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Charge Your Cellphone In 20 Seconds (Eventually)
New submitter GoJays writes "An 18-year-old from Saratoga, California has won an international science fair for creating an energy storage device that can be fully juiced in 20 to 30 seconds. The fast-charging device is a so-called supercapacitor, a gizmo that can pack a lot of energy into a tiny space, charges quickly and holds its charge for a long time. What's more, it can last for 10,000 charge-recharge cycles, compared with 1,000 cycles for conventional rechargeable batteries, according to the inventor Eesha Khare." This one in particular has been used so far only to power an LED, rather than a phone or laptop, but I hope in a few years near-instant charging of portable electronics will be the norm as supercapacitors grow more common.
My phone battery has a capacity of 2.1Ah. To charge it in 20 seconds would require a current of 380 Amps. What kind of charger could safely supply that?
Yes. The article was terrible. She almost tripled the energy density of supercapacitors. From her paper:
"National Security is the chief cause of national insecurity." - Celine's First Law
Correcting myself: She claims to have increased mass specific capacitance by almost 3. I'm not sure how her volume specific capacitance compares - I'd think that would be more important for cell phone use.
Mass energy density of commercial supercaps is 3-5 Wh/kg, but 85 has been seen in the lab, according to Wikipedia. Her's is 20.1, which may be significant if it can be commercialized.
"National Security is the chief cause of national insecurity." - Celine's First Law
Drop a spanner on the poles of a truck battery, and the battery does not exactly explode (the poles may get damaged). But molten metal flying around is still not fun. The problem is not the capacitor, the problem is whatever may do the shortcircuiting.
Sigh! Supercapacitors are inherently stable and generally won't explode unless you actively force them too (i.e. most things explode when you put 1kV up it's arse).
High energy densities and high currents are emitted when shorted and you end up with maybe a spark. Quite a safe spark though given the pathetically small voltages they can store. The same can be said for non-super capacitors too. The only only ones which really let go with a bang are tantalum caps, and even they are quite stable run under their rated voltage.
Sorry to drain the FUD out of your sarcastic post but with caps your biggest risk is electrolyte running down your ear.
but unless she has achieved actual breakthroughs in the field, this is again not nearly as newsworthy as the headline suggests.
She has. The only problem here is that the news itself is dumbed down to the point of being utterly pointless.
Science reporting at it's finest.
A very cynical person might say that the reason for the award was in the photo.
They might, but since she has constructed a novel supercapacitor, they'd be wrong. Don't let the "it's political correctness gone mad" people win.
One problem with capacitors is the charge is stored a lot like water in a tank. As you use water the water level drops, in any capacitor, as you use it the voltage drops.
The governing equation is Q = 0.5 *C*V*V.
A single cell (in a battery of cells) is composed of two materials of different chemical states and they produce a constant voltage until one of the chemical states is depleted. Charging reverses this, again at a constant voltage. The charge and discharge voltages in a theoretically perfect cell are ~~ the same, in a real cell, resistance caused voltage drops and departures from irreversibility lead to differences in the charge discharge voltage. You must charge with a high voltage than you get on discharge.
A second problem, is the fact that a bulk material changes state in a cell, this inherently stores more charge than a capacitor, which is a surface layer of added charge. It is true that since the capacitor involves no change of state, that the life is more or less infinite, and because it is a monolayer of charge, you can charge and discharge at speeds limited only by the current limits of the wires.
The net result is the energy density of the best capacitors is barely as good as the worst batteries.
Battery graphs here http://tinyurl.com/autjb7l
Capacitor graphs here http://tinyurl.com/byqbdje
Direct comparisons here http://tinyurl.com/b9zwcdw
As long as you design a downstream voltage regulator to use the declining voltage to power your circuit at its required constant voltage, then ultracaps will find a niche in many pieces of equipment from Cars(as a peak acceleration source) to tiny items as the sole power
Interesting numbers. Just to compare, here's the energy densities of lithium-polymer batteries and super-capacitors, taking the values for best easily-available components I could find.
LiPo: 168 W.h/kg, 370 W.h/l
Super-cap: 5.1 W.h/kg, 6.6 W.h/l (I'm being slightly generous to the capacitor here, by counting the energy to discharge it to zero volts. In practice that last bit of energy will not be usable.)
The volumetric figures are most critical for phones, and in those terms batteries are 56x better than super-capacitors. So an improvement of 3x is interesting, but there's a lot more work to do.
Forgot to mention self-discharge rates: 0.007 C/day for LiPo batteries, and 0.08 C/day for super-caps (12x greater)
Even smarter, not one super capacitor but a whole series of them, which discharge into a low capacity rechargeable battery
Let's take a look at why that is not smarter. You are throwing away the energy density and quick charge properties, and increasing complexity by adding, most likely, another entire charge controller. As well, there is absolutely no need to use an array of supercapacitors, because supercapacitors are the solution to the problem of needing an array! They have fast charge and discharge, they already act wide and not just deep.
You're throwing away energy density by wasting space on having two power systems, and you're throwing away quick charge by including a power system without quick charge. You'll want a separate charge controller for the separate power system, and that means still more efficiency loss and still more cost. It just doesn't make sense.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Ok did the research, she "invented" the wheel, they have been using this method since at least 2007. Her method uses "a novel core-shell nanorod electrode with hydrogenated TiO2 (H-TiO2) core and polyaniline shell. H-TiO2 acts as the double layer electrostatic core. "
http://www.usc.edu/CSSF//History/2013/Projects/S0912.pdf
Not so novel: "Incorporating the utilization of carbon nanotubes cathode and TiO2 nanotubes anode in energy storage, a nonaqueous hybrid supercapacitor was developed in order to significantly increase the energy density of the supercapacitor."
http://www.ncbi.nlm.nih.gov/m/pubmed/18019169/
Also dr yat li which she claims was "supervising" her seems to think he invented it a year ago without her help. Notice his name is on this article with other doctors but her name is missing: "Hydrogenated TiO2 Nanotube Arrays for Supercapacitors"
http://pubs.acs.org/doi/abs/10.1021/nl300173j
She basically did a chemistry experiment that had already been done and published, she invented nothing
my karma will be here long after I'm gone
Um, you and everyone commenting has missed a major detail. Don't you geekheads know about circuit breakers? Your room is probably wired to a 20 or 25 amp circuit. Check the breaker and replace it with a larger one, say a 30 and you will probably be able to run everything at once without a fire.
I think you're just trolling, but if anyone is reading this and thinks just swapping out the breaker or fuse is a good idea, remember that it's the size of the wire that determines the safe current limit of the circuit, not the size of the breaker. In the USA,NEC specifies: 14 gauge wire = 15 amp, 12 gauge wire = 20 amp, 10 gauge wire = 30 amp. (but these are maximum values that may need to be derated in some conditions, like multiple conductors in conduit, especially long circuit runs, etc)
The article is brief on facts but i would bet my money she has just repeated the graphene super capacitor experiment done by and explained in detail by these guys https://www.youtube.com/watch?v=_oEFwyoWKXo all you need is a light scribe dvd player some grpahite oxide and a dielectric.
Rocket Surgeon.