Underdiscussed point: one reason we want such high capacity power storage is that recharging takes hours. Society has internalized long charging times as normal. Would we fuss quite so much about run time if a recharge took seconds instead? (Am thinking cell phones/tablets here, not the dangerously high power issues of recharging a car in one minute flat.)
You can already buy flashlights with supercapacitors that have low run times but recharge in seconds, and there is a bus in China that recharges its supercapacitors at every stop. In addition they last for many times more discharge cycles.
For many applications, we can get the equivalent of fast recharging by swapping batteries. Yet, we still want long battery life because swapping is inconvenient.
Fast recharge is also inconvenient. Just as you must have a set of batteries to swap, you must have the means and opportunity to fast recharge. Note that a fast recharger is probably at least as big as a set of batteries. And, I can swap batteries in places where I can't plug in the recharger.
Yes, fast recharge is less inconvenient than slow recharge.
Quick thought experiment: right now, you can go out and buy a portable charger with a battery inside. For $40 or so, you can get one roughly the size of carrying a second smartphone with 5000mAh, which is several full charges for your average smartphone. You can throw it in a purse or spare pocket and have it when you need a charge and you're not near another power source.
It's not fiddly like opening the case of a phone and swapping out the battery, but the big problem with this is having to leave it hooked up while it charges if you're still using your phone. With fast recharge, this would go away. Hook it up for a minute, charge the phone up, unhook it, put it away. Easy peasy.
For me, at least, this would be a huge win. YMMV
Edited to add: with fast recharging, you could also recharge the portable charger itself if you ever come in contact with an outlet. So let's say you have two really long flights with a short layover. Find an outlet for a minute on the layover, recharge the charger, and you now have your charger ready to go for the next flight. Win.
I don't think swapping batteries is a good analog for fast recharge. For one, the cost of a kilowatt hour in AA batteries well exceeds $100, even buying in 20-count lots. From the wall, it costs less than a dollar. Swapping batteries is also significantly more effort than plugging in a microUSB or whatever.
Still way to cumbersome. I would love to be able to get a quick fix but I won't trade any battery life for it.
If I'm ever around to recharge quickly I can just as well let it sit there for a while, at least the vast majority of times. Please note how convenient it is to charge from a USB-port, a micro usb cable is all that is needed to be able to charge pretty much anywhere (and they are cheap enough leave one at home/work/laptop/pocket. With a fast charger I'd have to bring it along and plug it in everywhere - not worth it. And I most definitely would like at least the same poor battery life that we have today, otherwise you wouldn't be able to last a day without a charge and that it just unacceptable regardless of how easy or fast it is to recharge.
It sure won't be a microUSB port. To charge a middle-of-the-road 2500mAh capacity battery in, say, 10 seconds, you must flow something like 70A @ 5V, and that's ignoring the fact that capacitor charge curves are of the exponential decay variety (i.e. drastically higher initial power draw).
(A real-world application would probably kick up the voltage and lower the current, but USB is always 5V)
Taking the article at face value, it sounds like they're talking capacitors with an energy density comparable to lithium-ion, and that's on the first try. (Although just looking at the chart it looks more like at least an order of magnitude lower.)
But we're used to being disappointed by articles about graphene... Anyone got a reason this isn't as good as it sounds?
A key point here is the tradeoff between energy density (how much energy the battery or capacitor can hold) and power density (how quickly the energy can be released).
I'm not an expert, but just working from the graph in the article, the best energy density they show for the new graphene capacitors is roughly 1/8th the best energy density for lithium-ion batteries. What's interesting is that capacitor has roughly 500x the power density of that battery. Or if you look at a battery tuned for power density (lower-right end of the red arc in the graph), there's a capacitor that can offer 200x or more power density with the same energy density.
More simply: for low-discharge-rate applications, lithium-ion still wins, though the new capacitors may narrow the gap a bit. For high-discharge-rate applications, these capacitors win by a mile. (Ignoring considerations not covered in the chart -- cost, durability, temperature sensitivity, safety, etc.)
