Super Battery

I've often wondered what are the advatages/disadvantages of Lithium versus capacitors (such as these nanotube ones)?

No memory effects for either...faster charge for caps...longer life for caps...more controlled and longer discharge for Lithium, meaning caps would be great for quick bursts, lithium good for a lengthy discharges?

Any other insights here?

With ALL the newer battery tech that is here now and up-coming, I just can't see where hydrogen will compete, especially when u do the energy requirements math...

cheers,

Curt.

 

In 30 years we will all look back to vehicles that prompted the advances in electric propulsion and storage. Vehicles like the Insight, Prius, the Segway and your everyday Electric scooter.

 

That's and exciting idea. You won't see it in five years though.

 

<div class='quotetop'>QUOTE(finman @ Jun 9 2006, 11:49 AM) [snapback]268614[/snapback]</div>

The discharge rate of a capacitor is controllable by the amount of resistance or load placed in series with it. Our familiar concept of the capacitor as a "quick discharge" element is based on the fact that the capacitances previously available were small. Peak power output is a function of how fast you can discharge a capacitor, and so far, in cases like xenon flashtubes, the capacitances have been very small.

However, breakthrough announcements like these are essentially saying "we believe that we have raised the capacitance of these capacitors to a level where their storage capacity is essentially the same as batteries." That is, charge one of these capacitors to 12V, and you could essentially discharge it at the same rate as a you could discharge a standard 12V battery over the same amount of time. The implications of this are astounding, as I see it, as capacitors like these will eliminate batteries.

What you bring up about the quick discharge rates of capacitors is, of course, true. However, if you were to try to discharge one of these capacitors as quickly as, say, a photoflash capacitor, you would end up with what would likely be something like Mega Watts of power - seriously. I'm not going to go into all of the formulas as there are many sources of them available, and if you doubt what I am saying, I encourage you to play with the math a bit and see for yourself. An example (not based on the actual discharge rates of real automobile batteries) of how to approach it might be to calculate the total energy capacity of a battery like this:

12.6V nominal voltage, times 2 Amperes for 2 hours. This is 50.4 Watt-hours. Now, multiply by the number of seconds in two hours, i.e., 7,200: gives 362,880 Watt-seconds. The Watt-second is equivalent to the Joule. The formula for the energy storage of a capacitor in Joules is (1/2)*(C*V^2) where C is in farads. If you solve for C, you get the capacitances that these researchers are talking about. These capacitances are huge compared to what was previously attainable.

If you were to discharge a capacitor with the equivalent capacitance as this example in 0.3 seconds, your peak power would be slightly in excess of 1.2 Mega Watts, i.e., 1,200,000 Watts. This is a huge amount of power (over 1,600 horsepower) , and most electronic systems would never be able to handle this amount of power in an instantaneous surge. I think that it is highly likely that a capacitor with this level of storage would almost certainly never be used in a manner that would allow this type of power discharge unless it were being used in weaponry.

My point here is that while capacitors are capable of providing quick discharges and high peak powers, these capacitors would almost certainly never be used in a manner where they would be discharged like a photoflash capacitor (outside of a military use, of course). Their main advantage (other than quick charge times, the complete lack chemicals, and practically infinite lifetime) is their capability to store large amounts of potential energy that will then be used relatively slowly over time in a manner similar to the way a battery is used (although they do have that added bonus of being able to supply high peak powers (more so than batteries can) when necessary).

Much agreed. IMHO, hydrogen is not the way to go as I see it.

 

Has any team investigated the long-term effects of the introduction of carbon nanotube structures into our environment?

I love the ideas that have cropped up recently in nanotechnology, but I have to wonder... The carbon nanotube structure is relatively benign and extremely strong, but it is also difficult to break the structure apart and destroy it once formed... carbon nanotubes do not biodegrade, do not break down in water, etc.

If in 100 years our technology incorporates carbon nanotubes into every type of device, even just as a storage battery, surely significant quantities of discarded nanotube products will wind up in our landfills, in the air, and in our environment.

Does the body expel nanotube fragments that are inhaled? Or do they lodge into our tissues, never to be degraded? Does it matter?

