site  contact  subhomenews

Air car for Australia

June 25, 2008 — BarryK
I've been following this for awhile, and last year when I read that the air car was going to be manufactured in Australia, I wondered if it was just another plan that goes nowhere. Here is a news item:

It seems to still be just talk though. Apparently they don't even have a site at Melbourne to build the factory, even though they are talking about manufacturing the them by 2010. There have been many announcements of imminent production around the world, going back to 2002.

Interesting, while searching for info on the French MDI air car, I stumbled across another air-engine project in Melbourne, the Di Pietro engine. This video showcases both:

The Di Pietro home site:

The video claims that the MDI air car can go right across Australia or the US on one tank, and apparently that is actually feasible. The reason is that by heating the air after it comes out of the storage tank they can get incredible efficiencies -- I came across a site that explained the thermodynamics of this.

Two comments though -- Firstly, the French engine is incredibly noisy. Secondly, even though they say the carbon-fibre tanks have a split-seam so they won't explode, I wouldn't want to be sitting on top of one when it does fail.

Some prototypes with the Di Pietro engine:


Air, alcohol, water - you name it.

Re: Oz innovation
Username: BarryK
"In some cases it's because bright minds have migrated here. The engineer behind the Di Pietro engine is not just a backyard mechanic -- he was one of the designers of the original Wankel rotary engine in Germany.

Username: prehistoric2
"Your reference to thermodynamics was frustrating. I found only one report I could get my teeth into, "Thermodynamic Analysis of Compressed Air Vehicle Propulsion." by Ulf Bossel. This confirmed my previous experience. If you have a better link, I'd love to see it. Basically, a reasonable paper design with 4-stage compression and expansion recovers around 40% of the energy put into it. This is the efficiency going into the drive train. Energy is not being created, so we must also factor in the efficiency of the power station and electrical distribution system which provided it. Adding this onto most existing systems results in a car without its own emissions, but with a substantial carbon footprint somewhere else. That analysis above assumes interstage cooling on compression and interstage heating on expansion. An important point here is that this heat energy is treated as essentially free, drawing on ambient temperature sinks/sources to remove heat in one case and supply it in the other. Adding heat in the process can result in startling efficiencies, if you don't count energy introduced at above ambient temperatures as a cost. This is one way of sneaking in a heat engine. One desirable feature of a vehicle running on stored energy is regenerative braking. The system described above could not do this. Conditions for efficient compression appear too restrictive. For me this comes back to three central problems with compressed gases: 1) energy storage density is low; 2) full-cycle efficiency is quite limited; 3) high pressures needed for reasonably high density require substantial containers and special safety measures.

Username: prehistoric2
"We are not talking about the pressures that fill tires. A typical 300 bar tank has pretty much the same pressures as a 5000 psi hydraulic system. This is nothing to play around with. The 50 MJ in a typical case study vehicle has the energy of about 10 kg. of TNT. Call it a small artillery shell. If this is released all at once the effects are similar. I have even seen shrapnel which passed through concrete block walls. I believe most of the energy savings in these vehicles comes from reducing total power requirements to move them, not from a new source of power. The same engineering could be applied to a variety of power plants.

Re: heat engine
Username: BarryK
"I don't know where I read the thermodynamic stuff. The French MDI people have an engine that they say can be made to burn just about anything, even wood chips. Anything that produces heat.

Username: prehistoric2
"Barry, I'll try other searches for the thermodynamics reference. I wish you could supply a few keywords which would move the page you saw up in rank. Right now, I'm getting a lot of chaff with very little wheat. For the purpose of eliminating flames, sparks and noxious exhaust from operating environments, compressed air energy storage works well. A good deal of urban traffic could be housebroken if it worked this way. I don't want to destroy enthusiasm for finding alternatives to current practices. I do want to distinguish between power generation and storage,and place efficiency figures where they belong. Too much alternative energy boosterism resembles a perpetual motion machine, with a carefully concealed source defeating thermodynamic analysis. Biofuels had a problem in my mind even before people recognised the inherent conflict with food production. Considered as a method of tapping solar energy, the overall process efficiency is something like 1%. Crude steam engines did better some time ago, and had no problem burning wood chips. Distillation of ethanol using fossil fuels for power was a makeshift which could only be justified in order to demonstrate part of the process. This was turned into a political football good for justifying agricultural subsidies. Many people were willing to collect subsidies without modifying the process, few were doing any development at all on processes which would obsolete the makeshift and make subsidies unnecessary. We have a lot of creative accountants and fewer creative engineers. Guess which have better retirement prospects.

What next
Username: ANOSage
""...carefully concealed source defeating thermodynamic analysis" - that's exactly what I said! I've advocated ethanol as the ultimate fuel for several decades. There are several caveats. It needs to be prepared by fully enzymatic conversion which substantially improves the overall efficiency when the end use is as a traction fuel. These reactions are batch rather than continuous. They are endothermic, meaning you need to wait around rather a long time for a decent recovery yield at room temperasture. The good news is that fractionation doesn't require much control as the byproducts also have good fuel value. Solar furnaces may be useful, here. If the -C-C- splitting inefficiency can be cracked (pun for the cognoscenti!) then direct fuel cell exploitation would be extremely successful. But beware, 2nd Law is not violated by these devices as incorrectly stated in many textbooks. In this overall context, it may be of interest to know that Don Wales, a relative of Sir Donald Campbell, having failed to improve the land speed record for an electric car a few years ago, is about to try for the record in a steam-driven vehicle. Don't know whether this will be at Pendine, Utah or the Outback.

Tags: general