A lightweight, flexible thermoelectric fabric called Power Felt could generate enough electricity from body heat to power a small electronic device, like an iPod, or iPhone.
The fabric, composed of carbon nanotube/polymer thin films, was developed by a team headed by researchers at Wake Forest University's Center for Nanotechnology and Molecular Materials. Power Felt generates an electrical charge from temperature differences, converting thermal to electrical energy. Examples include the difference between room temperature and body temperature, or between the temperature of a jacket liner next to the body and that of a jacket exterior exposed to cold air. Alternately, the fabric could be layered under roof shingles, line car seats, be wrapped around hot water pipes, or be integrated into a wound wrap to power medical monitors.
Alternating p-type (red) and n-type (green) nanotube/polymer heterogeneous thin films, with insulating polymer films (blue) between the conduction layers, form a lightweight, flexible fabric that could generate enough electricity from body heat to power portable electronic devices. (Source: Wake Forest University)
The fabric consists of a carbon nanotube/polymer composite thin film comprising multiple layers of multiwalled carbon nanotubes and polyvinylidene fluoride. The multiple layers are alternating p-type and n-type nanotube/polymer heterogeneous thin films with insulating polymer film layers between conduction layers. Layers are pressed together vertically and heated to about 425K to 450K to melt the polymer enough to bond the layers together and form a felt-like fabric. The resulting thermoelectric voltage results in increased power output as layers are added.
Generating electricity with thermoelectric material requires high efficiency levels. High-efficiency materials, usually made from bismuth telluride, have been used for CPU cooling and mobile refrigerators, but their cost (as much as $1,000 per kilogram) makes them too expensive for high-volume consumer applications. The researchers say Power Felt can be less expensive to manufacture, lighter, and easier to process than bismuth telluride, so it is more suitable for a number of applications, including portable electronics.
Wow, this is really cool stuff. Think about all the crazy applications and gear that would come out by taking advantage of this technology. I would imagine beyond powering up simple consumer devices, there could be huge applicability for life-saving medical applications.
There do seem to be a lot of interesting and novel materials applications coming out that are based on, or incorporate, CNTs as an important ingredient. I wrote about some early methods for constructing CNTs about a decade ago and wondered how long it would take to see them start to be actually used.
naperlou, I remember the push for wearable devices you are referring to. It actually wasn't that long ago, a decade or less. I seem to remember that keeping them powered was a problem. Looks like we're getting closer to that solution.
Another interesting application of carbon nanotubes.This is a very interesting technology, and very appropriate for so many of the devices we use every day.With the advent of platforms that use ultra-low power processors the applications should be wide.It is also interesting to contemplate using the waste heat from a device to power that device.
Years ago there was a push on for ubiquitous, wearable computing devices.These were seen as wearable computing platforms.This is a technology that might help bring that area of research back.
Another interesting aspect of this is the parallel with nuclear space power.Although there have been active nuclear power generation systems for space, these have been rare.One of the issues, of course, was the moving machinery.The most common type of nuclear space power is the RTG, or Radioisotope Thermal Generator, converted a delta-T to a delta-V. And there are no moving parts. These are the devices that power the interplanetary flights.The principle is the same, but the materials completely different.Of course, you would not want to wear a RTG since the heat source is pure plutonium.
Kevin, thanks for your comments. As the story points out, current high-efficiency TE fabrics like bismuth telluride are very expensive, and this particular fabric is aimed at high-volume low-power consumer apps, or medical apps like wound wraps, which those more expensive materials don't or can't address. What other types of applications did you have in mind?
Nice article, Ann. One thing I like about this material is that it's not based on movement or vibration. The U.S. Military is using a wearable generator attached to the boot. But it requires movement. The self-charging batteries for remote sensors rely on vibration. A power generator based on temperature variations wouldn't require motion or vibration. Cool.
Thanks Rob. Good point about not needing movement to activate energy harvesting, like that Army boot. OTOH, considering the amount of walking around soldiers do, it makes sense that the military would be looking at apps that harvest energy from movement. And also considering the lack of exercise many people get, it might make more sense to motivate us by working on movement-activated energy harvesting for consumer devices. I guess it makes sense to have different technologies that can harvest different kinds of energy.
Ann, if such innovations are happening, it’s a bonus for the gadget users. Most of us experience the power crunch, while using phones/IPad/ Smartphones. So whenever the battery power goes down below a certain level, it can be recharges immediately from the fabric, wonderful idea and hope then onwards no power drain.
To the user wearing the fabric it would provide a cooling effect. This would be advantagious for the foot soldier, especially when also wearing the boot generator. Overall efficiency is increased when both are employed together.
Energy harvesting is the need of he hour. Autonomous systems with energy harvesting will offer better workflow soultions and that will in turn result in better products. I am working on a structural health monitoring system with energy harvesting and I know and I am sure like this wearable fabric may other invention will soon see the light of the day in coming days.
@Chas - I was wondering the same thing. What happens when you are not wearing anything to be powered. On top of that, with some concerns about the unknown effects of power lines and such, I wonder what the acceptance will be about having your body wrapped in a generator. Not saying I agree with those concerns, but if the questions are out there....
