Breakthrough In Use of Graphene For Ultracapacitors 250
Hugh Pickens writes "Researchers at the University of Texas at Austin have achieved a breakthrough in the use of a one-atom thick graphene for storing electrical charge in ultracapacitors. They believe their development shows promise that graphene could eventually double the capacity of existing ultracapacitors. 'Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power,' says one of the researchers. Two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors, which are becoming increasingly commercialized but are not yet well known to the public. Some advantages of ultracapacitors over traditional energy storage devices such as batteries include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance. Graphene has a surface area of 2,630 square meters, almost the area of a football field, per gram of material."
EEStor (Score:5, Interesting)
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There's 10 years from lab to product.. at least.
Re:EEStor (Score:5, Interesting)
No. This isn't even close to EEStor's claimed energy density. I personally put EEStor in the BS bucket a long time ago, but last week I found some very interesting news on wikipedia's EEStor page [wikipedia.org]: competitors. It seems that several companies now have patents on materials they claim are similar in energy density to EEStor's claims. We may not get ultra-cheap batteries for electric cars any time soon, but at least the raw science seems to be real.
Re:EEStor (Score:4, Interesting)
Yeah, except there are also patents on glass pyramids that keep razors sharp, cures cancer or something like that. And don't forget the patents on playing with your cat with a laser pointer.
When people say anything can be patented, they're pretty much spot on.
EEStor AND Graphene (Score:2)
As I understand EEStor's patent, they are creating a dielectric that they claim has an extremly high breakdown voltage. This allows them to make it micron's thick and still run the voltage up to 3500 Volts. They then sandwich this between two aluminum plates. So other than the dielectric, EEStore is creating a traditional capacitor.
Supercapacitors seem to provide about a 100-fold increase over traditional capacitors. By creating more surface area to store charge the activated carbon/electrolyte supercap
Re:EEStor AND Graphene (Score:4, Informative)
No, capacitors don't have to. In fact even the tiny capacitors you can get at radio shack hold enough power to fry most electronics if it were released at once.
Capacitors only release all the power they hold at once when they fail catastrophically...then they blow up.
However the output voltage of a cap is related to the energy they store so as the output voltage must be adjusted as the capacitor discarges to maintain usable voltage. By oncreasing the resistance in the circuit you can slow the discharge rate of a capacitor to usefull levels.
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Look up introductory electrical engineering stuff, searching for RC time constant and RC curves. This appears to be a good page. [tpub.com]
The overall idea is that charge cannot move instantly through a resistance. Think of a capacitor like a bucket of water, and the resistor a hose hooked to the bottom of the bucket. The bucket can drain only as fast as the hose is wide. And the less water there is in the bucket, the slower it will drain (since there is less weight/pressure pushing on the water at the bottom of
Cost. (Score:2)
More or less than traditional batteries when production is at commercial levels? Will they be prohibitivly expensive to have electric cars using these?
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You say the energy density is horrible compared to lithium batteries, but 20% is within 1 order of magnitude. That sounds pretty impressive to me for something that lasts for decades. Electric cars may not use them for a while, but charging stations for electric cars might since they're not as space constrained.
advantages of batteries (Score:4, Insightful)
Some advantages of ultracapacitors over traditional energy storage devices such as batteries include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance.
By contrast, two advantages of batteries are 1) vastly higher energy density, and 2) the fact that they exist.
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Re:advantages of batteries (Score:5, Insightful)
I know you're trying to be cleverly ironic here, but you can buy ultracaps today [digikey.com]. The higher power capability, swifter charging, longer life, wider thermal operation range, more flexible packaging, and lower maintenance are already there and have been for years [edn.com] along with the superior environmental characteristics. However, "lighter" isn't true yet, since the energy density of an ultracap is an order of magnitude lower than that for a dry cell [wikipedia.org]. That's why a breakthrough such as in this article is such a big deal.
