DIY Peltier Chiller for $20-$60

[Kevw99]

37 Watt Peltier Module $8.95

 

40mm Heatsink and Ball Bearing Fan $12.00 (cheaper if you can find without the fan)

Pic Here

 

ARCTIC COOLING SLIM SILENT PRO $7.99

Pic Here

 

Thermal Grease Compound $1.00

(no pic... i'm lazy)

 

Cheapo HOB Filter... Maybe you have this on hand... if not $15.00

 

12V ~4amp power supply (laptop transformer) @ surplus store $15.00

 

Total cost not including shipping is... $60.00

 

If you are like me, you have some of this stuff already. Look in your phone books for electronic surplus and give them a try. (if you live in northern california, look up HSC in Rohnert Park) You may be able to get some of the heatsinks and fans cheaper there. I estimate that I will purchase the aquaclear HOB at petsmart for $21.00 - 15% hook-up. So All in all, you may be out as much as $60 but i think it'll make a quality cooler.

 

On to the design.

We'll have to cut out the 40x40mm square for the heatsink in the back or side of the HOB. I will probably set up a guide and use my dremmel. If you got a 40x40mm with a fan... take the fan off. Get some 2 part epoxy from HD and let it sit in hot h2o. Cut the tip off and depress plunger (try to get like a dixie cup or something small to put it in. You may actually want to buy 2 syringes of epoxy to ensure that you can "dunk" the heatsink. Also, if you don't have some, get some aquarium silicone.

So we dunked our heatsink and hung it upside-down so that the excess epoxy will run off the prongs (haven't figured out how to suspend it though). Let dry and cure (heating prolongs dry and cure times). Ok, so it is cured. Go and slap that sucker in the hole you made on HOB and see how it looks.

 

After that, plug in your peltier for only a few seconds to figure out the hot and cold side. Stick the epoxy'd heatsink onto the cold side of the peltier with your thermal paste. Stick the other heatsink (can be and probably should be larger than the 40x40mm surface that the peltier unit is) to the peltier with the paste. Apply a little aquarium silicone to all 4 sides of the "peltier sandwich." Let it tack up then place assembly into hole on HOB. Apply more silicone to create a watertite seal (hold in place with masking tape... or gravity).

 

Ok... for the math and theory...

 

A 37 Watt Peltier is suppose to do 85 BTU. British Thermal Units. The quantity of thermal energy required to raise one pound of water at its maximum density, 1 degree F. One BTU is equivalent to .293 watt hours. So if we are making 85 pounds of water change 1 degree, we have selected the proper peltier. If you need to cool down a 5 gallon tank 5 degrees... 5 gal x 8 lb/gal = 40lb X 5 deg = 200 BTU. We wouldn't have a big enough peltier device. However, for my application, i have a 2.5 with a ton of LR and sand so it only holds about 2 gal. My max cooling would be 2 gal x 8 lb/gal = 16 85/16=~5 deg of change.

 

So the big question would have to be... what size is your tank? I would assume anything over 4 gallons in a hot environment (like my apartment) could not feesably use a peltier system unless you got a huge one and had a gignormous powersource. However, their are many other things to consider. Could you set your AC (if you have it) at like 80 so that the tank would be working with your ambient temp, not against it? Could you consider spending the money and making a low volt LED custom hood (ive been reading up on those... very interesting). Other considerations would be to find out how much your pumps, PH, etc are affecting your temp. I'm sure their are some things you could do to test this out (Qbomb comes to mind but it scares me at the same time).

 

Ok, now please remember that i have not tried this out yet. I have little dinero at the moment. it'll take some time to get this together then even longer to put it together. Please share some thoughts about design and (sigh) design flaws. Anything would be appreciative.

[krazieone]

OOoo... please post pics as soon as you are done... :>)

[Kevw99]

Originally posted by krazieone

OOoo... please post pics as soon as you are done... :>)

 

Dude, it's going to be a while. Shout out some thoughts on the design though. I'm totally not an electrician nor am I a physicist. I do however, enjoy reading your comments.

 

Somewhat unrelated topic... Is there such thing as a rheostat that I could use to turn the chiller "on" when the tank reaches a certain temp? I need a cheap and innovative solution that can also be feasible for the moderate minds.

[jhupp]

A rheostat is the same as a potentiometer (sp), just a variable resistor. There are some nice, simple thermostat circuits at Discover Circuits.com which would be easily adaptible for controlling a TEC.

 

Jay

[Kevw99]

Thanks for the info jhupp. I'll have to do some research on that.

[Kevw99]

Just an update, it's been a few days since any posts. I was looking at 2 part epoxy from HD today and I had a general question. Does regular epoxy give off anything that will kill my reef? I was kind of thinking that since it is so hard when it dries that it is virtually bullet-proof. The other thought I was thinking was to use fiberglass resin (just the resin... not the fiberglass) because I think it dries to be about the same hardness as an epoxy.

Hit me up with some knowledge yo!

