Thermoelectric Cooling+Heating Blanket

Using Arduino Project Guidance
#1

I want to build a blanket or mattress pad that heats the head and feet areas and cools the rest of the body.

I want to achieve this with thermoelectrics: these are solid state components that use electric power to pump heat. One side becomes cold and the other side becomes hot.

Here are some thermoelectric components I ordered from Amazon:

I imagine that such a device would probably need three materials:

  • A thermal conductor to distribute the temperature treatment throughout the blanket or pad. Ideally, I could find a fabric-like or at least flexible thermal conductor with reasonable conduction speed and efficiency.
  • A thermal insulator to keep the hot and cold areas separate.
  • A surface fabric to protect the user from extreme temperatures, but still allow the temperature treatment through. This should probably be in between the insulator and the conductor material.

Any ideas or suggestions on these? I feel like the basic premise is viable, I'm serious about putting effort into this, but I suspect some feedback from more experienced people would be extremely helpful at this stage.

This is a prototype for a product that could potentially be a consumer product. The prototype has to work, but simplicity is preferable.

Is there a better web site to ask this or is this site a good choice?

#2

I want to achieve this with thermoelectrics: these are solid state components that use electric power to pump heat. One side becomes cold and the other side becomes hot.

How do you plan to sleep on both sides?

#3

PaulS:
How do you plan to sleep on both sides?

Very funny.

The temperature from different two-sided areas of the bed pad or blanket would be thermally connected to the different sides of the thermoelectric component.

#4

Its not funny
Thermoelectric effect just mones heat from one side to another , you still have to remove or gain heat frome some sort of sink, without the sink it can only get hot.

#5

I understand that. really... maybe a diagram will clarify?

This is a side-view of the blanket. The middle is cool. The ends (head/feet) are warm.

the black represents insulating material. the gray is the moderate conductor that would be close to the user's skin. This isn't to scale obviously.

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#6

thermodale, I see that you are serious about this.

To get low temperatures, the peltier is used, or with pressure/vacuum like in a refrigerator, or by vaporating liquids.

You have a peltier, mostly called 'TEC'. Those are not flexible and require a lot of current, and a heatsink on both sides.

The main problem is to get the cold and heat away from the TEC and distribute it.
That would need perhaps copper plates of at least 1 or 2 mm thick. I think you can never ever do that with a fabric.
If you want it to be flexible, you need a liquid to get the heat and cold from the TEC.

I suggest to buy a number of those TECs and test them.

They are only 2.50 dollars (inclusive shipping)
When you power them, you see how much power they need, and how easy they overheat on the hot side.

When you have about 10 of them, you would need 10A or 100A. So you also need a big power supply.

I suggest to look at other options.
You could use warm and cool air and pump that into perforated tubes. That way, there are no electrical wires on the mattress which is safer.
You could use a unit under the bed that uses TEC modules with heat sinks to create both hot and cold air.

Instead of air you could use a fluid, and have that pumped around. With two closed circuits (one for the hot fluid and one for the cold fluid), the TEC modules can make it hotter and colder everytime the fluid passes the unit under the bed. But one day, it will start leaking. The leaking doesn't have to be very bad, the fluid is not pressurized and also some cold and hot packs have safe fluids (some are more gel-like).
http://www.icepower.net/en/products/ice-power-cold-hot-pack

The tubes for the fluid can be flexible silicon tubes. The standard as used for an aquarium are 4mm inside and 6mm outside, but there are also thicker tubes.

#7

You could try diving suppliers for information as its a common way of warming wetsuits in severe conditions.
Edit

Sorry i mean drysuits.
A garment is worn next to the skin with tubes in carrying water or brine .

#8

Heating vests are easy to make, just a heating wire and a battery.
A Cooling suit is something else.
Most use air blown into a suit, others use an ice pack.
This uses ice : http://www.veskimo.com/
Some use a suit with tubes and fluid through the tubes, and a backpack with a heat exchanger with a peltier. But I can not find a good working example for that.
Or you can wear a refrigirator on your back : http://stsl.gatech.edu/research-wearable.html

#9

First, thank you so much for the detailed feedback.