If grapheme could reliably be utilized to create the sort of energy density posited here, any application requiring large amount of batteries (such as electric cars) would benefit greatly. Unfortunately, since capacitors are more prone than dry cells to losing energy over time due to internal resistance, this won't eliminate the need for dry cells entirely.
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Unfortunately, since capacitors are more prone than dry cells to losing energy over time due to internal resistance, this won't eliminate the need for dry cells entirely.
I don't see them replacing batteries at all, but augmenting them instead. Batteries are limited in the power they can absorb. They are much more efficient with storing energy if you spread the charge out over a longer period.
The efficiency of regenerative braking in cars is limited by the ability to pump the energy recovered by the brakes back into the batteries. Lots of energy is generated in a few seconds, but there isn't enough time to force that energy into the batteries.
The big benefit from ultracap
Re:advantages of batteries (Score:5, Interesting)
I don't see them replacing batteries at all, but augmenting them instead. Batteries are limited in the power they can absorb.
Yes, but the limit isn't especially limiting in practice. Power density is important, but any modern battery with sufficient energy density to be useful in the EV industry has plenty of power density. Some types of lithium cells (let's pick A123 since they're well known) have outrageous power densities (hence their use in power tools where you want high torque) but rather poor energy density, yet their energy density is an order of magnitude better than the best ultracaps.
Round trip energy efficiency for lithium type batteries is already on the order of 90%. Even if your hypothetical ultracap system were 100% efficient, you're only looking at an ~11% improvement. But of course your hypothetical system won't be anywhere near 100% efficient, and the cap voltage is dramatically higher and the discharge curve is different, so you have to account for additional power electronics losses involved in moving the charge back and forth between the battery system. And if you just doubled the complexity of your power electronics, you've added significant cost and weight.
In short, I'm an electric vehicle engineer, and I have yet to see a situation where adding caps makes more sense than adding more cells to the battery.
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By contrast six advantages of EMBs (Electromechanical Batteries) or Flywheel Batteries have over both lead acid and ultracapacitors are that they have the highest power density of any energy storage system currently available, thye are so reliable they can be buried or even sent into space, they hold huge amounts of power, they can be recharged very quickly, they do not burst into fire, they are not hazardous and you can even buy them today.
Specific Power
EMB (5-10kW/kg)
Lead Acid (0.1-0.5kW/k
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By contrast, two advantages of batteries are 1) vastly higher energy density, and 2) the fact that they exist.
I've found existence to be highly overrated.
Single reason why Supercaps beat batteries.... (Score:2)
The single reason is Sharks, man. Sharks.
Caps are the only way to power a petawatt laser [slashdot.org], and you'll need an energy storage to use the lasers unplugged and mounted on sharks' head.
So it's supercaps for you.
graphene surface area (Score:5, Informative)
I found this image from Nature magazine useful in imagining how 1 gm of graphene can have such a large surface area..
http://www.nature.com/nature/journal/v427/n6974/fig_tab/nature02311_F1.html [nature.com]
surface area of a football field (Score:2)
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Re:surface area of a football field (Score:4, Insightful)
If 1 gram of graphene has the surface area of a football field, what's the surface area of a football field of graphene?
One football field, of course. They're both units of area. Now, if you were to ask what the surface area of a VW-Beetle-equivalent of graphene is ...
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Oh, and before I forget, that's going to be a large number in football fields. Use Rhode Islands instead (or, if the number is still too large, Texas').
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Forget Rhode Island or Texas... always use Wales.
http://www.simonkelk.co.uk/sizeofwales.html [simonkelk.co.uk]
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One football field, of course
But how much would that weigh?
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Now, if you were to ask what the surface area of a VW-Beetle-equivalent of graphene is ...
About half the size of Delaware.
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Get your torches! We have to stop these mad scientists before they destroy the world!
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That would be a football field to the power of a football field.
I think a more relevant question is: if 1 gram of graphene has the surface area of a footbal field, what weight are the football players? And is that "football" or "Soccer"?
Sizes of American and association football fields (Score:2)
And is that "football" or "Soccer"?
