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Cars that run on compressed air

This technology is showing great promise. The tiny, rotary, compressed engine has many, many applications.

MDI’s current vehicles which presently use aluminum could also be made from light-weight fibreglass. FRP (Fibreglass Reinforced Plastic) technology is very well developed and could reduce the manufacturing costs. via Infoshrew.

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  • outside temp should not affect operation….but I’d suspect the ‘milage’ would drop.

    The easy-button way to work around this, IMO, would be to use weak electric heaters in the air-tank wrappings, and temp
    sensors inside, to monitor and keep the in-tank temp relatively constant.

    -5.75,-4.05 “I am in earnest; I will not equivocate; I will not excuse; I will not retreat a single inch; and I will be heard.”
    William Lloyd Garrison
    US abolitionist & editor (1805 – 1879)

  • by fanciful promises being made about compressed air engine technology. The engines themselves are basically little steam engines compressed by electric power instead of heat, but with some important disadvantages by comparison.

    – Their conversion efficiency is horrible, much worse than internal combustion or steam engines. Much of the energy used to compress air is lost as heat upon compression, then as cooling upon decompression in the engine. Steam engines became practical, not to say efficient exactly, when condensing chambers came onto use to draw out some of the energy from the phase change of the steam. Compressed air offers no such phase change to exploit. The net result is a car that drives like a golf cart but consumes energy like a Hummer (but like a steam locomotive, it most likely derives its energy from coal).

    – Unlike a steam engine whose source pressure remains more or less constant, a compressed air tank has pressure that falls continuously as it is drained. That means the car will have diminishing power and performance throughout its operable range.

    – 300 bar pressure tanks are bombs. They may not hold nearly as much total energy as a tank of liquid fuel, but they can release all of it in the blink of an eye (quickly followed by flying chunks of minicar). The potential for these things to cause lethal explosions is way higher than, for instance, the failed car bombs just found in London. Incredible claims of safety are made for the fiber reinforced composite tanks that these tiny vehicles depend on to get useful range, but I think such claims rest on the public’s unfamiliarity with the materials in question. From my experience with bicycles, I know carbon fiber reinforced plastic as a material that’s much more likely to fail by shattering than aluminum or steel are. Besides, carbon fiber itself is already expensive and in short supply due to current demand from aircraft manufacturers. Put a few giant CFRP tanks in a few million cars and see how expensive it can get before production capacity catches up. (Hint: Boeing can outbid you.)

    Right now, compressed air cars are doing just what battery electric cars do, but using a whole lot more energy and costing a whole lot more money in the process. They have lots of room for improvement, but their theoretical maximum efficiency is still a lot less than that of internal combustion engines. They have the advantage over ICEs in being able to run on electricity (which is also fundamentally what hydrogen powered vehicles are able to do), but their terrible system efficiency means that we’d be using a lot more energy than we do now to accomplish the same job, if we switched over to air cars from smoggers.

    Don’t be taken in. These projects are not designed to change the way we get around; rather they are tools for parting credulous investors from their money.

  • Compressed Air Technology

    From what I understand the car uses ONLY air.

    When I grew up, I lived not far from a roundhouse. Enormous-size steam-engine trains came to the roundhouses to be repaired. Steam powered trains did use coal as fuel. Modern compressed air technology is a completely different system. Steam powered cars, trains and ships did use other fuels to produce the steam.

    Boats use fibreglass fuel tanks and they don’t explode. Fibreglass is often reinforced with carbon fibre (and from what I read, these tanks do incorporate it.) FRP can also incorporate kevlar which is what bulletproof vests are made from.

    Chalo, what I don’t understand is why you are so negative about a car that holds promise of relieving countries from using fossil fuels?

    Read FAQ about the cars.

    “Countless test have been carried out in the most extreme conditions (gun shoots, resistance to fire…) to guarantee passenger safety in every possible condition. The high pressure tanks have been developed using a similar technology to those used in natural gas vehicles and by firefighters. All are produced with carbon fiber over plastic.

    The tanks that MDI puts in its vehicles are similar to those already in use in natural gas busses in Germany and other countries.”


    Here’s another link that attempts to explain How it works

    Yet more links about Compressed Air Technology

    To the best of my knowledge, there is no shortage of resin. We order it and in two days, a barrel of it is delivered. Some of our boats are made from polyester resin, but most of our boats are made from epoxy resins (which Haydn is allergic to)–epoxy resins cause him to have to use a gasper to help his breathing, but he’s unaffected by polyester resins.

    BBQ’s use propane under pressure and very few of them explode. Cars do get into accidents and I don’t have the actual data of the crash tests that were conducted. Do you? But I do understand that ‘air’ is not a fuel…it’s what you do with the stored air that is important. Mentioned were electric motors in the car.

