the usual suspects

Supercapacitors

Okay, tech boys! The latest focus of my curiosity is supercapacitors - any ideas whether this is a viable R&D angle for payoff sometime in the next five years?

The prompting article is behind the link below, or you can read it in its original context at that great bastion of cutting edge science (NOT!), ABCNews.

A New Charge
Powering Up New Uses for Supercapacitors

By Paul Eng

Aug. 10, 2004 -- Last year, when a massive power outage plunged most of the East Coast of the United States into darkness, many scrambled to snap up that staple of modern life: batteries.

From flashlights to portable radios to cell phones, the common chemical-based battery provided some source of electricity while engineers struggled to get massive power plants back online.

While the battery has become the dominant form of portable power, some say its reign will soon be challenged by a "super" opponent: the capacitor.

Like batteries, capacitors provide electrical energy using chemicals stored within a container. But one of the traditional drawbacks of capacitors is that they don't provide nearly enough juice as a common battery of a similar size.

Alfred Siggel, global technical manager at Honeywell Specialty Materials in Seelze, Germany, says the company has developed a chemical solution that will help make so-called supercapacitors.

Like batteries, these devices could hold enough energy to power portable devices, computers, or even cars. And they could be recharged within seconds, not hours like traditional rechargeable batteries.

The heart of Honeywell's solution is a fluorborate salt, a chemical whose physical structure allows it to store a tremendous number of electrons. The chemical is dissolved in a special solution at high concentrations -- about 300 grams of salt per liter of solvent -- and then embedded onto carbon plates.

Siggel says that this chemical process is important because it improves how capacitors store and deliver energy.

"The main difference, compared to batteries, is that the battery uses a chemical reaction to generate electricity," he said. "[In a capacitor], it's a pure physical process. The [chemicals in the] plates are where you are storing the electrons."

But by using special chemical concoctions such as Honeywell's salt, Siggel says supercapacitors can now hold about a million times more energy than of capacitors of similar size ? and without losing the important advantages of ordinary capacitors.

For example, storing electrons in a capacitor doesn't require any chemical reaction. That's why capacitors can be charged in seconds and release huge amounts of power quickly, too. (A typical use of capacitors is in electronics such as camera flashbulbs.)

Another advantage of supercapacitors: their extremely long life cycle. Batteries can produce electricity only as long as their chemicals hold out. Even rechargeable batteries have a limited life since their chemicals wear out from repeated charging and discharging.

"For a capacitor, this [charge-discharge cycle] is typical," said Siggel. "There is no overcharging, no effect on the lifetime of the chemicals, and 100 percent capacity all the time."

Such characteristics, says Siggel, now make supercapacitors an ideal candidate for uses traditionally filled by conventional rechargeable batteries. One such new use, for example, would be in new hybrid electric cars.

Currently, hybrid cars such as Toyota's Prius use heavy, rechargeable nickel-metal hydride batteries to store energy recaptured when drivers step on the car's brakes. That energy can then power a small electric motor to move the car at slow speeds, saving the car's engine -- and gasoline -- for higher speeds.

Siggel says a supercapacitor could easily do the job of the hybrid's battery without the weight or cost.

"Panasonic charges $4,000 or $5,000 for a Prius battery," he said. "If you have to replace it because the chemicals have worn out, that can be quite unreasonable for the car's owner."

Automobile makers have reportedly been working on supercapacitor-equipped cars. A Toyota spokeswoman says the Japanese company had a few years ago shown a Prius concept car using what it called an ultracapacitor. But the company says it's unlikely such a car will make it to showroom floors anytime soon.

Many say that even with chemicals such as Honeywell's fluroborate salt, supercapacitors won't catch up with the capabilities of traditional batteries. And there are several disadvantages that still need to be worked out.

For one, while a capacitor may hold energy comparable to a battery's, it typically releases it quickly, in large bursts. In other words, it would be hard to make a capacitor that can deliver a steady stream of electricity for days or even hours at a time.

Although a backup power system made up of just supercapacitors would be impossible, Siggle says the devices could have a role in protecting a regional power grid and perhaps prevent wide-scale blackouts such as the one that struck last year.

"In the power blackouts of last year, you had one system that crashed and the others tried to make up for the sudden loss of power," he said. "When they couldn't make up the demand, they began to fail as well."

Siggel theorizes that large banks of supercapacitors might have been able to take up the slack momentarily, providing just enough power and time for system engineers to react properly.

"If there was a buffer in between [the failure of one system], maybe the next system [down the line] wouldn't have crashed," he suggested.

But until more supercapacitors are developed, tested, and put to practical use, Siggel's idea might be just another spark in the dark.

Posted by thinkum at August 10, 2004 08:57 PM