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Ultracapacitors Soon to Replace Many Batteries?
einhverfr writes "According to an article in the IEEE Spectrun, the synergy between batteries and capacitors — two of the sturdiest and oldest components of electrical engineering — has been growing, to the point where ultracapacitors may soon be almost as indispensable to portable electricity as batteries are now. Some researchers expect to soon create capacitors capable of storing 50% as much energy as a lithium ion battery of the same size. Such capacitors could revolutionize many areas possibly from mobile computing (no worries about battery memory), electricity-powered vehicles, and more."
I believe it depends on the type of rechargeable. The nickel cadmium did. Lithium does not.
The problem I've had with all of them is their life span. After a year of regular use, they then to hold a fraction of their original charge. It appears ultracapacitors have a much longer life span. rock on
In the early 60's i was working part time at a TV repair shop to augment my military paycheck. I was working on one of those old huge TV's in the wooden cabinet type of thing. i had traced the problem to a paper electrolytic of fair proportion.
I changed the capacitor and confidently looked at the waveform on the scope knowing now that there would be no more ripple on the line but to my amazement there was even more ripple. I looked closely at my installation job noting it was across the right terminals and the polarity was correct.
I pulled my head out of the TV cabinet to look at the schematic to envision what else might be wrong when the capacitor blew up like a small bomb leaving a boiling hot liquid paste where moments before my head was peering.
It turned out that the paper cylinder was installed backwards on the capacitor reversing the positive and negative terminals.
Even if the paper cylinder was backwards... one can still note the metal case of the capacitor being the negative terminal. I failed to do this.
This occasion added a new check I made each time for every capacitor installed after that.
And in the end, the love you take is equal to the love you make
How about not writing such obscenely bloated software that it needs a mainframe-on-a-chip to show an address book?
You want to save energy? You want to reduce cost? You want to reduce carbon footprint? It's not by making yet another technology, it's by refining what we already have. We don't need Javascript code that takes seconds to execute a simple text display on a multi-GHz processor. Start there. And we won't need capacitors with the energy density of an explosive to run a freaking phone.
Rapid energy storage, with very low effective series resistance, is perfect for regenerative braking, and for burst acceleration. If a vehicle starts with full batteries and capacitors, then uses the capacitors first in acceleration, they would be discharged when braking was required, allowing them to rapidly store the power from the motor/generators. The batteries (and fuel cell or combustion engine), then are sustained energy for overcoming losses, powering accessories, and long uphill grades.
In about that same time period I was working on a homebuilt power supply for a ham transmitter. I had temporarily bridged in more filter capacity and shortly thereafter absentmindedly picked up the still-charged electrolytic by both leads - *one in each hand*. The PS was about 350 volts. Fortunately the muscle contractions flung the thing out of my hands. They say a learning experience is anything we survive...
The "supercaps" are designed on similar principles to batteries but with a very different physical design strategy. Capacitors are built like a roll of paper towel, and have a very large surface area of contact between the plates. (several square feet for a small capacitor in a computer) This allows them to very rapidly charge and discharge because the current is distrpbuted over a large surface area. They store their energy as an electrical charge, and as you draw from it, the "pressure" lowers in relation to how much energy you have removed.
Lead acid and other chemical batteries store their energy as a changed chemical state. The chemicals build and maintain a fixed charge on the plates. This allows a 12 volt battery to hold 12 volts until it is almost discharged, unlike capacitors whose voltage drops as they are discharged. It could be quite a challenge to deal with this change in basic operation. Capacitors have another advantage in that they are able to directly produce a very high voltage, limited only by the quality of the insulating materials they are made with. Capacitors can easily hold hundreds of volts, and there are industrial caps that can hold many thousands of volts.
There's an interesting similarity for those of you familiar with paintball. Capacitors behave almost exactly like high pressure nitrogen tanks - they have very high energy and can have a very high capacity, their "pressure" drops during use, and a regulator is required to output the correct pressure. (voltage) "CA" tanks (Constant Air, CO2) on the other hand rely not on high pressure, but on a supply of liquid CO2 in the tank which changes state as gas is drawn from it, boiling to return the tank to the preset pressure. (voltage) When the supply of liquid CO2 is used, it falls just like a dead battery.
Traditional paintball guns can run on a nitrogen tank if they are equipped with a regulator to knock the pressure down to a level the gun can handle. In the same way, electrically a cap could replace a battery with not a lot of modification, but the design is very different.
Paintball air tanks are roughly the same by volume, but a modern high capacity nitrogen tank can provide more shots than a high capacity CA tank. CA tank capacity is limited by its physical size - like nitro, the more liquid (gas for nitro) you can fit into it the higher the capacity. Nitro tanks have the added advantage of the max pressure the tank can take. Stronger tanks can hold more pressure for the same size, so increases in technology allow for a greater power density in Nitro but not in CA.
I expect the same should be true of caps vs batteries - you can only put so much electrolyte in a battery. You can look for better electrolytes, but you eventually run out of better solutions. Capacitors are limited by their electrolyte and the quality of the insulators. (a bit like the ability to hold pressure in a nitro tank) Assuming technology can continue to improve on that front, capacitors may catch up with or surpass traditional batteries in power density.
