Compressed air at 300bar/4350psi has roughly the same energy storage density as regular old lead acid car batteries, and about 1/3 that of NiMH or lithium ion batteries. So for an equivalent sized car, the compressed air car will have only 1/3 of the operating range of a modern electric vehicle.

MDI’s claimed specification for the air car are fantastic. In both meanings of the word. Wonderful, exciting specifications. Also hard to believe.

They would be more believable if MDI hadn’t claimed the same sort of specifications back in 2000, with production cars supposed to have been available in France in 2000, in South Africa in 2002 and Mexico in 2002/2003. See the two BBC articles from 2000: http://news.bbc.co.uk/2/hi/africa/988265.stm and http://news.bbc.co.uk/2/hi/americas/992431.stm
I don’t know if the Zero Pollution Motors that intended to have productiona air cars in salesrooms in 2002 is the same as the Zero Pollution Motors in the USA, but the parent company, MDI is the same in both cases.

If you look at the MDI website looking for results of tests on their prototype cars, you will find only one page. No longer on the website, but available from the archives at the wayback machine. The actual tested range was only 7.22km (a bit less than 5 miles) before running out of air.
http://web.archive.org/web/20071011200005/http://www.theaircar.com/tests.html

I look forward to seeing if they can ever meet the claimed performance.

I agree with you that the intuitive assumption that an air car is better is not necessarily true.

I wish sometimes that I specialized in one engineering or scientific topic, but alas, I do not. The topic “Environment” involves almost every aspect of human life and consumption, and try as I might, I admit that some of my post’s may lend towards more curiosity of a subject, than an answer of it.

This being said, the purpose of this site is to inspire that curiosity and discussion about it. To answer questions when I can and offer other alternative knowledge sources when I cant.

I’m going to look into your two questions “Which total process is more efficient? And which is cleaner?” and will report back to you with some further data.

Thanks for the comment and questions,

Adam

One of my questions was about energy efficiency. Because the energy must go through two processes, 1. Pressurizing the tanks and 2. Running the car’s motor – it is twice robbed by the incidental inefficiencies of each process. The energy for pressurizing the tanks must come from somewhere. If you live next to a hydroelectric plant and your power is drawn from that, than perhaps the relative inefficiency of twice used energy (assumed by me) is incidental. If your electric energy is obtained from a nuclear or coal plant then perhaps one does less environmental pollution with an energy efficient gas automobile.

Of course, gas doesn’t come out the ground as gas, there is a refining process to make gas and energy is lost in that process as well. I guess what I’m asking is: Which total process is more efficient? And which is cleaner? I don’t know that electricity must be cleaner – although if obtained from wind or water it likely would be. And I suspect that gas is more efficient. These are questions that it would take some patient study to answer clearly, but my point is that the intuitive assumption that an air car is better is not necessarily true.

Thanks for the comment. Here is some more on how the “Air Car” functions.

“What a compressed-air car does is use the force of super-compressed air to move the engine’s pistons up and down, as opposed to explosions produced from injecting a small amount of fuel.

To get things moving on compressed air, weight reduction is a top priority. MDI’s aluminum-based engine weighs half what a normal engine does, and the frame is also built out of lightweight materials (US version will be aluminum?).

ZPM’s US model will store about 3200 cubic feet of compressed air in carbon fiber tanks at 4500 psi. Carbon fiber tanks are used for safety reasons since they tend to split open (as opposed to explode) when punctured.

Compressed air from the tanks will run directly to the engine under speeds of 35 miles per hour. That means that under 35 mph the car qualifies as a zero emissions vehicle. At higher speeds the engine will burn a small amount of fuel to create more compressed air, sort of like how a plug-in hybrid like the Chevy Volt produces on-the-fly electricity. The hybrid air-car setup should be able use any number of fuels, including gasoline, propane, or ethanol.

1 tank of air + 8 gallons of gas = 848 mile range

The car’s compressed air tank can be refilled in about 3 minutes from a service station. To fill it up at home the car would be plugged in, where an onboard compressor would refill the tank in about 4 hours, at an electrical cost of about $2.

If you aren’t sure whether turning electricity into compressed air is really that clean, here are some numbers: at speeds over 35 mph the air car emits about half the CO2 per mile as a 2007 Toyota Prius (0.141lbs of CO2 per mile, while that the Toyota Prius emits 0.34 lbs of CO2 per mile).”

For the full article, you can go to http://gas2.org/2008/07/15/an-air-car-you-could-see-in-2009-zpms-106-mpg-compressed-air-hybrid/

I agree with you. If someone makes a car that runs on something other than something that is taxed, then that “something” shouldn’t be taxed. I like seeing people that take their decision making ideas, and voting dollars to create things that work for them.

Thanks for your comment. Good hearing from you.

Adam

I’m betting the air car it doesn’t give the equivalent energy efficiency of a good gas engine. Even so, if the energy used to generate the electricity is cleaner and local, perhaps the air car is worthwhile.

Funny thing, here where I live there are a couple guys who run their diesel pick-ups on used cooking oil that is discarded by restaurants. Oddly, the used oil burns better in diesel engines than fresh cooking oil. Guys who burn this used oil have to change their fuel filters more often but that is a small price to pay for nigh free transportation. There are politicos hereabouts who are trying to make it illegal to burn untaxed and discarded cooking oil in vehicles. The argument is that persons burning such fuel aren’t paying road taxes when they fill their tanks. If the suits get their way it will mean taxes and fewer cooking oil powered pick-up trucks. That’s a shame because it a lot nicer to drive behind a truck spewing exhaust that smells like French fries (seriously) than the diesel stinkers we are all used to.