While batteries make most of the headlines when it comes to the energy storage requirements of electric cars, the capacitor could be an exciting and viable alternative. Unlike batteries, which store chemical energy and make it available for use as electrical energy, capacitors store energy in the electric field between a pair of conductors. Supercapacitors, or ultracapacitors, are currently being developed which could rival batteries in the amount of energy that they can store. Whether capacitors see use as part of a hybrid drivetrain or as the sole source of electricity for a pure electric vehicle, we expect to see them make a dent in the automotive sector as the future unfolds. Then again, we've been expecting some news on this front for a while (EESTOR, anyone?), so we might have to keep waiting.

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The most important part of an electric or hybrid vehicle is often said to be the battery. With all the breakthroughs in energy storage and the emergence of new companies, it can be a difficult field to keep up with. If you are a potential investor or just a curious onlooker you might be interested in how Mike Millikin has graded what he believes to be the top dozen companies in the field.

In a three-part article for EnergyTechStocks.com, the founder and editor of the informative Green Car Congress hands out report cards for the leading battery and ultra-capacitor companies out there today. All the big battery names you read about on AutoblogGreen are represented as well as the secretive EEStor ultra-capacitor folks and impressive upstarts like Valence. While nobody gets an "F," Mike pulls no punches with a frank assessment of each. We thinks he is pretty much "on the money" but if he's slipped up, we are sure you'll let us know.

[Source: EnergyTechStocks.com]

Researchers at North Carolina State University have developed a new type of capacitor which allows up to seven times the electrical storage potential as standard capacitors available today. The breakthrough apparently is a polymer called PVDF which can act as a high-performance dielectric, which is an insulating material between two metal surfaces. Electricians are used to using a dielectric grease on electrical connections, so this may be a familiar concept to some of our readers.

This is good news for the electric and hybrid car industry, as capacitors are a possible alternative to batteries. Unlike batteries, which use a chemical reaction to release their stored energy, capacitors use no chemicals and are capable of storing and releasing a given amount of energy quickly. The problem is that capacitors generally store less energy than batteries. This potential, but untested breakthrough could alleviate some of that deficiency, allowing the capacitor to store more energy while still enabling that energy to be charged and discharged rapidly. EEStor is a name that has been thrown around on our blogs, as they claim to have a capacitor based system which rivals expensive batteries in power output, and possibly at less cost. We'll keep our ears and eyes open for more capacitor news, and we'll be sure to pass it along.

[Source: Science Daily, thanks to Matt for the tip]

Automotive DesignLine reports on a hybrid bus design by ISE Corporation which incorporates ultra capacitors. What are these ultra capacitors, and why are they needed in a hybrid vehicle? Regenerative braking, the key to the increase in fuel economy of hybrids, allows a vehicle to recapture and store part of the kinetic energy that would otherwise be lost to heat when braking. We’ve all been stuck on or behind the city bus while it is making frequent stops, and you can imagine the tremendous potential to capture all this braking energy with a hybrid electric drivetrain. This scenario sounds great in theory, but current battery technology doesn’t necessarily allow us to implement it in the most optimal way. One major drawback of current batteries is their limited ability to capture and regenerate energy during braking and to provide bursts of high power during short duration events. You can only push electrical energy in to a battery at a specific rate, and you can only draw it out at a specific rate.  These rates are often too slow to capture all the braking energy from the constant brake-acceleration cycles of a heavy city bus.

One possible solution to this problem is the use of ultra capacitors to complement the battery performance. An ultra capacitor is an electrochemical capacitor that has an unusually large amount of energy storage capability relative to its size when compared to regular capacitors. These ultra capacitors perform well in cold weather, have a long life-cycle, have a higher efficiency than batteries, have a high power output, and can effectively capture energy from braking. They probably won’t be seen on smaller vehicles any time soon, since the problem is more critical with heavier vehicles. I really have no idea how expensive these are, but I assume their are cost issues as well.

[Source: Automotive DesignLine]