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Ultracapacitors Soon to Replace Many Batteries?
Posted by
Zonk
on Sun Nov 04, 2007 06:46 PM
from the zap-zap-zazp dept.
from the zap-zap-zazp dept.
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."
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HEY! (Score:5, Funny)
I want my friggin 15 hour battery life laptop first! You promised!
Re:Interesting - crashes? (Score:4, Insightful)
Parent
Re:Interesting - crashes? (Score:5, Insightful)
Either that or a power cord. This would be either replacing batteries in a hybrid or in a traditional EV. Supercaps can basically solve the fundamental problem with EVs: battery life. Unlike batteries, supercapacitors don't rapidly lose their ability to take a charge over a few years. They also are more efficient, produce less waste heat, and are generally considered much safer than Lithium ion cells. These aren't jut to capture waste energy. These have the potential to store huge amounts of energy for a fairly significant period of time with relatively low leakage.
The big disadvantage is that they haven't reached the same capacity as batteries per unit of mass or volume, last I checked, and are nowhere near the density of gasoline. One big advantage, however, is that you can put them in places where you could never put batteries for thermal safety or serviceability reasons.
Parent
Re:Interesting - crashes? (Score:5, Informative)
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.
Parent
Re:Interesting - crashes? (Score:5, Funny)
The solution if you run out of energy? Just wait for someone to hit you.
Parent
Re:Interesting - crashes? (Score:4, Insightful)
Then the vehicle gets lousy mileage, just like somebody pulling jackrabbit stops today.
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?
At the point of an accident, the charge on the caps is irrelevant except for arranging to discharge it in a preferably safe manner. They're more worried about preventing injury to the occupants at that point.
just get the guy riding in the car behind you to bump you a few times and he's out of 'gas'.
Bumps wouldn't do it. Hitting it hard enough to set off airbags probably would. Of course, at that point the police are going to want to talk to you.
Seriously, I see this being more useful for non-plug hybrids than a pure electric vehicle - An EV already has enough battery capacity to take the current of a pretty hard stop. With a current type hybrid they're constantly working on making the battery smaller - it only really needs to be able to hold power for one run up to speed, and one deceleration, after all. They have to oversize the battery for that use to get the current capacity. Otherwise you just can't pull enough power out to get good acceleration, or be able to charge the battery on decel.
Depending on how long it can hold the charge - might be useful for portable products that use a lot of juice quickly, but can also be plugged in quickly. At half the storage density of LiIon, it'd better be quite a bit cheaper, or use charging/regulation tech that takes almost no space in order to make it worth it.
Parent
Re:Interesting - crashes? (Score:5, Interesting)
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.
Parent
Re:Interesting - crashes? (Score:5, Interesting)
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.
Parent
Re:Interesting - crashes? (Score:4, Interesting)
These two processes are essentially the same thing - invert the current inside the electric machine and it will brake the vehicle. The only problem is how to do this. If you want to do that in a manner that every single joule finds it way to the battery, breaking torque will decrease as the speed decreases and you will have to apply mechanical brakes in one moment.
If you do this by forcing the same braking torque all the time strictly by the engine, which is quite simple to do, in one moment energy flow will not be toward the battery, but from the battery. This is due to internal resistance of the electric motor.
In general, electric vehicle must have mechanical brakes simply as a safety measure. But electric vehicles are essentially more safe that IC-based ones, as they always have two truly independent braking systems.
Parent
Re:Interesting - crashes? (Score:4, Informative)
However, in a hybrid, there are usually one or two intermediaries between the wheels, electric motor, and battery storage. The intermediaries are the gearbox and power electronics. Both of these intermediaries convert input power to output power: input torque and shaft speed to output torque and shaft speed, input current and voltage to output current and voltage. The efficiency of the conversion varies depending on design and operating conditions, but is theoretically 100%.
With some intelligence built into the powertrain (i.e., computing power, algorithms, control laws), you can adjust the gearbox setting (by shifting gears) and the power electronics (by modulating frequency or duty cycle) such that braking torque can be constant throughout deceleration. The deceleration power in the mechanical and electrical subsystems won't be a constant, though.
My understanding is that the main reason the Prius has to use its mechanical brakes at all is that the components in the regenerative powertrain have maximum power ratings. For instance, the batteries have some maximum charging current limit. So the computer has to augment the regenerative braking (which is power-limited) with the mechanical brakes (which don't have that limit in normal usage).
This is why having ultra-capacitors in place of or augmenting the batteries will be so useful - they have almost no current limit, and can absorb the spikes for accelerating and decelerating in stride.
Parent
Re:HEY! (Score:5, Funny)
Parent
Don't short it out... (Score:4, Interesting)
Re:Don't short it out... (Score:5, Funny)
Parent
Do they burst and leak fluid? (Score:4, Interesting)
Re:Do they burst and leak fluid? (Score:5, Interesting)
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.
Parent
Re:Do they burst and leak fluid? (Score:5, Interesting)
Parent
Re:Do they burst and leak fluid? (Score:5, Insightful)
Parent
Re:Do they burst and leak fluid? (Score:5, Funny)
Parent
Re:Do they burst and leak fluid? (Score:5, Funny)
Parent
Re:Do they burst and leak fluid? (Score:4, Funny)
Parent
Re:Do they burst and leak fluid? (Score:4, Interesting)
Someone somewhere in the supply chain had gotten a reel of caps that had been loaded in the reel backwards -- I have no idea how. Anyway, the pick-n-place machines stuck them down, just like normal, some 500 per board or so, all with reverse polarity. We were building that type of board at about 30 per hour, and it took almost an hour for the first boards to get to functional (power-up) test.
At that point, the RP caps all vaporized at the same moment.
