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

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

[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.

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.