An American football field is 360 by 160 feet including end zones, or 5351 m^2. A soccer pitch is significantly wider; it can be anywhere from 100 by 64 m to 110 by 75 m, or 6400 to 8250 m^2.
Safety ? (Score:3, Insightful)
As a teenager I was slightly injured by a 50-year-old 3300mfd cap I'd salvaged from a valve radio, which went off like a small bomb despite only holding 12 volts at the time. I for one would treat an ultracapacitor as a potential source of devastation until proved safe by a long period of use...
Re:Safety ? (Score:5, Interesting)
That's one of the serious problems with any exceptionally high density energy storage technology. How do you keep the genie in the bottle, and protect the public from the critically stupid in our society.
There was a very cool design for a car whose power source was a high mass flywheel in a magnetic housing. You go to a power station, and the station would spin your flywheel up to some insane RPM rate. The possibility of using this in a hybrid vehicle meant you could get really excellent energy storage and return, it was very efficient.
The only drawback, was that if the bloody thing ever got out of containment, you had a death dealing juggernaut that would buzz-saw a swatch of destruction through the middle of wherever the now flying flywheel was pointed. Then some bright child imagined such a flywheel driven vehicle on a crowded freeway causing a chain reaction of thousands of other similar vehicle, and suddenly you pretty much have a scenario for mass destruction that looks like front row seats to Armageddon.
Whatever technology you finally pick, you'll need to make it very safe, or decide it's a Darwinian herd thinning tool.
Re:Safety ? (Score:4, Interesting)
Actually not.
The RPM rate is so high that flywheels get insanely hot as soon as the vacuum is broken, and it has to deal with friction from the air.
With metallic flywheels, this means it breaks apart, and you've got thousands of bits of white-hot magma flying through the air, in a straight line from the direction the flywheel was spinning. Of course your car is going to turned into swiss cheese, and the two cars directly in front/back of you are likely to get damaged as well, but it's not Armageddon.
With carbon-fiber flywheels, the flywheel material is completely incinerated instantly, and DOESN'T risk turning into such deadly projectiles. HOWEVER, you have to have a very good design to deal with the HUGE amount of unimaginably hot air now erupting out the top of the flywheel housing. Mount it properly, eg. externally, on the roof of your car, with a nice thick base-plate, and your vehicle quite quite likely wouldn't face any structural damage. Though, you can definitely expect to need a new coat of paint.
It's all a manager of energy (Score:3, Insightful)
The fact of the matter is, it takes "X" number of joules of energy to move your typical car 300 miles.
Whether that energy is stored in a tank of gasoline, a capacitor, batteries, or a spinning flywheel, you still have X number of joules of energy that have to be safely stored and protected against unrestrained liberation.
Re:Safety ? (Score:4, Interesting)
Simple - mount it in a gimbal [wikipedia.org]
Re:Safety ? (Score:5, Informative)
Large-scale systems of this sort are actually in use, just not inside vehicles. There are some electric train systems that use it to recapture energy from trains arriving in the station, and then assist trains as they accelerate out of the station.
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The way I'd do it is by having two contra-rotating flywheels, one on top of the other. It doesn't solve all the problems, but it gets rid of the most obvious one.
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My understanding is that this is already being done in some flywheels, except that instead of a ribbon, the flywheel is coiled carbon fiber. When the container is breached, instead of spinning off and destroying everything in its path, it simply burns up.
I imagine it gets rather hot -- after all it would be converting a horrific amount of kinetic energy into heat -- but it gets hot in a stationary manner.
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Hate to break it to you, but if you replace the ultracapacitor with a battery of the same volume, or, heaven forbid, the same volume of gasoline, you're looking at even _more_ stored energy, and no one's too worried about that.
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Genda may not of quite nailed it on the head in writing but does have a point: capacitors have the ability to discharge a huge amount of their stored energy at once. All the people I know that used to fix TVs have stories of being thrown across their rooms by forgetting to bleed the charges on (non-super-cap) capacitors and letting something short. In comparison, batteries and gasoline even seem have a limit on the amount of discharge they provide in any period... though a comparable example for gasoline mi
Re:Safety ? (Score:5, Informative)
More energy, true, but slower release-rate.
