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Capacitors tapped to boost electric vehicle energy storage potential

By | March 4, 2011, 5:23am PST

Summary: Hey, here’s something to think about on a pre-spring Friday. Most of us have been conditioned to think of batteries as the primary energy storage option for electric vehicles, but chances are increasing that ultracapacitors will also play a role in extending electric vehicle ranges and utility. Oh yes, and helping decrease the cost. Consider the [...]

Hey, here’s something to think about on a pre-spring Friday. Most of us have been conditioned to think of batteries as the primary energy storage option for electric vehicles, but chances are increasing that ultracapacitors will also play a role in extending electric vehicle ranges and utility. Oh yes, and helping decrease the cost.

Consider the fact that one of the better-known players angling for this market, Maxwell Technologies, this week was awarded a $7.01 million cost-shared technology development contract by the United States Advanced Battery Consortium. (Cost-shared means that Maxwell will also put up money for the research and development.) The consortium is part of the United States Council for Automotive Research, which is backed by companies including Chrysler, Ford and General Motors. So, there’s a pretty good chance that this technology will find a commercial application as quickly as possible.

The moolah that Maxwell will get directly is about $3.5 million, but here’s the skinny: Maxwell is leading a team that has been charged with creating an energy storage system that meets the specifications outlined in the consortium’s Lower Energy-Energy Storage System for power assist hybrid electric vehicles (aka PHEVs). The aim is improvements in energy and power density compared with existing capacitor systems. The goal is to double existing capacitor density from 10 kilowatts per kilogram to 20 kilowatts per kilogram, while doubling energy density from 15 watt-hours per kilogram to 30 watt-hours per kilogram.

As I mentioned in my year-start post, energy storage technologies continue to be one of the most critical components of the green energy movement. This is another great example of what needs to happen.

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Heather Clancy is an award-winning business journalist with a passion for green technology and corporate sustainability issues.

Disclosure

Heather Clancy

Writing publicly about what the high-tech industry is actually doing to help itself and the world get greener or more sustainable is one way I figure I can contribute more meaningfully to said effort. I am also a big OMG-kind-of-fan of smart leadership, which is why the goodly folks who publish this blog let me go on about this topic and why I am always on the hunt for forward-looking business management ideas.

My daily writing is focused on looking for topics for my blogs, GreenTech Pastures and Business Brains. I also write often about emerging technology trends such as mobile computing, unified communications and cloud computing. Occasionally, I will pop up at an industry conference in some sort of speaking capacity. In cases where a speaking engagement involves a sponsor that may be covered in this blog, that fact will be disclosed in coverage as appropriate.

My corporate writing work usually consists of crafting research white papers about some aspect of technology. In the event that my commentary (in written, audio or video form) mentions a company for which I have provided consulting advice, I will disclose that fact. However, there is no connection between these projects and the topics that I am covering in my blog.

Biography

Heather Clancy

Heather Clancy is an award-winning business journalist with a passion for green technology and corporate sustainability issues. Her articles have appeared in Entrepreneur, Fortune Small Business, The International Herald Tribune and The New York Times. In a past corporate life, Heather was editor of Computer Reseller News, where she was a featured speaker about everything from software as a service to IT security to mobile computing.

Heather started her journalism life as a business writer with United Press International in New York. She holds a B.A. in English literature from McGill University in Montreal, Quebec, and has a thing for Lewis Carroll.

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RE: Capacitors tapped to boost electric vehicle energy storage potential
opcom 6th Apr 2011
"Even 4 gauge (about as big around as your thumb) can get hot" - someone has a very small hand! AWG 4GA=5.2mm, so maybe maybe 7.2mm if with a 1mm insulation.

http://www.66pacific.com/calculators/wire_calc.aspx
the ultra quick recharge times sell me. Batteries suck, replace them all...
@Johnny Vegas Yes, but consider the consequences of those ultra-quick recharge times.

Over time, you could find large capacitors in use in large mobile audio systems, typically those with big subwoofers. The standard has typically been a 1 Farad capacitor, about the size of a large frozen orange juice can, or a little larger.

It was required to charge one of those capacitors through a resistor (or, cool trick - a light bulb to provide the needed resistance, gradually dimming as it charged). Why? To intentionally slow the charge.

