backtop


Print 36 comment(s) - last by NicePants42.. on Jan 25 at 2:52 PM


Professor Peidong Yang led the University of California, Berkley team who discovered silicon nanowire's thermoelectric properties.  (Source: University of California, Berkley)

A scanning electron microscope image of a thin silicon nanowire stretching between two heating pads, one as a heat source, the other as a sensor.  (Source: A. Hochbaum)
Silicon heat capture could allow cheap refrigeration and energy saving

Among the many valuable properties of silicon is its ability to capture solar energy to create electricity via its photoelectric character.  Now scientists are discovering that silicon, when properly prepared, can form a very good thermoelectric as well.  This opens the door to a plethora of uses, including refrigeration, solar heat power generation, and power generation from other heat sources, such as computer waste heat or car heat.

A thermoelectric device has two  basic modes of operation.  When a thermoelectric is placed over a heat gradient, it generates an electric current.  The other mode is the reverse; when a thermoelectric is exposed to an electric current, it creates a heat difference, cooling one side of it, and warming the other side.  Thus thermoelectrics are applicable to power generation, refrigeration and heating.

Traditional thermoelectrics, which have been around since the 1960s, rely on either bismuth telluride or lead telluride.  These materials are relatively expensive due to scarcity and lack of a large manufacturing infrastructure.  They are also bulky and require more material, which further increaese their cost.  While thermoelectric coolers have achieved modest commercial usage in seat coolers and picnic coolers, they have yet to realize their full potential.

A new breakthrough may change that.  Professor Peidong Yang and his colleagues at the University of California, Berkley published in last week's Nature journal the results of years of research into using silicon as thermoelectrics.  Their results show that silicon can be a viable thermoelectric.

The key is in the preparation.  The researchers prepared thin nanowires of silicon.  When these wires are exposed to a temperature difference, they generate electricity.  Standard silicon is a poor thermoelectric, but according to Dr. Yang, "the performance of the nanowires is already comparable to the best existing thermoelectric material."

A good thermoelectric needs to have two key properties -- good electrical conduction, and poor heat conduction.  Silicon typically conducts both very well, but by producing 50 nm nanowires, the heat conduction of silicon is reduced to one hundreth of its normal levels, while electrical conduction remains unchanged.  The material is comparable to commercial thermoelectrics.

Two possible uses of the technology are to generate electricity from waste heat of car engines.  Current thermoelectrics are too expensive and large to make this a practical possibility.  Nanowire silicon layers, though could provide a means to recapture some of the energy lost to heat during the conversion to mechanical energy in a car engine.  This extra savings could be stored in batteries, to give next generation electric vehicles, such as the Chevrolet Volt, even better efficiency.

It could also find a home in solar power cells.  By coupling it with traditional photoelectric cells, much higher efficiencies could possibly be reached.  Yet another application is to put the materials in computers to provide energy savings, which would be particularly valuable to mobile computing.  Further, it could be used in refrigeration applications, as well.

Much work needs to be done before the process is perfected.  The physics behind why nanowires of silicon lose their heat conduction is not understood, which stands in the way of refining the efficiency of this class of devices.  Further creating a thermoelectric on the macroscopic scale, by creating a network of nanowires, has yet to be accomplished.  Still, the discovery of these properties in silicon promise a way to eventually use replace current less ideal thermoelectrics with an abundant material with a large processing infrastructure.


Comments     Threshold


This article is over a month old, voting and posting comments is disabled

Cool.
By StevoLincolnite on 1/21/2008 4:30:56 AM , Rating: 2
Only two gripes that I have found during the article, the first being a spelling mistake and the second caused me to read the sentence a couple of times.

which further increaes their cost.

and



These materials are relatively expensive do to scarcity and lack of a large manufacturing infrastructure.


I think this would be handy to have on the bottom of my laptop to turn the heat into electricity, and have solar panels on behind the Monitor, Mind you it wouldn't come cheap but it would be perfect for road warriors.
Or perhaps those who work out in the middle of no-where, like Farmers.




RE: Cool.
By Visual on 1/21/2008 7:42:47 AM , Rating: 3
i imagine it's not meant for the bottom of the laptop, it is good for being built-in into the chip, or maybe between the chip and heatsink.


RE: Cool.
By mmntech on 1/21/2008 9:48:23 AM , Rating: 2
It would certainly revolutionize electronics, and electrical engineering in general. Electrical appliances waste huge amounts of energy producing excess heat.


RE: Cool.
By captchaos2 on 1/21/2008 12:37:17 PM , Rating: 2
So, could I overclock my processor and power my house from it?


RE: Cool.
By dflynchimp on 1/22/2008 12:21:49 AM , Rating: 2
wouldn't work. In a perfect environment you can only get back as much energy as you put in, and assuming your computer used some of that energy for computation purposes you'd get back less energy than you put in. But if you were to loop the generated power back into your computer you're overall power consumption could be cut drastically.