A battery has significant internal resistance, even if you short-circuit it the power-levels are limited. (high, but limited)
A capacitator can recharge significantly faster.
Put differently, the thing may only hold 10% of the energy in a battery. But if that energy is released a hundred times quicker, you're still looking at hell of a bang.
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I drive a diesel car. It feels safer (low-volatility compared to petrol)
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I doubt those numbers. Capacitors in valve radios were more like 32uF, and typically work at hundreds of volts. Values like 3200uF are used in low-voltage power supplies, not in valve equipment, unless it's some very specialized equipment from the 1950s with hundreds of valves, perhaps.
But you are right that charged capacitors can be dangerous. I mys
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Most of it dated from the mid 40s to early 50s and was 40-50 years old at the time, I learned a lot from it but my memories may be confused as to what came from where. I remember a love of the design of the large tube capacitors with their crenellated electric-bl
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I see no reference (anywhere) to the likely internal resistance of these posited ultracaps. It's great that you can store all that energy in them, but if it all turns to heat when you try to get it out, it's not much use.
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I drive my car every day, sitting in front of a tank with HUGE amounts of energy, in the form of gasoline... So no.
Capacitors are CURRENTLY used for high instantaneous storage/use of power. They aren't yet used for energy STORAGE. As soon as they are seeing significant use as battery replacements, you can expect
am i the first to make a flux capacitor joke ? (Score:2)
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I don't know! Waaaaarrrrrggghhhhh!!!
reedeeculous as a capacitor plate (Score:2)
It's golly-gee wonderful if they can make a one-atom thick graphene sheet. Give them a lollipop.
But in making a capacitor, you need other attributes than just thinness. You need a capacitor plate that can carry current, remain in place in the face of strong electrostatic fields, be compatible with dielectrics, be reliable, and be manufacturable.
A one-atom thick sheet is not going to be able to do any of those things. Capacitor makers have been depositing thin electrodes for 60 years now. They know full
RTFW (Score:2)
Read the fine wikipedia entry. It's not replacing the plate, it's replacing the granular activated charcoal in existing ultracapacitors.
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A relative of mine's Panasonic Toughbook CF-W5 is rated 11 hours and actually gets her 5-6 hours of word processing and internet on battery. Maybe you should try better-quality laptops.
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First poster didn't seem to. Times were when you only got 1.5 hours of word processing time, and these days people have their wifi enabled all the time. Anyone with a mobile phone will know that that is a major drain on the battery. We're getting the same battery life as before, but we're able to do much before in that time.
By the time affordable ultracaps everyone will probably be complaining of 'only' 11 hours solid gaming usage on their laptop.
Here's the deal (Score:5, Insightful)
Human resource usage expands to consume all available resource...
That is the history of humanity in one sentence. In fact, it can be generalized to all life.
Re:Here's the deal (Score:5, Insightful)
Human resource usage expands to consume all available resource...
That is the history of humanity in one sentence. In fact, it can be generalized to all life.
Agree with your first statement. The difference, however, between humanity and other forms of life is that humans increase available resources in order to be able to expand usage.
Comment removed (Score:4, Insightful)
Re:Here's the deal (Score:4, Informative)
No but the organisms which produced the oxygen first probably weren't the ones which needed it to survive, oxygen was waste, a poison to them.
Although there are animals and plants which by one means or another make more space for themselves to live in.
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There's a fungus growing inside the post-meltdown reactor at Chernobyl that appears to be using the radiation as an energy source (capturing the energy with melanin I believe). Using radioactive waste instead of sunlight, check.
There's a bacteria found in a factory out-flow somewhere, capable of digesting certain nylon byproducts. Eating garbage, check.
