Stacking of Peltier units - Part 1

[@paulpease1788]

We had spoken years ago about cooling with peltier units. I am still working on that. I think I'm heading towards a combo of better insulation to protect the cooled air and gallium pipettes as a phase change material (PCM) to store the heat to be removed through ice and a volatile positive pressure airflow to get the air cool from the start. The cooling chamber needs max insulation (which can be foil coated polyisocyanurate) heatsinks on the peltier are cooled with the condensation of ice packs until they reach equilibrium with the temp of air in the cooling chamber and no longer create condensation. Then a hollow plastic 1/4"×3"×6" (~6.3mm×75mm×150mm) with gallium inside will begin melting as air heats up and the phase change begins in that plate. Peltiers are mainly used to extend the life of the ice.

[@CuriousScientist]

Sure, I remember you from the early days. I have difficulties imagining your project but if you have any videos to share or any kind of documentation, please feel free to do so.

[@isidoromaich7226]

33:50 "We will see if it works in the reality" that really got me for the next video 😅

[@CuriousScientist]

Haha! Well, I do not want to tell any spoilers, but I can tell, that the upload process is at 80% when I am writing this comment. So the cliffhanger will be about 30 minutes long and you will see what happens. I should use those silly clickbait titles for my videos like "This guy stacked 2 Peltiers, and you won't believe what happened after that!". :D

[@isidoromaich7226]

@@CuriousScientist Oh! those clickbait... XD there are a lot... lol

[@VrishiSpin]

Would it be possible to reach -200 degrees celsius on the cold side of a module with stacking?

[@CuriousScientist]

Not at all. You can reach about -50°C or maybe -60°C, but that's really the physical limitation of the cooler. Tech Ingredients tried to cool it with liquid nitrogen and he also got stuck at around -50°C-ish temperatures. I also tried to cool it with dry ice and I couldn't go below the above mentioned limits.

[@VrishiSpin]

@@CuriousScientist would it be possible to achieve this temperature with any type of peltier module that exists today with or without stacking? If not, are there any other efficient cooling methods other than liquid nitrogen that uses electricity?

[@CuriousScientist]

@@VrishiSpin You cannot reach below -60°C (approximately) with Peltiers _at all_ . It is their physical limitation. The range (-200°C) you are talking about is a totally different dimension, you can't just put a few things together at home and reach such a low temperature. These low temperatures are typically achieved by using liquid nitrogen anyway. You cannot really avoid it. Whenever you see some low-temperature stuff, you will always see some liquified gas (LN2 or liquid helium) used as a cooling medium.

[@durlin84]

you can but you need to make a superconductor peltier first, which can be done, just have to make it. normal peltiers are just less and less performant the cooler they get, the electrons dont like traveling when its cold, ask elon muks and his electric cars and performance in the colder places, electron no like the cold, only in first-class vehicles (like maglev trains and the like)

[@durlin84]

oh yeah, you could just cool the peltier stack to absolute zero and you have a superconducting peltier, that solves that problem

[@jawedsuria4858]

Thanks for details working 👍

[@CuriousScientist]

You're welcome! I am glad to help!

[@EmadFouad97]

Hi, I want to thank you for these efforts, then I have a small question, the last step you side DT2= -56, I could not catch this step, Where the -56 must be at which surface or at which points, or the difference between What and What, please explain it for me, I got the surfaces of -20 degrees and the 14 degrees, but -56 is for which difference. thank you a lot again.

[@CuriousScientist]

I think that part confused you a bit, sorry for that. In the beginning I showed why a large performance Peltier should not be on the top of the stack. We just simply cannot move such a large amount of heat (265 W) with Peltiers. Then, at 12:54 I start the real exercise and start with the TEC1203 as the top unit. So, with this unit, I just try to max out the DT and all the parameters and see what kind of cooling power I can achieve (~5 W). Then, based on these parameters, I know that I need to remove about 71 W of heat from the hot side of the TEC12703 using the bottom Peltier. So, I pick the proper parameters from the TEC12715's performance chart to get that 71 W moved away from the hot side of the TEC12703 on the top. At this part, I know that I can fix the hot side temperature of the TEC12715 (that depends on the heatsink), and then I can pick a corresponding current (15 A) which will give me a DT value (36°C). I wanted to maximize DT, so I picked the largest current. Since I fixed the hot side (heatsink) to 50°C, the DT of the bottom unit will result in a 50-36 = 14°C cold side temperature which is also the hot side temperature of the top unit. We fixed the DT of the top unit at 70°C, so 14-70°C is -56°C which is the hypothetical cold side temperature on the top.

[@EmadFouad97]

@@CuriousScientist Wow that was amazing explaination, thank you a lot, and for sure all these charts 03,8 and 15 A with out loads right.

[@CuriousScientist]

With a very minimal load. Peltier stacking is not made for cooling serious thermal loads, but it made for reaching very low temperatures.

[@JoyGadang]

nice explaining .. i new about this peltier

[@CuriousScientist]

Thank you!

[@DmitryMyadzelets]

When you got 14 degrees at the cold side of the second stage unit, you'd have to have the chart for that temperature for the first stage unit. But you have it for 50 degrees, not 14. The performance of Peltier modules lowers with lower temperatures. One way to solve the problem would be to build a mathematical model using the curve for different temperatures at the hot side. Then you'd have curves for any T hot and delta T.

[@CuriousScientist]

Yes, the calculations are not super exact due to the available data I could access. But as a guideline to understand how to evaluate their performance, it is good enough (for me).

[@paulpease1788]

Great idea

[@simonpercival-f6r]

Very useful thank you v much

[@CuriousScientist]

Glad to hear it! Cheers!

[@jawedsuria4858]

I am waiting your final result Please share us temperature down chart like every minute change of temperature if possible

[@CuriousScientist]

I am editing the video of that part right now, I will upload it within 3-4 hours. I did not record the chart, but you can watch the video and see the temperature.

[@jawedsuria4858]

@@CuriousScientist okay I'll

[@CuriousScientist]

The video is up! :)

[@yonglinalbontiong6092]

Try stacking 5 peltier vs 1 peltier at full amp. And check the COP. By stacking more Peltier will gives you higher COP with lower temperature drop each stack. Cause from the datasheet, the ower the delta Temp, the higher the COP. So if all 5 chips at high COP, the efficiency will be high and it might rivals gas pumped refrigerator.

[@yonglinalbontiong6092]

So the second chip power is twice the first chip, and the third chip is twice the power of the second chip and so fourth until the 5th chip. There will be a cutoff efficiency at how many peltier you can stack.

[@CuriousScientist]

You are still limited by the Qc of the bottom Peltier cooler. All that stacking do is just makes DT higher between the top and the bottom of the stack.

[@yonglinalbontiong6092]

Limit the voltage drop by each chip so that each chip delta T will be limited to maybe 10 degree. Then you stack them.

[@CuriousScientist]

I pretty much know how to do it. But you won't be able to get out more performance than the performance of the Peltier at the bottom.

[@CoyzCoins]

I just dont get you. You have the equipment why dont you create demo video measuring all junctions that can be measure then just compare it to the chart. Much better content that pure computation.

[@CuriousScientist]

I just don't get you. You could have gone through my videos and see that I have done a lot of experiments with Peltier coolers. You won't really see such detailed experiments and discussion on Peltier coolers anywhere else on KZbin than my channel.

[@benmedka]

Up

[@CuriousScientist]

Thanks!