From the standpoint of thermal dynamics, I would assume that since the fabric produced electricity it also causes the cool side to warm up and the warm side to cool down. So if I as a consumer buy a coat made of this fabric to stay warm and charge my phone with it. Since the warm side is being cooled, will the coat be able to keep me warm?
On heat transfer:This material is converting the energy (temperature) differential to another form of energy differential (electrical potential, or Voltage), which creates electrical current.I would believe that this would not change the heat storage characteristics of the coat, etc., significantly for two reasons:
1.Entropy:The material is not "creating" energy, but routing it.
2.Magnitude:We're probably talking microAmperes, or at best milliAmperes – probably not a significant enough energy exchange to be felt...
This whole concept sounds like a great idea to me - in our low-power device world - if applied well and if efficiencies can make it up to a useful level.
On ESD (electrostatic discharge): I would not think such a material would build a static field charge, but rather dissipate it (or maybe even USE it?).
Walt is correct. Energy is generated from a temperature differential, for example, as the story says, "between the temperature of a jacket liner next to the body and that of a jacket exterior exposed to cold air." In that case, the generation of electricity would not cool down the wearer of the jacket. This is explained in more detail in the journal article. I don't recall seeing anything about static electricity, and I don't see why that would occur with this material. If it did, I suspect the material would likely make use of it.
The material works in the lab. I'm interested in use in the real world. Put the jacket on, head outside.
How will PowerFelt perform when the wearer perspires? When it rains?
Earphone wearers who exercise frequently complain when their stereo headsets stop working because of perspiration. One would expect similar problems with anything electrical in nature in close proximity to the human body.
Good question, TJ. Since the lead author on the journal article, Corey Hewitt, mentions several different uses that are exercise and sports related, he may have already thought of that. I suspect this would be much less of a problem if it's used in a jacket liner material.
I re-read this article, Ann, and now I am wondering how long this material could power an iPhone. That seems like it would take a pretty fair amount of current compared to the tiny sums I've seen in energy harvesting.
I don't have all the details, but there are quite a lot in the journal article I linked to in my article:
Unfortunately, it's a for-pay article, although the university's PR office sent me the original, which of course I can't share. In any case, thermoelectric fabrics and materials are different from some of the other schemes I've seen, they appear to be more efficient, and this one seems to be a much more efficient energy-harvesting method. Plus, because it's wearable, it's supposed to be continuous.
Having played some with generating power from bismuth telluride modules, I have to wonder what they think "high efficiency" is. To me it's dismal, and the fabric will fare no better. You need high delta-T, established by high heat flux, to get any useful output. A well-heat-sinked 20W Peltier module on my stove was hard pressed to power its own cold-side muffin fan, whose draw is something like an active iPhone (tens of mA). At a much higher delta-T than a human body would produce against any tolerable ambient. You can't have high heat flux at the skin, and comfort both. Defeats the whole purpose and function of clothing.
The energy harvesting space is the new home for snake oil. Yeah, the energy you collect (over a period of hours) can power your portable device (for a period of seconds to minutes). Those bits of info never seem to escape the editing process when marketing runs the show.
Ann, that is my PhD thesis. I am planning to use Energymicro lowpower processor and energy harvesting from Linear technology. I will update you as I progress. my mail id is email@example.com . Please do give me your mail id so that i can send you my review paper and also synopsis if you are interested to read. i am trying to explore the possiblilies of energy harvesting for SHM for aricrafts
I am a biomedical engineer and i am keen to explore this in vital parameters monitoring too. Do enlighten me about your ideas so that i know more about energy harvesting. I will update you about my PhD as time progresses.
Thanks for the reply, vimalkumarp. My area of coverage for DN is materials, not energy harvesting per se, which is why I wrote about the Power Felt fabric. Several of us DN editors report on energy harvesting and SHM (although none of us are experts) and I'm especially interested in materials that aid SHM for aircraft. I've passed on your contact info to my colleagues. In any case, please do let us know when you are done with the thesis and have your results.
energy harvesting is excellent idea but one important aspect is that the design should consume less power. This is how an energy harvesting application can complement or vice versa a low power consuming design.
Reading the title of this article and the first paragraph has left me at a loss for words.
Is the author commissioned by Apple to write the article? Or is it just that all journalism students are weaned on the idea that Apple provides the only technology on planet earth? There appears to be no valid reason to relate this technology to a specific manufacturer.
Perhaps a more appropriate title should have been "Wearable Fabric Could Power Your Mobile Devices"
and the first paragraph should read:
"A lightweight, flexible thermoelectric fabric called Power Felt could generate enough electricity from body heat to power a small electronic device, like an MP3 Player, or Mobile Phone."
Kirk, I don't understand your critique. The iPhone is the most well-known cell phone, and our headlines have to be short. Ergo the headline we chose. Generally, lead sentences and paragraphs also need to be short and concise (which are not always the same thing), ergo the lead sentence we chose.
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