As for tailpipe fumes... well quite a lot of things use CO2, I believe they're called plants. The other gases in exhaust fumes are still fairly poisonous but
Re:Here's the deal (Score:5, Funny)
Re:Here's the deal (Score:4, Insightful)
We don't seem to have expanded to use all oxygen yet, we don't seem to have used up all the salt water, both are freely available to a great many people.
Human resource usage expands to quite a high point but to assume it's infinite is a little presumptuous.
It was assumed that the human population would continue to increase exponentially but in some developed nations we're seeing a birth rates drop below 2 children per couple.
People multiply insanely when the chance of their children reaching adulthood is low, people try to obtain stupidly large amounts of resources when resources are scarce.
Average resource usage may not increase forever. It'll probably still has a way to go but I can see the average leveling out at some point.
Re:Here's the deal (Score:4, Interesting)
Remove the bottleneck for growth, and the expansion will continue till the next bottleneck stops growth.
In our case, with our 'intelligence' we appear to be stretching all our resources to the extreme... till our growth is limited by food, water, land, and perhaps other resources like oil. Then we either have starvation (of food, or of oil or of whatever) or wars (that knock off population).
Or until we invent... (Score:5, Interesting)
Or until we invent fertilizer (18th century)...for food
Or until we invent pesticieds/herbicides...for food
Or until we invent underground farming...for food
Or until we invent land reclimation...for land
Or until we invent skyscrappers...for land
Or until we invent seasteading...for land
Or until we invent lunar colonies...for land
Or until we invent large dams...water, food and power (oil)
Or until we invent water treatment...water
Or until we invent reverse osmosis distillation...water
Or until we invent atmospheric condensers...for water
Or until we invent nuclear fission...for power (oil)
Or until we invent fusion...for power (oil)
Or until we invent photovoltaics...for power (oil)
Or until we invent bio fuels...for power (oil)
Or until we invent direct CO2 conversion to hydrocarbons...for oil (from power)
and a big one is:
Or until we invent a trully good electrical battery, one that stores a lot of energy, has high power density, does not wear out, does not use environmentally harmfull components and is cheap (something like these graphene supercapacitors will be under mass production)...for oil
My point is simple. Humanity ran out of resources about 20,000 years ago. We are designed to be hunter/gatherers. The earth can only support a few million hunter/gatherer human beings. It was only through the invention of agriculture and other technologies that we are able to continue. While we will probably ALWAYS have some resource limitation (probably power) there are technologies that exist now that if used can prevent any Malthusian collapse for the indefinet future.
Re:Or until we invent... (Score:5, Interesting)
Or until we invent a trully good electrical battery, one that stores a lot of energy, has high power density, does not wear out, does not use environmentally harmfull components and is cheap (something like these graphene supercapacitors will be under mass production)...for oil
Well, let's compare the modern automotive li-ions to see how well they meet your requirements:
* "A lot of energy" -- The automotive li-ions on the market are generally 90-110Wh/kg (not as good as the ~160Wh/kg for conventional li-ion). There are about a dozen different chemistries in the lab right now that offer 2x, 3x, or more energy density than this; I could go down the list if there was interest. Now, while this is notably less than gasoline, there's a couple factors that have to be considered, such as the fact that most of the energy in a battery goes into providing torque to the wheels, while only a tiny fraction of the energy in gasoline does (most gets wasted as heat). Secondly, batteries are heavy while electric motors are light; internal combustion engines are heavy while gasoline is light. It's an opposite paradigm; in a typical electric car equivalent, batteries are competing for the space and weight freed up by the lack of need for an internal combustion engine, transmission, and all of the supporting hardware, while the motor is about the same size and weight as a full fuel tank. As a result, to match a typical car in range for a given amount of weight, you need about 300Wh/kg. So, they're not a match for gasoline cars yet, but they very well could be in a few years. Even as it stands, it's not hard to get enough batteries to take you for two hours at highway speeds (general highway safety advice is that you're supposed to take a break every two hours or so).
