Someone forwarded an email to me about this car. But there isn't much about it online unless they've changed the name. The article was dated 2005.

It's 3-person car called the MiniCat, that runs on compressed air (only), with a tank that could be filled up at a station or at home, and would run about 10 hrs on a full tank.

It SOUNDS like a good idea, but is it for real? Are they producing it? Or was it just a lot of theory and hot air?

MiniCat car

Sue

From where does the energy needed to compress the air come?
-Blast

A number of manufacturers had plans to roll out air-powered models by now, including India's powerhouse Tata, but all of them ran into trouble and delays along the way, so no, none of them are in production yet.

It's an intriguing concept that seems a bit more practical to me than hydrogen, since compressing air is a lot easier than getting around the challenges of producing hydrogen gas. I've been waiting for these cars for a number of years now just to see what can be done. Then again, the first air powered cars were invented way back in the 1920's, I believe. Heck, they even had battery-powered electric vehicles back then. We just keep reinventing the wheel when it comes to transportation, it seems.

All the usual sources, I would assume. They've had compressors at gas stations all my life. People have compressors at home and at some job sites. I don't know if you would need a special kind or size.

It just seems that if you can plug in a Nissan Leaf to an outlet in your garage, it would be almost as easy to use a compressor to fill a tank in this kind of car, and eliminate the gross ecological damage of nickel production for car batteries like the one the Prius uses: Prius has larger ecological footprint than a Hummer

The linked article was from Jan. 2005, when gas was about $2.50/gallon. It said the car would run 62 miles on $1 worth of air. My cost then was about $0.08/kwh, and if we said that was average in the U.S. (but maybe not), it would take about 12.5 kwh of power to fill the tank.

I pay about $0.10 per kwh now, so that might be about $1.25 per 62 miles. If I had a car that got 31 mpg, that 62 miles would cost me $7.50 at WA's gas prices today ($3.75/gal).

One tank of gas (12 gallons) would get me about 375 miles and cost almost $45.

If the MiniCat did what it says, the same 375 miles would cost me $7.50 in electricity.

Extrapolating that to 100,000 miles (assuming you didn't get flattened by a 17yo texting while driving his 3.5-ton pickup):

100,000÷375 mpg = 267 tanks of gas @ $45 = $12,015
100,000÷1613 tanks of air @ $1.25 = $2,016

Add to that last line a $2,000 compressor and you would still be far ahead of a smaller Chevy using gas.

Of course, that's if my math is correct, which is no sure thing.

But if they really do exist and work, where are they? Who is making them? Or are they just pie in the sky?

Sue

You won't get 10 hours run time from 100 psi air found at gas stations.

3000psi air at scuba tank filling stations would be more like it.

A compressor capable of pushing that much air is loud as hell, not something I'd want running while I'm home eating/resting (when the car is being charged).

First off the source isn't the most reliable and unbiased news source, this is the same place I ended up at a few years ago looking for solar and wind generation options for my cabin. They didn't want to offer much advice since I wanted to use evil batteries instead of connecting to the grid to share my generated electricity with everyone else despite my explaining that I would have to cut a path through the trees a mile up the side of a mountain to run electric lines to connect to the grid to share that electricity and which is why I wanted to generate my own in the first place. This also the site who will publish an article on how the energy grid is run at higher than 100% capacity so we all need to conserve more and then turn around and tell how great it will be to charge our electric cars on the extra electricity at night (hint, if we are over 100% already where is the extra). I was labeled something called a repub and told I must watch some news about foxes (I rarely watch tv and even then its a show on netflix with my wife).
(Hope I didn't get too political there, wasn't the intent just showing that the articles there are not that unbiased or well researched).

Laws of thermodynamics come into play, the higher the pressure you compress the air the more power it takes to compress it. More heat is generated, the tank has to be stronger and therefore heaver. Or you could make the tank larger and then sit on top a big tank and of course the larger the tank the heavier it gets.
The power used goes up exponentially so once you scale up from a small tire filler that can run a few hours for 1$ to something that can compress enough air to run a car for a few hours it costs more to run.

Or think about it this way, I have a couple small hand held air tools like a grinder and air ratchet. Both the size of a small drill. My little compressor with a couple gallon tank can run one of those for maybe a minute before it needs to refill.
To make the calculations easy lets say 1 gallon of compressed air would give 1 minute of run time to this little 1/4 HP motor. Now scale up to car size, 50HP motor would need a 200 gallon tank to run 1 minute, 2000 gallons to run 10 minutes, 12000 gallon to run 1 hour unless you start to compress to higher pressure. So you go from 200psi to 400psi so you can regulate it down, now you need a compressor thats eve bigger and consumes more power.


