Thermoelectric Cooling
 

I was reading on Newegg and I saw some one mention peltier cooling and I didn't know that it was so a quick google search gave me everything I needed to know.

http://en.wikipedia.org/wiki/Peltier_cooler

Peltier coolers are being used in some CPU heatsinks and allow extreme over clocking because they get so cold with just a 12V power supply. Then I thought if they are using it on a CPU couldn't you use it on an ESC and get the same results and not have to worry about a fan (maybe not because one source said condensation may be a problem).

Then I looked for the prices and they are pretty cheap and I really want to give these things a shot.

http://www.virtualvillage.com/45w-th...eltier%20Plate

Seams like it could be a very good option for people who just HATE fans...
cough* *cough* BrianG *cough*

Let me know what you think?

Not too good for R/C use. First, the pull at least 3A of current, so that would hurt runtime. And then, you still have to use a fan to cool the "hot" side.

You are using power to create a temperature gradient. The one side gets cold, but at the expense of another getting hot. You need to have a HS and really a fan on this side to dissipate the heat. You would need quite a bit of power to create meaningful cooling for our purposes, and quite a bit of electrical infrastructure. BrianG would flip his freaking lid. ;)

Its really not very practical.

that sounds nice but 1 hot wire makes 1 cold, off what "pump"? I thought id just let BrianG answer that 1 as i shock myself with the carpet for fun and still don't see the issue with eating lead paint chips. If it worked well and was $7.99 im sure someone would have used it by now

Here lists the physics of how it works, but the simple answer is you are trying to fight the laws of thermodynamics. You can do it, but it requires energy.

Basically you are using energy to force heat from one location to another. Its not 100% efficient either. The heat you removed (plus the energy you lost in inefficiency) has to move somewhere and be dissipated.

ok i get it (somewhat) I didn't mean to sound like a jerk in my previous post with the if it was $7.99 and no ones used it thing. I was serious, if anyone can get this to work maybe some of you can, does anyone have a pic of this small heat pump ? LINK I need more. Feed me

Yesp, not worth what you get IMO. There are ultimately three ways to deal with heat:

1: More efficient components.

2: Less current.

3: Heatsink with thermal mass and surface area.

Everything else is just adding complexity.

I have two Quark 125's that use the top plate (connecting the three diffs) as a heatsink and it works wonderfully without the need for any additional active cooling. The chassis is another good heatsink and gets lots of airflow. I just wish more ESCs were built similar to the Quarks in how the FETs are mounted...

You want pics of a phase change heat pump? How about seeing the real thing in person. Just walk over to your refrigerator/freezer, or house/car air conditioner.

Any current method of active cooling requires a substantial amount of energy; whether that is with Peltier junctions, or condensor/compressors. The advantage of Peltier junctions is that they have no moving parts to wear. Another interesting thing about them is that you can reverse which side is cold and hot simply by reversing the polarity of the input power. Many portable camping refrigerators use these devices.

The way I was understanding this technology was that it just turned electric heat/ energy into cold. My fridge and stuff as I understand it have freon or the greener version now which does it. (im no hvac but I was debating going to school for it as my marketing degree has proven worthless). I have fingers I can look around I dont want to be a dense annoyance and I don't expect you all to educate me for free lol but maybe a hint or 2 where to look or just keep going on the OPs topic and ignore me and ill learn from there.

So if the extra power consumption wasn't a big issue then the quark would be one of the better esc's to try this on, right? Mount the plate between the esc and chassis. Like you said, it just transfers the heat and the chassis has thermal mass with lots of surface area and lots of air flow.

I can't see it benefiting other esc's like the mmm, rx8, hw150...etc without having to modify the casing.

But if you do work something out, we'll need to see pics :mdr:

Yes, your fridge/AC uses a coolant which needs to be compressed and pumped to cool. The Peltier junction does the same thing, but electronically instead of mechanically (or would it be chemically?). Don't feel bad about the degree, my AAS has also proven worthless. Neat for this hobby, and to fix odd stuff around the house, but useless otherwise.

Yeah, but any type of active cooling is going to draw a decent amount of power. In a home appliance, the difference in weight or the difference in "runtime" in a 1:1 vehicle is irrelevant (unless you are concerned about fuel economy). But in the R/C world, both of those are major considerations. A Peltier junction big enough to pump ESC (or motor) heat would take at least 20-30watts. That can put a big dent in runtime. The point I was making wasn't necessarily about the Quark specifically, but more about how its design was ideal for mounting in such a way to use the chassis (or mounting plate) as a natural heatsink without the need for fans or active cooling devices.

Muchmore racing has a unit for RC but it's for cooling the motor prior to racing..... and a lil more than $7.99

http://www3.towerhobbies.com/cgi-bin...?&I=LXTYY8&P=7

Brians right it takes a lot of current and they will never handle the loads placed on them in a RC. I have used them for a lot of things playing around with them and they are very fragile, basically you have 2 ceramic plates with a bunch of what look like surface mount caps sadnwiched between (these are the PN junctions). Wiki is not the area you want to look for real information on this (or anything else for that matter). They are very brittle and can break easily Shear loads are real bad on them and I have ruined a few just from dropping them on a table.