* High power density: Already got this one licked. 100 kilograms of lithium phosphate batteries will give you up to ~250kw or so (335 electric horsepower, which due to the wider max power operating range, is more like a gasoline car with 500hp or so). 100 kilograms of titanate cells will give you 2-3 times as much. Even despite having far less research put into them, EVs are already challenging gasoline cars for speed records (esp. accel, but even top speed, such as with the Eliica). The motors and inverters are actually the limiting factor, not the power source.
* Lifespan: LiP and stabilized spinels will lose 20% capacity in ~7000 "gentle" cycles or so, while the titanates take tens of thousands to lose that much capacity. They also show little to no loss of capacity with age, as they resist lithium plating. By "gentle", this means a cooled pack, charge times of at least a couple hours, and discharge times of at least a couple hours. Under abusive conditions -- overheating, 5-20 minute charges, 5-10 minute (impossibly fast) discharges, etc, you'll get ~1000 cycles out of LiPs and spinels, more out of the titanates. Under a normal mix of fast and slow charging, with reasonable discharge times, you can expect a couple thousand cycles. For a car with 150 miles range, 1000 cycles = 150,000 miles, so a couple thousand cycles means around half a million miles. Adjust appropriately to your situation.
* Does not use environmentally harmful components: Two common types of batteries -- PbA and NiCd -- are highly toxic, and must be recycled to avoid serious environmental consequences. NiMH aren't great for the environment, and should be recycled, too, but they're not as bad as PbA and NiCd. Li-ion with a LiCoO2 cathode, like conventional li-ion and AltairNano's titanates, are minorly toxic; it's not as bad as NiMH, but it'd be best to recycle, and proper disposal is required in most places. LiP and spinel li-ion are nontoxic; the worst thing you can say about them is that their electrolyte is corrosive.
* Cheap: Current prices for LiPs in bulk straight from the manufacturers is about $0.50-$0.60Wh/kg, which most kinds of cars, is already low enough that the purchase price premium can be amortized into the car's operation
Re: (Score:3, Interesting)
Lithium is not scarce at all. Lithium is about as common worldwide as some common steel alloying agents, such as vanadium, chromium, and nickel. Lithium carbonate, the "raw" form most commonly purchased commercially, costs about $6/kg. To produce it from seawater, which is a virtually boundless supply, is estimated at $22-$32/kg. 1kWh of li-ion batteries takes about 1kg of lithium carbonate -- thus, a 30kWh pack, with the lithium produced from seawater, with pessimistic assumptions, takes under $1,000 w
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We don't seem to have expanded to use all oxygen yet, we don't seem to have used up all the salt water, both are freely available to a great many people.
We're working on it. :)
Re:Here's the deal (Score:5, Funny)
If you car has a graphene ultracapacitor, resources consume you!
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If it is the latter: "seldom-seen fetishes" good news! You have found an under-served area of the over-saturated porn market, and are in a position to make a fortune by developing and operating a site serving that particular segment. Congratulations, and good luck. Let me know if you are looking for a cameraman, and/or MySQL admin with some PHP experien
Re:Here's the deal (Score:5, Funny)
Rule 34 (Score:4, Informative)
If his fetish is, say, truckers and fat mexican grannies with mustaches, do you still want to be the cameraman?
Must... resist... urge... to verify... Internet Rule 34 [xkcd.com]....
Ghaaa !!! 22k+ pages found [google.ch]. The Google, it doesn't do nothing.
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Do you take paypal?
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http://www.quantumg.net/eeepc.txt [quantumg.net]
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My 4 year old PowerBook still gets 3 hours, unplugged.
Re:How? (Score:5, Informative)
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Generally things that are one atom thick are much more fragile than things that are millions of atoms thick. When they get this working in cars and not 'losing capacity' aka frying you when you go over a speed bump it'll be a pretty good replacement for batteries...
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Look into how capacitors [wikipedia.org] work. It's capacity is largely based on the surface area of internal parts. You get that by making things thin. Thin is huge for capacitors, even the normal kind you have in the computer you used to type that post. Capacitors are all wound up i
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It's capacity is largely based on the surface area of internal parts.
