Converting heat directly to electricity? Thermoelectric nanomaterials are the answer

Thermoelectric Materials
Silicon nanowires transform heat into electricity

Thermoelectric materials convert temperature gradients into voltages and vice versa. If one end of such a material is hot and the other is cold, a voltage is generated, which can then be used to create electrical power.

For a material to have good thermoelectric properties, however, it must be a good electrical conductor and a poor thermal conductor. Because bulk silicon is good at conducting both electricity and heat, scientists had ruled it out as a possible thermoelectric material. Two teams have now independently discovered that by nanostructuring silicon, they can reduce its thermal conductivity, making the material promising for thermoelectric applications (Nature 2008, 451, 163 and 168).

(*snip!*)

"It confirms a growing sense in the science community that proper nanostructuring of materials will yield very significant enhancements in thermoelectric performance," he says.

The ability to convert heat directly into usable energy is significant. Imagine the possibilities relative to circuitry. Heat is the biggest obstacle with faster computing. Being able to rapidly dissipate this heat (and convert it back to electricity) would be a big step forward in processing speed.

Or electric automobiles, converting tire heat back into electricity. How about putting shingles on your roof that turn the ambient and solar heat into electricity to help power your home?

ATSers, there ARE solutions out there. I have shown you quite a few already. Our "energy woes" are either going to be shortlived, or we are being screwed over. One way or another, the gig is up.

Over the next several days i will begin to chronicle some materials science breakthroughs that can, to be honest, completely mind blowing. Everything from new superconductors at room temperature to the conversion of light directly to electricity (and vice versa).

If we can keep from killing ourselves, the future can be amazing.

I have a few new items to update this thread with. It may take a little longer to finish the more relevant material. But, in the meantime, i thought it would be interesting to discuss prior research by the lead scientist (and likely most well known) in the group mentioned in the OP article:


www.technologyreview.com...

Next Step: Although the cells' electron transport was better, their overall light conversion efficiency was low compared to that of some nanoparticle-based solar cells (which have achieved efficiencies of up to 10 percent). Zinc oxide harvests electrons from the dye less efficiently than does titanium dioxide -- a material more commonly used in nano solar cells. The researchers are now making their nanowires out of titanium dioxide, a more challenging manufacturing process. The nanowires also have a smaller surface area than a network of nanoparticles, so they carry less light-absorbing dye. The researchers are consequently shrinking their nanowires to 10 nanometers in diameter so that they can fit more nanowires onto their arrays and increase the total surface area. Yang predicts that with thinner and more numerous titanium wires, his team will be able to achieve a conversion efficiency of 10 percent or more, which could make these nano solar cells a viable source of energy.

Photovoltaics are quite different from thermoelectric. However, given the recent finds from the cloaking piece, the field of photovoltaics is poised to really take off.

The key here is that we are finding new uses for old materials. We have discovered that there are REAL reasons behind the properties of materials. For example, why gold looks the way it does. Why it is the color it is, how brilliant it is. There is something to say about how it is polished, how it is formed. This is all done on a macro scale. Perhaps, with polishing, you can change it on a microscale. however, take it down another step or two, get down to the nanoscale, and if you can make changes to the material you can further change other properties it exhibits.

In the same way a large lump of gold has the property that it exerts greater force (due to the force=mass*acceleration concept) when dropped on your foot. On the nanoscale such changes in size, shape, contour...they all have further affects on the overall material. This is how you turn paper into a superconductor. Or how you make silicone have thermoelectric properties.

I am willing to bet that if we controlled design on even smaller scales, we could further create unkown, fantastic properties within the same old materials that litter the universe.

www.cchem.berkeley.edu...

Dr. M. M. Zhang
Materials Research Department, Toyota Technical Center, Toyota Motor Engineering & Manufacturing North America (TEMA) Inc.
2350 Green Road, Ann Arbor, MI 48105 (USA)

I find it interesting that Toyota is involved in research, as well. Even stranger, the paper filed on this was funded by the National Science Foundation:

www3.interscience.wiley.com...

