Does the air-powered car really work?

Zero Pollution Motors is drumming up press again, with claims that an improved version of its “air-powered car” can travel 848 miles on a single tank of compressed air.

The comments in response to the New York Times article run to the skeptical side (“I bet it can fly too“), which seems a little bit ironic, because — unlike the water-powered car — the air-powered car is a perfectly respectable piece of technology. As air is released from a compression tank, it drives an engine that moves the lightweight foam-and-fiberglass vehicle. A similar idea is being contemplated on a much grander scale to generate steady electricity from intermittent wind or solar energy.

The question is not whether the air-powered car works, but whether it works well enough. As an energy storage mechanism, compressed air has certain built-in advantages over lithium ion batteries. An air tank is far cheaper than a battery, quicker to charge, and easy to maintain.

On the flip side, the air-powered car suffers from the same problems that have doomed so many other attempts to move beyond the internal combustion engine: limited range and a lack of refueling infrastructure. Zero Pollution Motors claims to have addressed the range issue with the addition of a small fuel-powered heater, which boosts the efficiency of the air engine. Although the heater gives the lie to the “zero pollution” claim, such a system still represents a considerable efficiency improvement over conventional gasoline-driven cars.

Nevertheless, skepticism is warranted. The company has been claiming that production versions of the air-powered car are just around the corner since 2000. This time, the claims might be better grounded in reality, but other companies haven’t been sitting still. In 2010, Zero Pollution Motors may be battling GM and others for dominance in the clean car market.

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  1. nunugenius - September 17, 2008

    may be on the future the air powered car really work better

  2. Keely Killpack, PhD - September 17, 2008

    This car is such a great concept, I absolutely cannot wait to buy one of these! Zero Pollution’s business (manufacturing/supply chain/distribution) model is the best example toward sustainability in any commercial industry.
    Their innovation should be rewarded, supported and motivating to the competition.
    For the skeptics about refueling infrastructure, consider the millions of households with a garage that could recharge your car(s) while you are sleeping. For those without garages, let’s build refueling garages (or retrofit existing ones) and hire valet’s to park and recharge them overnight.
    Need more details? Watch this video: http://www.youtube.com/watch?v=jgwfpIOOb-c&feature=related

  3. autonomousvehicles - September 17, 2008

    They are using many of the same tricks used in other high mileage designs: low rolling resistance tires, light weight, low drag coefficient, etc.
    The problem is that the efficiency (energy in to energy consumed) of compressing air and then running compressed air motors is far lower than an all-electric system. I would like to see a calculation of the total system energy efficiency of this concept before claiming success, including the energy used to compress the air.
    Put an all-electric drive in their car and the overall efficiency will, I’m sure, be higher.

  4. mynalee johnstone - September 17, 2008

    Whatever is an alternative to whats been out there for far too long needs to happen NOW!!

  5. David - September 17, 2008

    I get skeptical when a company makes misleading claims like “zero emissions” and “runs on air” as if you were really getting something for free.
    Just like an electric car needs electricity to charge, an air powered car needs energy to compress its air. The same amount of energy is needed to move any mass through our atmosphere. Then there are physical limits to the efficiency you can achieve. The less energy wasted by heat, drag, extra mass, the better the vehicle. Also, the cheaper the energy source, the better.
    Compressed air tanks are heavy, but still lighter than an array of batteries for energy storage. However, they are much less energy dense, leaving you with shorter range. The air motor is heavy, though, and almost negates the weight savings. Electric motors are relatively much lighter. There are also safety issues with driving around with 4400psi (300 times atmospheric pressure). In order to make this vehicle feasible, it has to be dangerously lightweight, which may not meet the safety demands of any consumer or regulatory body.
    I don’t think compressed air storage is the most viable option at this point.

  6. Chas - September 17, 2008

    There will always be naysayers about any new technology–whether it is “new” or not. Compressed air technology has been around a long time. The article does not mention its greatest asset, which is the ability to very quickly re-capture a large percentage (80-90 percent) of braking power by re-compressing the air back into its tanks. This capability is far superior to existing “hybrid” battery cars where only 20-30 percent of the braking energy can be recaptured by the battery due to the limitation in the rate at which electricity can be put back into the electrical battery. Compressed air has no such limitation. Previous air-powered engines used pulsations of air to improve efficienices. I would guess that the fuel needed to heat the air in this engine design is only needed in the morning before the engine warms up, after which time the friction of the engine can take care of air pre-heating.
    But here’s my main question for all of you H2 Water heads out there….
    How much kinetic energy (in the form of a highly compressed gas) is in a 10kg container of hydrogen as would be used in a fuel cell vehicle as compared to the chemical energy of that same 10kg container of H2 at the same pressure?
    My intuition tells me that there is more kinetic energy than chemical energy and the performance of the vehicle discussed in this article seems to confirm this suspicion.

  7. steve - September 17, 2008

    Hum….
    got a car small and light enough to go 800 miles on compressed air? how about putting a little engine in it and get the 100mpg 20 million xprize! Whould make a great bridge to future zero pollution cars.

