Whoosh

[filkertom]

This has hit, like, a half-dozen blogs, and if it turns out to be as big as I think it might it'll hit a lot more soon. It's not available in the US -- not yet. But... oh, if it was.

Ladies and gentlemen... the Air Car.

Comments

[solarbird]

I'm doing some math.

Assuming I have the right numbers via T3h Web (I checked multiple sources, please do feel free to check my work), a US gallon of gasoline is about 125,000 BTU, which is 37 kWh. They're claiming 125 miles at 22kWh. So they're claiming effectively... 210mp(us)g equivalency, more or less.

According to Wikipedia, the current record for any production automobile is the 78 mp(US)gallon diesel (the Volkswagen Lupo 3L). Diesel engines run at 45% efficiency; assuming 100% efficiency in that case yields 173mp(us)g equivalent diesel, but diesel has more Kcal per USG than gasoline (129,500), so it doesn't match up properly with the figure above for efficiency considerations. Normalising across calories per gallon, that yields about 167mp(us)g gasoline at 100% efficiency, interpolated from the record-holding liquid fuels car, or:

2.79 times the most efficient (in mp(us)g) liquid fuels production vehicle ever made, or:
26.7% more efficient than 100%-efficient gasoline consumption in the most fuel-efficient gasoline scenario to date.

So. I'm ... curious about these claims. Not saying it's impossible; just saying I'm... very curious.

Please do feel free to point out errors in my math.

[filkertom.livejournal.com]

I have no idea about the math myself. I will point out that, however they've done it, it very likely does not involve a direct correlation between gasoline-generated energy and compressed-air power. Literally, comparing dinosaurs with balloons. I'd like to know how it works myself, and what they had to modify where in the physical design of the car (as a for-instance, the fiberglass body they have rather than the more common steel) and how it affects... well, everything.

[solarbird]

I will point out that, however they've done it, it very likely does not involve a direct correlation between gasoline-generated energy and compressed-air power.
Yes, it does, in the end. In both cases, I converted to kWh for my calculations, and they give kWh numbers. (And kWh-equivalents are easy to get from gasoline.) Yes, I converted back to mph-equivalents for the purposes of comparison, but that's mostly because they're units with which most people are familiar.

Energy is energy. And I'm sniffing at this and not liking the efficiency (miles per kWh, if you prefer, over miles per gallon) that they're claiming.

Also

[solarbird]

They're claiming their onboard storage tanks are 300bars. 300 bars is a bit under 5,000 PSI, for those working in American units. They make this claim:

In the case of a major accident, where the tanks are ruptured, they would not explode since they are not metal. Instead they would crack, as they are made of carbon fibre. An elongated crack would appear in the tank, without exploding, and the air would simply escape, producing a loud but harmless noise.

I've worked in labs with 5,000 PSI tanks. If those things rupture, and you're in the way, you are fucked. But it's not because of any "explosion," it's because the shrapnel will be fucking dangerous. Now yes, those are metal, not plastic or fibre-composite - but it's not going to be just a "loud but harmless noise," even so. This may just be corporate-speak for "it's not going to generate a ball of fire," but it bothers me.

Re: Also

[palenoue.livejournal.com]

Re exploding tanks: Yes, metals are dangerous and can cause shrapnel. Plastics and fiber-composites, on the other hand, can be be made so they don't. They can also be made to prevent ripping, so a small puncture won't grow into a bigger one, and tailored a hundred different ways for different uses and different safety features. I haven't heard if any of these developments are in these air cars as they are now, but should they come to market I'm sure they'll be sporting composite tanks of some kind, as the metal ones are just so heavy.

Now as for the math, as I mentioned before you've got a lot more options for powering the compressors because they can be installed in a permanent location and don't have to move. Thus you can have a nifty hybred system that uses solar cells on the roof, a small wind turbine on the garage (with a customized pirate flag on the tail, of course), and as a standby, a small fuel burning generator that uses biofuel in a clean way. So straight number crunching comparisons really can't be made until you know how the compressor is going to be run.