[xeon]

Just a few questions... in line with the other DIY Peltier thread. How do you think the epoxy will affect the thermal properties of the heatsink? I know they make epoxy that has pretty good thermal properties and is used with transformers and such... but how well does your garden variety epoxy inhibite or decrease thermal conductivity?

[marc nichols]

Interesting project. Look forward to the results.

 

I have 18 months on a 12 gal reef. My summer ambients reach 89 deg. What I did was install a thermostat controled fan in my hood. Then a top off system consisting of a Ultralife float switch and a Aqua Lifter pump. The fan runs when the lights are on unless I'm letting the house stay hot at night when i switch it to full time. The heater keeps min temps at setting and evap works against the heater. Temp varies 1 or perhaps 2 deg at most. It uses a lot of RO water to stay cool, but otherwise works great and keeps the tank topped off as well.

[Kevw99]

My thoughts on that are as follows xeon...

I was actually told by an associate at HD that the resin will form a better protective layer around the heatsink. I still believe that when you heat up the resin, it will become thinner and therefore create a thinner coat on the heatsink than non-warmed resin.

The reasoning behind the thinner coat is that the transfer of heat will occur at a higher rate when the distance between the 2 mediums is decreased. I also chose to use a heatsink for the cold transfer rather than the iceprobe "dowel" because it will have a greater surface area for the water to flow over (unless it all freezes and i get an ice ball). So regardless of the conductivity, if i coated it thin enough and increased the surface area, i SHOULD (ideally) get the same results or better than an iceprobe (in terms of heat transfer).

Xeon, thanks for the questions. I need to do more research on the K values because i did some research and they are all around 1.1-1.4.

[offsprg01]

i dount that you heat sink will freeze in ice water. to loazy to explain the principal but if you've ever made home made icecream you get the picture. salt water freezes at a much lower temp than fresh water. HTH

[B16A2NR]

I like your idea but need you to clear up a few things that I don't understand. Why are you planning on coating the heatsink fins with epoxy? The heatsink fins are on the opposite side furthest away from the water and have no direct contact with water so they shouldn't have to be protected. Adding epoxy will only insulate the heatsink and make it less efficient. If you plan on reversing the heatsink so the fins are glued to the peliter, why? From the looks of your design the only thing touching water is the peliters cold end. Also why do you recommend taking the fan off of the heatsinks hot end? The theory behind the fan is to disipate your hot heatsink quicker with cool air, so it can extract more heat from your tank faster. If you remove the fan your left with a peliter with an inefficient heatsink in my opinion.

 

Also you state that "I also chose to use a heatsink for the cold transfer rather than the iceprobe "dowel" because it will have a greater surface area for the water to flow over" the Iceprobes probe is far from the size of a "dowel" in the water. The surface area of the probe is many times larger than 40x40mm that your flat peliter is. So in theory it should have much greater cooling efficiency being an area with larger mass.

[Kevw99]

Why are you planning on coating the heatsink fins with epoxy?

Check out the pic... I think your confused with the idea. I need to coat the internal heatsink (in contact with water) cause it's metal. Simple Redox rxn principles.

 

If you plan on reversing the heatsink so the fins are glued to the peliter, why?

Nope, you'll see in the pic. The gradient represents my heatsink, squint and it almost looks like one

 

Also why do you recommend taking the fan off of the heatsinks hot end?

I stated that if you purchase 2 heatsinks with the 40x40mm footprint and they both happen to come with fans, you need to take off the fan on the heatsink that is going to be in the HOB.

 

the Iceprobes probe is far from the size of a "dowel" in the water. Dowels come in all sizes.

 

The surface area of the probe is many times larger than 40x40mm that your flat peliter is. So in theory it should have much greater cooling efficiency being an area with larger mass.

I think you'll get the idea by now.

[B16A2NR]

Thanks for the diagram. I understand the concept that you are going for now. I'm Very interested in seeing how this all turns out. Just curous but do you think thermal grease can really hold the weight of those heatsinks from falling off? I think its pretty dangerous having an opening in the filter blocked by two heatsinks and a binding liquid. Just worried that overtime the seals will go on the sealant, and water will leak onto your fan, etc.

[Kevw99]

Originally posted by B16A2NR

Just curous but do you think thermal grease can really hold the weight of those heatsinks from falling off?

 

naw... I'm going to use the aquarium silicone to seal the peltier and the 2 heatsinks. I may use thermal tape rather than paste just to give it more adhesion. Also something i might do is use some superglue gel on the corners of each side (the hot and cold) to hold onto the heatsink better. Or, a combination of all of that to ensure the overkill factor kicks in (I will be able to sleep better at night). I also plan on making a little jig to make sure my dremmel doesn't cut more than i want it to. I may try to outfit the square with a little bit of silicone way before i place the fixture into it so that it has time to cure and strenthen up. Other thoughts are to use marine epoxy on the outside edges of the HOB to make it rock hard and bulletproof... hopefully.

 

Thanks for the thoughts... i'm thinking about all of this while I reply. I hope this thread will make it extremely easy for me to do this all in one shot!

