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Mechanism behind capacitor's high-speed energy storage discovered « Scientific Information « Technology
 
Fri, 24 Feb 2012, 1:50am #1
DGDanforth
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Mechanism behind capacitor's high-speed energy storage discovered


EEStor Hopeful.

"Make it as simple as possible, but not simpler" A. Einstein
"Alas, simplicity is rarely simple" curiositEE

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Fri, 24 Feb 2012, 3:35am #2
Seakell
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This is stupid bullshit, capacitors doesn't need more power they need more energy (density). If batteries are too slow, why improve capacitors (that aren't)?

"There are no batteries that can power that type of acceleration because they release their energy too slowly.", -What a f-ck! Tesla doesn't exist?

"..you don't get out much more energy than you put into the system." Whata...???

"Hopefully these findings will bring us even closer to developing capacitors that will give electric vehicles the same acceleration capabilities as gasoline engines"
Wut, wut???


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Fri, 24 Feb 2012, 3:48am #3
Technopete
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Usually when materials change from a polar to non-polar state it's a chain reaction – starting in one place and then moving outward. In terms of creating an efficient capacitor, this type of movement doesn't work well – it requires a large amount of energy to get the atoms to switch phases, and you don't get out much more energy than you put into the system.

In the case of the PVDF mixture, the atoms change their state all at once, which means that you get a large amount of energy out of the system at very little cost in terms of what you need to put into it.

Hopefully these findings will bring us even closer to developing capacitors that will give electric vehicles the same acceleration capabilities as gasoline engines

[Technopete's emphasis]
And it produces extra energy for free.

What a capacitor! Where do I order?

As a matter of interest, are there any capacitors which can only discharge so slowly that you cannot get virtually the whole charge out in the 2-4 seconds it takes supercars to accelerate from 0-60 mph?

Regards,
Peter


Assumptions: 1) E=1/2CV2. (Only dummies assume this). (I am one of these dummies).

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Fri, 24 Feb 2012, 4:59am #4
Lensman
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Seakell wrote:

This is stupid bullshit, capacitors doesn't need more power they need more energy (density). If batteries are too slow, why improve capacitors (that aren't)?

Indeed. Is it normal for science-made-stupid articles to be posted at Physorg.com?

And in the article I find this:

Imagine an electric vehicle that can accelerate from zero to 60 miles per hour at the same rate as a gasoline-powered sports car. There are no batteries that can power that type of acceleration because they release their energy too slowly.

Gosh, someone needs to let all those owners of the Tesla Roadster, the Fisker Karma, and all those electric drag race cars owners, know that they can't beat a gasoline-powered sports car. Somebody needs to tell the people who have made the Lightning GT prototypes, too.
http://i56.photobucket.com/albums/g194/Lensman03/Smileys/SmileySmlGiggle.gif

I think they would all enjoy a good laugh.


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Fri, 24 Feb 2012, 10:36am #5
sydd
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I think this is the interesting part of the lurid written article:

From the source web site
http://news.ncsu.edu/releases/ranjanprl/

Abstract:
Using first-principles simulations, we identify the microscopic origin of the non-linear dielectric response and high energy density of PVDF-based polymers as a cooperative transition path that connects non-polar and polar phases of the system. This path explores a complex torsional and rotational manifold and is thermodynamically and kinetically accessible at relatively low temperatures. Furthermore, the introduction of suitable copolymers significantly alters the energy barriers between phases providing tunability of both the energy density and the critical fields.

From Physical Review Letters
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.108.087802

a much better report...

Synopsis: Plastic Capacitors

One of the biggest speed bumps hindering widespread adoption of electric vehicles is energy storage: conventional liquid fuels offer a stored energy per unit weight that is hard to beat. The two current approaches to overcoming this limitation are batteries, which use a chemical reaction to generate electricity, or capacitors, which directly store electricity then discharge it when needed. Capacitors take the lead in applications requiring quick delivery of energy. In essence, capacitors are made from two metal surfaces separated by a dielectric; the capacitance can be improved by bringing the surfaces closer together and by using a separator with high dielectric permittivity.

Computer simulations reported in Physical Review Letters by Vivek Ranjan of North Carolina State University, Raleigh, and colleagues predict that mixing a ferroelectric polymer with a pinch of another polymer could yield a sevenfold increase in stored energy compared to the pure dielectric. The calculations offer insights at the molecular level about how this occurs, showing the polymer atoms collectively rearrange from a nonpolar to polar state. Transition paths uncovered by the work have low activation energies and are accessible at technologically reasonable temperatures. The results point the way toward research into creating such optimized polymer dielectrics, which would make capacitive systems roadworthy for powering electric vehicles. – David Voss

can someone with access please at the following paper:
http://prl.aps.org/abstract/PRL/v108/i8/e087802

Phys. Rev. Lett. 108, 087802 (2012) [5 pages]
Electric Field Induced Phase Transitions in Polymers: A Novel Mechanism for High Speed Energy Storage

cheers sydd


Chat from 5 pm Mon, 9 Jan 2012:
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"But there are no farking long or short dipoles to speak of. Just some residual short dipoles relative to the plate" - Prof Bombay

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Fri, 24 Feb 2012, 11:32am #6
BigMig
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The big deal about this somewhat sensationalist title: NCSU team et al have simulated an effect which has been known for some time already....

Somewhere in the hallways at PSU, its MRI, and the Institute Franco-Allemand de Recherches are Baojin Chu, Xin Zhou, Kailiang Ren, Bret Neese, Minren Lin, Qing Wang,F. Bauer,and Q. M. Zhang are laughing about this since they were the ones who really did a lot of the original research on this area of combining PVDF combined with fluoroethylenes variants epecially ter-polymer fluoroethylenes (CFE, CTFE, PTCFE, etc.) to get better dielectric characteristics!

Here are some quotes from the original PSU work which sound just like the ones you are reading from the NCSU 2012 news:

PSU,MRI gang,IFAdR wrote:

We demonstrate that
a very high energy density with fast discharge speed and low loss can be obtained in defect modified poly(vinylidene fluoride) polymers.This is achieved by combining nonpolar and polar molecular structural changes of the polymer with the proper dielectric constants, to avoid the electric displacement saturation at electric fields well below the breakdown field...
These relaxor-ferroelectric terpolymers P(VDF-TrFE-CFE), P(VDF-TrFE-CTFE) are multifunctional i.e. electrostrictive material, dielectric for electric energy storage...
A reversible molecular change between the non-polar to polar forms can generate large polarization change, large strain, and large change in other properties

The PSU team with ~600V/µm excitations and their polymer blend (P(VDF-CTFE)) (which also acts as a relaxor ferroelectric) and process got around ~17-20J/cc back in ~2005/2006 time frame. See graph below

http://www.theeestory.com/files/PSU_2005_poly_blend_PVDF-CTFE_energetics_graphs.jpg

All in all I can summarize it as:
a. "NO NEW SCIENCE" and
b. sometimes you have to be diligent before you feel amazed and get a sense of wonders on originality and results by some new title on "newly" published research.

Last edited Fri, 24 Feb 2012, 12:19pm by BigMig


Big Mig
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