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Comment by mpweiher | Hacker News Reader

Very cool tech, and the manufacturing process looks doable as well. :-) Except for us poor mac-heads, how is iTunes going to make me some Graphene??

I was a bit disappointed that there weren't any numbers in the film, so I looked them up: http://www.extremetech.com/extreme/122763-graphene-supercapa...

Energy density (storage capacity) does seem to be in range of Lithium Ion batteries, better than some, but still around a factor 7 or so worse than the highest density there (but slowest to discharge). Considering the extra effort managing the batteries (Boeing, Tesla,...) you might just come out ahead already.

On the other hand, Graphene apparently also makes Lithium-Ion batteries significantly better: http://www.extremetech.com/computing/105343-graphene-improve...

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There also exist hybrid supercapacitors, which use a chemical reaction but act like capacitors. The best use of high-power capacitors is not as a replacement, its as a supplement. Current technology is not quite sufficient, but ideally it would mean that anything under a 20 minute drive could run off just the capacitor, which could(with sufficient infrastructure) charge in under a minute. It's not quite filling up on gas, but its closer.

I would like to see more investigation into turbine powered cars again, it may be more feasible now to build a car like we build trains (A prime mover generates energy for locomotive motors). I think the best way to transition from gasoline to electric would be to take advantage of existing infrastructure and make hot-swappable battery units. For medium drives you use batteries, which can be switched in a garage with a capacitor bank for short drives, or a unit with a small battery, a helicopter turbojet and a gas tank (Which, ideally, would run at a higher efficiency than an ICE).

The reason we haven't used turbines in the past as far as I know is mostly the start-up times and inability to idle. They don't really slow down, so sitting in stop and go traffic you engine is basically still on full blast. Ameliorate that with a battery and you're good to go, hopefully.

I believe turbines have efficiency problems as you scale them down.

Ah yes, graph here… http://www.dg.history.vt.edu/images/image5_2.gif which is from http://www.dg.history.vt.edu/ch5/turbines.html

And then notice that the smallest turbine on the plot is about two orders of magnitude larger than you need in a small car.

The graph relates to intended use not just physical limitations. Backup generators are generally more concerned with cost and matinace issues than efficecy. So they tend to be simpler and have much lower tolerances. That said, the automotive market is huge so if they ever became popular for say plug in hybrids something in the 30-40% range is vary possible even at 100hp.

Chrysler made a turbine powered car in the Sixties. It would run on nearly anything. Unfortunately, Chrysler never pushed it to mass production, then the oil embargo put paid to that idea. But it was one of those beautiful futures of the Sixties.

http://en.wikipedia.org/wiki/Chrysler_Turbine_Car

Fascinating. At the end there's a link to an earlier Fiat I did not know had existed: http://en.wikipedia.org/wiki/Fiat_Turbina (the photo reminded me of something familiar, took me a bit to figure out it was a guppy fish ;-)

Turbines are not fuel efficient for vehicles that are stationary as they idle at 20k rpm. Also the exhaust is highly polluting.

Well, maybe not if you try to directly couple them to the tires. You might have better luck if you try powering a generator to charge batteries. What do you mean by "highly polluting"? Highly polluting compared to what?

They run extremely lean, consequently they produce nitrogen oxides like you wouldn't believe.

If you'd quote a source I might believe.

Probably not 100% convincing, but http://en.wikipedia.org/wiki/Chrysler_Turbine_Car:

"Nevertheless, the turbine generated nitrogen oxides and the challenge of limiting them proved an ongoing problem throughout development."

If the amount produced were low, I doubt it "proved an ongoing problem"

Also: https://wpweb2.tepper.cmu.edu/rlang/RenewElec/CEIC_White_Pap...:

"Gas turbines operate best at full-power steady state conditions where they are at their highest fuel and emissions efficiencies. Deviations away from this tuned set point result in significant inefficiencies (particularly with NOx emissions)"

Mechanical to Electrical back to Mechanical is not efficient unless you can turn off the mechanical at idle.. thats not possible with a turbine...

60 mpg hummer. Turbine + capacitor:

http://www.fastcompany.com/60868/motorhead-messiah

>Energy-wise, we’re talking about 1.36 milliwatt-hours per cm3, about twice the density of activated carbon, and comparable to a high-power lithium-ion battery.

That's not really comparable to any "high-power lithium-ion battery" at all - Wikipedia quotes 250–730 Wh per litre for Li-ion (so 250-730 mWh/cm^3), and a quick calculation with a laptop battery I have on hand agrees - 84 Wh stated in 27x4x2cm = 388 mWh/cm^3.

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