I took steps that I think are even better long term. Instead of living within city limits and driving a hybrid car 5-10 miles each way to work and back I found a place outside the city where my commute to work is .5 miles so I walk when I can. Kids school is 1 miles away so if gas got expensive I could just walk or bike. Even on rainy days my 20mpg truck goes .5 miles compared to the 40mpg hybrid driving 10 miles (or more the average is more like 20). Instead of taking the suggestion of getting a minivan (25mpg) and renting trucks to haul things or having a weekday commuter and a second vehicle for weekend needs I just went with one that can do everything and live close enough to work to not need a vehicle. Sure I'd like to live in the country but until the kids are grown and out of school it works out better to stay close to the school and work and save that way instead of beta testing an unproven technology to let me drive long distances.

and then look at the flow rate a human breathes, it would run a tiny motor for a while but not a motor big enough to run a car.

I amost missed the part about 300km in 10 hours which is less than 19 MPH.

Energy is energy. Every time you move it, change it's form or even try to store it, you lose some. You can use grid electricity to charge batteries that will run an electric motor, or you can use grid electricity to run an electric motor to compress air that runs an air motor.

Hydrocarbons are just such a darn convenient way to store energy for mobile use that most everything else pales in comparison.

As Don Lancaster points out, there's more hydrogen in a gallon of gasoline than there is in a gallon of liquid hydrogen.

Well, I guess it sounded too good to be true. And that's probably why no one seems to be selling them.

Thanks for the information, guys!

Sue

It still sounded like a good idea, so I contacted a longtime friend's husband who is a physicist. He says the technology exists. But I'm certain they will have to revamp those gas station pumps that take five minutes to fill a car tire!

From Steven:

"I first heard of the air powered car about a year ago. I think that it was first developed in France. I'm not sure just how the power cycle on the engine works, but I know there are working vehicles using this technology and the power source is very high pressure air.

"The actual range between refuels will depend on the air tank size, air pressure, vehicle weight, accelerations, driving terrain and driving speeds, etc.

"From what I remember, the vehicle is very light weight and will probably have trouble getting approved here in the US, at least with regards to freeway driving and I doubt that it will have many luxuries (limited power and torque).

"If an owner invests in a commercial air compressor, you could drive one of the cars around town for virtually free. For non freeway driving and two passenger use, I think this technology will blow the socks off of the 'mini/small' electric car market and maybe even put a dent in the mid sized electric vehicles.

"So, to answer your question, yes this technology exists. Whether it becomes commercially viable remains to be seen, but I suspect that there is a market and we will be seeing air powered cars in the near future."

The physicist may not be sufficiently familiar with the problems of very high pressure air. (I've worked a bit with 4500psi air)

Transfer rate of very high pressure air from storage to an empty tank has to be slow because the sudden pressure buildup in the empty tank/lines causes heating. In the presence of combustible material (entrained oil from the compressor) this can cause "dieseling" in the piping which would destroy it. It's also really, really LOUD.

Commercial air compressors are generally not of really high pressure. A compressor capable of very high pressure requires a large motor and thus home air compression wouldn't be "free."

Storage of really high pressure air requires good tanks and piping. I'm sure that there would be certification and OSHA issues that go with.

It's unclear to me whether the energy storage capacity is adequate to serve real needs. Let's see them start out on golf carts and fork lifts before requiring me to buy one....

Newspaper articles often are methods of gaining funding for projects rather than actually informing of breakthroughs in technology.

I'm still waiting for the flywheel-powered buses and the flying cars that Popular Science wrote up when I was a young teen.....
The Moeller Air Car has been a recurring theme for 30 years. But I still don't have one in my garage.

You're pretty much looking at a steam engine powered with compressed air instead of steam pressure.



Accurate. Also, there's a pretty good writeup on it in Wikipedia.
http://en.wikipedia.org/wiki/Compressed-air_vehicle



Whole clothe, marketing hype, and natural fertilizer. Commercial air compressors only generate arounf 0.1 KSI (100 PSI). The car requires an air compressor that can handle up to 4.5 KSI. For that you need a high pressure air compressors, and they typically run $10,000-$20,000. Add to that the loss of efficiency during compression, and loss of heat from the tank, and you're far from "virtually free".



It's been proven in small scale (RC plane engines, etc.), but the physics of scale, and the accident hazards are going to make this a curiosity. But, not a mainstream solution.

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P.S. From my perspective the overriding problems are efficiency followed by infrastructure. The most promising technologies within the foreseeable future will be a combination of alternate fuels (including electricity), hybridization, and cascading power cycles using waste heat (e.g. radiator and exhaust losses).