Super-Duper-Uber Capacitors On The Way!!

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
valveitude

valveitude

Member
Joined 2005
The boys at MIT are developing a new family of ultra-caps with a storage density 50% of a lead-acid battery!! They accomplish this with the use of carbon nanotubes...

nanotube.jpg

Photo: Riccardo Signorelli/MIT

From the article..The Charge of the Ultra-Capacitors
"By virtue of their dimensions, it struck me that those nanotubes held the promise of even higher porosity than the activated carbon used in commercial ultracapacitors. Together the nanotubes have an enormous surface area, and their dimensions are more uniform than those of the activated-carbon pores, making them more like a paintbrush than a sponge."
Click to expand...



Casey
 
auplater

auplater

Member
Joined 2005
nanotube-capacitors!!

But.. won't they sound "fuzzy and congested"?? what with all that "density" and such???

Or perhaps the music will be "painted over a broad landscape awash with vibrant colors and textures attributed to the micro-fine ciliary structures"...:D

John L.
 
BWRX

BWRX

Ex-Moderator
Joined 2005
"Another advantage of nanotubes over activated carbon is that their structure makes them less chemically reactive, so they can operate at a higher voltage."

One major roadblock for current ultracaps are the low voltage ratings. Higher voltage ratings would really make these things take off.
 
J

JohnG

Member
Joined 2002
These caps are "super-capacitors," otherwise known as double-layer capacitors, and there operational principle falls somewhere between a battery and a capacitor. I forget the physics and chemistry, but they are not an electrostatic capacitor. the upshot is that they have an effective ESR that increases dramatically, and non-linearly, with frequency. They are also inherently low-voltage devices (~2-4V), since higher voltages will start an electrochemical reaction, ending the device's proper operation.

Note that you can already buy double-layer capacitors, even from Digi-key I think.

John
 
valveitude

valveitude

Member
Joined 2005
They are also inherently low-voltage devices (~2-4V), since higher voltages will start an electrochemical reaction, ending the device's proper operation.
Click to expand...

From article..
Another advantage of nanotubes over activated carbon is that their structure makes them less chemically reactive, so they can operate at a higher voltage. And certain types of nanotubes, depending on their geometry, can be excellent conductors—which means they can supply more power than ultracapacitors outfitted with activated carbon.
Click to expand...
 
scott wurcer

scott wurcer

R.I.P
Joined 2004
Somewhere else they actually mention a 300V target for super-capacitors and go on to say they have already solved the safety issues (which I am more skeptical of). Think many mega-joules charged to lethal voltages crushed in an accident. They also dismiss the several thousand amp currents that it would take to charge the thing in the claimed time as "no problem".
 
auplater

auplater

Member
Joined 2005
mega-joules... and more!

My thoughts as well...

think about the "crowbar on a car battery" scenario..:bigeyes:

I can imagine exploding carbon nanotubes scattering debris :hot:

"They also dismiss the several thousand amp currents that it would take to charge the thing in the claimed time as "no problem"."

Having dealt with thousands of amps (in chromium and nickel plating, electropolishing, etc.) I can assure you, it's anything but "no problem"... sounds like researchers looking for follow up funding rather than competent enigineers developing practical applications. Think 350 x 10^5 amp-seconds to determine reasonable recharge rates... not to mention the particulars of distributing this charge into the capacitor uniformly and repeatedly... not a trivial pursuit

John L.
 
J

JohnG

Member
Joined 2002
All double-layer caps that I'm aware of achieve higher voltages via series combinations of caps. The voltage limitation on a single cap is there to prevent an electrochemical reaction from starting. They say a higher voltage due to nanotubes, but not how much higher. This probably means they are purely speculating, or it is not substantially higher.

I'm not dissing the technology, which, if it pans out and the cost is reasonable, it likely to be very useful in energy storage applications. I think it's unlikely that it will be much good for audio. Just my own speculation, though.

John
 
valveitude

valveitude

Member
Joined 2005
I think it's unlikely that it will be much good for audio. Just my own speculation, though.
Click to expand...

If they have comparable ESL/ESR, and voltage limitations, to the current ultra-caps, I would tend to agree...but...if a cap with a couple dozen Farads at around 12V or so surfaces at a reasonable cost I can see some uses. First thing that comes to mind is a filament/bias supply that charges while the amp is "off", then disconnects from the line while playing. Ditto that for the B+ if the voltage capacity is available (pre-regulator of course).

Of course, as you've said, this is all speculation until we see something tangible. It is exciting to see the new nano technologies starting to take off though.

Casey
 
J

JohnG

Member
Joined 2002
If not ultracaps, a promising battery technology is Li-Fe phosphate, such as that made by A123 . Energy density is probably a lot higher than an ultracap can reach, and they are available today. You can find them in high-end DeWalt cordless tools, and I've seen them for sale by R/C hobby companies.

Not cheap, though.

John
 
scott wurcer

scott wurcer

R.I.P
Joined 2004
JohnG said:
All double-layer caps that I'm aware of achieve higher voltages via series combinations of caps. The voltage limitation on a single cap is there to prevent an electrochemical reaction from starting. They say a higher voltage due to nanotubes, but not how much higher. This probably means they are purely speculating, or it is not substantially higher.

I'm not dissing the technology, which, if it pans out and the cost is reasonable, it likely to be very useful in energy storage applications. I think it's unlikely that it will be much good for audio. Just my own speculation, though.

John
Click to expand...


I lost track of the patent they were waving around, but these folks were definately fishing for money. Their spin was that electric cars won't catch on until you can "fill 'er up" in about the same time as a tank of gas.

Another non-trivial problem is the swiching regulator you need to deliver constant voltage as you discharge the capacitor.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom