Comressed air powered car conversion

[Bicycle Bob]

I just have to second that comment on the inescapability of the laws of physics. Combined with some back-of envelope calculations, they have shown me that several slick brochures were frauds. The air car was a prime example. After half an hour of checking figures, I advised an editor I knew to print a retraction. He scoffed, but kept an eye out for experimental evidence, and it showed up two years later.

[Dr. Jerryrigger]

I don't know about this one, seems like we have better ways to store energy. Never mind the true range of these, that safety factor is what will keep them off the roads (hopefully, I'm still a little scared of the Chevy volt as I know how a small Lithium ion battery explodes). I heard, some years back, the French came up with a flywheel storage system; where when you hit the brakes the wheel was spun up, and when accelerating you used some of the wheels power. Then they did crash tests, and the wheel would shoot off in some direction with enough force to rip through another car. They switched to a ceramic wheel that would shatter, but I assume nothing has come of this, as I haven't heard about it since.
Anyone who has worked with high pressure tanks seems to think this is a bad idea. And as I imagine a cylinder flying at me from some relatively far away accident, I agree.

[idtent]

here's a link to flywheel recovery page 98 Popular Mechanics - Google Books

But as far as compressed air goes I think one of the best design is Di Pietro rotary air engine.- info

http://www.youtube.com/watch?v=Dq8aZVLpf-c

Also EPIndustries has a unique design of a motor/pump that seems to have a pretty good output- CEM Co. Carbon fiber can be built to be extremely tough. I remember seeing a video on youtube of a carbon tank filled with hydrogen being shot at with 50cal guns. I would think that an air powered vehicle would be about as good of a choice as electric plus you would have a quicker refill.

[oil pan 4]

I know I'm grave digging this post.
I ran some numbers and they look so bad I hope they are wrong.

To supply the 10 horsepower needed to power a car at 55mph it looks like it would take up to 700cfm at 90 psi.
To compress 700cfm to 90psi my engineering tool box calculator says that will take 106 horsepower with a single stage, about 10% less for 2 stage and a little less for 3 stage.
(this is not the requirement for compressing it to storage tank pressure of 2000 to 3000 psi)
Then add 15% to 20% to over come friction.
I know the air compressor power requirement numbers are correct, those are already well established.

So we are looking at about 10% efficiency.
If 2 or 3 stages of current turbines were sized properly and connected in serries the efficiency might get up in the 15% to 20% range and that is with me being overly optimistic.

This requirements I found were likely for a current air turbine type motor, which aren't real efficient. So these guys building the air powered cars have to come up with something vastly improved over current air motors.
It has to beat current 200 year old technology by leaps and bounds.
If these companies could make their single stage turbine 10 times more efficient than current ones I still dont see a vehicle going very far even then. I think they could make a real good, real cheap, very low maintenance, all mechanical short distance vehicle.

I hope they can do it, it just ain't looking good.

The compressed air powered vehicle videos I have seen they were showing off NEV or golf cart like performance.

[NeilBlanchard]

Compressed air powered cars need to be parked next to the unicorns...

Your numbers sound quite plausible.

[Bicycle Bob]

Imagine a city full of compressed air cars at rush hour. One accident, and a chain reaction blows up a whole traffic jam, and any nearby parking lots. Compressed air is the equivalent of high explosive as a fuel, requiring no oxygen or time to release the full potential.

[rmay635703]

Originally Posted by Bicycle Bob

Imagine a city full of compressed air cars at rush hour. One accident, and a chain reaction blows up a whole traffic jam, and any nearby parking lots. Compressed air is the equivalent of high explosive as a fuel, requiring no oxygen or time to release the full potential.

Sorry but the danger issue is not that real.

Using many of the same techniques used in CNG and hydrogen cars air tanks can be made safe. (at least as safe as a gas tank)

Far as I know all high pressure vessels (and for as long as I can remember) are Leak before blow. This means even under diress they will mearly leak quickly but not blow.

Next while air has explosive force (if the tank were not leak before blow) that can be easily diffused with a relatively small lightweight baffling around the tank with an obvious ejection point.

Although it still would be frightening if it went, it would not cause enough damage to anything around to cause a chain reaction.

Finally this is all moot since the range and efficiency suck.

The only efficient way of compressing air would be to use the depth (and temperature gradient) of a cold ocean on a massive scale, even then there are no efficient motors to use the efficiently compressed air.

Cheers
Ryan

[niky]

Originally Posted by Bicycle Bob

Imagine a city full of compressed air cars at rush hour. One accident, and a chain reaction blows up a whole traffic jam, and any nearby parking lots. Compressed air is the equivalent of high explosive as a fuel, requiring no oxygen or time to release the full potential.

Imagine a city full of gasoline-powered cars at rush hour. One accident, and a chain reaction causes a wildfire inferno consuming a whole traffic jam, and any nearby parking lots.

[Frank Lee]

[Ryland]

Why is compressed air still seen as a viable idea? even the companies who make them say it takes 65kwh of electricity to go 62 miles, that same amount of electricity can make my electric car go 260 miles of course the air powered car weighs 1/3 of what my electric car does so I imagine that if I had lithium batteries and narrower higher pressure tires like the air powered car does that I might be able to go well over 300 miles on that same electricity! all because the big selling point is that they are able to sell a 500 pound, two passenger car with a top speed of 55mph for $8,000.... right.