Compressor-free refrigerator may loom in the future

Aug 07, 2008

Refrigerators and other cooling devices may one day lose their compressors and coils of piping and become solid state, according to Penn State researchers who are investigating electrically induced heat effects of some ferroelectric polymers.

"This is the first step in the development of an electric field refrigeration unit," says Qiming Zhang, distinguished professor of electrical engineering. "For the future, we can envision a flat panel refrigerator. No more coils, no more compressors, just solid polymer with appropriate heat exchangers."

Other researchers have explored magnetic field refrigeration, but electricity is more convenient.

Zhang, working with Bret Neese, graduate student, materials science and engineering; postdoctoral fellows Baojin Chu and Sheng-Guo Lu; Yong Wang, graduate student, and Eugene Furman, research associate, looked at ferroelectric polymers that exhibit temperature changes at room temperature under an electrical field. These polarpolymers include poly(vinylidene fluoride-trifluoroethylene) and poly(vinylidene fluoride-trifluoroethylene)-chlorofluoroethylene, however there are other polarpolymers that exhibit the same effect.

Conventional cooling systems, -- refrigerators or air conditioners -- rely on the properties of gases to cool and most systems use the change in density of gases at changing pressures to cool. The coolants commonly used are either harmful to people or the environment. Freon, one of the fluorochlorocarbons banned because of the damage it did to the ozone layer, was the most commonly used refrigerant. Now, a variety of coolants is available. Nevertheless, all have problems and require energy-eating compressors and lots of heating coils.

Zhang's approach uses the change form disorganized to organized that occurs in some polarpolymers when placed in an electric field. The natural state of these materials is disorganized with the various molecules randomly positioned. When electricity is applied, the molecules become highly ordered and the material gives off heat and becomes colder. When the electricity is turned off, the material reverts to its disordered state and absorbs heat.

The researchers report a change in temperature for the material of about 22.6 degrees Fahrenheit, in today's (Aug. 8) issue of Science. Repeated randomizing and ordering of the material combined with an appropriate heat exchanger could provide a wide range of heating and cooling temperatures.

"These polymers are flexible and can be used for heating and cooling, so there may be many different possible applications," said Zhang, also a faculty member of Penn State's Materials Research Institute.

Besides air conditioning and refrigeration units, applications could include heating or cooling of a variety of clothing including cooling of protective gear for fire fighters, heating of mittens and socks or shoes for athletes, sportsmen and law enforcement officer and even cooling of mascot and cartoon character costumes. Another application would be in electronics, where small amounts of the polymers could effectively cool over heating circuit boards and allow closer packing, and therefore smaller devices.

Source: Penn State

Explore further: Information storage for the next generation of plastic computers

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User comments : 22

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thales
4 / 5 (1) Aug 07, 2008
Thermal sponges.
magnumpc
3.7 / 5 (3) Aug 07, 2008
I can hear my 4-year son complaining to me that he's hot and his shirt isn't working... :)
drel
3.3 / 5 (3) Aug 07, 2008
So how would this work? The panel gives up heat then the panel absorbs heat. Place it inside an "icebox" and the box heats up, then the box cools back down, repeat. So what is the mechanism by which heat would be transported OUT of the "icebox" thereby cooling the contents?
Noumenon
4.9 / 5 (49) Aug 07, 2008
Interesting, similar to peltier devices or thermoelectric cooling, except with plastics.

Good to see the mascot suite over heating problem finally solved,... I mean why even mention anything other than processor and circuit cooling.
SLam_to
5 / 5 (2) Aug 07, 2008
Yes, glad to see electronics cooling is in the "others" column, and "mascot cooling" is one of the primary uses.

You know I keep mentioning this, but what is the material's efficiency? What about of cooling do you get for the number of watts you put in. I think Peiltier coolers are 15% efficient, compressors have gotten up to 40-60% efficient (ala Wikipedia).
Sean_W
1.3 / 5 (3) Aug 07, 2008
Drel: (I am no expert so if I screw up the explanation someone correct me.) It seems that unlike conventional refrigeration which transfers heat out of a space, this system created order which the heat is used to destroy. There would be heat created (or some kind of increase in entropy) at the electricity generation source but not in the fridge or AC. It would be as if the electricity were creating a type of ice in the substance which the heat in the local environment was used to melt, reducing the local temperature.
gopher65
5 / 5 (2) Aug 07, 2008
drel, a normal refrigerator uses a radiator to rid the compressor of heat (on mine the entire back of the fridge is covered in the radiator). I suspect that this would use exactly the same heat dissipation mechanism, it's just that the method of transferring heat from the interior of the fridge to the radiator on the back will change from a compressor to this "new" approach.
bredmond
4 / 5 (1) Aug 07, 2008
Can they use this to cool materials to a superconducting state?
Sonhouse
5 / 5 (2) Aug 07, 2008
Not at this time, superconductors still are far below zero and these devices are generating only about 20-25 degree temperature difference. Another issue is, like Peltier devices, it still takes energy to run. The main question, can it be more efficient than mechanical refrigeration?
In my field of photonics, we use Peltier's about the size of a small postage stamp to keep a photonic circuit at an exact temp, like 34 degrees C exactly within 1/100th of a degree, that is how we tune the frequency of the laser output (the infrared 'color'). There is a circuit that turns the direction of current flow 'backwards' to cool and 'frontwards' to heat, so with tiny temperature sensors called Thermistors and tiny amplifiers, the act together to acheive some exact temperature. The same could be done with these plastics. The key to a viable and improved device is the energy efficiency, that is to say, how many watts does it take to move X amount of calories or BTU's, however you like to call heat, is it going to actually be more efficient than mechanical refrigerators.
E_L_Earnhardt
2.7 / 5 (3) Aug 07, 2008
Sure! "Heat" is energy. It is expressed by the electron spin and speed. Spin up an electron and you have "heat". Slow it and the temp. goes down.
All we do with the freon is crowd it into a small space, decreasing orbit, and it speeds up!
Graeme
not rated yet Aug 07, 2008
How it could work:
Perhaps a belt of the polymer could be made, inside the fridge it leaves the field, absorbs heat, and outside in the radiator part it enters the field and liberates heat. Or alternatively perhaps beads of polymer could be pumped around in a fluid, or just keep the polymer in place and pump the heated or cooled fluid to appropriate places.
Arikin
not rated yet Aug 08, 2008
Is there any magnetic fields generated from these?