Now, for "actual use" energy efficiency, I have to say that in what I've seen over the last few years people for the air cars are always quoting "projected" or optimal numbers, while the test cars actually built fall far short. I have no problem with the concept, and I'm sure if you get a lot of clever people together they can refine the air powered engine into something noteworthy (like "Junkyard Wars" but over six months instead of one day), but so far I don't think it's ready to hit the streets.

Re: Also

[solarbird]

Fibre-composites can do plenty of damage. Sure, less mass, and that's good. But I'm still disturbed by the way they dismiss this.

And when it comes to the math, where and how you get the energy doesn't actually matter. (Also, they say that the car has a built-in compressor that can charge the vehicle in four hours without external unit.) What they are claiming is 125 miles for 22kWh. That's their number. Where that comes from isn't relevant; how you get it (solar, etc) doesn't matter. The only thing I'm analysing here is:

What are they claiming, indirectly, when they say 125 miles out of 22kWh?

And what they're claiming, when you go to that number and that number alone, when compared to the same numbers from current vehicles, are efficiency leapfrogs generations above current piston (and rotary) engines.

I am absolutely not saying that this is impossible. I am not making that argument. I've just done a little math to come up with comparisons between their (implicit) claims of efficiency and world-best real-world efficiency demonstrated to date. Maybe they've done it; indeed, I hope they have. But given the long, long history of air-powered-automobile fraud, I want to see empirical data.

(edited to fix repeated(!) numeric typo, sry.)

Re: Also

[palenoue.livejournal.com]

Fiber-composites really shouldn't considered as a "one disaster fits all" kind of thing because it's inherently different. For instance, two composites that I know of go like this: water repellent-generic binder - tear resistant - compression strength binder - wear-resistant material is good for certain things but lousy at others, meanwhile, tear resistant - compressed binder - water repellent - generic binder - wear-resistant is good at the things the first is lousy at but bad at the things the first is good at. This probably isn't the best way to explain it, so think of it like this: how you layer the composites and the material you use make a _BIG_ difference in how they are used and how they react to disasterous failures. One could explode from pressure and send pieces flying everywhere, another could not only become stronger due to high pressure, but when damaged keep the hole small and dissipate the pressure in a controlled manner.

However, one problem with composites is lifetime. Regardless of how they're made, most have a limited active life. True, there are ways to extend the life and they're working on making them better, but I wouldn't be surprised if you had to replace the composite air tank on these things every four years or so, if they use composite tanks at all.

As for what they say the energy numbers are, I never go by that. People always quote the best, or worst, possible numbers regardless if they are "best possible lab conditions" or "theoretical extremes." The only numbers I go by are when they have independent labs run the tests on the actual product, then I make sure the labs are really independent. I look mostly at how things would work in the real world and the possibilities for diversity/advancement. The air engine has a lot more going for it in this respect not only because there are better ways of designing the engine (which use less moving parts, fewer resources, less mass, etc.) but also because the air compressors can be made to handle a lot of diversity. For instance, you could have a quick-charge compressor at a gas station that's powered by a high-octane biofuel with a heavily filtered exhaust, or a home unit that's slow to recharge but uses wind and solar power to fill up while you're at work or asleep.

Still, neat as this idea is, I'll believe it when I see it on the road.

Re: Also

[bryanp.livejournal.com]

Indeed. Explosions and shrapnel are not the only things to worry about. I used to work for Pepsi Cola. I may be an IT geek, but I've seen what happens when a 20 pound CO2 tank falls off a truck and the nozzle snaps off. The newly created rocket blew through the side of the truck, arced over the top of the building and (fortunately) landed harmlessly in the neighboring cemetery.

Pressure like that is not to be trifled with.

As for the efficiency claims I'll be glad if they turn out to be true, but I remain skeptical.