It was like a miniature war zone: the caps would blow out tiny flaming chunks of stuff, leaving little spirals of smoke, while tiny flames shot upwards and downwards out of the test racks. It was awesome, although I'm sure glad I wasn't standing right over the first boards when they went. They burnt holes deep into the 22 layer circuit boards.
Then we had the job of finding, removing, and replacing, by hand, 500 caps on each board, and if we missed even one: fwoom! there goes another board.
I don't think we managed to get a single board from that lot repaired and out the door.
Much smaller than your experience, but very impressive nonetheless.
Parent
Re:Do they burst and leak fluid? (Score:5, Informative)
The most common thing you see are electrolytic capacitors, which can indeed burst if they're of extremely poor quality (and cause an environmental hazard along the same lines) -- but of course, saying that is true of many many things. Take paint for instance -- we cover everything in it, and it's generally safe, with only a few exceptions like lead paint, which will make you sick, or the stuff they coated the Hindenberg with, which could also be used as rocket propellant...
Modern electrolytics are much better, although their operating characteristics aren't the greatest -- they have a high capacity, and that's about it.... they're not at all reliable or tolerant of varying operating conditions. Fortunately, many applications don't require this...
You can use all sorts of other things inside a capacitor: paper, glass, ceramic and kevlar are used to name a few, or you can forego the dielectric completely, and put a vacuum between the two plates.
Oh, and supercapacitors don't use electrolyte as the dielectric. That's not to say they won't go boom -- I have no idea how they operate, but they're not filled with the same stuff as what you're thinking of -- if they were, they'd still just be plain old unremarkable electrolytic capacitors.
Parent
Re:Oldest and sturdiest? (Score:5, Funny)
You must be new here... idiot.
Parent
Better tasers? (Score:3, Funny)
Re:Better tasers? (Score:5, Informative)
The capacitor is charge via the battery, and the charge is released over a shortened interval. Same deal with a camera flash.
The could already make tasers lethal in nearly all cases if they wanted to, but the point of them is that they aren't lethal in most cases.
Parent
obvious (Score:4, Funny)
Yes, but are they as incendiary as a SONY battery of the same size?
Re:obvious (Score:4, Informative)
Parent
Vaporware (Score:5, Insightful)
I doubt it will be viable in notebooks (Score:3, Insightful)
I could see this in devices where you need a high current for a short time, but not for slow drain devices. I personally want a battery (or whatever) that last longer than a Li-ion or Li-polymer in a notebook or phone while staying the same size or going smaller.
Re:I doubt it will be viable in notebooks (Score:4, Insightful)
Parent
I doubt it *won't* be viable in notebooks (Score:4, Insightful)
Parent
Re:Can you? There are other limits. (Score:4, Interesting)
Parent
Re: (Score:3, Insightful)
I've got an idea! (Score:5, Insightful)
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.
regenerative braking (Score:5, Insightful)
Could someone explain the jargon? (Score:5, Funny)
Are Ultra capacitors like flux Capacitors that you can use to go through time once you're travelling at 88mph? If so I don't think this will be very efficient at all since they require 1.42 Gigawatts!
Re:Could someone explain the jargon? (Score:4, Informative)
Parent
Wake me when they actually achieve something. (Score:5, Insightful)
I have been hearing how eestor would have its ultra caps in cars in 2006, then 2007, and I can only assume 2008 now. Not only are they not in cars, they haven't demoed as much as a since cell. Yeah I know it is not just eestor, but I am getting tired of empty hype.
I love hearing about technology, but at some point, they get to the "put up or shut up" point. That point has past for me.
You know you read qwantz.com too much when... (Score:5, Funny)
Re:Myth (Score:5, Informative)
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
Parent
Re:Myth (Score:5, Informative)
Plastic film capacitors will wear out if they are operated at excessive currents.
High-k ceramic capacitors degrade partially over time.
Parent
Re:Myth (Score:5, Informative)
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
Parent
mod parent up (Score:4, Informative)
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.
The above is spot on.
Another common cause of what is incorrectly thought to be "memory" is the corollary myth that you MUST deplete NiCd batteries completely before charging. While a full discharge can, in fact, sometimes be useful for certain types of cells, this is generally untrue for real-world batteries (comprised of multiple cells). A battery with several cells in series will always have slightly unbalanced cells, and the weaker cells will lose charge first. As the weakest cell begins to collapse, its neighbors in the string will crush it to zero volts, and then to a negative (reverse) voltage. To permanently damage a cell more effectively, you'd really have to apply yourself.
ALWAYS stop using the battery at the first sign of depletion -- continuing to use it will just kill one or more of its cells.
Parent
Re:mod parent up (Score:4, Interesting)
Parent
Re:Myth (Score:5, Interesting)
This is the main reason why it's recommended that you charge Li-Ion batteries as often as possible, and even "top them off" when used regularly[1]. If you use a quarter of a charge per day, your battery will last much longer if you charge it daily or every other day than if you charge it every three or four days, even though the "cycles" used are the same.
I recommend keeping anything below 1/3 full for "emergency use" -- there when you really need it, but avoided otherwise.
If you frequently use a laptop (or cell phone) until it runs out of power, or even gets very low, it's better to go with a NiCd or other battery, cause Li-Ions will have a seriously short life span if used that way.
[1]: If a Li-Ion/Li-Polymer battery is stored, half charged is better -- the self-discharge and chemical damage done from this is lowest at around 40% charge, which due to the protection circuitry equates to about 50% on the meter.
Parent
Re: (Score:3, Informative)
NiMH are also affected, in a different way. (Score:3, Interesting)
Re:Myth (Score:5, Informative)
Parent
Re:Myth (Score:5, Interesting)
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.
Parent
Re:near-instant recharge (Score:5, Insightful)
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.
Parent