I find it really sad that no one has responded to this thread. This a good find, and I agree with you that there will be more interesting discoveries in the near future. I think that a lot of things have been out there, but no one would listen until the price of energy got so high. The sooner we WILL START looking at alternatives, the better off we will be.

reply to post by MBF


This is only part of it.

In the "big picture" there are countless ways to capitalize on energy that was once unrecoverable.

I will be launching a new thread in the next day or two dealing with a completely new form of energy generation from the world of nanotechnology.

Combine it with this, and the new superconductor materials that are available, and it is easy to see how you could build a house that was capable of sustaining all your energy needs.

There are also new materials that provide superconducting batteries which provide a very promising future for electric cars. Of course, the same technology that can run your home can also run your car (but repair costs would be almost prohibitive, even under ideal conditions).

Just about anything you can imagine is awaiting us at the end of our next breath.

If I remember right, there is 1 kilowatt of energy hitting every square meter during the day. If you calculate the area of a roof alone, you can more than generate enough power to run a house. Most homes run on 10-20 KW peak. If you start recovering lost energy, you can save a lot of energy. Most people could save a lot of energy by just doing simple things. I put weather stripping around the doors and put a cover over a window unit air conditioner and that alone made a big difference. We put a shade cloth over a patio a few years back and our central ac unit just happened to be under it and that alone dropped the light bill $40-$50/month during the summer. The shade cloth cost $60. We bought 3 because we didn't think they would last very long. Thats been about 7 years ago and the original one is still there.

The heat my attic can contain in the summer will commonly exceed 115 degrees. My grandfather and my uncle each owned air conditioning business. they both wanted me to take over when they retired. i wasn't going to spend my life crawling around in attics (no place for someone who is big, fat, and furry).

regardless, i worked with them a lot growing up, and learned a good deal about air conditioning/heating systems. Not much of an electrician (local law requires us to contract electrical work to a licensed electrician, which was also fine by me).

The problem then presents itself with how you are going to cool it enough to generate a current. Would you be able to generate enough current by accessing cool air from the household air conditioning system? Surely you could generate enough current to power a home?

The concern, then, would be northern climates, shaded areas, etc. What would be needed is a low cost heating option. I don't think you can make something quite efficient enough to be "overunity" (yeah, it doesn't literally apply...but you get the idea). But a "backup" system for heating the nanofibers would be a good idea. As well, efficient, low cost batteries. Something that could actually be part of the building material would be good. Yeah, sounds far fetched. Just wait till i have time to prepare the presentation.

[edit on 11-2-2008 by bigfatfurrytexan]

I don't know how much of a temp difference you would need, but if it isn't much,you could get cool air from under the house or an underground system. If you need a higher temp than 115, you could make a parabolic system and really heat that sucker up. I had a friend that had a slaughterhouse. He rigged up a parabolic dish(satellite dish) to heat the water that he used. It worked fine when it worked. He said that the biggest problem was with tracking the sun, of course this is about 35 years ago so I think you could get better equipment to track with now. He said that you would be surprised how good it worked on a cloudy day. The copper globe that was at the focal point would glow so bright that you couldn't look at it.

I worked on an attic fan for a lady one time with the temp in the attic 123. It was kind of warm. I'm a farmer and I grew tobacco up until a few years ago. I would have to check the barns constantly. One time, one of the boys that was helping me wanted to see look in one of the barns. I let him. He stuck his head into the inspection door and jumped back fast, it was 125 in there. We went to another barn that was 165 and I asked him if he wanted to look in and he said "NO!!!". I went to the other end of the barn and started to go inside and he said "what do you think you are doing?", I said that I was going inside to check it. He said "I'll bet you $5 you will not go in there." When I came out about 5 minutes later, he handed me $5 without saying a word and turned and walked away.

That is a good idea.

