A scientific accident that could change the world • Hacker News Board

Re: A scientific accident that could change the world

#61

Post by lostlogin » Sun, Mar 24, 2013, 6:21 PM UTC

frankus wrote: post #43

gus_massa wrote: post #37

Earlier quoted context omitted.

I searched a little, but the information is confusing. The superchargers (apparently) use 90kW/480V=~190A. I want to highlight this: 190A!!! A usual home connection can handle only up to ~10A, so 190A is a lot of current. To handle this you must use very thick wires. To charge faster you need move voltage or handle more current, probably you will need even thicker wires and to be careful with the safety measures. Add…

A typical new house in the US is wired for a 200A 240V circuit, or about 48kW. By contrast the energy flux of a garden-variety gas pump is in the tens of megawatts.

Is that at the fuse box or the power point on the wall? Sorry if this is a silly question, it's just that here in NZ it's nowhere near that at the wall as the fuses are 10 amp ish.

Re: A scientific accident that could change the world

#62

Post by ScottBurson » Sun, Mar 24, 2013, 6:22 PM UTC

Someone wrote: post #57

mbell wrote: post #49

Earlier quoted context omitted.

I've heard this argument a few times: "It charges so fast that the density doesn't matter". What often gets missed is that for it to charge fast, you need to provide a lot of power, a lot more than any current changer and laughably more than any inductive system can provide. Lithium Ion batteries can already max out the power offered by the 10W charger that comes with the iPad and charging off computer USB is often s…

Also, you would need customers brave enough to charge that tiny device they are holding in their hands at 1000W. A mobile has about the surface area of a 100W incandescent, so if charging is 90% efficient, your mobile would have to radiate about as much heat as such an incandescent would do in about 3 seconds. It won't get as hot as that lamp, because your phone has a larger heat capacity, but I doubt it would stay c…

Charging capacitors is normally much more than 90% efficient. They're not like batteries, where a chemical reaction occurs during charging. Resistive losses in capacitors are normally negligible. In this case they will probably still be negligible, I'd guess, because of the high conductivity of graphene.

Re: A scientific accident that could change the world

#63

Post by kefka » Sun, Mar 24, 2013, 6:23 PM UTC

frankus wrote: post #43

gus_massa wrote: post #37

Earlier quoted context omitted.

I searched a little, but the information is confusing. The superchargers (apparently) use 90kW/480V=~190A. I want to highlight this: 190A!!! A usual home connection can handle only up to ~10A, so 190A is a lot of current. To handle this you must use very thick wires. To charge faster you need move voltage or handle more current, probably you will need even thicker wires and to be careful with the safety measures. Add…

A typical new house in the US is wired for a 200A 240V circuit, or about 48kW. By contrast the energy flux of a garden-variety gas pump is in the tens of megawatts.

Seems pretty simple to me: You create a grid for your house, so it will always have electricity. You trickle charge a rack of graphine Supercaps for your house using mains. You dont need to send that power all at once.

The standard devices to handle passing from mains to battery should be able to be used.

Re: A scientific accident that could change the world

#64

Post by mbell » Sun, Mar 24, 2013, 6:38 PM UTC

ScottBurson wrote: post #62

Someone wrote: post #57

Earlier quoted context omitted.

Also, you would need customers brave enough to charge that tiny device they are holding in their hands at 1000W. A mobile has about the surface area of a 100W incandescent, so if charging is 90% efficient, your mobile would have to radiate about as much heat as such an incandescent would do in about 3 seconds. It won't get as hot as that lamp, because your phone has a larger heat capacity, but I doubt it would stay c…

Charging capacitors is normally much more than 90% efficient. They're not like batteries, where a chemical reaction occurs during charging. Resistive losses in capacitors are normally negligible. In this case they will probably still be negligible, I'd guess, because of the high conductivity of graphene.

True but you've got to consider the numbers we're looking at here.

As an example an iPhone 5 has a 5.45Wh battery, if you wanted to replace that with a super-cap and charge it to 5V in 20 seconds you'd need to provide ~1000W of power or 200A @ 5V. Even if the super cap had very low ESR, call it 1mOhm, which is extremely low compared to current super-caps, you'd still end up dissipating 40W as heat with ~96% efficiency.

