Multiple Lower Pelts vs. 1 Higher Power Pelt?

[XyBeRWaReZ]

I've been pondering about the effectiveness of multile lower power pelts that equal the efficiency of 1 higher power pelt.

So my question is:

Is it more effecient to cool down something say 4"x6" with multiple lower power pelts that would equal to about 400W

or

Use 1 pelt that equals 400W?

I figure that maybe using multiple lower power peltiers would cool better given the fact that I would be using either 1 large heatsink that would be big enough to cover the multiple pelts or multiple heatsinks, one for each peltier.

Then again I also think that when using only 1-400W pelt with an equal size heatsink would maybe cool down 400w worth of energy better because of the smaller size?

I also have another question regarding peltiers as I'm slightly confused about.

I've seen peltiers of a certain wattage, but seen them in different sizes. So does the bigger peltier work better than the smaller one, even though they are both the exact same wattage? Or is the bigger one better because it would have a larger cooling surface area?

I've read around on forums and tried to understand the technical information written about peltiers, but it's kinda hard for me to grasp as they are TOO technical and I'm no electronics genius or scientist. So I ask here so maybe someone can help to explain in laymen terms for all of us to understand.

[murray13]

Using your numbers, I think of peltiers this way, they can 'pump' 400W of heat with a zero deg difference in temp OR they can 'pump' 200W of heat with about half of their rated temp diff. approx. 32 deg.

As an example, I am going to be using 20 50W pelts (1000W) running with about 120W of power applied to lower my approx. 250W heat load by about 15 deg C.

Hope that helps.

[XyBeRWaReZ]

Originally Posted by murray13

Using your numbers, I think of peltiers this way, they can 'pump' 400W of heat with a zero deg difference in temp OR they can 'pump' 200W of heat with about half of their rated temp diff. approx. 32 deg.

As an example, I am going to be using 20 50W pelts (1000W) running with about 120W of power applied to lower my approx. 250W heat load by about 15 deg C.

Hope that helps.

Yes, I kinda understand what you're saying. But if I truly do understand then what your saying still doesn't really answer my question.

I've read that peltiers are not all the affcient. In fact they're most efficient at 50 percent load, anything higher than that, they start losing effciency of cooling capacity, even though it still cools to some degree.

Your comparison is between two different examples and wattages. I'm trying to compare the exact same amount of wattage, but the only difference between the two setups are:

1st Setup - (4) 100W Pelts with a 4"x4" heatsink and fan

2nd Setup - (1) 400W Pelt with same 4"x4" heatsink and fan

Also keep in mind, that the 400W pelt is the same size as 1 of the 100W pelt.

So my theory is that with the more surface area of the 100W pelts, it would cool down more efficiently than using that single 400W pelt with 1/4 of the area size.

Is that correct?

[TerraMex]

bouncing ideas or do you have a real cooling objective in mind ?
chilling a water loop, etc?

[XyBeRWaReZ]

Originally Posted by TerraMex

bouncing ideas or do you have a real cooling objective in mind ?
chilling a water loop, etc?

Nope I have a real objective. I want to use it as an air conditiong system, but need to know what's more effective, mutiple lower power pelts, or a single higher power.
There really won't be any load on the cold side of the peltiers, besides the ambient temperature, which is usually about 27-30C around here in Hawaii.
I see plenty of pictures of people lifting up the pelt, attached to a cold plate and it gets all icy. What I never see is people using a multiple peltier setup. I've seen the professional made industrial setups using multiple peltiers, but they use some major heavy duty stuff and it's well over $1000 and incredibly big.
I'm assuming that the multiple pelt setup would work better because of that reason too. If using a single super high power pelt would work better, I think that the companies would have used that method. But I'm not sure if that applies to smaller and less powerful setups.
That's why I really need help on this before I spend more money than I have to on this project.

[derraa]

air conditioning? wouldnt you be better off looking into a phase change system, IE airconditioner?

[XyBeRWaReZ]

Originally Posted by derraa

air conditioning? wouldnt you be better off looking into a phase change system, IE airconditioner?

Phase change, if I could I would, but even then there are a couple of problems I don't like with phase change units.

1. They're damn expensive!
2. They're pretty noisy
3. If something should leak, I could DIE!!!
4. I have kids, not a good combo.

Peltiers is what I'll stick to. Thanks for the suggestion though.

[derraa]

well, what exactly are you trying to cool? pelt setups are not exactly cheap, especially on the energy bill.

[Ls7corvete]

multiple large peltiers undervolted. better efficiency and performance for your situation

1. With HSFs cooling the hot side the heat load at full/high voltage the temps will be too high for the cooling and reduce performance.

2.You dont need the full 70c dT that you will get at full voltage, you are better off with the higher COP at lower voltage than the higher dT at higher voltage.

