Making a Beefy Peltier Cooler!

I wanted to make a more efficient cooling element for my electrically powered cooler so I went ahead and ordered the necessary parts from Amazon.com.

Heatpipe heatsinks are really good at cooling CPUs (those 2 pictured can handle 160Watt TPD easily) so they are perfect for cooling 40mm Peltier chips. I used a 12volt 6amp rated Peltier for this project.

Step 1: Putting the Heatsinks and Peltier Together.

Using thermal paste that came with the heatsinks, I sandwiched the Peltier between both and bolted everything together while making sure the Peltier was evenly placed between them.

Just a note, the printed side of the Peltier is actually the cold side once the polarity of the wiring is followed.

Step 2: Cutting an Opening on the Cooler Lid.

Marking out the shape of the heatsink, I cut an opening in the cooler's lid. I used a sharp knife to clear the burrs off the edges then my vacuum cleaner to remove all the mess.

Step 3: Bolting the Heat Exchanger to the Lid.

Using 3 inch long stainless steel bolts, washers, nuts and wing nuts, I secured the entire exchanger onto the lid. Once fitted I installed the fan for the cold side heatsink to circulate the air.

Step 4: Putting the Electricals in Place.

I soldered the 12volt and 0volt wiring respectively to give a low impedance and reliable solution. The temperature meter I stuck onto the lid with black silicone adhesive. The thermal sensor I stuck inside the cold heatsink fins.

For power, I used a 12volt plug to allow easy use in the car.

A quick test shows the internal temperature drop to below 9C with an ambient of 28C within half hour. The heatpipe heatsink is very good at cooling a 65watt Peltier! I also included thermal images of this preliminary test.

Step 5: Adding Thermal Insulation.

Most folks don't know this but windshield sun screens, the silver type, are a very good heatshield and insulator. I cut a section of this from my stockpile and silicone stuck it onto the lid, both upper and underside.

Step 6: Fixing the Handle.

Due to the large size of the hot heatsink, I needed to replace the carry handle with a strap. I used an old bag strap to complete my Peltier cooler.

Step 7: Testing.

Letting it run with nothing in the cooler, the ambient being 29C, in half hour it reached to below 17C. I'm quite happy with this cooling performance.

Peltier coolers work best with pre-chilled foods since they can't freeze food on their own in hot environments. Mind you though the cold heatsink is pretty large but I don't mind the loss of storage volume given how well it works.

An interesting note is that at 9 volts the cooler will get colder but take a bit longer to achieve this. This is due to the heating losses within the Peltier being directly proportional to the current used.

Step 8: Improvement!

The inside fan is a nasty heat source and I didn't want to degrade the cooling capacity so I just plain removed it. Now the temperature difference is so much more! Amazing!

I hope you found my instructable interesting and for a total cost of 700TTD, I have a cooler that is rugged and can keep groceries cold until I reach a refrigerator. No more need to buy stupid ice and having to clean the resultant mess.

Update July 2016:

Do to the ridiculous size of the cold heatsink, I reduced its size to about 30% with no loss in performance:

https://www.instructables.com/id/Cutting-a-Heatpipe...

Comments

[Shaund222]

Great stuff. Could you add solar panels to power this or would you need so many that it becomes unwieldy?

[ShannonC125]

The heat pipe on the cold side probably doesn't do much. The heat needs to generate enough vapor to actually move the heat. You would probably do just as well with a passive element on the inside. See https://www.1-act.com/operating-temperature-range/

[Kinnishian]

This is a really good point. Thanks for bringing it up! I totally overlooked it in a different application I'm working on. Thanks.

[Mjtrinihobby]

Correct. I actually decommissioned that design years ago.

[garagebuild]

Hi, thanks for the great build. Regarding a lower voltage, are you saying that dropping it to 9V makes the unit ultimately get COLDER, but takes longer? So, at 12V you will experience a faster drop from ambient, but the final temperature will be higher than it would be if you used 9V? Also do you have any experience with building a simple, compact absorption cooling unit?

[SeaH4]

Cool project (pardon the pun). Do you have any performace data? Did it work well for your application?

[corradini]

VERY interesting point that higher voltage takes longer but gets colder. (Makes you think about what "efficiency" means, from both a thermodynamics and a practical standpoint. :-) So it seems it'd be smart to start out with a lower voltage, to get a quick drop in temperature (and save power), then up the voltage somewhat - if you want things colder. You could do it manually, or for the extra points (and expense) throw a 'duino or similar into the mix.