It's also largely based on the inverse of the distance between internal parts. And this distance also decreases when you make things thinner.
Thin is huge for capacitors,
Yep, it's huge^2, even, since you're increasing surface area and reducing the distance if you make the internal structures thinner.
Graphene's properties (Score:5, Insightful)
Don't worry that the Graphene layer would rip. It's a very, very strong material and the connections between the atoms are strong conjugated double-bonds.
This is the same structure as in Carbon Nano Tubes and Fullerens (C60), just flat (and not cylindrically or spherically rolled up).
The problem to implement Graphene based technologies is rather the synthesis of it, since it's not yet easily possible to create a homogeneous Graphene layer on a large area (i.E. at my Applied Physics institute they create Graphene layers that are not even 1 mmÂ).
It's not just the area that matters here (Score:2)
It's also the distance between the electrodes. The thinner the dielectric layer, the more charge the capacitor will hold. The problem is then to avoid the electrical breakdown of the dielectric.
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But you wouldn't even be able to taste the carbon on your football field that way. Seems silly to me.
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Reminds me of Dilbert-
"Imagine a donut, fired from a cannon at the
Re:How? (Score:5, Funny)
If you wanted a thin layer of carbon, wouldn't it be easier just to toast the bagel?
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The only thing wrong with your analogy is that it doesn't sufficiently involve cars.
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When two cars crash into each other, oil and petrol go all over the road. So, er, work with me here!
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Re:How? (Score:5, Informative)
Yes, massively folded. Similar technology has been in used for many years to produce multi-Farad 'dime' capacitors, whos surface areas start around the size of a tennis court and go up from there.
These sorts of capacitors have very high capacitances (in the multiples, even tens of Farads) and a 20-50 year life span (or longer depending on how they are built), but also tend to only be able to be charged to fairly low voltages (3v, 5v, etc), and also have fairly high internal resistances (though this might be different for the newer Graphene-based caps), limiting the discharge rate.
This means they won't be replacing batteries any time soon, but the advances we're seeing are pretty cool.
We mostly use these things to run real time clock chips and provide backup power for static ram... i.e. very low current applications.
-Matt
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For many things a higher current is more important then the low voltage as you could employ them in series to bring the voltage up. I just installed an electric drive system in my boat. Its a 48 volt system yet I am using 6 volt batteries so that I can get a better run time (more AH), you could do the same with ultra capacitors. Though I admit it will probably be a while before I will be able to run my boat on them. Still there would be many advantages as the charge rate could be much quicker, the life
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Surface area is the size of a football field, but because it is very thin it can be rolled up in to something very small.
Think about a roll of toilet paper. When rolled up it is about 10cm x 10cm x 10cm. If you roll it out it might be 50m long.
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So why not just use toilet roll as a capacitor?
The cylinder capacitors that handle the bigger charges most of the time pretty much look just like that if you crack them open.
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Re:How? (Score:5, Interesting)
Because it doesn't have to layers that are insulated against each other?
However, if you're talking about two toiled rolls, soaked in electrolyte, with an insulator between them, rolled up and packaged nicely, then yes, you can use that as a capacitor (we'd all be thrilled about a capacity measurement and some pictures when you try it out, please?).
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lab exercise one, what happen to a resistor with more current than it can handle.
result: charred resistor and white smoke.
lab exercise two, what happen to capacitor with more AC current than it can handle.
result: a pop corn, sometimes a juicy pop corn.
lab exercise three, .....
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I wonder how practical is graphene capacitor used as a memory storage cell compare to SRAM or DRAM we have today.
Err ... you do know that one of the main differences between SRAM and DRAM is that the latter uses a capacitor (and fewer transistors) than the former per memory cell, and therefore requires to be refreshed occasionally (hence "dynamic", as opposed to "static" memory which will keep its contents as long as it is supplied with power)?
I'd say that graphene capacitors are as uninteresting as it get