Caltoa:
If you want it to be flexible, you need a liquid to get the heat and cold from the TEC.

We already have a basic prototype with regular heat sinks, fans, and air channels. That's using fluid convection to transfer heat. I was hoping that a conduction system would be a competitive option, but maybe the answer is no.

Caltoa:
Instead of air you could use a fluid, and have that pumped around.

Air is a fluid. Fluids include both liquids and gases. I know what you meant though :slight_smile:

Caltoa:
That would need perhaps copper plates of at least 1 or 2 mm thick. I think you can never ever do that with a fabric.

If I google "thermal conductive fabrics" I see a lot of options. One arbitrary example:
http://www.foams.saint-gobain.com/US/TIM/ThermallyConductiveElectricallyInsulatingFabrics.aspx

That is targeting higher end commercial buyers. I'm a student/hobbyist and was hoping to try something out in the $100 consumer price range.

There are also articles discussing recent advances like this:

Caltoa:
I suggest to buy a number of those TECs and test them.

I have a handful of these.

#10

Those thermal conductive fabrics are for a heatsink. The heat is transfered straigth through the 'fabric'. Some heatsinks have them attached, I think some Intel stock coolers have a rubber sticky patch, that is almost a 'fabric'.
You can buy sheets of that on Ebay, I read in a glance 2,3, and 4 mm thick.
http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=(thermal%2Cthermally)+conductive&LH_PrefLoc=2

There are other kinds of silicone/sealant/elastomere:

But those materials are not even close to a copper plate of 1mm or 2mm.
You would want the heat to be transferred to the sides away from the TEC.

Your second link "High-Thermal-Conductivity Fabrics" still relies on tubes I think. The goal is to have better heat conductivity from the body to the cooling tubes. I think that would still not be good enough for you, despite the carbon nano stuff.

If I must, I can think of a way to do what you want:
When you use a water mattress. And TECs on it covering on the whole surface. On the TECs the silicone/rubber heat conductive matrial. That way you can control every TEC and they can release the cold/heat at the bottom to the water. You might need 180 TECs and it might need thousand amperes. Well, that's not very practical.

What is the medical goal ?

#11

Caltoa:
But those materials are not even close to a copper plate of 1mm or 2mm.

The standard metric of thermal conductivity is W·m?1·K?1 (Watts per meter per kelvin)

Copper isotropic thermal conduction: 385 W·m?1·K?1
Carbon nanotube axial thermal conduction: 3500 W·m?1·K?1
Carbon nanotube radial thermal conduction: 1.52 W·m?1·K?1

Radial conduction is basically non-existent, but axially, carbon nanotubes conduct heat at over nine times the rate of pure copper.

These numbers are from wikipedia. Carbon nanotubes can be made in different ways with different properties, and I suspect that thermal conductivity varies quite a bit based on that, but that these numbers are still probably reasonable ballpark figures.

Carbon nanotubes and nanowires have many properties that make them candidates for revoluationary improvements over copper and silicon in electronics, and they are hyped accordingly. However, that technology isn't ready today. My suspicion is that the same thing is true with carbon nanotube based materials for thermal conduction.

Caltoa:
Your second link "High-Thermal-Conductivity Fabrics" still relies on tubes I think.

carbon nanotubes. Those are "tubes" but quite different from macro scale water tubes.

Caltoa:
...use a water mattress...

ChiliPad is a commercial product that does something similar. I don't know if they use TEC or not.

Caltoa:
What is the medical goal?

There's a ton of research on temperature treatments helping regular people fall asleep and stay asleep through the night. Specifically, having cold hands/feet is a problem, so warming the feet is helpful. Also, warming the neck has shown to be helpful. However, people usually fall to sleep best when their body temperature is dropping, hence the cooled middle.

This is a prototype to help a company making fancy temperature controlled beds for normal people. I'm a university student working on a project, not an employee.

Huge thanks again for the thoughtful help.

#12

I read the document and the "High-Thermal-Conductivity Fabrics" is in my opinion used to transfer the heat from the body to the tubes of a few mm thick with liquid. So it would be an improvement, rather than a new way for cooling.