It is not just about high discharge. In return you also get fast recharge. Something that can suck in a large chunk of power, hold it for a short time, and then dump it out again rather quickly has certain advantages. Consider the energy storage system for regenerative braking, for example, which needs to absorb a lot of energy quickly -- the trick is then figuring out what to discharge it into, starting a vehicle rolling is the prime candidate but there may be other uses of an intermediate storage device like this.
In most cases I think that this will not displace Li-ion but would instead augment the existing battery setup.
Yeh, that's the really cool bit-- would you be okay with your iPhone only getting an hour of battery life if you could fully charge it in a couple of seconds?
I mean, obviously not, but it's interesting to think about.
But what about a hybrid system where you could add an hour or two of usage in that first few seconds of charging?
Would be great during a layover in a typical US airport where you might have to sit on the floor in a corner to use a power outlet. You could plug in for 10s to fill the cap, eat lunch while the cap charges the battery for an hour, plug in again for 10s before you fly out having something close to a full battery.
A cellphone battery is say 1 Amp Hour. Assume an equivalent capacitor is 3600 Amps for a second. Assume the capacitor is charged to 10x the Voltage, and is charged in 10 seconds. That needs 36 Amps - copper wires a bit thicker than those in a kettle cord. Bad approximations made, but right order I think.
Also there are real safety issues with something that can be charged that fast, because it usually implies it can be discharged faster. A shorted Li ion battery may burn, but a low-resistance capacitor will cause an explosion. Capacitors are fun :-)
An iPhone battery is roughly 1400mAh at 3.7V, which gives 5.2Wh or 18720 watt-seconds. A standard power outlet in the US supplies 15A at 120V, for a maximum of 1800 watts. So if you could charge your phone using the maximum power available from a standard outlet, it would take roughly 10 seconds. A typical laptop might take about 1-2 minutes. (That's assuming 100% efficiency, which is unrealistic.)
Even if it only has 1/8 the energy density, it might have less than 1/8th the weight. If 8 graphene capacitors = 1 LiIon battery, it might be a lot lighter. That could could for a lot in some circumstances. (Mobile computing devices not being one of them)
Yeah, I think some salt needs to be applied. Any discussion of energy density needs to involve the manufacturing process (because how small you can make something depends on more than just the active ingredients). And this was just done in a lab. They're probably extrapolating from the film thickness or somesuch.
But until someone finds a way to package an actual component into something that looks like a supercap or a battery, no one will care.
I've got solar panels on my house. During the day, on good days, they generate more power than I use in a 24hr period, except I'm grid tied because I can't economically store that power.
Back when maxwell tech [1] was using them to start diesel electric locomotives I did the math to figure out how many I would need in my house foundation to 'carry me' over from day to night, and it was an additional $128,000 and probably 1000 sq ft of 'foundation' space to hold them.
Graphene, and other high surface area + high conductivity solutions seem like they will make this configuration more feasible in the future. It would be interesting to be 'off grid' but without the cost/hassle of maintaining a bunch of batteries.
I read this with great interest when it came across another site. I have watched many of people explode bolts or something with homemade capacitors. This seems to imply that a home a solution for experimentation could be derived, but at this time it seems that while a DVD burner may be in the mix, it is in the middle of a very advanced lab and the further processing such a material would require for application.
Does anyone know or have the capability to accurately estimate what the volumetric power density of these capacitors are (assuming they commercialize well)? In terms of replacing cell phone batteries or something, that's what matters, and I only see areal densities.
Thats the discussion. In reality, you care about both. Power density to move the energy into and out of the cell quickly to shorten charge times and supply thirsty loads. Energy density to run lower loads for longer.
These might replace other kinds of capacitors, but at the listed energy density, there is no way they are going up against cell phone batteries or car batteries. According to wikipedia, the lithium iron phosphate battery has an energy density of 220 mWh/cc. These are weighing in at 1.36 mWh/cc, according to the article.