Could you create a current by exposing the tops of such filaments, with the bottoms buried in the ground? Then you could setup massive vertical arrays over acres of Nevada and Arizona. I can find you a few acres that no one wants to live on near Groom Lake.

In all seriousness, our biggest problem is efficiency. I need to do some research on this to see the how efficient this is, but photovoltaic organics run close to 6%, right? Silicone solar cells (the traditional design) are currently around 30%.

However, what is the cost differential to generate the 6%? The silicone substrates are fairly expensive. However, in the photovoltaic organics you end up with a much more cost efficient design. They are using SARAN WRAP as the substrate....isn't that remarkable? So mundane, yet being used by scientists to build classified technology (photovoltaics are not classified....but other variances "may" be).

BTW...when i was a teen i used to do roofing. The temestuous summer storm season in West Texas has, in my experience (on more than one occasion) yielded softball sized hailstones. Imagine that combined with a macroburst or tornado. Its like tens of thousands of nolan ryans throwing oversized hardballs at you. Cows die, roofs are "swiss cheesed", car hoods end up with fist sized holes covering them. Lots of roofs to repair.

Once it got up to about 112 on the ground. Up on the roof, when you are standing on tar paper, 130 isn't unheard of. And those early morning showers? They turn hell into Satans Sauna.

We would work for 20 minutes, then take a 1 hour break. It got to where we would work under floodlights at night (if the homeowner could find a night or two of other accomodations). Talk about job safety.

My dad used to always yell, "If you fall, you're fired before you hit the ground."

I wonder what the efficiency is of the new solar cells that are sprayed on the foil. We just put a tin roof on our house, I think it would be a great idea to make the sheets of tin into solar panels this way. Instead of having solar panels on your roof, your entire roof would be a collector. Even at 5 or 10% efficiency look how much power you would be generating. With a 2000 ft.^2 house, that would be 10-20kw. More than enough to run a house.

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We've had some of that softball sized hail here too. I'm glad the cows were smart enough to hit the woods.

Anybody that installs roofing in the summer has my respect. It was hot putting the tin on. I never fell off the roof, but I have slid down that slick tin.

Needless to say, nanotechnology is a field that i am watching very closely at the present moment. The breakthroughs coming forth are on par with the industrial revolution, and we are seeing a whole new world created before our eyes.

There is a new photovoltaic nanostructure that is being developed currently. Within 5 years they expect an efficiency rate of about 20%. This is getting close to the 30% seen with current solar panels. But the kicker is the cost. These materials are likely to be much cheaper, and much more durable than current solar cell technology.

www.technologyreview.com...

Researchers at McMaster University, in Ontario, say that they have grown light-absorbing nanowires made of high-performance photovoltaic materials on thin but highly durable carbon-nanotube fabric. They've also harvested similar nanowires from reusable substrates and embedded the tiny particles in flexible polyester film. Both approaches, they argue, could lead to solar cells that are both flexible and cheaper than today's photovoltaics.

The material being used has historically been prohibitively expensive. However, with the advent of the ability to "grow" it in nanoscale formats, the material being used is in much smaller amounts:

Storing Solar Power Efficiently

Solar proponents love to boast that just a few hundred square kilometers' worth of photovoltaic solar panels installed in Southwestern deserts could power the United States. Their schemes come with a caveat, of course: without backup power plants or expensive investments in giant batteries, flywheels, or other energy-storage systems, this solar-power supply would fluctuate wildly with each passing cloud (not to mention with the sun's daily rise and fall and seasonal ebbs and flows). Solar-power startup Ausra, based in Palo Alto, thinks it has the solution: solar-thermal-power plants that turn sunlight into steam and efficiently store heat for cloudy days.

"Fossil-fuel proponents often say that solar can't do the job, that solar can't run at night, solar can't run the economy," says David Mills, Ausra's founder and chairman. "That's true if you don't have storage." He says that solar-thermal plants are the solution because storing heat is much easier than storing electricity. Mills estimates that, thanks to that advantage, solar-thermal plants capable of storing 16 hours' worth of heat could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas. "There's almost no limit to how much you can put into the grid," he says.

