Charge Your Cellphone In 20 Seconds (Eventually) 295
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.
Re:supercapacitors are cool (Score:4, Interesting)
In a reverse-car analogy it's like having a 2 Mbit DSL to the Internet. Downloading a movie is going to take a long time a Gigabit home network won't help.
We have overland lines a few hundred yards from our house, and there is a gas pipeline running right under the stables. It should be easy to recharge either an electric car or a natural gas powered one in the course of milliseconds.
The problem are the taps. As a result, our AC is quite less dependable than the buzz of the overland lines, and we don't even have gas in the house, instead having to make do with (quite more expensive) oil heating.
Maybe we should go for inductive car charging and park the car under the overland lines.
Re:little light on the science details. (Score:4, Interesting)
Hmm, I don't understand these numbers. 20 Wh/kg works out to 72 kJ/kg, which is much less than the 1.08 MJ/kg Wikipedia quotes for supercapacitors. On the other hand the article on supercapacitors claims 15 Wh/kg to 30 Wh/kg as the typical range of commercially available values, so perhaps the other number unrepresentative. Anyway, these numbers would place the 20 Wh/kg result in the article squarely inside the range of commercially available supercapacitors when it comes to energy density. This is also about 10 times lower energy density than rechargable lithium batteries. So not exactly something you want in your mobile phone.
Re:supercapacitors are cool (Score:5, Interesting)
To extend the reverse-car analogy, the correct analogy is the use case of wanting to transmit a large movie to a USB stick so you can watch it on your TV. Doesn't matter if you have the best-of-the-best USB stick and USB 3.0 in your computer. The bottleneck is still the internet connection. So what you do is that you set your computer to download that large file while you're out doing whatever it is you're doing all day, and copy it over to your USB stick quickly when you get home. (You could even conceivably automate this process or remote control it from your cell phone.) In this scenario, having USB 3.0 *will* help since it'll cut down on the time on getting the movie from your computer to the USB stick.
Analogously, the way you'd do it for a residential charger, is that you'd have the power grid trickle charging a supercapacitor that you have at your home (ideally under some kind of control from the power company, so that they can manage the load on the electric grid) over the course of a few hours, so that when you need the power, you can just plug it in and almost instantly get your car charged up.
Although while we're on the subject of analogies, a better reverse-car analogy would be that of a flush toilet, slowly building up a reservoir of water to then quickly release it when required.
Re:supercapacitors are cool (Score:4, Interesting)
Even smarter, not one super capacitor but a whole series of them, which discharge into a low capacity rechargeable battery (that high output discharge will actually extend the life of the battery as it would prevent crystalline build up), in sequence to provide smooth delivery of power. The series of small super capacitors can still be charged at high speed and via a more regular rechargeable battery provide smooth delivery of current.
Re:supercapacitors are cool (Score:2, Interesting)
I don't know what the parent poster has seen or worked with, but I have worked with capacitors that are fused and have seen what happens when they fault. In some cases where the capacitors were isolated, a simple wire was used and that makes quite a mess of molten metal, in what many would describe as an explosion. Other cases, where more traditional fuses were used, it was a little better, at least for the fuses that were a bit large compared to what I picture being used in a cell phone. The smaller fuses didn't contain the energy as well, so then you go a spray of molten metal and glass.
I'm not saying it can't be done, but it is far from trivial to make fuses for such systems. And then you still have to deal with internal faults that capacitors can rarely develop, especially high density, cheaply made ones, which will bypass the fuse. I'm used to the rule of thumb that if a capacitor has more than 10 J in it, it needs to be treated with some care, and over 100 J needs some actual safety considerations... for a 5 V battery, those energies correspond to batteries with 0.5 mA hr and 5 mA hr storage... a lot smaller than what you see around now.