The ChiliPad is very interesting. The big fan in control unit indicates a heatsink for a TEC.
In Google cache for ChiliPad I found "Through the use of thermoelectric devices" (that is no longer on the website).
And also the ChiliBed mattress uses the tubes of a few mm thick on top.

My only solution (and only if I must) was a large matrix of TECs, which can get rid of the heat or cold on the bottom side of the TECs to a large amount of water.

I think there is no better way for cooling that with tubes of liquid or air.

Did you try Google Patents ?

Even a TEC mattress is patented:

I think it is a bad thing that vague and non-specific patents can be requested on something that was not even build, not even as proof of concept.

Good luck on your project.

#13

Caltoa:
I think it is a bad thing that vague and non-specific patents can be requested on something that was not even build, not even as proof of concept.

Yes patents suck for this.

I have often thought that once filed , apatent should only be valid for a period of time and extention to full patent can only be made by presenting a constructed device.

I have been frustrated by this before , with so called inventors trying to charge silly licences for doing nothing.

#14

I seem to remember seeing a dual temperature waterbed mattress when we were shopping for a new waterbed several years ago so each sleeper could have different heat settings. Could the same principle be applied but with 3 separate zones head to foot instead of 2 side by side?
Combined with electric blanket head and foot heating and a water pumped centre section for cooling. The water could be pumped over your peltier plates cold side and into the blanket.

#15

Riva:
I seem to remember seeing a dual temperature waterbed mattress when we were shopping for a new waterbed several years ago so each sleeper could have different heat settings. Could the same principle be applied but with 3 separate zones head to foot instead of 2 side by side?
Combined with electric blanket head and foot heating and a water pumped centre section for cooling. The water could be pumped over your peltier plates cold side and into the blanket.

I suspect the pumped water bit would violate the existing patent.

#16

Boardburner2:

Riva:
I seem to remember seeing a dual temperature waterbed mattress when we were shopping for a new waterbed several years ago so each sleeper could have different heat settings. Could the same principle be applied but with 3 separate zones head to foot instead of 2 side by side?
Combined with electric blanket head and foot heating and a water pumped centre section for cooling. The water could be pumped over your peltier plates cold side and into the blanket.

I suspect the pumped water bit would violate the existing patent.

#17

Caltoa:
I think there is no better way for cooling that with tubes of liquid or air.

aka convection. I think you are right... for now. Conducting fabrics with CNT look like a simpler cheaper more efficient future system that isn't fully ready right now.

Caltoa:
Did you try Google Patents ?

No. I'm just an engineer. The legal department can deal with that garbage.

Caltoa:
Even a TEC mattress is patented:

It's fairly obvious to use TEC them to cool a mattress surface. The other choices are passive cooling or a full traditional AC compressor system which is way to bulky to be practical. People always patent the obvious stuff and they can't always sue... I'm not into that legal stuff.

#18

Riva:
I seem to remember seeing a dual temperature waterbed mattress when we were shopping for a new waterbed several years ago so each sleeper could have different heat settings. Could the same principle be applied but with 3 separate zones head to foot instead of 2 side by side?

Yes, this is actually a great idea. The heating part is easy.

I suspect it might be impractical to cool a large water bladder with TEC. You could heat the water if you need to throttle down the cooling, but I suspect your max cool would be to simply cool the occupant towards the water temperature. If the bed is kept in a warm room, of say over 90 F, that might not be enough, but otherwise, if the bed is kept in more normal indoor temperatures, that is probably adequate.

#19

Caltoa:
I think there is no better way for cooling that with tubes of liquid or air.

How about PGS (Pyrolytic Graphite Sheet): http://industrial.panasonic.com/www-data/pdf/AYA0000/AYA0000CE2.pdf

"Excellent thermal conductivity : 700 to 1950 W/(m·K) (2 to 5 times as high as copper, 3 to 8 time as high as aluminum)"

The second heat path seems much more efficient than the first:
TEC -> heat sink -> air/liquid fluid -> surface
TEC -> PGS thermal conduction sheet -> surface

waste temperature would still be carried away by heat sink + air convection.

#20

We are still in 2014 !
You are 20 years ahead.
That Pyrolytic Graphite Sheet is only 100µm thin. It can never be use to transport any amount of heat sideways.