  • …are correct – compressing air heats it, the heat dissipates (energy is lost, so pressure is lost), so less energy is recovered when it comes out than when it went in. Thus, not very efficient.

    I think comparing to steam is unfair. You constantly generate steam. Compressed air acts as a battery. A low-tech, light and relatively cheap battery.

    The fact that the Aussie engine is very light and the “batteries” are light means you need less power per passenger mile, which is really how you should be measuring the efficiency of transportation (or weight mile, for commercial transport).

    You don’t have to use coal or fossil fuels to generate electriciy. We do, but that’s a different story.

  • …of break on doing geothermal. Bush’s Crawford ranch uses it. It takes a huge investment and quite a bit of land, but then heat and A/C are there for the price of running a smallish heat pump.

  • and I’m not prepared to live underground like a mole. Sure the frost level is 4′, but getting the heat into the rest of the house requires fans, pumps and other stuff that require electricity, the cost of which offsets the benefits of the warmer earth below the frost level. In most instances I’d have to live to be over 200 years of age to recoup my investment on getting the geothermal heat that is produced below ground.

  • I was talking about many hundreds of feet of pipe buried about 12′ down where it’s ~55F. Use a heat pump (basically the guts of a refrigerator) to ‘concentrate’ the heat, and dump the resulting chill into the pipes to be heated back to 55, letting the heat into the house. Reverse in summer to cool. Awesome stuff if you happen to have a huge yard of suitable soil & drainage and a large pile of money to invest. After that, maybe $10 / month for electricity and your house is 70F year round.

  • See below. This stuff is popular in Manitoba. Yeah, the up front is huge. Here in Maine we have relatively sunny winters (compared to the middle of the country) and wood galore, so when I build, it will be passive solar / wood stove.

  • that will disappear in the internet because the big corporations don’t like it.

    repressive governments mix administrative clumsiness & inefficiency with authoritarian tendencies.

  • high pressure tanks are. Aluminum scuba tanks holding 80 cubic feet of air at a pressure of 200 bar weigh about 35 pounds empty; about 6 pounds more when full of air. One of those can’t hold nearly as many joules of extractable energy as a lead acid battery of the same weight (to say nothing of nickel metal hydride, lithium ion, or other high performance batteries).

    Carbon fiber reinforced plastics can be made lighter for a given volume and pressure, but these air car folks are talking about 300 bar pressures. I bet the tanks weigh as much as the rest of the car combined, and represent the bulk of the vehicle’s cost as well.

    Note that cooling on decompression reduces the amount of work that the expanding air can do by missing all of the expansion that the cold air does as it warms up after expulsion from the engine. Those efficiency losses are just as significant as the losses to heating upon inflation.

    My comparison to steam engines is based on the similarities between these two engines which both run on non-combusting pressurized gas. Mechanically, they are necessarily going to be comparable. I think the efficiency challenges are also comparable– its hard to turn most of the heat of combustion into steam, and hard to turn most of the steam’s expansion and condensation into mechanical work. Surely steam engines are closer to their theoretical maximum efficiency than compressed air engines are, but my understanding is that the best we can expect from compressed air is less than that.

    Compressed air is not a new form of mechanical work, after all; these new developers are not going to get order-of-magnitude improvements over preexisting designs.

    It’s true that electricity can be made by more benign means than fossil fuels, but our sustainability problem is in the scale of consumption, not the means of production. If we continue to hog energy with wasteful lifestyles and industries and an intrinsically energy-wasteful capitalist economic structure, then new energy technologies will allow us to make other problems for ourselves that are just as severe and complicated as climate change and pollution are now.

  • has nothing to do with which big corporations do or don’t like it.

    It’s just horribly inefficient, and it won’t make any sense until we can make electricity for a tiny fraction of what it costs to make it by burning fossil fuels. Until that point, we’ll burn a lot less fossil fuel by putting it directly in the car. Dig?

  • prices increase in developed countries. Changes to life style take time…extinct will be huge houses, cars that get poor mileage, and/or anything else that squander what resources there are.

    Scientists ‘may’ find an answer to the dilemma, but in the meantime, mankind will be forced to adapt to being kinder to the planet. Air travel will become so expensive that only the rich will be able to afford to fly. The mighty buck may well prove to be the determing factor in how well the world uses what is available.

  • if the supply of fossil fuels runs short before we suffer an irretrievable ecological collapse. Enforced conservation through scarcity may be the best thing that could happen to us in the long run.

    We certainly haven’t taken the initiative in moderating our energy consumption just because it’s the right thing to do. Imagine the disaster if the folks who thought petroleum would last forever had been right!

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