Talk-Polywell.org

skippy wrote:

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).

Let's see...

1 Mlb or 453 600 kg vehicle, say (747-8 equivalent),
10 minutes at (very roughly) 5 GW to reach orbit,
(10/60 h)(5 000 000 000 W) = 833 333 333 propulsive Wh required,
overall efficiency, say, 75% --> 833 333 333/0.75 = 1 111 111 110 stored Wh required,
(1 111 111 110 Wh)/(0.01 Wh/cm^3) = 111 111 111 000 cm^3 for energy storage,
(111 111 111 000 cm^3)(1 m/100 cm)^3 = 111 111 m^3,
so the capacitors needed could fit into a cube with edge length of (111 111 m^3)^(1/3) = 48 m or 158 ft.

Bigger than my backyard, just for energy storage. No beer cooler. No go.

GIThruster wrote:The real issue with the folks making it with a Lightscribe is they found a cheap process for manufacturing it.

I wonder about the quality achievable with this method, though. Press articles just mentioning the fact that graphene is a layer just a single atom thick always make it sound as if they just produce a single macroscopic, planar molecule. But from the photos and Figure 2c (http://www.nature.com/ncomms/journal/v4 ... s2446.html) it's pretty obvious that it's more like a collection of curled flakes of various sizes.

JoeP wrote:

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.

That is correct. Say you are using one to power a 32KHz osc for back up time. 1uA current draw. The super caps self discharge will run from 1/2 that to 2X that depending. Roughly. Film caps are much better. But they don't hold much charge.