Ultra capacitors

I think ultracapacitors have a huge potential. Their power density and longevity are unmatched - but they're still lacking in energy density compared to lithium batteries. Using nanotechnology, the surface area can be increased significantly - and since the surface area of a capacitor is directly proportional to its energy density, I see no reason why such a "nano-ultracapacitor" couldn't eventually surpass the energy density of the best batteries.

... and since the surface area of a capacitor is directly proportional to its energy density, I see no reason why such a "nano-ultracapacitor" couldn't eventually surpass the energy density of the best batteries.

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Real physical things never scale linearly over orders of magnitude.
"Surface area is directly proportional to its energy density" actualy means the error in calculating it in this way is insignificant. But this changes dramaticaly as you start to reach ultra high densities comparable with intramolecular bonds. When that happens linear scaling disappears. People that know something about making ultracapacitors don't see how this limit could be overcome buy simply "scaling up" of current principles.

Oh, my mistake then. I know the energy density is related to the surface area and the thickness of the dielectric. But I was incorrectly assuming that at those "nano" scales it would remain fairly linear. Still there's got to be a lot of room for improvement ... theoretically at least.

Argonne project mixes lithium-ion batteries with ultracapacitors

Big Growth Seen in Ultracapacitors for EVs. And Here Comes Ioxus. | BNET Auto Blog | BNET

This is an interesting ultra capacitor project http://chargecar.org/

Ultracapacitors to Boost the Range of Electric Cars - Technology Review

A startup called Nanotune says its ultracapacitor technology could make electric cars cheaper and extend their range. The company, based in Mountain View, California, has developed a way to make electrodes that results in ultracapacitors with five to seven times as much storage capacity as conventional ones.

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That could be the connection that has Elon excited again.

Norbert said:

Ultracapacitors to Boost the Range of Electric Cars - Technology Review

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They say they might reach 40Wh/kg by the end of the year. About lead-acid/ni-cad levels. Still a ways to go before matching nimh or li-ion. Price is probably a bigger issue if it wants to be used in hybrids.

stopcrazypp said:

They say they might reach 40Wh/kg by the end of the year. About lead-acid/ni-cad levels. Still a ways to go before matching nimh or li-ion. Price is probably a bigger issue if it wants to be used in hybrids.

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Yes, I guess this part: "which have the advantage of delivering fast bursts of power and can be recharged hundreds of thousands of times without losing much capacity" makes them good candidates for use in hybrids. The article doesn't really indicate whether doubling the capacity, which they hope to achieve by the end of the year, would already make them competitive also on a price basis, but it seems they may be able to achieve 40 watt-hours per kilogram using the not-so-expensive conventional electrolyte.

If it is true that they could "eventually" achieve "500 watt-hours per kilogram", then that would certainly put them in the range that Li-Ion may have in several years (hopefully), or even above. Same for the cost, if they are able to achieve "$150 per kilowatt-hour". Though that sounds very very optimistic.

Norbert said:

The article doesn't really indicate whether doubling the capacity, which they hope to achieve by the end of the year, would already make them competitive also on a price basis

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They say "$2,400 and $6,000 per kilowatt-hour." Given a hybrid usually uses 1-2kWh, it's a bit high. I know the Honda replacement battery costs $2k and it's ~0.9 kWh. Prius replacement battery is $2,588 and ~1.3kWh. That's price to consumer too (not bulk price). And the cost is only coming down in recent years.

Interesting they don't mention power density or cost per kW as that is more important for hybrids. Volumetric density matters too (the brake backup supercaps in the Prius and the Leaf actually take up a lot of space; for the Leaf it takes up a big chunk of the "hump" in the trunk). Anyways as a whole, I feel they have a decent chance in the hybrid market, but still a long way to go before being adequate for EVs.

Electric power = voltage times current. Miniaturization reduces tolerable voltage. Electrical engineer Martin very skeptical. Other problems: Electric double-layer capacitor - Wikipedia, the free encyclopedia .

Rice University | News & Media

Rice University researchers have created a solid-state, nanotube-based supercapacitor that promises to combine the best qualities of high-energy batteries and fast-charging capacitors in a device suitable for extreme environments.

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Another day, another university breakthrough.
Lets see the game changing products hit the market already!

...continued...

But traditional EDLCs rely on liquid or gel-like electrolytes that can break down in very hot or cold conditions. In Rice's supercapacitor, a solid, nanoscale coat of oxide dielectric material replaces electrolytes entirely.

The researchers also took advantage of scale. The key to high capacitance is giving electrons more surface area to inhabit, and nothing on Earth has more potential for packing a lot of surface area into a small space than carbon nanotubes.

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This seems to avoid some difficulties associated with some other super-caps, however here:

ScienceDirect - Carbon : Three dimensional solid-state supercapacitors from aligned single-walled carbon nanotube array templates

they merely talk about "the ability to achieve energy densities above 10 W h/kg", which doesn't seem interesting for EV energy storage, but there seem to be other areas of application. And interesting in so far as they seem to develop more and more ways to use nanotech.

TEG said:

Another day, another university breakthrough.
Lets see the game changing products hit the market already!

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This seems to be an early research result, unlike the use of nanotubes as an alternative to copper for wires (currently same conductivity at a sixth of the weight) which I just posted in the Off-Topic section, for which they are now working on a manufacturing process (i.e. ready to leave the lab).