Air Car

[RussSchultz]

funny, i was just thinking on how $30k for a car seems cheap.... but then I've been looking at the "fancy" cars.

From knowing your financial situation based on how you've described it on this forum, buying that car, or any car that ties you into a $6-800 payment, is a huge mistake.

actually, I was looking at like a 1600-2000 a month payment. financial situations change... when was your last update on mine?

I know you're working in Dallas now.

But locking yourself into a payment like that is insane. Your fortunes can change as quickly to the negative as they can in your case to the positive.

Which is why I suggest you not do it.

 

[Sage]

well it's not like I don't have investments that I could use to cover me if I absolutely had to.

 

[Druga Runda]

I believe that car would be incredibly dangerous to drive on public roads.

Looking at the pic digi posted, you can see it has some very large door/roof posts located near the center of the driver's field of vision. Since the seat is relatively far back in relation to the windshield compared to a normal car, this means the posts end up more towards the middle of the driver's vision, creating large dead zones.

Very, very bad. Besides, the aerodynamics look like they're crap with the sharp angles between front and sides, means more fuel consumption and lots of noise from the turbulence at highway speed. Also, with such small wheels it'll be a bumpy ride too I wager.

All of those criticisms are easily rectified. What intrigues me is that while running off fossil fuels it actually using compressors to keep the air tanks full, which doesn't sound very efficent to me. That gives 3 (or even 4) energy conversion process where efficency loss will occur, as opposed to the 1 process for standard engine.

I didn't see any mention of power output varying with the tank's pressure either (funnily enough). I wonder how they get around that.

Still, it's another option for environmentally friendly commuting, so I'd like to see it succeed, even if it seems a little ill-conceived.

well it uses compressors that can be filled in from your domestic "plug" in 4 hours, or if there was an "air station" in 3 minutes. So all that is used up is the amount of electricity that takes to pressurise the air.

Don't know how much it will cost to recharge those 4 hours but shouldn't be too much comparing to current costs to travel 150-200 or so miles.

 

[Nathan]

Yeah, for commuting it seems like a reasonable solution, but I'm just a bit mystified why they added all that extra complexity for long distance travelling when renting a normal car is probably a much better solution. I think making the car more tightly focused on commuting would allow the cost to be considerably less. The loss of long distance capabilities would not be a big issue anyway, since the car undoubtedly sucks on the open road. Why have an internal combustion engine at all? :?

 

[Guden Oden]

If it absolutely has to lug around on a fuel-powered engine, it really should be a gas turbine. These things are not only much MUCH lighter than a piston engine, if they run at a constant RPM they're considerably more energy efficient too. It could power the compressor to recharge the air tank in minutes, and/or a generator to drive the wheels via an electric motor.

Gas turbines run on most anything that is liquid/gaseous and combustible too, it could run on cooking oil for the budget-conscious... Or perfume for that matter. They're a more than a tad pricey though, and I hear they produce fair amounts of NOx emissions, though maybe there are ways around that. Still, it's a neat idea...

 

[Squeak]

If it absolutely has to lug around on a fuel-powered engine, it really should be a gas turbine. These things are not only much MUCH lighter than a piston engine, if they run at a constant RPM they're considerably more energy efficient too. It could power the compressor to recharge the air tank in minutes, and/or a generator to drive the wheels via an electric motor.

Gas turbines run on most anything that is liquid/gaseous and combustible too, it could run on cooking oil for the budget-conscious... Or perfume for that matter. They're a more than a tad pricey though, and I hear they produce fair amounts of NOx emissions, though maybe there are ways around that. Still, it's a neat idea...

I wonder why we never hear about new turbine engine projects.
It's always electric motors or piston engines.
Up until the mid-eighties, turbine engines seemed a popular field of research for environmentally safe alternatives to the regular combustion engine, now it seems as though the field is anything but dead.
The main problem with turbines, as I understand it, is that they have an optimal RPM for which the blades are adjusted; therefore they are very slow to accelerate and work best at a constant load (not good with regular stepped gearboxes).
The classical solution to that problem is adjustable blades, but the mechanism for that was always very fragile, and the blades still could have only one "adequate" shape.
I was thinking, why not move the jet nozzle(s) instead? Like a modern version of Heros steam engine, only with nozzles that retract toward the centre of the shaft when the turbine accelerates.
Also instead of a stepped gearbox something like a Variomatic gear could be used.

 

[Basic]

Or why not use the turbine in a hybrid system. Let it power a generator, and always run it at its optimum speed.

And how about stirling engines? Aren't those supposed to be quite efficient.

 

[Squeak]

The generator idea is not good, because by converting one kind of energy into another, you are always going lose a lot to heat production (entropy)
The stirling engine with its characteristics, is not suited for a car at all, read the article in Wikipedia

 

[Basic]

Stirling:
OK, good engine, but not for a car.

Generators:
And still that's exactly what's done in many hybrid vehicels (except for the turbine part), with excellent efficiency. And with the turbine's tricky requirements on load and rpm, it seems even more beneficial with a generator.