I would assume not very much but... I don't want gramps with his pacemaker dying because he went to the frig to get a sandwich.
AncientSkyman
5 / 5 (1) Aug 08, 2008
An interesting feature of the Peltier device is that you can apply heat to one side, and if you can keep the other side cool, it will GENERATE electricity. I've been experimenting with Frensel lenses focusing solar light to a sharp point, and get around 400 degrees F. I keep the opposing side cool with a CPU heat sink sitting in a water bath. I'm getting about 15 watts from a Peltier about 2" square. I know I can do better, but it's a start!
visual
5 / 5 (1) Aug 08, 2008
An interesting feature of the Peltier device is that you can apply heat to one side, and if you can keep the other side cool, it will GENERATE electricity. I've been experimenting with Frensel lenses focusing solar light to a sharp point, and get around 400 degrees F. I keep the opposing side cool with a CPU heat sink sitting in a water bath. I'm getting about 15 watts from a Peltier about 2" square. I know I can do better, but it's a start!


what is the lens area?
and at what heatsink temperature does your system stabilize? is it even stable at all?
AncientSkyman
5 / 5 (1) Aug 08, 2008
To Visual:

Lens Area = 750 cm2

Heatsink stablization temp time = Approx 8 minutes

Heatsink Temp = 58 degrees Celsius

I use a solar powered fountain pump to move water from the bath into a 8" diameter copper cooling coil, which moves the water down thru the 'cooling tower' and back onto the heatsink . . so there is constant flow of cooled water going on the heatsink.

Hope this helps . . .
AncientSkyman
not rated yet Aug 08, 2008
Caveats: I live in South Florida, and this is in full sunshine. Even a few clouds drop peltier surface temp. very quickly and power drops accordingly. . .
googleplex
not rated yet Aug 08, 2008
Another factor is decay of the material over time. How stable is the material?
The dirty secret of photovoltaics is that they have a half life of 12 years or so. This as to be factored into the total cost. Perhaps they can be recycled and a discount given for the new version.
mrlewish
4.5 / 5 (2) Aug 08, 2008
Isn't anybody going to point out that you can run refrigeration without special gasses and that regular air will do in a system designed for it? Sure it bulkier and less efficient (per energy spent) but no need for special gasses/liquids.
Alexa
3 / 5 (2) Aug 08, 2008
Nice video, which illuminates the principle a bit...

http://www.youtub...CiSyI9oE
Soylent
5 / 5 (4) Aug 08, 2008
Sure! "Heat" is energy.


Heat is the transfer of thermal energy from one object to another; the word you're looking for is internal energy.

It is expressed by the electron spin and speed. Spin up an electron and you have "heat". Slow it and the temp. goes down.


Nonsense.

There are many forms of internal energy. Absent chemical reactions or phase changes the most important are the rotation and translation of molecules, electrostatic potential energy and vibrational states of molecules. Bound electrons have access to only a few energy levels that are far inbetween; excited electron states do not make a significant contribution to internal energy at room temperature. Conduction band electrons in conductors can be thought of as almost free-moving in the crystal; they make a signficant contribution to the internal energy and heat conduction of those materials.

Electrons are spin-half particles. If you measure their spin the only result you can get is spin half up and spin half down. Absent a strong magnetic field those states are at the same energy level. They are not a significant way to store internal energy.

All we do with the freon is crowd it into a small space, decreasing orbit, and it speeds up!


Nonsense. Compressing a gas heats it up because you are doing work on the gas. Moving a piston will on average give freon molecules an extra push when they bounce of the piston, making them bounce around faster, rotate or vibrate faster.
Sowdi
4 / 5 (1) Aug 10, 2008
So how would this work? The panel gives up heat then the panel absorbs heat. Place it inside an "icebox" and the box heats up, then the box cools back down, repeat. So what is the mechanism by which heat would be transported OUT of the "icebox" thereby cooling the contents?


It's really quite easy, simply layer the material with an electrical insulator but a thermal conductor and set the layers going such that thermal energy released by an interior layer is absorbed by its adjacent layer which closer to the outside of the box. Supposing that the outer layer is cooler than the inside of the fridge then the overall heat flow should be going outside. While changing the frequency would allow you to control the heat flow and hence the temperature inside the fridge.

EDIT: I also want to add that 22.6 degrees Fahrenheit converts to -5.22 degrees Celsius, wow!
jeffsaunders
3.5 / 5 (2) Aug 11, 2008
Great stuff - thermal underwear - refrigeration and heating by application of electricity.

Of course we do that now with bar radiators and heat pumps but I gather we are expecting the electricity consumed by these field generators to an order of magnitude less.

Perhaps I am being overly optimistic and that the consumption of electricity will not be any less than already existing heaters and coolers. Lets hope that is not the case. If the consumption of power is no less than currently used but also is not much greater, then these things still will find plenty of applications. As the heat exchange mechanisms that may be used in conjunction with electric fields may include innocuous substances.

I do enjoy explanations that can be understood by lay peoples in all fields but I think a cost factor in terms of power consumed would not be out of order.

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