The air car

In 2003 I found a representative of the MDI company trying to set up a production factory in the SF Bay Area. At the time MDI had a business plan where they would do a design and then license factories in countries around the world for local construction of the design. I was talking with these people in California, as a potential investor, who were gearing up get a license and start production. I haven't heard anything from them for awhile and had thought MDI had fizzled. It's good to see that they're still alive.

It's very interesting technology. In 2003 MDI wasn't claiming range anywhere near what this video claims... They were claiming approx 100 miles per "charge" (IIRC) and they discussed with me an idea to use a small heater to heat the air going into the air engine, so that they would be able to get a bigger range per charge. That may be what the guy in the video described but the explanation was mangled and unclear.

It obviously outsources the emissions to an electrical power plant of some kind. The air is not a fuel, it is an energy storage medium. The energy comes from somewhere, the most likely being the electricity required to run an air compressor.

That other guy - I've never heard of him. However why hasn't that fruit market invested in electric forklifts? That's such a "duh" thing, electric forklifts are a very well understood technology.

Anyway, isn't a rotary engine what Mazda is famous for? It looks cool.

http://www.theaircar.com/acf/

http://www.cyber-media.com/aircar/

http://en.wikipedia.org/wiki/Air_car

http://www.wired.com/cars/energy/news/2003/09/60427 - NOTE: This is a 2003 article.

http://peswiki.com/index.php/Directory:MDI_Air_Car

http://www.gizmohighway.com/autos/aircar.htm

http://www.treehugger.com/files/2004/10/mdi_air_car.php

...autobloggreen.com/2008/01/11/tata-motors-mdis-air-car-requires-nearly-two-years-of-work/

=gusharI have an old, very small weedeater that I no longer use. Wonder if I could take the motor off...remove the carb, muffler, etc....and try putting air pressure via my electric air compressor/w tank into it and actually turn the motor???

It might work for a while. Your weedeater is likely a {gag}, {cough}, {spit} 2-stroke engine that requires oil in the fuel for lubrication {ralph}. If you did get it running I would expect the piston to heat up very quickly and destroy the engine. This, in my opinion, would be a net win for the planet.

--
Do I have a problem with 2-stroke engines? Why do you ask? :-)

I think there's definitely something to the first company, MDI. Tada invested 27 million according to your 2nd link.

What's really neat about the technology is the energy versatility. You could use just about any energy source to compress air. The fact that it contains an on board compressor powered by electricity makes it even more useful.

Unfortunately, their specs may be grossly exaggerated much like the electric vehicle manufacturers do. This is from the wired article (even though there may be more substantial published testing now):

In fact, in the only published road test to date, one of the cars traveled a little over seven kilometers (4.5 miles) on a full tank of air. With the proper materials and a few refinements, MDI insists it will go much farther.

It looks like the technology is more innovative than past attempts. Here's from Technology Review's Jan 16, 2008 article

To propel the vehicle, compressed air from the tanks is injected into a small chamber, where it expands and cools. This expansion drives a downstroke of the piston. But as the ambient temperature begins to reheat the air in the first chamber, that air is forced into a second neighboring chamber, where it expands again to drive an upstroke. Using ambient heat helps capture more of the energy in the compressed air, ultimately improving the efficiency and expanding the range of MDI's Air Car. And compared with four-stroke combustion engines, in which half of the strokes are wasted to pull air and fuel into the chamber, the air engine makes use of every stroke.

Ulf Bossel, a mechanical engineer consulting in Switzerland and organizer of the European Fuel Cell Forum, is cautiously optimistic. "I think there's something to it," says Bossel, one of the few who has performed a comprehensive analysis of MDI's approach. Even though one of MDI's compressed-air tanks would carry the energy equivalent of just one gallon of gasoline, the use of that air in the engine is 90 percent efficient.

The energy balance would improve substantially, he argues, if the compressed-air systems located at filling stations or in car owners' garages were designed so that any waste heat during compression could be captured and used to produce domestic hot water, for example. If the compressors could interact with the grid and be programmed to only compress and store air during off-peak hours, or when solar and wind energy are in greater supply, the emissions profile of the Air Car would also improve.

However, due to the chassis construction method, and the potential danger of 4,500 psi in air tanks, I'm not so sure about safety.
From the Tech Review article:

The ultralight bodies of the vehicles would be made of glued-together fiberglass and injected foam, and the aluminum chassis would also be glued, not welded, to simplify manufacturing.

Due to the low cost, I think it has potential in the US. The "dual mode" version that can run on gasoline could make it a better and cheaper plug-in hybrid technology with the big advantage that it can be run cheaply on just air pressure generated from electricity with a decent range and speed profile (if specs hold up). Compare this to existing plug-in hybrids that are expensive and most likely need the engine most of the time to offer decent range and speed (hence not much of a practical possibility of kicking gas completely while in town).