I ask this not to be a naysayer, but to be proactive. Nanotubes offer us the potential of great advances in engineering, from energy efficiency, size, and strength in many products. But are we equipped to handle the consequences (if any) of nanotube production on ourselves and the environment?

- Bob R.

 

<div class='quotetop'>QUOTE(Screwdriver @ Jun 9 2006, 09:30 AM) [snapback]268636[/snapback]</div>

Cough*EVs*cough
THE vehicles that brought us the NiMH chemistry might just BARELY be remembered if people actually knew they existed. One day not long ago, we had actual BATTERY cars. We've now stepped way back and are powering our battery cars with gasoline. Please don't forget the *real* battery cars! We'll be back there soon enough, and the pioneer vehicles will hold a dramatic place in automotive history.

 

umm, its been a while since physics, but all they're doing is increasing a capacitors capacity (no pun).
capacitors dont hold a charge for very long (leave the car with charged caps off over-night, the cap will be depleted.)

 

<div class='quotetop'>QUOTE(smackoww @ Jun 9 2006, 12:06 PM) [snapback]268730[/snapback]</div>

It's been awhile for me, too, but I thought that some capacitors made from certain types of material exhibited little or no leakage.

Once the energy is store in a capacitor, if it is disconnected from a circuit completely, wouldn't the only way for energy to escape be via heat or ionization? (Warning, warning, getting way outside my degree field...)

I had another question about these new extra-super-capacitors: Is it possible to construct a capacitor in such a way that sudden complete discharge is nearly impossible (for safety) but that rapid charging is still possible? In other words, if you incorporated multiple stages of current limiting resistors or some other technique throughout the capacitor, so that puncturing it or shorting it wouldn't cause a total and immediate discharge, can you still allow the capacitor to rapidly accept a charge? Perhaps using a layer of semiconductor acting as a diode? (A little knowledge is a dangerous thing... sorry if I'm way off base here.)

- Bob R.

 

I predicted in an eaten-long-ago-by-a-forum-crash post that there would be new and fantastical advances in battery technology. Necessity being a mother. No reason to with an ICE car. But with hybrids...every reason to improve them.

And when the batteries are developed for cars....the plug in becomes very VERY viable.

 

A physicist to the rescue!!! Of course I really dont know much about nano-crystal physics *grin*. The way people have made large capacitors in the past have been to put dielectrics of various materials inbetween, this allows you to get more storage for a give size. But I'm curious if you start upping the capacitance too much especially if its using a trick by using a large surface area of lots of tiny things (nano-tubes/crystals/monkeys) will there be an issue of arcing that occurs?

Large capacitance = large electric field (at full charge) doesn't take much to get arcing to occur (potential difference of 10kV per cm in dry air IIRC)

 

<div class='quotetop'>QUOTE(bobr1 @ Jun 9 2006, 01:59 PM) [snapback]268695[/snapback]</div>

Can they be recycled into roadbeds? Flexible for tires?

 

<div class='quotetop'>QUOTE(DeadPhish @ Jun 9 2006, 03:12 PM) [snapback]268889[/snapback]</div>

Well, when you are talking about carbon nanotubes, they are microscopic and once they are sheared or severed, they do not tend to adhere to anything, and are harder than diamonds.

Here is a Wikipedia entry on carbon nanotubes:
http://en.wikipedia.org/wiki/Carbon_nanotube

- Bob R.

 

<div class='quotetop'>QUOTE(ScottY @ Jun 9 2006, 06:56 PM) [snapback]268962[/snapback]</div>

"Fullerenes and carbon nanotubes are not necessarily products of high-tech laboratories; they are commonly formed in such mundane places as candle flames."

It looks like you don't need to imagine it..

 

<div class='quotetop'>QUOTE(benighted @ Jun 9 2006, 11:20 PM) [snapback]269085[/snapback]</div>

Scrape the back of a used fireplace with your finger... if you looked under an uber-high powered microscope you'd see millions of carbon nanotubes under your finger nail

 

<div class='quotetop'>QUOTE(MikeSF @ Jun 10 2006, 06:44 PM) [snapback]269353[/snapback]</div>

Well, OK, that's why I was asking about them as a question... if they are that common, I'll (mostly) stop worrying.

Still, it's not hard to come off with the impression that they're something completely new and different, given the mainstream press coverage.

- Bob R.