And existing battery chemistries can already charge fast enough such that the limiting factor for electric car recharge times is the grid. My Nissan Leaf can charge most of the way in 25 minutes at a L3 charging station. But PG&E levies enormous fees for people who want to pull down that kind of power, so there isn't a single operable L3 station in the whole bay area.
To me the most astonishing part of this article is that they can 'bake' graphene out of graphite oxide with consumer-grade tech. Did I miss something, or is that not a huge step forward for graphene synthesis?
And if lightscribe can produce usable graphene for super capacitors an industrial machine that does the same thing faster and better shouldn't cost too much, and I can't see any reason why the low-tech approach can't scale up easily.
Sure, we have limited supplies of hydrocarbons in the ground, but to me the key energy technology would be "synthesise hydrocarbons from water + CO2 + energy in". i.e. stop focusing on hydrocarbons as a source of energy and start thinking of them as a 'transport' of energy.
That would also mean we can move to clean, renewable power generation without retooling the globe's transport fleet.
The solid-state engine has much lower efficiency than a regular power engine would (a hypothetical 12%/realized 5% vs. a realized efficiency of about 30%), but it can be made much smaller - and even at a 5% conversion rate, the energy density just blows everything else out of the water. Aside from being energy dense, it's also much cheaper than high-end lithium-ion batteries; and unlike regular fuel-cells, the technology is just based on regular photovoltaics, and is relatively easy to manufacture.
Awesome, so we'll have the tech to consume the hydrocarbons, but where is the production side?
What do we need to be able to hook up a nuclear power plant, a supply of clean water and a big air pump and starting sucking in H2O+CO2 and piping out CnH(2n+2) and pumping out O2?
My understanding is that hydrocarbon using fuel cells run hot, really, really HOT. Which is why they are regularly used in race cars, but not in many other places.
The energy density of hydrocarbons may be high but the thermal efficiency in most applications is horrible. Gasoline automobile engines are only about %20 efficient for example.
I'll preface this by saying that I want my next vehicle to be electric.
Here's my concern with regards to electric cars: There's a huge difference between failure modes of electric vs. gasoline powered vehicles in crash scenarios.
In a great deal of cases a crash with a gasoline-powered car results in no spills or fires. No problems. In a few cases a spill might result. Fires are only a factor when gasoline vapors are involved.
If a pure electric vehicle has a range equivalent to that of a gasoline-powered vehicle, say, 200 to 300 miles, this means that it is storing a tremendous amount of energy. Also, due to i-squared-c losses it is very likely that the system will be a high voltage system (hundreds of volts).
In the case of a bad accident this energy could be released violently. There might come a day when we hear of an entire family electrocuted to death in their car after a crash. I hope this never happens, but I have a feeling it could.
As I see it this is the PR problem with the technology: Huge amounts of energy that could do serious damage if something goes wrong. In contrast to that, a gas tank is a relatively harmless device.
Yes, there are safety measures that can and are being utilized, like fusible links between batteries and intelligent management systems. Still, it doesn't take much at, say, 500 volts, to cause a lot of damage quickly. As someone who has worked with and designed very high power DC motor controls and have tested many designs to destruction I have to say that this is an area that really needs to receive a tremendous amount of attention.
The last thing the industry needs is the media devoting weeks to cover how a family got fried in their electric car while the fire department was powerless to aid them until the batteries fully discharged (which could take a long time). That would be a truly horrific sight to behold and a potential industry-killing event. Close your eyes and imagine that for a moment. Then imagine trying to convince someone who saw that on TV to buy an electric car.
Super-capacitors could help in this regard in very meaningful ways. If we could get battery packs to be small enough that leaves a lot of room for creating a crash and intrusion protection barrier around the battery.
Today battery packs are very large and heavy. And, while I am sure that a lot of work has gone into safety, they could be made far safer if the batteries had higher energy capacities.