If the cheapest model just uses air than it could be a viable 2nd vehicle option for many due to the low cost.

Another video here:
http://rawstory.com/news/2007/Air_car_runs_on_compressed_air_0104.html

BTW: MDI's website really really sucks. I'm almost unsure of their credibility due to publishing such a crappy website with no useful information whatsoever. Also of note, is the video in the topic post is a bit dated.

I would like to see MDI partner with an existing golf cart/NEV company in the US in order to gain some exposure and credibility on a less expensive scale. I don't think the air engine is the magic silver bullett, but I'm certain there are several useful applications.

A member on another forum made the interesting suggestion that a compressed gas such as methane or Hydrogen could turn the main motor of a small MDI vehicle, then the spent gasses would be saved in a low-pressure surge tank. They would be burned as produced in a small ICE generator which would capture some of the energy to charge a small battery pack, and also provide series-hybrid help via the electric axle. (I know...Google "Hindenburg"..)

The main front axle is air-engine for 15 MPH and higher, rear axle is compact electric drive for accelerating from a stop, and also drawing what series-hybrid power is available (50cc Honda, David?).

The air-engine is designed from the bottom up to be exactly that, as efficiently as possible. Even so it's performance isn't blowing anyone away. The body has so much glued plastic to make it as light and cheap as possible, it will never pass US crash regs.

A heavier US freeway compliant body would make the air-engines chances even worse, but a 40-MPH NEV or golf cart wouldn't concern me.

I think throwing hydrogen into the mix would just be an unnecessary complicating factor. It's true that you could store a lot more energy, but than you'd need to generate hydrogen, and that requires much more of a capital investment than just a large tank and a compressor. In addition, any ICE or internal combustion engine is going to generate a lot of heat in the combustion process, and that equals inefficiency and waste. Not exactly the goal.

In fact it's very interesting that they are NOT using hydrogen. Isn't it ironic when we have been playing around with hydrogen fuel cells for so long that just plain compressed air offers a better solution that just happens to be economical and practical? Which begs the question: why bother with hydrogen at all? Then comes the "ah" experience. Hydrogen + carbon = hydrocarbon = big oil industry = $$$ = US government influence.

Actually, I think being able to use hydrogen in the engine is a great idea.

The thing is: air needs heat to expand. The problem with air engines is the opposite of gas engines; they get too COLD to work efficiently. If you were using hydrogen instead of just air, you could burn the hydrogen after it expanded to heat up the engine, which will make it run much farther for a given volume of gas. Of course, since it IS an air engine, pretty much anything under pressure will work, so you wouldn't have to use H2 all the time.

On an interesting side note: if I remember correctly, basically ALL the power that you get from expanding air is from the ambient thermal energy in it. In other words, all of the work the compressor does is dissapated as heat. I recall something along the lines of a self-filling air tank, which made use of a heat pumping process to keep itself pressurized and full. I took a good look at it, and I don't see why it wouldn't work. I don't know what sort of power you could get out if it, but it looked very interesting. It would be very useful, to say the least.

I'll have to experiment with it when I get some equipment }:).

Is the "air engine" at all similar to the "hydraulic engine"? There's a company in Ann Arbor that's been working on a hydraulic engine...

The "base model" air car could just use air instead of H2. It would be very easy to add a tiny series-hybrid engine as a range extender for those who desire it, and are willing to pay for the addition. Might get a couple people out of land yachts.

You make some good points, but the other forum poster was only suggesting that if you filled the tank with H2 instead of air, it would provide a "no-carbon" ICE range extender without a separate fuel tank.

As a side note, parts of the air cycle resemble an air conditioning cycle. Air is compressed into a tank, and as its ambient heat energy is concentrated, its apparent heat goes up. As the tank then sits and cools after several hours, its compressed temperature reaches near ambient. Then, as it is passed out the engine, the pressure release dramatically cools it. The air engine will run very cold.

Two things interest me in the air engine (if you don't mind short range, I don't)

you can have a quick refill by having a large air tank in your garage at a slightly higher pressure than the car tank. By attaching a quick disconnect fitting, then opening a ball valve, the large tank will equalize with the small vehicle tank, but at the vehicles rated pressure. The large home tank can re-fill slowly, perhaps in the middle of the night if you so desire (for off-peak rates).

The second possibility I see is in wind-generated air pressure. Some farmers have been using air-tools and air-pumps that are run by air-tanks (expired propane tanks at salvage prices) filled by wind-pumps.

I'm not saying that anyone can depend on wind-pumps to generate enough air pressure and volume all the time, but if half your air is provided by wind, only half needs to be generated by other means. Still better than a gasoline car for short trips (or a bicycle in the rain).