This is what is being done in Australia. I would honestly have to say that, if Spain doesn't do it, Australia will. This great nation is researching highly out of the box concepts, and then putting the money into their development.

It is interesting.

I am a chemist good at making some nano-materials also, but I am not familiar with the mechanism of generating electricity with the material mentioned in the original thread.

I prepared some nanowires and I can make it self-assemble into a certain pattern. This nano-wire material is electrically semiconductive e(-5) S/cm but thermally nonconductive. I just wonder if this is also good for the above-mentioned heat-electricity conversion purpose.



Please see www.klchemtech.com...

So, you got any ideas?

I'll post a thread for this tomorrow. With some of your comments I may contact the authors.







[edit on 17-2-2008 by fuelcell]

Excellent. Cross link your thread here so i can follow.

I am unsure about your design and its similarity. While i am not a scientist (i do call center operations), i am fascinated with nanotech, and have done a considerable amount of research (and been supplied a considerable amount of information by kind third parties) and would love to track your research.

Thanks for your post. I'll get the paper and try to contact the authors.

I'll post here the progress, if any.

www.technologyreview.com...

Turning Waste Heat into Power
Research shows that silicon is as efficient as pricier materials.

Silicon, in the form of photovoltaic cells, is good at generating electricity from sunlight. New research shows that it could also make a good thermoelectric: a material that converts heat into electricity and vice versa. Since silicon is more abundant than the leading thermoelectric materials and has a vast manufacturing infrastructure behind it, it could eventually yield cheap devices for generating power from engines' waste heat or from solar heat.

In this week's Nature, University of California, Berkeley, chemistry professor Peidong Yang and his colleagues report having fabricated silicon nanowires that generate electricity when a temperature differential is applied across them. Until now, silicon has been considered a bad thermoelectric material. But according to Yang, "the performance of the nanowires is already comparable to the best existing thermoelectric material."

Cool customer: This image, produced by a scanning electron microscope, shows a rough silicon nanowire bridging two heating pads--one serving as a heat source and the other as a sensor. Researchers have found that 50-nanometer-wide silicon nanowires have drastically lower heat conductivity than bulk silicon but retain their electrical conductivity. Thus the nanowires show potential as thermoelectric materials--ones that convert heat into electricity and vice versa.

I love it when you see technological breakthroughs start seeing applications so quickly.

The use of thermoelectric materials could revolutionize transportation. Heat is generated in the engine, the tires, our breath....


Fuelcell any progress to report? Do you need any help?

BFFT, you should pick up the latest issue of SciAm. They have a very interesting section in there about exactly this subject, nano-sized thermal power units. I was intrigued by the possibility of using the technology to power nano-sensors inside the body by the body heat itself. The article may be on their website, but I haven't had time to check. Back to the road...

TheRedneck

Thanks a lot, bigfatfurrytexan, for your help.

I have gathered some more papers on this topic and talked with some physical majors. I got some more ideas.

Tentatively I believe I can do something in this field. for example I would prefer synthesizing extreme long nanofibers for this application with my system, for example, over 500 nm long fiber with some 20 nm diameter, assembling in a special pattern.

Different than solar/photovoltaics, where the energy is kind of two-dimensional and the thin layer can acquire all the enrgy, the heat/thermo is volumatic, and the think layer only contain some fraction of the thermal energy at a limited time. And the electricity can be generated by the temperature gradient (E linearly proportional to the temperature difference). If the length of the nanowire is not long enough, the temperature difference should be small no matter how large the gradient is. In that case the energy efficiency should be low. So I decide to prepare extra-long nanowires.

The above is what I think so far. I'll start some preliminary work soon. Sorry I am not going to report the progress here very often. But hopefully I can have some publications in the field in the future.

I appreciate your help very much.

These nano-materials sound like a good way to take advantage of solar energy. I wonder how it would work in geothermal areas that have a constant heat source and therefore no worry to the passing clouds.