(I'd be curious as to whether it'd then stay at the lower temp if you reduced the voltage again. That'd obviously depend greatly on the real-world properties of the cooler and system, but not sure whether it's just ultimately the heat-loss-proportional-to-voltage factor anyhow.)

[Mjtrinihobby]

No thanks.

[mtairymd]

Nice job - looks very professional. The windshield screen was a nice touch. As for the last step, people often ignore the heat of the fan in a sealed/insulated enclosure. With the fan, you are also increasing the heat transfer coefficient from the walls to the inner ambient which lowers the thermal resistance to the hot side. This lower resistance might account for some of the additional heat rise. It's fun to run experiments like this and look at the data - yep, I'm an engineer.

[corradini]

Now THAT (thermal transfer from walls) was a clever insight that nobody else picked up on. I had to think about it for just a sec, but yeah - the more air circulation is going on the more you're using the walls of the box as kind of (really poor, but still) 'heat sink fins'! The walls are inherently warmer than the contents of the box, so moving air around must increase the speed of external heat transfer into the box. You want the inside air nice and still.

[Mjtrinihobby]

Thank you greatly for your compliment! From the way your wrote your comment and the technical content I had a good idea of your line of work. You see, I'm an engineer too.

[mtairymd]

I figured you were as well :). I've only used them once at work which was an application where we needed to keep a component locked at a certain temperature while the ambient varied from from 0 to 50C - used as a heater and cooler.

I did think of an interesting application for a car but I haven't run the calculations to see if it's feasible or economical - most likely neither. What if I mounted Peltier coolers to the exhaust manifold (hot side) while the cold side was placed on a heat sink in the air stream under the car. I assume the temperature difference would be in excess of 250 C. The energy would be used to replace or reduce the load on the alternator. Ignoring the catalytic converter issues, what do you think?

[Mjtrinihobby]

Ah.. The Peltier is terrible at power generation. Plus it will fail rapidly at exhaust temperatures since the soldered joints would liquefy. I like what you did for your work project. I was worried cycling a side of a Peltier from cold to hot would cause it to experience thermal overstress. Maybe two separate heat exchangers, one for heating and one for cooling.. Great way to double the service life! I hope you keep your comments coming on my instructables and share ideas. It's great to communicate with a like mind!

[mtairymd]

Yeah, I know the COP is less than desirable.
It looks like the melting point of 60/40 Tin/lead solder is around 188C. I think the solder joints could be handled by
placing the peltier farther downstream of the engine. I'm just trying to think of a way to
capture some "free" energy. I figured it was a bad idea since auto
manufacturers are not using it

[ccopyrites1986]

Curious, what solder is in question here? The heatsink solder I assume?

I could see if the tailpipe had a welded plate that the peltier is in contact with and the heat sink (on the cool side) being solid copper/aluminum or whatever is your favorite mounting onto the plate (sandwiching the peltier). There would be no solder required other than the wires.

Note: I'm assuming you won't need as much of a sophisticated heatsink because you have high wind speeds cooling it down and you could get away with a larger solid piece because it's hidden under your car.

Note 2: I had a similar idea but with a 'funneled' wind generator. a small fan (or series of fans) mounted into a tin can or pipe to shield it, when you drive it could potentially help power a smaller backup battery or something?

[mtairymd]

I think the OP is concerned with the electrical connections between the silicon and the electrical conducting plates. I think these are typically solder joints.

https://en.wikipedia.org/wiki/Thermoelectric_cooli...

[rmoody3]

Just because the car companies aren't doing it doesn't mean it's not a good idea.

[mtairymd]

I did a quick patent search. Car companies are considering it.

https://www.google.com/patents/US7426910?dq=7,426,...

https://www.google.com/patents/EP2636079A2?cl=en&d...

https://www.google.com/patents/CN202713201U?cl=en&...

[quick_dry]

you have to be careful where you remove heat from in a car - particularly the exhaust manifold as it is an area tuned for the exhaust pulses and flow e.g. to enhance scavenging.

If you take heat out of a turbocharged car in the exhaust manifold, you'd lose engine power - since the turbo relies on the energy of the gases coming out of the engine.

There are very good reasons why there are so many manufacturers of engine component heat coatings - some to insulate and keep temp out, many to keep the temperature "in" (i.e. not transferring from the gases to the pipes around them)

As for the fan idea, that is what aircraft do with a RAT - on a car you'd only want something like that if your alternator died, otherwise you'd be better pulling power for backup batteries from that. Don't forget, if you'd getting power from the free stream of air the car is moving through, the car will spend more energy to move a certain distance

[Mjtrinihobby]

good points!