I'm not counting on it though. Although capacitor technology is far from reaching its pinacale, most of the major breakthroughs have already been made. The advent of carbon fiber made Nitro tanks the better deal. Unless a new technology of the same magnitude comes up for capacitors, I don't think we'll see them in our laptops anytime soon. There's also a safety factor when you are trying to push any form of pressure really high. Nitro tanks are downright dangerous if mishandled, and must be treated carefully under the best of conditions. Jacking up the voltate on your laptop's supercap to 100kv... even if it becomes practical, I don't know if I want to carry THAT around.
I work for the Department of Redundancy Department.
Thank you. You just gave me a new sig.
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.
Does being on slashdot mean that you must be rude?
:)
You must be new here... idiot.
Random and weird software I've written.
No, thank you.
Plastic film capacitors will wear out if they are operated at excessive currents.
High-k ceramic capacitors degrade partially over time.
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a. You are climbing up and down ladders all day and don't want to trip over power cords
b. You work in a space with limited or no continuous power supply
c. You have 2 or 3 fully charged batteries and a quick charger
d. Not all tools work with compressed air
e. You kept slamming the cord to your old tool in the tailgate of your F350.
f. all of the above and a lot more.
Memory is a very specific occurrence in very specific conditions with a very specific type of cell (sintered plane nickel-cadmium). It exists. You've never seen it.
>>I have an 2 year old cell phone that doesn't hold a charge at all and it has a lithium battery.
It's not memory. It's worn out (too many cycles) or reached the end of its calendar life (since manufacturing, not since you bought it - newer-generation LiIon cells are much better at this aspect). Or both. All cells do this eventually. 2-3 years for a consumer grade cell is not at all unusual. Yes, there are exceptions; I own a few of them.
Capacitors have a lifespan of "functionally forever." You're right: perfected, they'll be a whole lot better than any type of cell we have now.
R
If a car powered by this technology wrecks or impacts with another car, would it not be feasible that a significant amount charge would be depleted during an impact because the energy could not be fully recovered?
If I'm reading your post correctly you're worrying about a loss of kinetic energy not being recoverable for recharging the capacitor. That's not more of a problem here than with any car. Air friction already produces similar energy losses without any crash. My Prius suffers from the problem you describe, but it's no big deal. It has ordinary mechanical brakes in case the regenerative braking cannot recharge the battery fast enough to slow down the car, but they rarely engage and the car has never needed a brake job because the battery (plus friction) is already pretty good at absorbing the energy.
With capacitors, the danger with a crash is an explosion. This could in theory release much more energy than the cars had in kinetic energy upon impact (like when an ordinary car's gas tank ruptures and ignites). While people like to worry about 911 workers with can openers unwittingly shorting out the NiMH batteries in a Prius, a short-circuited battery can only discharge energy as fast as the chemical reactions inside will allow. You don't necessarily get this protection with a cap. Basically the pulse width you can get from a capacitor is mediated only by its internal resistance and its magnetic induction.
That can still be considerable. I used to have a 100000 uF cap (they were just coming out in the early 90s, and this one was the size of a small stack of dimes). When I charged it to 5V and discharged it, I had to wait a few minutes for the thing to drain. It had electrical characteristics similar to those of a worn out rechargeable. But when one of those big HV paper-and-oil caps shorts out, wow. A friend of mine made a can crusher for the Rutgers physics department out of a car-battery-sized HV capacitor. It was the size of a car battery not because of its capacitance (it had an unimpressive 100 uF in that regard) but because of the high voltage rating (at least a few kV). Most caps can only handle 35 or 50 volts. The stored energy in a capacitor rises only linearly with capacitance, but quadratically with respect to voltage. This thing discharged through a coil of copper piping (6-7 turns) wrapped around a plexiglass tube with a soda can inside. When it discharged through the coil, it induced a circular countercurrent in the can. Then the magnetic repulsion between the coil current and the can current crushed the can into the shape of a pencil in an instant- BANG! It woke up all the engineering students, that's for sure. I think they still use it.
In terms of dumping current, yeah, the capacitor is very dangerous. That said, the amount of current contained (per device) in the largest supercaps I've seen thus far is not significantly greater than what an automotive-grade lithium ion battery pack can dump in a fraction of a second. The difference is that when you short out the supercap, only the shorting material catches on fire instead of the battery and any combustible materials nearby.
Unlike lithium ion cells, supercapacitors don't spontaneously combust when exposed to oxygen, react badly to conventional fire suppression systems, and release a highly caustic smoke that can cause severe lung damage if you breathe it. They don't burst into flames when overcharged or shorted. They don't get so hot that they can ignite adjacent materials when shorted. And so on.
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No, it really isn't. There's this marvelous technology, instantiated in these crazy devices we call "fuses", see...
Seriously, all you have to do is fuse the array internally on a per-block basis, and any shorted module will blow the fuse(s) to its neighbors, and that's the end of it. No explosion. No nothing. Just pffft and some new fuses (which might take a service call, but heck, you just ran into someone else, that's the least of your problems.)
One of the many benefits of capacitor systems is that you can arrange them many ways for many varied benefits. Paralleled caps simply add, so there's no reason not to break a high energy system up into blocks, and many reasons to do so. Not the least of which is the above issue, but it also makes replacement and service less expensive, less complicated, and allows use of smaller, easier to manufacture parts. And of course it allows various kinds of charging models.
I'm inclined to trust the engineers. If I can think of it (and I am an engineer, but not that kind) then they've probably though of it a hundred times over. The main issue here is energy per unit volume, and to a lesser extent, per unit weight. When and if those issues are really solved, we're golden.
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