[XyBeRWaReZ]

How much should I undervolt a pelt?

When you mean multiple large, do you mean size or higher wattage pelts?
I'm assuming you mean higher wattage peltiers.

So using my example then, what would you suggest?
Should I use two 400W peltiers and run them at only 200W each, giving me a total of 400W in the end?
If not that, then what would be the best way to achieve about 400W of cooling power using peltiers?

[bigben2k]

The answer to your (original) question really, is, which one is composed of the more efficient elements?

Each TEC is composed of many, many small junctions.

I say it doesn't matter which way you go, but if you're looking for efficiency, then you want to pick the most efficient TEC, and work your way up from there.

Otherwise, 400W Pelts are not common; it might be cheaper to go with smaller units.


Undervolting seems to produce the most efficient results around 70 to 85% of Max rated voltage, but you'll need to check the specs (you might have to do a bit of math).

[XyBeRWaReZ]

Originally Posted by bigben2k

The answer to your (original) question really, is, which one is composed of the more efficient elements?

Each TEC is composed of many, many small junctions.

I say it doesn't matter which way you go, but if you're looking for efficiency, then you want to pick the most efficient TEC, and work your way up from there.

Otherwise, 400W Pelts are not common; it might be cheaper to go with smaller units.


Undervolting seems to produce the most efficient results around 70 to 85% of Max rated voltage, but you'll need to check the specs (you might have to do a bit of math).

Wow, thanks for the good info. It's pretty much what I was hoping for.

Sorry, 400W was just an example, I didnt' research all the exact different wattages yet so I just wanted to throw something out there so everyone gets the idea.

I'll be searching through the different companies for the most efficient pelts. In the meantime, do you have any suggestions on which models would be, in your opinion?

[Ls7corvete]

Should I use two 400W peltiers and run them at only 200W each, giving me a total of 400W in the end?

Something like that, see below

you might have to do a bit of math

Yup, or run kryotherm.

pick the right TECs from the start or you are doomed, dont build around a certain pelt, choose a pelt to suit your system.

[TerraMex]

Phase change, if I could I would, but even then there are a couple of problems I don't like with phase change units.

1. They're damn expensive!
2. They're pretty noisy
3. If something should leak, I could DIE!!!
4. I have kids, not a good combo.

Peltiers is what I'll stick to. Thanks for the suggestion though.

1) By comparison on what you need to buy, the number of tec's, psu's, blocks, etc, i really have my reservations on that statement. You can get a resonable AC system for 200 bucks, complete, including assembly.

2) that's why they have ajustable settings . And the main unit sits outside of the house.

3) hardly.

4) keep the remote hidden.

[XyBeRWaReZ]

Originally Posted by TerraMex

1) By comparison on what you need to buy, the number of tec's, psu's, blocks, etc, i really have my reservations on that statement. You can get a resonable AC system for 200 bucks, complete, including assembly.

2) that's why they have ajustable settings . And the main unit sits outside of the house.

3) hardly.

4) keep the remote hidden.

Sorry, not trying to ruin anyone's party but I'd still have to stick with the pelts. There are a couple of other things that I forgot to mention.

1. I don't own my place, I rent unfortuantely for now.
2. Air conditioning units must have a lattice cage around it for the asthetics of the property as a whole. Can't have ugly parts hanging out the window. I can get kicked out of my place. Lots of rules here, like over 50 pages of them! Crazy Bastards!
3. AC system, WAY TOO BIG!!! With a pelt system, I can put the computer where I want. The only mods is maybe to my case which is a mid-tower, or just get a full tower.

I have not doubts that this will work. It's just that I need to make sure that I don't waste as much time and energy as possible while doing so. I don't mind the trial and error method, but I don't have the funds or the time to do so at this particular moment. Maybe a little bit later when I have tons of cash and free time, then I wouldn't really care, it's a good learning experience and I'd be able to tell from experience, and not just quote other people and using theories.
I'd rather use what little resources I have at the moment to find out as much as possible, so when it looks good on paper, then hopefully everything should flow smoothly when actual build time comes.

I've found another little question regarding this setup. When blowing air over heatsink on the cold side of the pelt, is it better to use a typical type case fan or using a crossflow design fan? I've read up a little bit more about it and I've found out that supposedly using crossflow uses less power and is more efficient. With typical fans, you have a dead area directly underneath the motor area of the fan so any heat in this area isn't cooled very much at all, which kind of defeats the purpose. I believe that this would hold true to moving cold air also. The cold air in the middle would not do much to cool anything else, except maybe the motor of the fan some.
With the crossflow design, air would move over the entire surface of the heatsink and push more of the cold air out and making it an overall more effective unit.
I'd greatly appreciate it if someone could confirm if this is correct or if there are other factors that need to be involved or might affect the performance.

Thanks everyone for your help on this project.