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To peltier or not to peltier, that is the question

  • #21
bullet proof.... oh and not pictured is the pulse width modulation control unit I added for ya
You will have adjustable fan speed control on the cool side

(had one laying around from a project I built a couple years ago...)

;)
 
  • #22
That is fantastic mate. Let us know about its effciency.
 
  • #23
Pure efficiency (usable output/input ) will still be crap... hard to turn do-do into ice cream
Buttttttttttt on such a small scale this level of inefficiency is acceptable as long as it works, so temperature drop is the metric to judge it by.

If it will drop the temp 10-15f overnight I will consider it a success (this trial is based upon a small 30w module... so it can run 8-12hrs w/o much danger of over cooling, power supply demands stay reasonable and resultant heat remains acceptable)

As the technology stands today, I personally don't see peltiers being a viable option for anything over a 5 or 10 gallon microchamber...

Av
 
  • #24
AV,
I have had a chamber for a bit over a year and a half, and while it cools
it isn't the most ideal system as you noticed.
I am still hoping to get it working better, but it isn't the best route to go so far.
(I think I have pics out on my "terrarium" on the forum from about a year back.)

Glad to see you are having fun doing it!
It is nice and "clean" & simple compared to compressor systems,
but indeed it does lack in the efficiency dept!

Take care
Paul
 
  • #25
Paul,

I remember the thread, I also remember us talking about heat issues but forgot/didnt recall you using a peltier...

very kewl... :)
Butch
 
  • #26
Butch,

Yea, it was low profile!
I am still working up an improved version, and have learned a lot from my first prototype.

Well, good luck.
 
  • #27
Cool!
 
  • #28
30w Peltier Trials...

#1 Last night
Conditions: 10 gallon empty aquarium with top covered in styrofoam.

Results: 5f drop from ambient after a couple hours. Maintained temp differential from ambient but no further drop.

#2 This morning

Conditions: 10gal aquarium, top covered with styrofoam and bottom covered with used CP substrate to a depth of approx 2"
4 of 4"x4"x4" net pots filled with sphagnum placed in chamber (could hold about 10-12)

Results: Temp drop significantly faster, after one hour 6.3f drop from ambient.
(Trial still running)

To be continued... still want to see what filling the usable area up with pots will do. Then try the same trial with insulated sides and rear ;)
At first glance a 6.3f temp drop doesnt seem like much, but if we also have a 5f rise from the lights (very probable) then our total delta T is already over 11f

Paul, since you have "been there and done that" mate, any words of wisdom?

Av
 
  • #29
30w peltier trials.... continued

Still working on increasing efficiency of the module assembly

Sorry for the cheesey cell phone image, but it's all i have handy
peltier_ice.jpg

Notice the ice formation on the cool... errr cold side ;)
Ambient room temp 70F

Cheers'
Av
 
  • #30
Tip of the week:

Insulation is a bigger friend than you could possibly imagine!

Thermal mass takes time to release its stored heat, so every day the battle must be fought, unlike a refrigerator which stays closed most of the time. (We don't bring everything to 72 degrees every day, but on these unite we expect to.) It is not that the units are bad in and of themselves, but we are asking a lot from them.

For me it has become a balancing act. Make a list of all the variables and you will understand what I mean. I have a Peliter unit on a chamber about the size of a 20+ gal tank. A LOT depends on ambient temps.

And Insulate! Insulate! Insulate! And then Insulate some more!
If you add enough insulation until it looks bulky and ugly, and then add more!... you will be close to the amount you are gonna need! (Like people are finally finding out with insulation, it saves a lot of energy and makes up for its cost in no time!)

Av, lots of time, study, experiments and effort and that's all I have for you right now!
By the way, what is your motivation for this project?

Hope some of this helps!
Paul
 
  • #31
That puppy looks nice it's working like a charm there Butch! Next project is too make it cool a 12 pack :-D

Insulation is a bigger friend than you could possibly imagine! And Insulate! Insulate! Insulate! And then Insulate some more!

Sounds like we're halfway there. I'm wondering if insulating the outside of the tank would help any? Insulation/glass/insulation. I'm guessing though that at some point we reach a plateau since this is just going to be a 20 gallon tank.

By the way, what is your motivation for this project?

Heheheheheh......
 
  • #32
Paul,

My goal was to make a "feasible" 30w/10 gallon UHL tank... Yann wanted to try pushing the envelope. So we are going to try the 30w module with a 20 gallon tank.

I'll be honest, I still dont know if it will work.... as you stated there is a lot of thermal capacity to deal with. Yann has insulated the sides, rear and bottom of his tank and the top will be removable Plexiglas.

My last recommendation (if needed) would be to make the front glass a sealed "double pane" by framing the inside perimeter of the front glass with strips of insulation foam as a spacer, then silicone in a secondary Plexiglas layer

The fact that the 30w module I built will now freeze over in 70f ambient temps does give me a warm and fuzzy feeling.... but of course that is with minimal airflow.

I have no doubts about a 30w/10gallon, but we shall see how this works...

I still have a 70w assembly to finish... Ive got the power supply, etc etc etc... that will be my next trial

That may be my "tepui" tank ;)
 
  • #33
Hey Butch,

My peliters are hack-outs from other applications. Things looked promising, and I had hoped to make units to sell eventually, to give everyone an affordable way to actually grow the plants we finally have access to. (Without the resources to actually grow the plants, people are limited to having them long enough to kill them!) I kind of hoped to contribute something of value to the "growing world", and hoped to market something even a kid could pretty much afford. (I find $800 for a terrarium with a cheap light and thermostat/heater is a bit high in my book, but apparently people are buying them! Perhaps my age and inability to see what something is worth gets in my way.)
I have moved along sporadically, as my resources and time interfered with my progress, however I have come quite far to understanding what is needed and what to do. There are more variables than I originally considered.

Double pane glass is a good idea, and while I had concerns about them at one point, they will help the insulation-situation. (Didn't know I was a poet, huh!) :-D

Well, keep us posted on your results. I am sure it will be interesting.
 
  • #34
It would be nice to have true "double pane" glass with the Argon in the middle.... but the evacuation and replacment with Argon is a wee bit difficult for the average hobbyist. Even so, it still can be a major improvement. Glass is an excellent thermal conductor... which is not a good thing in this application.

It mainly just fun to see what can be done, plus Yann is an intelligent and enthusiastic "student"..... otherwise the parts would still be laying in a box somewhere like so many of my "projects"

Thought you were about to break out with a schoolhouse rock song LOL....


Butch
 
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