The other way super capacitors might be able to help could be as paradigm shift enablers. Picture the case of not needing a range of 300 miles. For most of us, 60 miles might be enough. If that battery pack is small enough gas stations could morph into battery pack swap stations. The fact that a super-capacitor has a useful life of tens of thousands of cycles means that there would be no concern of receiving someone's almost-dead battery. The cost of re-fueling would include some amount of money to deal with packs near or at their end of life. If you did need to go farther maybe cars could be designed with room for a second range-extension pack or some other means to connect a larger battery pack.
From a safety standpoint, I want to see the kinds of tests companies like Volvo and Mercedes are known for: Fling a car through the air and roll it multiple times. In other words, extreme stuff that is unlikely to happen in most accidents. After the tests the cars have to remain in a state that is safe enough for egress as well as for rescue personnel to approach, touch and render aid.
In other words, electric cars have to be better in terms of safety than gasoline powered vehicles.
Driving any sort of car has such a high likelihood of killing you and your whole family in so many dozens of ways, it's hard for me to see how the battery issue is something to get hung up on (not that any safety improvement isn't a good thing).
But I agree that a death-by-car-electrocution scenario would be big news, and not a good thing for electric car makers.
A capacitor could internally short, releasing all of its energy at once. Imagine all of the gasoline in your car going off at once. Its a bomb. That's quit a different scenario from other car-crash situations.
We've all seen the laptop-going-nuclear videos when Li-Ion batteries short. This could be worse, given the high discharge potential mentioned in the article.
...but you will see it on TV. And that is what will stop the industry on its tracks.
People are used to gasoline. They are comfortable with it, if you will. Electricity is another matter. People fear electricity. They don't understand it. If electric cars are seen as roving high-tension wires that can electrocute you and your family in a crash that will be the end of the industry. People don't care about statistics but they react very readily to anything that triggers fundamental fears.
Families have burnt to death horribly in gasoline fires, too. They don't tend to show that kind of thing on TV at all (and I don't think that burning to death is significantly less horrible than electrocution).
I don't understand why robomartin got downvoted. His comment is very valid.
You only need ONE case of this accident covered on TV to get the industry into serious problems. Electric cars are new, thus interesting for media, and will capture attention (read: scare people).
And people really don't care about statistics, they do care about what they see in TV. Unfortunately, news services break our perception of reality. See: http://en.wikipedia.org/wiki/Availability_heuristic. That's why people freak about shooting in schools when the chance that their child gets run over by a car is much, much higher. Or, [insert random post-9/11 paranoia] vs. cancer rates. Or, what Chernobyl and Fukushima did to public perception of otherwise safe nuclear power.
You know I thought most people know that gasoline burns and that they have to be really fucking careful with the stuff.
Same thing they also already know about electricity.
So, I am not sure that you could stop the electric car industry by worrying people that the energy store could kill them, as everybody who has been on the roads long enough has seen burned out cars from pile-ups at some point.
>If a pure electric vehicle has a range equivalent to that of a gasoline-powered vehicle, say, 200 to 300 miles, this means that it is storing a tremendous amount of energy.
The gasoline powered car contains much more energy. The average gasoline engine is about 20% energy efficient. Electric power systems are more like 80%.
> There might come a day when we hear of an entire family electrocuted to death in their car after a crash.
How do you expect the entire family to become a better path to ground than anything else? Especially considering the nature of the virtual ground in such a system?
>The last thing the industry needs is the media devoting weeks to cover how a family got fried in their electric car while the fire department was powerless to aid them until the batteries fully discharged (which could take a long time).
Not if they are so shorted they are "frying" something.
That is impossible and a very silly thing to worry about. First of all, this problem has already been solved with fuses.
Furthermore, keep in mind that both batteries and capacitors have a limited power rating. Power is the energy that can be spent or released per unit time. Thus a limited power rating means that the batteries/capacitors can only release a limited amount of energy for a given time. Thus they cannot release all the energy they have stored for driving 300 miles in a second. That is just not physically possible. Since the power rating is usually an engineering constraint, this generally means that the stored power for driving 300 miles can usually only be released around the time it takes to drive for 300 miles. Perhaps a little quicker. But the idea that all this energy will get released instantaneously frying everyone in the car is just impossible with current battery technology.
