The Air Car
A co-worker told me about this car he saw on the Discovery (or Science or something) channel, and we found the web site for it:
The MDI Air Car - the world´s cleanest car.
A car that runs on compressed air. My first thought was, okay, how clean is it really? Because people tend to forget this with electric cars: the electricity has to be generated somewhere, and it’s probably a polluting coal plant that’s doing it. But their site says they have a fuel/air hybrid (I’m just guessing, the fuel part is for an internal compressor maybe?) that gives the car a range of 1200 miles. I wish I saw the show or it had more detail here, though, the site seems like mostly rah-rah we’re great stuff.
August 29th, 2006 04:39
Correct, you have to have an electric powered air compressor to fuel it. However, cars that are ultimately electrically powered are still much cleaner than gasoline powered cars. At least I’ve never had the EPA or some watchdog organization poking around under the hood of my gas powered car every two weeks.
I got nothing on air-powered cars, but a comparison on gas car emisions versus the emissions generated by an electric powerplant to generate enough electricity to move electric vehicles the same number of miles can be found here:
http://people.qualcomm.com/karn/ev/ev_emissions.html
Yeah, I’m one of those crazies that want to reduce our dependancy on foreign fuels.
August 29th, 2006 13:35
INSANITY!
Hrm, well it’s cool to have an actual analysis, thanks. And thinking about it, I suppose it would be more efficient to make it in one place in bulk. I guess there’s still secondary costs like the infrastructure required to get electricity from one place to the other, but that already exists (in the general) for gas in different forms, so.
August 29th, 2006 15:25
I did a little looking around for the air powered car, and I have to say that I’m impressed!
“The Nègre engine is used to power an urban car with room for five passengers and a projected range of about 100 to 200 miles (160 to 320 km), depending on traffic conditions. The main advantages are: no roadside emissions, low cost technology, engine uses food oil for lubrication (just about 1 liter, changes only every 30,000 miles (50,000 km)) and integrated air conditioning. Range could be quickly tripled, since there are already carbon fiber tanks which have passed safety standards holding gas at 10,000 lbf/in² (70 MPa).
“The tanks may be refilled in about three minutes at a service station, or in a few hours at home plugging the car into the electric grid via an on-board compressor. The cost of driving such car is projected around 0.75€ per 100 km, with a complete refill at the “tank-station” at about US$3.”
Source: http://en.wikipedia.org/wiki/Air_engine
That’s a pretty good range, especially for an alternative-fueled car, and very cost-effective. Unfortunately, it says nothing about torque or horsepower (because we americans have to go REALLY FAST!)
August 30th, 2006 11:37
Yeah, but the notion of a 10k lb carbon fiber bomb in the trunk makes this scuba diver nervous. I suppose the fact that CF tanks tend to split rather than turn into shrapnel (like aluminum or steel tanks) is consoling. But 3 minutes? Really? It takes half an hour for an active pump to fill my piddly little 80cuft tank to 3000 psi, and at least 10-15 minutes for a staged filling system to fill it safely. (Staging is where a pump fills a permanent tank to 4-5000 psi, then pressure is bled into my tank.)
I suppose if the tanks can get an _exceptionally_ hot fill to 15k and then cool to 10k it’d be possible, but oy, that’d be exciting as all hell.
August 30th, 2006 13:26
Well yeah, but driving around 100 pounds of liquid fuel should theoretically be scary, too, but it isn’t.
I was surprised at the time differences, too. Either three hours at home or three minutes at a commercial station…that must be a hell of a compressor.
August 30th, 2006 15:44
Well, gasoline isn’t particularly explosive, high pressure gasses are almost excitingly so. (Versus flammable. Gas tank fires are exciting as well, if you can manage it.) And the difference in fill rates is one is a cascade system and the other is a staged compressor like you have in any well equipped machine shop. A cascade system allows you to have a huge whangin’ high pressure tank at some pressure greater than your recipient pressure that you bleed the compressed air into. For scuba that’s something like 960cuft at 5000psi will give you approximately 8 fills of a 80cuft tank to 3000psi in 5 minutes per fill. *waves hands at the math* After that you have equilibrium and that’s all she wrote, you need to re-pressurize the main tank. For low enough volume, that means you fire up the main compressor at the station and let it grind away for 30 minutes getting your stage tanks back up to 5kpsi. For a usage scenario that replaces gas stations? I’d think it would get outrageous fairly quickly.
And that’s not even approaching the DOT regulations regarding high pressure tanks - you need to have an annual visual inspection inside and out and hydrostatically tested every 5 years to 150% capacity with water, etc.
August 31st, 2006 07:12
Just FYI: Gasoline flammability
Bear in mind that this is only what I remember from my gearhead days and should not be taken as fact!
Gasoline liquid is not flammable. It is only as Gasoline turns to a vapor that it becomes flammable. The air/fuel ratio has to be at 14:1 for gasoline to ignite explosively, which is why your car controls this mixture so acurately, since its power comes from an explosive reaction. Also, gasoline under normal circumstances will only igniite from an open flame or an electrical spark.
I would think that for a high-pressure air tank you could probably find a way to direct an explosive decompression event up into the air through use of shielding, but then I’m not an engineer.
August 31st, 2006 12:41
Yeah, I haven’t been able to find any of the “sweet merciful jesus that was a cinderblock wall?” pictures of exploded scuba tanks I’ve seen before, but that’s probably apples and oranges compared to a wrapped HP vessel, anyway.
I wonder if the fire conditions apply here, too. Scuba tanks, when full, are reasonably safe during a fire as the internal pressure will exceed the burst disc rating before the tank loses structural strength leading to a much larger explosion. On the other hand, it wouldn’t be rocket science for a vehicle to tie an explosive valve to the tank and slaved to the airbag system to just cut the air loose in the event the airbags are fired to prevent a potential explosion.
August 31st, 2006 13:04
I’m not taking about the flammability of gasoline, but the scariness of carrying around a hundred pounds of it. Because really that’s what Kyol’s talking about, not whether it’s safe, but how much it’d worry him. I have to imagine some people in the early days of internal combustion engines had similar fears.
September 1st, 2006 06:02
Well, let’s ask the important questions, here.
How does an exotic materials (such as carbon fiber) air tank behave when filled to full capacity then punctured? Will it bloom out in all directions like the clogged barrel of a rifle in a cartoon, or will the explosive decompression that will obviously occur be localized strictly around the puncture? If it’s localized around the puncture, would it then turn the instrument used to puncture it into an air-propelled missile? How does the tank behave when crushed?
And Spinn, I didn’t mean to seem to be attacking your statement about the flammability of gasoline. Let’s put it this way: When the chips are down I’d much rather die through the explosive decompression of a five-billion PSI air tank than through the slow death of a gasoline fire. The moral of this story is that I’d rather sit on a hand grenade than hug a flame thrower.
October 28th, 2006 11:29
So what is up with the “air car” concept (www.theaircar.com)? I have been googling around and I see nothing that resembles life??? My assumption is that there is either some major technical problem - otherwise someone would be producing these things? If so what was the problem? Any clues out there?
October 30th, 2006 18:06
Hm…
“Because people tend to forget this with electric cars: the electricity has to be generated somewhere, and it’s probably a polluting coal plant that’s doing it.”
Still, a single point source of pollution can be controlled, as opposed to our current model of millions of potential sources.
I still doubt this concept, though, especially since they don’t discuss hp. To me, that implies some unacceptably low speed, like 30 mph or something.
October 12th, 2008 06:02
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October 12th, 2008 10:30
Oooh! I love cryptoquote!