RE: Cool.
By StevoLincolnite on 1/22/2008 1:27:10 AM , Rating: 2
Hmm, I somehow was thinking about the Prescott whilst reading you're post...


RE: Cool.
By Samus on 1/23/2008 1:42:22 AM , Rating: 2
Think of it as capturing energy from a lightbulb much like a solar panel, but instead your capturing the heat instead of the light rays.

Of course it wont be 100% efficient, but even if it reclaimed 10-20% of the energy excerted from a refridgerator coil, that's 10-20% energy savings.

It could also extend into the automotive industry to replace alternators with thermoelectric generators that run inline with the coolant, reducing the lost horsepower from an alternator.


RE: Cool.
By dluther on 1/21/2008 8:21:30 AM , Rating: 2
Good eye -- Jason, you still have one lingering out there:

quote:
These materials are relatively expensive due to scarcity and lack of a large manufacturing infrastructure. They are also bulky and require more material, which further increaese their cost.


Should be "which further increase their cost".

I have often wondered if such a system could be used in conjunction with heat pipes to first dissipate heat away from the major heat-generating components and then converted back into electricity.

Obviously, such a system wouldn't be able to actually power things on heat alone, but it could extend the battery life, and probably by a good margin if the electricity regeneration cycle is efficient enough.


RE: Cool.
By PlasmaBomb on 1/21/2008 8:52:39 AM , Rating: 2
If we are pointing out mistakes...

Second paragraph -
A thermoelectric device has two __ basic modes of operation.

(two spaces between the words two and basic).

Third paragraph -
further increaese their cost.

increases

Sixth paragraph -
heat conduction of silicon is reduced to one hundreth of its normal levels.

hundredth

On the whole though, an interesting article. Thanks :)


RE: Cool.
By SkyOwner on 1/21/2008 9:02:22 AM , Rating: 2
How about UC Berkley?

It was Berkeley last time I checked (A)

But overall it's an interesting technique, however, it'll probably take real long until it will be implemented in actual products.


RE: Cool.
By dluther on 1/21/2008 9:25:13 AM , Rating: 2
quote:
Second paragraph -
A thermoelectric device has two __ basic modes of operation.

(two spaces between the words two and basic).


I think this can be forgiven due to the fact that a proportional font is being used.

quote:

Third paragraph -
further increaese their cost.

increases


This is wrong on two counts. First, the paragraph opens up with "they", indicating a plurality (he increases, they increase). But if that weren't enough, he also gives two cases for the increase -- bulky, and require more material -- again which require a singular modifier in the case of equally applied, plural objects.

quote:

Sixth paragraph -
heat conduction of silicon is reduced to one hundreth of its normal levels.

hundredth


Now there's a good one.


RE: Cool.
By PlasmaBomb on 1/21/2008 1:23:42 PM , Rating: 2
Sorry, my mistake, should have pulled the entire line then I wouldn't have forgoten what the quote was ;)


RE: Cool.
By Polynikes on 1/21/2008 10:53:02 AM , Rating: 2
Wow, good job pointing out a mistake your comment's parent already did.


RE: Cool.
By GaryJohnson on 1/21/2008 9:44:37 AM , Rating: 4
Would it not better serve the community and the comments system to email the author grammatical and spelling corrections? Your basically hitting the 'Reply to All' button by posting a comment about it when it really doesn't apply to the rest of us.


RE: Cool.
By StevoLincolnite on 1/22/2008 1:30:34 AM , Rating: 2
Or, they could make it similar to Wikipedia so that the community could fix errors, or mis-information.


RE: Cool.
By dluther on 1/22/2008 9:04:19 AM , Rating: 2
You bring up an excellent point. However, there are two issues I have with your assertion:

1) In a public forum, the same mistakes tend not to be dealt with in multiplicity, save for the cases where they are simultaneously addressed. Additionally, the more eyes, the better.

2) Since Jason Mick has provided this story in a public forum, then Jason must also accept the responsibility of public scrutiny for either premise or presentation.

It's evident that Daily Tech doesn't have an editorial staff; if it does, it's certainly not a traditional one where style guides, proofreading and grammatical analysis are part and parcel of such responsibilities. That doesn't mean such responsibilities are unimportant or unnecessary; it probably means that Daily Tech simply can't afford to hire someone to fill that role.

I like Jason Mick's articles. I look forward to more from him, and wish him well in his endeavors here at Daily Tech.


"It seems as though my state-funded math degree has failed me. Let the lashings commence." -- DailyTech Editor-in-Chief Kristopher Kubicki

Related Articles













botimage
Copyright 2014 DailyTech LLC. - RSS Feed | Advertise | About Us | Ethics | FAQ | Terms, Conditions & Privacy Information | Kristopher Kubicki