is an awesome thread. I recently was inspired by the heated/cooled fermentors from B3, and I've considered adding a pelt to the side of my conical. I'm curious to see how this all shakes out.

I have one of those cigarette lighter coolers in my vehicle (dorm fridge size), and I may just have to scavenge some parts. :D
 
Take 3:

I've insulated the keg with several layers of bubble wrap and hooked up a 12A power supply. There should be no shortage of power now, and the keg is at least somewhat insulated.

Results from the last trial weren't very encouraging. Even with the improved design, I could only maintain 4 to 5 degrees below ambient.

I have it running again, and it's already dropped 1 degree in 10 minutes. I hope it continues that way...
 
Yuri, your experiments are leading me to want to hear from some people who own a morebeer.com conical cooled with their TEC's. Yours looks just as professional altough not a conical, and should be similar in cooling capacity. From what I have seen so far a wet towel and a fan sound better than TEC's. I can't wait to hear more, it just is kinda turning me off of the TEC idea now. You are deffinitley the man when it comes to projects, :), thanks for the good solid info.
 
these things are amazing.. I build cigar humidors and I use peltiers to cool the boxes in hot climates. The catch is that you need a decent circuit to run them and you HAVE to have very efficient ways of removing the heat and cold from either sides. I'm curently building a cigar cabinet that uses 10 peltiers in all (5 under each heatsink). Again AMAZING lil buggers!!! Ill post some pics when the cabinets wired up.

Cheers
 
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