While no capacitor is a truly theoretical capacitor, it still tries to charge fully as closely to "instantly" as is possible given the very little internal resistance that exists in a capacitor. If you were to hook up a capacitor to a car's 12v electrical system without charging it first, you would generate a spark large enough to weld the terminal you were trying to connect to the capacitor itself. You actually can weld, using a charged 1F capacitor, for that matter... but it's more of a shock when it happens to you accidentally.
And although that current draw may be brief, it's like lightning through some pretty thin wires. Even 4 gauge (about as big around as your thumb) can get hot, and that could damage your battery if the connection was direct. Although a battery has lots of internal resistance, that kind of current draw can still crack plates, especially on standard (non-deep-cycle) batteries.

Also, capacitors don't maintain a voltage, just a charge. The voltage fluctuates along with the system, where a battery maintains a relatively constant voltage... having a constant voltage is important, particuarly as our electronics onboard get more and more sophisticated. Current draw can fluctuate disproportionately with voltage, damaging electronics.

So there's lots of considerations to be had - not just speed of charge (which will need to be slowed down intentionally regardless, even with gas-pump-hose-sized power cable used for charging).
@Johnny Vegas I thought the current thinking was capacitors and batteries operating *together* to smooth out the disadvantages of the other?
This is just a waste of time and money. But hey, Maxwell is getting someone else to front up some R&D bucks to turn up some better caps. Good luck!
@CaptOska Would you care to explain why it a wast of time and money.
@Knowles2
A capacitor's energy storage capabilities are tiny compared to a similarly sized battery. Though it does have the ability to deliver and absorb high currents, any cap large enough to handle the requirements of a 20-40HP electric motor is going to be large. This space would be better utilized as battery space.
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Maxwell's Demon?
OVFlooring 4th Mar 2011
Will these capacitors permit perpetual motion?
@OVFlooring Nothing is perpetual motion but dust
Do we really need the next big step? like the discovery of electricity, When it comes it will change your lives and the World we live on?
I don't want to let the cat out of the bag, but they intend to use a "flux capacitor" in the body of a DeLoreon. They even hired Dr. Emmett (Doc) Brown to build it for them. He has conducted extensive research in this area.
@jabeno Poke fun if you will, but Doc at least knew how to pronounce "Gigawatt"!
Considering the output of these capacitors, how long will it be before some auto service technician turns himself into a "lightning bug"?
The capacitors in electronic flash equipment store enough power to cause extremely painful burns at a minimum, but can also cause death. These energy stored in these capacitors are small compared to the ones for the auto industry.
that talked about capacitors as a way of storing a lot of energy
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Regenerative Braking.
steve_jonesuk@... 5th Mar 2011
This is very exciting.
I'm led to believe that the energy recovered under braking by hybrid vehicles is a tiny fraction of the energy dissipated.
And that the reason for this is that the dissipation of a car's energy in a few seconds leads to huge amounts of power....
Batteries can't be charged quickly enough to absorb all of this energy in such a short time, so it's wasted.
If we have a faster-charging system, either a flywheel, capacitor or other medium, we can reclaim a lot more energy from braking.
The gains for efficiency are potentially huge and can be exploited without a huge battery as per a conventional hybrid.
Indeed, if this tech can be made cheaply enough, we could see it significantly boosting both the economy and the performance of otherwise-conventional cars.
What steve_jonesuk said.

Capacitors (and inductors too, but they are way too heavy) may store small quantities of energy but may take and deliver them in few instants. The time taken is about 63% of R * C where R is the resistance you'd put before the capacitor to avoid damage (to you and / or the capacitor).

Capacitors may be used as temporary quick "energy sponges". A battery could not charge fast enough during the short but high energy peak delivered during a brake. The same charged capacitor may be later be used to deliver a quick discharge to improve the car acceleration from a stop or may be slowly released in the battery to charge it up.
@dfumagalli@...

The 63% figure is incorrect for the time to charge a capacitor. An RC circuit, or a circuit that has a resistor (or a resistance from the terminals of the capacitor) and a capacitor will take 5 times the RC time constant to charge itself. This figure assumes a constant voltage source. If the voltage source charging the capacitor varies over time then the 5*R*C is not valid.
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I've never heard anyone talk about it but if the car was, say, painted with a solar conductive paint (or short term just have panels on the top) could a capacitor charge off that little of a trickle charge? Capacitors in general sound like a great idea because of their quick "charge" time. Not sure about their equally quick discharge time, but this seems like a pretty good answer to many of the problems.
"Even 4 gauge (about as big around as your thumb) can get hot" - someone has a very small hand! AWG 4GA=5.2mm, so maybe maybe 7.2mm if with a 1mm insulation.

http://www.66pacific.com/calculators/wire_calc.aspx

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