If you worry about instantaneous energy release you should worry about gas powered cars, because gasoline can release all of its energy instantaneously in a giant fireball. But even this is highly unlikely.
>That is impossible and a very silly thing to worry about. First of all, this problem has already been solved with fuses.
Fuses have nothing to do with not dying, fuses are not a life safety device. Your protected for the same reason your safe inside a car that gets hit with lightning, for electricity to pass through your body you have to be a path to ground more over you have to be a very good path to ground compared to other available paths, both of which are highly unlikely in the circumstance being discussed.
In terms of electrical energy discharge that would be determined by the voltage across your body and the resistance of your body given the contact points, environmental conditions and duration of contact. The ability of the battery to supply enough energy is really irrelevant, it takes a very small amount of current across your heart to send it into fibrillation. But, as just mentioned, you'd actually have to create a potential across your body first anyway.
> Since the power rating is usually an engineering constraint, this generally means that the stored power for driving 300 miles can usually only be released around the time it takes to drive for 300 miles. Perhaps a little quicker.
That is completely incorrect. I have no idea what constant your talking about but many/most/all batteries can discharge energy far faster than they would under standard operating conditions. You can even short them out and watch a nice explosion in many cases, which is far more likely to kill you than getting electrocuted in the example at hand.
If you carry with you a lot of energy packed in a small volume, it will find a way to kill you one way or another, no matter how it's stored. Yes, not all storage methods are the same, and batteries are probably safer than gasoline, but the reality is - lots of energy means lots of ways things could go wrong.
I vividly remember my teenage stupid stunts with large capacitors charged at high voltage - those things can do a lot of damage when shorted. Also, a typical lead battery can do a number of nasty things, like release hydrogen, when mistreated; or throw a thick copper bar on a lead battery's contacts, and watch it melt down in seconds.
I'm sure you could install safeguards against the various failure modes, but again, you're still carrying a big chunk of lightning in your car.
I'm sure it would be possible to build a system whereby the connection between each group of battery cells could be fed through (for example) normally-open relays. Any sign of catastrophic failure cuts power to all of these relays, and the result is that you have a car full of unconnected batteries, each one good for just a few volts.
The real trick would be to build the system that could reliably de-power the relays in the case of an accident, but would also be reasonably trivial to reset in the case of false alarm, e.g. when an accident ends up being sub-critical. An end-user reset might also restrict the car to 'limp mode' until it's inspected by a qualified person.
> Picture the case of not needing a range of 300 miles.
> For most of us, 60 miles might be enough. If that
> battery pack is small enough gas stations could morph
> into battery pack swap stations.
Or your car has a 60km range battery built in and for longer trips you stick an extra capacity battery in the boot and plug it in. It's a lot easier than adding/removing a gas tank as needed.
There's quite a few practical details that weren't addressed. Whats the self discharge of these caps? Sure, maybe they can hold a ton of energy in a small volume but who cares if it bleeds off in 2 hours? What's the performance over temperature? Does the capacity drop off at temperature? Does the available power drop off? A lot of conventional supercaps can even permanently age quite quickly at moderately high temperature.
One of the fantastic things about grapheme is that it is so easy to work with and abundant material.
This simple method of reduction means you could create a machine for making long sheets of grapheme just with an uniform focusing laser bar, this means mass scales and super cheap. Very exciting!!
The discs appear to serve only as a temporary platter for holding the graphite oxide film. Once scribed by a laser, the graphite oxide is converted to graphene and peeled from the disc for further processing. The discs aren't used in the capacitors. The article says that blank discs are used, but doesn't mention if they are reused or even if they must be blank, but I get the impression that a viable method of production probably won't depend on wasting disposable discs.
