Improved High-Performance Energy Storage

Physicists at the University of North Carolina have developed new improvements for high-energy-density capacitors that can store up to seven times as much energy per unity volume as common capacitors. "The amount of energy that a capacitor can store depends on the insulating material in between the metal surfaces, called a dielectric. A polymer called PVDF has interested physicists as a possible high-performance dielectric. It exists in two forms, polarized or unpolarized. In either case, its structure is mostly frozen-in and changes only slightly when a capacitor is charged up. Mixing a second polymer called CTFE with PVDF results in a material with regions that can change their structure, enabling it to store and release unprecedented amounts of energy."

Comments

We already have "ultracapacitors"....

[Joce640k]

Is this really newsworthy?

http://www.google.com/search?q=ultracapacitors

Shipstones

[Anonymous Coward]

In his novel Friday Robert Heinlein described a fictional device called a "Shipstone". This was an ultra-super electricity storage device.

Supposedly, the shipstone had a dramatic positive effect on the world. It was no longer a problem to get electricity from where it's made to where you need it. Big solar power systems were put in areas that get lots of sun, for example. Cars would run on Shipstones, and instead of gas stations, they had stations where you could swap the discharged Shipstone from your car for a fresh, fully-charged one.

I have been wondering if these new ultracapacitors might someday become practical "Shipstones". How close are ultracapacitors to, say, powering a car?

Can you drain the power slowly from an ultracapactor, to run a car for a few hours, or do you have to drain it quickly? Does charge leak out slowly over time from an ultracapacitor, or can you make it fairly inert?

Re:Shipstones

[guruevi]

Using gold capacitors (very expensive though) you would get a far bit already. I had a power amp with 2 1F (not micro-farad, plain farad) gold capacitors and 2 years standing in dry storage and the thing still had a charge (painful). Capacitors are already used as a power source instead of a battery in certain applications and the requirements in cars (high output in short time periods) make capacitors a great candidate. The problem of course is the power density and of course the leaks which is many times greater in current capacitors than in batteries. If they could improve this possible theory, you might get somewhere.

Re:Shipstones

[cartman]

I have been wondering if these new ultracapacitors might someday become practical "Shipstones". How close are ultracapacitors to, say, powering a car?

I should start by saying that I'm not an EE, however I've done some reading on this topic.

Ultracaps are still far from being practical for powering a car. Right now the best Ultracaps store 5-10 Wh/kg, which means they could only store enough energy to power a car for a few miles. Furthermore, the price of the ultracaps is about 10x too expensive for the car to be within the price range of what most consumers expect.

HOWEVER, Ultracaps have seen dramatic and encouraging improvements during the past 10 years. Ultracaps have decreased in cost/kjoule by a factor of about 3 over the last 5 years, and have seen dramatic improvements in energy density. At the current rate of improvement, in about 10 more years Ultracaps will be usable for plug-in hybrids that cost about the same as conventional vehicles and can run for 10-20 miles on electricity alone. Unlike batteries, ultracaps can be recharged extremely quickly and will not require replacement after repeated recharging.

Can you drain the power slowly from an ultracapactor, to run a car for a few hours, or do you have to drain it quickly? Does charge leak out slowly over time from an ultracapacitor, or can you make it fairly inert?

You can drain the ultracap slowly. However ultracaps can be more dangerous than batteries since they can discharge all their energy instantaneously.

Re:Shipstones

[tkw954]

Right now the best Ultracaps store 5-10 Wh/kg, which means they could only store enough energy to power a car for a few miles.

This may be an impediment if you're thinking about plug-ins, but if you're talking about hybrids the story changes. The major improvements from hybrid powerplants are load balancing by allowing the engine to run at the optimum operating point and by regenerative braking. Neither of these have large storage requirements: all you need to get the regenerative braking benefits is to be able to store enough energy to accelerate back to the speed you were at when you hit the brakes.

Wrong measure

[Anonymous Coward]

It's great that they have "seven times the energy per unity [sic] volume", but what is the energy density improvment per unit mass??? Seems like that would be a lot more important for mobile applications.

why compare to "common capacitors"?

[Eric Smith]

seven times as much energy per unity volume as common capacitors

It may well be a breakthrough, but I'm not impressed with that particular claim. Aerogel capacitors (e.g., Cooper Bussman PowerStor series) and Electric Double Layered Capacitors (e.g., Panasonic SG series "gold capacitors") already have at least 2000 times higher energy storage density than common capacitors.

Re:battery replacements?

[CaptainPatent]

Capacitors are rarely meant to be a battery replacement. They are meant to be used for fast storage and release of energy on the order of milli- or microseconds. The chemical reaction that occurs in batteries is far too slow to produce a resonating RLC circuit, or even power a bright camera flash where a capacitor is used in parallel with the battery. Likewise, the Capacitor has a much smaller operating output than a battery in general and they tend to leak thus requiring a load just to keep them at full charge.

The excitement isn't in the fact that they may be a battery replacement, it's that they can store a ton of energy for many other electrical uses.

Finally solving battery problems?

[MtViewGuy]

While I do agree that this research is still preliminary, the technology has the huge potential to finally overcome two major hassles in terms of electric power storage, namely charge times (after all, capacitors charge way quicker than any NiMH or Li-On battery pack) and density of storage.

This could open the way for two things:

1) A decent means to storage power generated by solar panels and wind turbines so it can be used when the Sun is not up and wind velocity is low. That could make it possible for true distributed power generation, where every home generates its own electricity and shares the excess with other people in the neighborhood.

2) A true, practical electric car. With supercapacitor batteries, we could dramatically increase the range of the electric car, reduce the size of the battery pack so it rarely inteferes with interior space, and charge the battery pack in about the same time you fill up a 20-gallon fuel tank! :-)

That's why I think people are still underestimating MIT's announcement of nanotube-based supercapacitor development. It could potentially make the whole idea of fuel cell power superfluous.

Intruiging

[martin_henry]

As an EE student in Virginia, I'm very interested in the subject of this article: unfortunately, it doesn't really say much more than the post above....

Re:battery replacements?

[jcorno]

But are they 10X as heavy, to provide the same power? Weight is more of an issue than size in a car.

Energy and power density are usually given by mass (Joules/kg or Watts/kg).

Re:battery replacements?

[the_13th_saint]

The one major thing to worry about though is that an item that can charge up incredibly fast, contain a lot of electricity, and store it efficiently, can also discharge rapidly and violently...

The trouble with ultracapacitors

[Animats]

Ultracapacitors are really impressive. They exceed the limits of what was considered physically possible twenty years ago. The newer ones can be charged fast and discharged fast; it's not like the older ones that could only deliver tiny currents. People have used ultracapacitors to start auto engines.

The problem, though, is that all the energy can come out at once if they're shorted or damaged. Lithium-ion battery thermal runaway is a problem, and laptop fires have resulted. Ultracapacitor failures will be worse. You don't really want to have a fuel tank's worth of energy stored in a capacitor. But saving the energy from braking a car is probably OK.