Re: A scientific accident that could change the world

#65

Post by sliverstorm » Sun, Mar 24, 2013, 6:54 PM UTC

mapt wrote: post #51

buster wrote: post #19

Earlier quoted context omitted.

There is a big miscalculation: Graphene seems to be extremely light weight. 1 liter of graphene will definitely not weight 1kg. Wikipedia [1] only gives measures for m²: Graphene is very light, weighing only about 0.77 milligrams per square meter. [1] https://en.wikipedia.org/wiki/Graphene

A square meter of a single-atom-thick layer of graphene isn't very relevant. Expect the final product to have a volumetric density in the neighborhood of graphite or diamond.

Probably closer to graphite, as to my knowledge graphite is literally just layers of graphene.

Re: A scientific accident that could change the world

#66

Post by sliverstorm » Sun, Mar 24, 2013, 6:55 PM UTC

BenoitEssiambre wrote: post #4

Conspicuously missing is any mention of energy density. Who cares about power density. That's juste how fast it can discharge. We don't need capacitors that can discharge faster. All capacitors are already much better than batteries with respect to power. We need capacitors that can store more energy. Capacitors typically suck at that and this article doesn't give any indication that these new ones are better.

Who cares about power density.

Well, cars do. As evidenced by the use of lead-acid batteries, power density > energy density for automobiles.

Of course, better power density is probably not the main obstacle to using capacitors in a car to replace the battery.

Re: A scientific accident that could change the world

#67

Post by brokenparser » Sun, Mar 24, 2013, 7:14 PM UTC

lostlogin wrote: post #59

philwelch wrote: post #55

Earlier quoted context omitted.

I visited the UK late last year and can confirm that your card readers can still read the magnetic stripes on our outdated American credit cards if they absolutely have to.

Unfortunately both types die with exposure to magnetic fields - I accidentally too mine into an MRI scanner. This may not Oruro at a lower field strength with the chip type however.

SYNTAX ERROR UNEXPECTED TO... Oh, :s/Oruro/occur/

Re: A scientific accident that could change the world

#68

Post by Selfcommit » Sun, Mar 24, 2013, 7:41 PM UTC

MichaelApproved wrote: post #47

Selfcommit wrote: post #45

Anyone else remember when this was posted a few months ago? (I wish my account was named pepperidge farm, just for occasions like this.)

This comment feels like its one step away from just being the word "repost". I really like browsing reddit but please leave these types of comments there. Hacker News is not reddit.

Yeah, I don't understand the down votes honestly. We've seen this - not just a few months ago.

Why is it ok to post again? Should I have provided the HN link?

Re: A scientific accident that could change the world

#69

Post by nivla » Sun, Mar 24, 2013, 7:50 PM UTC

lifeisstillgood wrote: post #17

I really don't want to come across as nit picky but is this one time when changing a linkbait headline to something more descriptive would help - on the iPhone this page did not render thE actual text for a full half hour (subjective) and I spent all that time with my brain whirring but not in gear - it was a little frustrating A headline like "DVD Graphene sheets store charge super fast in lab" would have helped me…

I agree with you, the title could have been a little more descriptive. I have seen the same video posted here and on Reddit multiple times in the past few months. Although I don't mind it being posted again, since there is always a group of people who haven't seen it, a descriptive title could have prevented me from getting overly interested about this.

Re: A scientific accident that could change the world

#70

Post by gus_massa » Sun, Mar 24, 2013, 8:06 PM UTC

lostlogin wrote: post #61

frankus wrote: post #43

Earlier quoted context omitted.

A typical new house in the US is wired for a 200A 240V circuit, or about 48kW. By contrast the energy flux of a garden-variety gas pump is in the tens of megawatts.

Is that at the fuse box or the power point on the wall? Sorry if this is a silly question, it's just that here in NZ it's nowhere near that at the wall as the fuses are 10 amp ish.

The 200A are at the fuse box (in new houses, old houses may have less).

The wall sockets usually have 110V-15/20A connections. But there are some especial sockets with 240V-30/50A for special applications, like clothes dryers and electric ovens.