Some hybrids connects both the combustion engine and the electrical motor directly to the wheels, but not all. Some put them in series engine=>generator=>motor, and with a battery pack to compensate for variations in consumed electricity.

Remember that generators can be a lot more efficent than combustion engines.

 

[RussSchultz]

Turbines are loud. Like, really loud.

 

[Nathan]

Yup. I did an experiment at university with a gas turbine. Even with earmuffs, it was painfully loud. Also, it was running at 3% efficiency, and there was a line on the floor we weren't allowed to stand behind incase the turbine disintegrated. But, hey, if you guys still want one in your car, who are we to stop you.

Actually, there have been gas turbine powered cars. However, they have their problems.

 

[Guden Oden]

I'm sure the turbine could be muffled, and as far as desintegration goes, you guys know there are transatlantic airliners these days with only two engines, right? And these engines produce a far FAR higher power output than a hybrid car ever would. Turbines are extremely reliable these days.

Volvo has a prototype hybrid turbine/generator car that gives I think about 100kW output from the generator itself, and hence a bit more still on the generator shaft itself. It could power a normal house actually. I read quite a bit about that concept model and never did it say anything about it being painfully loud.

 

[fallguy]

It just looks like a little cute toy car to me that would be a blast to tool around in and freak people out with...not to mention the kids would love it.

Unless they were more than 3 foot tall.. No room at all, in the back.

You Euro's have such odd cars. My tires on my lawnmower are bigger than those. Heck, my daughters Barbie Jeep's tires are close.

 

[MPI]

The generator idea is not good, because by converting one kind of energy into another, you are always going lose a lot to heat production (entropy)

Well now, let's not exaggerate too much. Lose energy, certainly. A lot? Depends on your definition of 'a lot'.

Electrical generators have an efficiency of about 96-98% Electrical motors well over 90%, depending. Besides, there's quite a bit of equipment that uses generator-motor conversion already, like for instance diesel-electric trains, nuclear subs, et.c.

The fundamental problem is that engines suitable for direct drive(diesel, petrol piston engines) have an efficiency anywhere from 20-40%. And if you stray from the most effective peak which can be a certain rpm at a certain throttle input, it is quite a fair bit less, then you have mechanical loss in the powertrain, ~10% and add to that the automatic gearbox the yanks are so fond of that has a 10-15% efficiency loss. There's a lot to gain in average efficiency if you could use an engine that is perhaps not suited for direct drive(turbines, stirlings, whatever) with say, a consistent efficiency of 40%, with a small buffer for surges, even with an over-all conversion loss of 10%.

Stirlings are probably just too big and heavy for it's power output to be used in hybrid cars.

Turbines are interesting, in power grid turbine generators you can get as much as 60% efficiency, but to get there you reuse the heat of the combusted gasses in heat exchangers to power secondary steam turbines... How much efficiency you could get out of a turbine in a car I don't really know. Would be interesting to know, though.

 

[Guden Oden]

If you ran the turbine on something really cheap/easily replenishable (like vegetable oil-based fuel), efficiency wouldn't be that much of a problem. Fuel cost would not be an issue, neither would carbon dioxide emissions, since it's from a biological source.

 

[MPI]

You can run diesels on vegetable oil aswell, running turbines isn't a goal in itself for me.

http://www.greasecar.com/

 

[_xxx_]

If you ran the turbine on something really cheap/easily replenishable (like vegetable oil-based fuel), efficiency wouldn't be that much of a problem. Fuel cost would not be an issue, neither would carbon dioxide emissions, since it's from a biological source.

Biological or not, burning stuff always produces emissions. Besides, diesel is also biological

 

[Clashman]

I think the SMART car, or this air car could sell in NYC, or Chicago, or any highly dense, urban setting where freeway driving isn't the norm and there aren't semi's to contend with.

As an aside, why wouldn't a SMART car be able to handle it on the highway? It goes 84 MPH, (which is electronically limited, by the way), 110 MPH for the roadster model, which should be plenty for most highway drivers. If safety was really that big an issue, I think you'd see fewer people buying SUVs, (with their high rollover rates), and convertibles (need I even explain why), and driving them on the highway. Not to mention the success that's been had with the Minis and "New Beetle" cars.

Plus, those SMART cars are damn cheap. If there were cars that looked like their roadster model available brand new for less than 20,000 bucks in the U.S., I think they'd sell like hotcakes.

I really think this "Americans only want big cars" is much more slogan than substance. It just hasn't been tried extensively.

 

[MPI]

Biological or not, burning stuff always produces emissions.

Of course, about the same amount that was taken from the atmosphere when the plant you squeezed the oil out of grew. Well, more or less.

Besides, diesel is also biological

That's the theory. 50-200M years ago or so. But unless you plan on regrowing 200M years of vegetation, I'll just categorize it under "introduced emissions".

 

[Guden Oden]

Biological or not, burning stuff always produces emissions.

That's a narrowminded way of looking at it. You're not looking at a net gain of carbon dioxide in the atmosphere with bio-fuels, unlike with fossile fuels.

Besides, diesel is also biological

No it isn't! By what measure could you possibly call diesel fuel "biological"?