Go here then start reading the rest of the info at the bottom of the page. There are a few.

http://www.ferrotec.com/technology/t.../thermalRef01/

a module that will draw 6A @ 12V will pump about 170 BTU's. With 6 of these modules I was able to pull a 2# block of aluminum down to 5.5F in 20 minutes using a water cooled system And drew over 36 amps continously. I have a little one that will bring a small heatsink to the point where it's white from condensation in a few minutes using a 3S A123 pack, but it draws 4 amps ALL THE TIME. I have it graphed in my eagle tree, I'll post it up when I get home. I also have a module that will draw 30 amps all by itself.

And you can also generate power with them as well, pretty cool


http://www.rc-monster.com/forum/showthread.php?t=23193

There is a pic in this thread with the water cooled one I made.

Dude! that's awesome! for 7.99 do you guys think I can stick that thing between my AMD Sempron CPU and it's huge heat sink? Or should I just go with a professionally made unit? I would love to give my cpu frost bite.....

I thought I remembered them being fragile too, but wasn't sure so I didn't post it. I too did some experimenting a while back, and they are pretty interesting. It's been a long time (and I don't feel like searching right now), but I have a question for you. I understand the application of current causes heat to be pumped from one side to the other. Now, let's say we are applying 12v @ 5A through a device. How much of that 60w is being dissipated as heat on the hot side? In other words, what is the efficiency. So, not only do you have to get rid of the heat being pumped, you also have to get rid of the heat produced from any efficiency losses.

You might need to either get a fairly large one, and/or stack them. They have a limited delta temperature rating, so the amount of cooling you get will be determined by the ambient air temperature, the amount of heatsinking you have, current flow through the device, and the device rating. I'm sure I don't have to tell you that if the device cools below room temperature, you will get condensation. So, your CPU will get frostbite, but also get waterlogged. Not good. :wink:

Brian,

On the efficiency 2 numbers pop into my head 30% and 65%, I'll look it up I have the notes, I think here at work.

You really need a large heatsink on the "hot" side (if you reverse polarity the change sides), they are capable of 70F temperature differentials so the colder you can keep the hot side the colder it gets on the cold side.

Think of this if the air temp is 100F and you can keep the hot side at 135F then you can only get the cold side to 65F. I used large fans or water cooling for my large projects. One thing you have to deal with on electronic applications is condensation. I shorted out a few devices (was able to fix them but that is another story), just because of that. They are really cool I have a dual probe digital temp (K-type) that I tracked temps with. It’s really neat to see the condensation form and then all of a sudden it starts turning to ice all across the plate.

Jeff

OK so since they won't work for cooling how about using the heat from the ESC to heat the pad up and create minute amounts of current to increase runtime. I don't think it would be anything substantial but just another idea...

It’s all about temperature differential the hot side can be hot but you need another heatsink to at least ambient temp. I had an array that was using the 6 70W units and had a ¼” aluminum plate painted black with a heatsink and muffin fan on the “cold” side and was able to charge a 12V battery at about 2.5amps in sunlight when water cooled I could get about 4.5 amps out of it. But that was with forced cooling and 6 wired in series.

They are fun to play with check out the Ferrotech link I posted there is all the tech you want there.

Jeff

Brian I couldn’t get any efficiency numbers because there are so many variables. Things like thermoconductivity of the heating and cooling sinks, losses from insulation between the hot and cold side losses from the cold side to ambient air and so on. From best I can tell from some of the units I have they are capable of pumping about 170 BTU and it takes 76 watts to do that so that comes to about 69.19% using a 127 thermocouple device.

Here are a couple of pics I took of a little setup I did a while back and fired up today on 4S a123. This one was made with a CPU heatsink and the fan attached I added a second larger fan because 1 just wasn't cutting it, the heatsink temp rose too much (about 45F above ambient and now it's about 20F above ambient). The cold side is a chunk of 3/8" aluminum 2"X3"X3/8" thick and a little baby heatsink I just stuck on it for the heck of it, it's about 1" square and 1/2" tall.

Jeff

You're absolutely correct.. I've tried cooling with the TEC from ebay... it was just a waste... although it's good for cooling the motor after running, but during running... it's just a waste... Although it could be good for a closed system water cooling for the bigger scale stuff.. if you could have the hot side exposed on the outside..

Not even for the big scale stuff the more transfers you have the more losses you have a well designed heatsink system will outperform even a watercooled system if you have real long run times (an hour), thermoelectrics add complexity and you are going to loose 30% right off the bat. Run off of a power supply they are great, but batteries even Li-po you are going to run out of power in a hurry. When I charged my 4S1P pack last night I put about 1.4Ah back into it and only ran it for about 25 minutes give or take 5. I was going to graph it but I didn't bother I may later today with the temps and everything so you can see how they can perform.

JEff