5 ms·

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,

by hwillis 14y ago

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.

jws 14y ago
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 http://www.dg.history.vt.edu/images/image5_2.gif which is from http://www.dg.history.vt.edu/ch5/turbines.html 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.
- Retric 14y ago
  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.
CapitalistCartr 14y ago
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 http://en.wikipedia.org/wiki/Chrysler_Turbine_Car
- ableal 14y ago
  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 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 ;-)
- rootedbox 14y ago
  Turbines are not fuel efficient for vehicles that are stationary as they idle at 20k rpm. Also the exhaust is highly polluting.
  - fnordfnordfnord 14y ago
    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?
    - HarryHirsch 14y ago
      They run extremely lean, consequently they produce nitrogen oxides like you wouldn't believe.
      - fnordfnordfnord 14y ago
        If you'd quote a source I might believe.
        14y ago
jamieb 14y ago
60 mpg hummer. Turbine + capacitor: http://www.fastcompany.com/60868/motorhead-messiah http://www.fastcompany.com/60868/motorhead-messiah
Danski 14y ago
Hey, sorry I'm a bit late to the party on this one but thought I should share my 2c. IMO jet engines will never be viable in cars because: cost, complexity, maintenance, noise, exhaust temperatures, and the operating requirements. The trade-offs to fit it into a car would greatly reduce the benefits over a conventional engine. For example, adding a necessary air filter and exhaust system will see the efficiency drop drastically as you strangle something that requires a free flow of air. Having a power transfer system to a gearbox or a generator/electric motor will also see a great reduction in efficiency. The speed at which a jet turns necessitates a second turbine as a power take-off and hence more losses to bypass. It's often thrown about that a jet engine is the simplest kind of engine, which is true conceptually, but to get any efficiency, practicality or durability out of it there's a lot of bolt ons that are needed. I could go on but will cut it short(ish).
Danski 14y ago
And just to address your point about the idle, next time you're taxing out to the runway have a listen, the engines will be very high pitched and whiny. That's a jet at idle (perhaps 20k rpm, 5% throttle). Then when you're about to take off listen for a point where it turns from a whine to a rumble, this is the compressor stage bypass valves closing forcing all the intake air through the jet. This is full power but the rpm has only gone up about 1/3.

by hwillis 14y ago

jws 14y ago

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 http://www.dg.history.vt.edu/images/image5_2.gif which is from http://www.dg.history.vt.edu/ch5/turbines.html 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.

Retric 14y ago
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.

CapitalistCartr 14y ago

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

ableal 14y ago
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 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 ;-)
rootedbox 14y ago
Turbines are not fuel efficient for vehicles that are stationary as they idle at 20k rpm. Also the exhaust is highly polluting.
- fnordfnordfnord 14y ago
  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?
  - HarryHirsch 14y ago
    They run extremely lean, consequently they produce nitrogen oxides like you wouldn't believe.
    - fnordfnordfnord 14y ago
      If you'd quote a source I might believe.
      - 14y ago

jamieb 14y ago

60 mpg hummer. Turbine + capacitor: http://www.fastcompany.com/60868/motorhead-messiah http://www.fastcompany.com/60868/motorhead-messiah

Danski 14y ago

Hey, sorry I'm a bit late to the party on this one but thought I should share my 2c. IMO jet engines will never be viable in cars because: cost, complexity, maintenance, noise, exhaust temperatures, and the operating requirements. The trade-offs to fit it into a car would greatly reduce the benefits over a conventional engine. For example, adding a necessary air filter and exhaust system will see the efficiency drop drastically as you strangle something that requires a free flow of air. Having a power transfer system to a gearbox or a generator/electric motor will also see a great reduction in efficiency. The speed at which a jet turns necessitates a second turbine as a power take-off and hence more losses to bypass. It's often thrown about that a jet engine is the simplest kind of engine, which is true conceptually, but to get any efficiency, practicality or durability out of it there's a lot of bolt ons that are needed. I could go on but will cut it short(ish).

Danski 14y ago

And just to address your point about the idle, next time you're taxing out to the runway have a listen, the engines will be very high pitched and whiny. That's a jet at idle (perhaps 20k rpm, 5% throttle). Then when you're about to take off listen for a point where it turns from a whine to a rumble, this is the compressor stage bypass valves closing forcing all the intake air through the jet. This is full power but the rpm has only gone up about 1/3.