[reefinnewb]

Why dont you use thermal epoxy instead of the grease or tape? Or is that what you meant by paste? In theory it should work. I am into computer water cooling and am very familiar with cooling with TEC units, just never got up the giggle berries to do it. I am very curious as to how this will all turn out. Make sure that heatsink doesnt have a copper core if your putting it into the water. Aluminum should work fine however. Also just a tweak, I think for the internal heatsink see if you can find one with the very large fins. This will help with dissapating the cold throught the water better than the tight finned heat sinks. Just a suggestion. Wish you much luck on this project, I am deffinatly going to follow.

 

Will a 37w TEC be powerful enough to be efficient?

[Kevw99]

Originally posted by reefinnewb

Why dont you use thermal epoxy instead of the grease or tape?  

 

Will a 37w TEC be powerful enough to be efficient?

 

First Question...

 

I did not know that their was thermal epoxy. Does it provide permanent adhesion? I guess I need to do more Homework.

 

 

Second Question...

 

37w TEC was rated at 80's btu so i hope that will be enough. Ideally, I only need to keep the water from getting hotter. I always wake up and check the temp and it's usually around 79F (living in southern california). I would only need it to sustain that temp throughout the day. Check my math in my first post though and let me know if my math and logic are right (or at least sound right).

 

Toodles

[reefinnewb]

yup thermal epoxy provides permanant adhesion and conductivity of heat not electricity. Your math is right and that should work, it was late last night and was half asleep and dint see the math. Good research.

 

http://www.coolerguys.com/840556003014.html

[Kevw99]

Originally posted by reefinnewb

http://www.coolerguys.com/840556003014.html

 

I am a sucker for a free mixing wand!

[reefinnewb]

lol guess a spoon would work if the mixing wand wears out lol just make sure to stick the spoon somewhere funny before it dries.

[Kevw99]

Latest Update...

I purchased the AC mini from Petsmart. If you print out the www.petsmart.com price, they will match it. The in-store price was $21.99 and the online price was $13.99. I dropped my calupera in it for the time being (it went back into the tank sometime last night). I need to get some screen material or something to make it stay in the HOB. Now... just need another paycheck or two...

[Kevw99]

Ok, here's the latest update. I purchased a 30 x 30 mm Peltier device, a power supply, a large heatsink and fan and I found a small and large heatsink for the tank. I am going to try out the DIY acrylic cement to create a thin barrier of acrylic on the heatsink. I'll let you all know what happens in a matter of hours. I just need some thermal epoxy. But I am going to cut the HOB to fit the peltier. Pics soon.

[tylernt]

I really dont think you need a heatsink on the water side. Water is very dense and the constant flow of water will mean a steady supply of warm water waiting to be cooled. Just the flat face of the Peltier should be fine. The reason you need the heatsink on the air side is there are far fewer molecules in air, so you need more surface area to touch the same number of them.

[Kevw99]

good point. I'm just testing it out by taking my temp probe in my ac mini and I took out the tube so it recirculates the same water. keep you posted

[doncb]

Greater surface area means greater heat transfer. That is why the CPU waterblocks have things in them to increase surface area and turbulence. It increases the efficiency of the device. VGA waterblocks (like used in the ICA) handle a smaller heat load and are usually a straight path.

 

If you use a heatsink you should realize better cooling.

[Philtur]

Your math seems right, but I think you have missed a few assumptions. Assuming 100% heat transfer with the water, you may get the full 85 btu out of the cooler and into the tank, but you are going to have some losses for pulling the heat out of the water, depending on how you mounted it. If the heat sink in the water is aluminum, it would have a decent heat transfer coefficient, but coating it with epoxy is going to reduce that a little. Also, You may only have 2 gallons of water in the tank, but you also have other thins in there which have mass and also contain water. Water may have a higher heat capacity than the rocks and corals, but they still factor into the mass that you are cooling. It's possible, but I don't know that you will see the full 5 degree temp drop. Maybe half to 3/4 of it.

 

I'm working on a simlar concept to cool a 10 gallon tank using a thermoelectric cooler. It's a 40mm ~90w and should be on its way. I'm going to attach it to a 6"x6"x1/8" aluminum plate, to spread out the footprint on the glass, and affix the plate directly to the glass tank. I don't know if it will crack the glass or not, but I suspect it won't. I'll test this on another tank first to see what the effects are. I'm going to try removing the heat a couple of ways. I've ordered a cheap 60mm heatsink and fan that I'm going to try forced convection with and see what the effect is. I'm also going to try an old Pentium II heatsink with no fan for natural convection. I'm wondering what effect the rate of heat removal will have on the differential temperature and overall cooling of the tank; I suspect forced convection would be more, but I'll see if I even need it.

 

----

I think for the capacity of Kev's cooler, tylernt is probably right about the heatsink. If you had a cooler with a larger capacity, a heatsink would be beneficial to increase the rate of heat transfer; you would need increased surface area for the increased capacity. With the capacity so low, I don't know that a heatsink will get it any cooler, but it could have a slight impact.