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Thread: To peltier or not to peltier, that is the question

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    Av8tor1's Avatar
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    To peltier or not to peltier, that is the question

    There has always been lots of questions concerning using thermoelectric cooling for Cp's
    A while back I bought a 300watt peltier chip. It didnt take long to realize that this was the easy part. The hard part would be a power supply for the thing as it would require a 12vdc/25amp power supply (and massive heatsinks) LOL.... cha-ching

    Recently I came across a 50(?) watt chip, now the power supply becomes more resonable. This one only needs 4amps at 12vdc. With a couple heat sinks, a fan and a couple power supplies some of my students and I were ready to give it a try.

    Here are the results of a simple bench top test

    The setup:


    The DVOM meter is indicating voltage, the adjustable power supply's display is showing current in amps.

    The large power supply is powering the peltier and the small power supply is for the fan.

    Immediately it became obvious that the bench top power supply could not carry the load. The best it would do is about 3 amps at approx 12vdc. This was maxed out, the power supply's heat sink (not visible in the pic) could fry an egg.

    The top heat sink of the peltier is the hot side and the lower heat sink the cold. Peltier's are very inefficent to begin with. Without the fanI belive the top heatsink would be hot enough to blister your finger.

    Initially it seemed to take about 30 mins for the peltier temp drop to reach maximum. As the delta T max is reached efficiency drops even lower.

    Room temperature is 68-70f

    It wasnt long before condensation was obvious:


    Input power levels:


    After a half hour or so, temps stabilize:




    I was curious if a greater delta T max could be acheived if I used a power supply capable of driving the peltier at full load.

    I found one and hooked it up, current jumped to above 6 amps and voltage levels were regulated at 13.8vdc

    Amazingly, it had very little effect on performance. Evidently somewhere around 3 amps a point of diminishing return was reached. Any additional temperature drop would come at a significant price in efficiency, power consumption and wear and tear on all components.

    So, where does all this lead me... I believe that a small terrarium would be an ideal application. Maybe a 5 or 10 gallon aquarium. But beyond that and beyond a 50 watt peltier... the disadvantages far out weigh the advantages. In that application a typical vapor cycle cooling system would be far superior.

    Having said all this, I will build a 5 gallon temperature controlled terrarium version using the setup shown. It should be the perfect nursery for N. villosa and other difficult Cp children. I have little doubt that I could use this to lower a 5 gallon aquarium to 50f, maybe even a 10 gallon.

    Hope this helps shed some light on the debate

    Cheers'
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    Tony Paroubek's Avatar
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    Why not just get one of those 12v peltier chilled coolers and take the lid off and replace it with some glass for lights?

    I have not done alot of research on them but my understanding is they are incredibly inefficient at converting electricity to cooling temperatures. A small dorm fridge with gas compressor would be cheaper and use less energy and chill a much larger area.
    Is that a Nepenthes in your pocket or you just happy to see me?

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    Av8tor1's Avatar
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    Quote Originally Posted by Tony Paroubek View Post
    Why not just get one of those 12v peltier chilled coolers and take the lid off and replace it with some glass for lights?

    I have not done alot of research on them but my understanding is they are incredibly inefficient at converting electricity to cooling temperatures. A small dorm fridge with gas compressor would be cheaper and use less energy and chill a much larger area.
    LOL well heck Tony, that wouldnt be no fun :P
    Actually, the main point was to play with the technology and see what the possibilities are and a 5/10 gallon aquarium is much more aesthetically pleasing

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    Tony Paroubek's Avatar
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    Well dang it how can I argue with that? lol
    Is that a Nepenthes in your pocket or you just happy to see me?

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    Av8tor1's Avatar
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    update: I had an odd feeling about that 6.6 amp reading with the other power supply, verified with two diff ammeters and it was in fact only 4.7

    That sounds much better, and works out better mathamatically

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    Mathematically, teacher. Never trust spell check, I swear microsoft is dummy-ing us down on purpose.
    Good growing, Jack
    "Never doubt that a small group of concerned citizens can change the world. Indeed, it's the only thing that ever has." - Margaret Mead, American Anthropologist

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    When it comes to my spelling, ya cant blame microsoft :P

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    I did a little research on peltier coolers a few month ago. You have gotten much further than me as I lack the know how. I have more knowledge of programming languages.

    I read that efficiency goes up if...

    1. The temperature differential between the two zones is great.
    - The cold side is in contact with heat and the hot side is in contact with cold.
    2. There is fast dissipation of heat and/or cold.

    Obviously #1 is not practical in a CP environment. More so for thier originally designed application of cooling electronic devices. With that said, have you measured efficiency in a very humid environment. Perhaps one that has a constant blowing of mist to transfer the heat from the mist to the cooling device? Air itself is not a very conductive material.

    Very interesting stuff. Thanks for posting.

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