Talk-Polywell.org

This loaner 'puter I'm on can't play falsh of any sort--just locks up the machine. I trust this is more about the folks at UCLA using a lightscribe to sinter graphene onto CD's and DVD discs?

Any numbers yet for bulk capacitors as compared to LiPo batteries?

Yes, they quickly show the 'how they made graphene' bit. But then move into the, 'holy crap' it is an awesome capacitor. A small sheet about 1inch square single layer (each side) in a flat capacitor configuration, is shown to be charged for a couple of seconds, and then run an LED(?) lamp for up to 5 minutes.

You could push a good spark if you rolled up a sheet of it I would think...

So, if it can charge crazy fast and discharge over time, and we can make it dirt cheap, can these be used for power generation? Build an array of a couple thousand or even million of them and hook the charging end up to a lightening rod or the post in town hall?

If the described capacitors can be made in volume cheap enough, applications for matching supply to load would be extensive.

bcglorf wrote:So, if it can charge crazy fast and discharge over time, and we can make it dirt cheap, can these be used for power generation? Build an array of a couple thousand or even million of them and hook the charging end up to a lightening rod or the post in town hall?

I haven't heard what the dielectric breakdown is, but I would be surprised if it were very high. Not sure sufficient banks of supercaps could be created to grab a lightning bolt, and even if this were dooable, i'm thinking there would be a repeatability issue.

Might be resolved by laser induced plasma path in a known lightning strike area.


Cheap/small supercaps will certainly open up some new horizons.

Thanks for posting the story. Very interesting development and creative use of a DVD burner with the inherent precision to cheaply manufacture these. Another article link: http://www.sciencedaily.com/releases/20 ... 100755.htm


I assume that leakage is still one of the major hurdles. I'm curious as to how well these hold charge.

Why would leakage be a hurdle?
Existing dielectrics seem fine. Especially for normal applications. The graphene would seem a nice cheap and low mass/volume alternative to existing charge plates/films.

Did they give a specific energy density as compared to LiPo's?

The thing that got my attention Using this technique, we have been able to produce more than 100 micro-supercapacitors on a single disc in less than 30 minutes, using inexpensive materials."

ladajo wrote:Why would leakage be a hurdle?
Existing dielectrics seem fine. Especially for normal applications. The graphene would seem a nice cheap and low mass/volume alternative to existing charge plates/films.

I'm not current on the latest capacitor specs, it was just my recollection that most capacitors has self-discharge rates that were inferior to batteries. That, and energy density was another thing that needed improvement.

GIThruster wrote:Did they give a specific energy density as compared to LiPo's?

I found a bug on the Nature website and was able to read part of the paper. It looked like their highest energy design had about 10^-2 Wh/cc. That's about two orders of magnitude lower than Li-ions. They could be nice caps for other reasons --I didn't study the paper that closely. But it doesn't look like their energy density is going to even be able to challenge existing battery chemistry (unsurprisingly).

Skippy,
Thanks for finding that. Like you, I am not surprised at the energy density being low relative to battery tech. I became suspicious when it was not mentioned in bold headlines. I guess it must be the form factor or ability to put it on a board, plus durability / longevity. Maybe they can do something with it with development work, but it seems the key is the dielectric.

Maybe they can come up with an "anti-graphene" as the ultimate super lightweight insulator and dielectric.

IIRC it is. Graphene only conducts along its surface. It doesn't pass charge through, So technically it is both a conductor and an insulator. At just a few atoms thick though, you can't differentially charge the surfaces as that would be way too much field for its dielectric strength. What you can to though is make electrodes that are just a few atoms thick. The real issue with the folks making it with a Lightscribe is they found a cheap process for manufacturing it.