  8. Craig Hunter - September 17, 2008

    Certainly these articles regarding alternate powered vehicles are interesting, yet are far from the solution and the reality humanity is faced with today. The air powered vehicle has been around for over a century and has been used in airports and aircraft carriers where the chance of a stray spark from electric powered vehicles or internal combustion engines was too dangerous. As with many obscure power sources, it is a technology that is merely gasping at straws regarding our current requirements.
    Once again, these pie in the sky ideas fail to include the simple math required to move an object from point “A” to point “B” at a predetermined speed for a predetermined distance with the greatest conservation of energy. High school math tells us that the air powered vehicle is simply unobtainable. The time spent on this technology would be better spent on developing a functional anti-gravity vehicle.
    We actually have a solution today that that solves two problems; clean air and oil dependency. CNG will give us the breathing room we will need to take us to the electric car reality. The technology is simple, requires no additional energy to use the product and is 75% cleaner than gasoline. The infrastructure is already in place for most major cities around the world and the technology is readily available to automotive manufactures and can be adapted to ANY vehicle or engine. Can everybody say $1.00 per gallon?
    Hybrids have been useful in proving that electric vehicles are to be the answer in the future and there will be hybrids in the near future capable of 200 MPG incorporating better battery technology, plug-in capability and a CNG powered internal combustion engines. CNG will not be the end game, however neither will hybrids and certainly not air powered vehicles.
    If there are doubters regarding CNG, think of this; For the past 4 years I have filled my own CNG vehicles right at my home for approximately .70 cents per gallon. My personal vehicle is a 4×4 3/4 ton pickup with a factory installed CNG system that runs cleaner that any hybrid built and recently did a 750 mile road trip for $83.00 with no problem finding fuel along the route (half the cost of gasoline). I would gladly pass on information regarding CNG vehicles and home fueling for those interested. (sea_hunteratyahoo.com)
    Sometimes we search for an instant high tech solution to our problems, overlooking the simplest solutions. CNG, while not the end result and will not even get us to the Star Trek “transporter” age, it will give us time to develop a truly economical and functional electric vehicle and making the world a little cleaner at the same time.

  9. autonomousvehicles - September 17, 2008

    Chas, what is your source that claims 80-90% energy reclaimed from regenerative braking? That seems exceedingly optimistic.
    Compressed air in an air powered car, electrically charged batteries in a battery powered car, and hydrogen (extracted from water) in a hydrogen fuel cell powered car are all different ways to move and store the energy used to move a car. They all loose energy to heat while it is being moved and stored. Compressing air into a storage tank (moving and storing the air) is the least efficient of those methods.
    Charging a lithium ion nano-phosphate battery (moving and storing electricity) is the most efficient. Batteries also have the distinct advantage that they can be charged directly from solar cells on your house.
    The other great advantage of electric power is that electric motors are the most efficient way to convert the stored energy into rotating energy.
    I am not a naysayer, I am an engineer after the truth. The truth is this:
    the whole system efficiency must be considered when calculating the efficiency of a car;
    that compressed air, electric batteries, and hydrogen fuel cells are simply different ways to store energy;
    and that electric batteries (as poor as they are) powering electric motors are the most overall efficient method to move cars.

  10. autonomousvehicles - September 17, 2008

    Craig,
    I couldn’t agree more. Sorry I forgot about CNG as an excellent source of energy to act as a bridge to electric cars.

  11. autoidea - September 17, 2008

    Dear autonomousvehicles,
    I agree with your enthusiasm. As for your criticism, you are right BUT you can have a windmill feeding the compressor. Talk about buffering the uneven power delivery of a wind turbine ! I hope you’re happy now with the concept.

  12. autoidea - September 17, 2008

    Craig, CNGs are OK, but compressed air gives you $1.00/gallon today.
    Plus you have to compress CNG anyway AND you have combustion pollution on top of that to use up your breathing air.
    BTW – the air motor is MUCH lighter than an internal combustion engine – no water pump, no starter, no catalytic converter, no exhaust system (OK, a small one), no air pump (hahaha), no intake system, no ignition electronics, no engine computer, etc., etc.

  13. Anonymous - September 17, 2008

    autoidea,
    Wind and Solar are clearly the best long term sources of electricity. Right now, wind is a little more tricky and finicky for the home owner to deal with than solar, which is why I mentioned solar in my earlier post. You could I guess compress air directly with a wind turbine, but again the source is quite erratic for most people.
    As for your thoughts on CNG and compressed air, any benefits from lighter the weight and simpler design of an air motor are outweighed by the much greater total system efficiency of an internal combustion CNG motor.

  14. autoidea - September 17, 2008

    Dear Anonymous,
    WHY do you think the CNG motor is more efficient ??? It’s just about the same

  15. Craig Hunter - September 17, 2008

    Oh come on, there’s definitely something in the air, do you realize how much energy is required to compress air to a 1 gallon of liquid, the only viable way for an air engine to be anywhere near efficient. You’re not going to be able to run this thing with your Craftsman compressor. Remember, energy in is always more than energy out; what a colossal waste of resources. Why does everybody come up with the magic bullet but fails to realize the source of the energy has to come from somewhere, hence the unobtainable perpetual machine. Just do the math, 1 HP = .746 kW, so when this air powered vehicle can go more than ten blocks at freeway speed with 4 people in it without “refueling” let me know, I’ll trade in my GEM.

  16. Craig Hunter - September 17, 2008

    Autoidea, CNG engines are exactly like gasoline engines, they are not more or less efficient than any other IC engine. The question is, how efficient from start to finish is a fuel. Gasoline and Diesel store a lot of energy per unit, but require refining, reformatting, special handling and transport. Electricity requires a power source (coal being the number 1 right now and in the foreseeable future) and for a vehicle requires storage (and the pollution required to build these batteries). Hydrogen produces less energy than is used to produce it (and more pollution), and is no more cleaner than CNG in the long run. CNG on the other hand comes directly out of the ground, is filtered and sent down the pipeline for consumer use. For those skeptical on the cleanliness, try BBQing with diesel or gasoline. Lastly, I can’t even buy an air powered vehicle, but I can buy a CNG vehicle, so your argument exceeds the boundaries of reason. This kind of rationalization is why we’re in the predicament we’re in today.

  17. autoidea - September 17, 2008

    Craig, we are talking compressed (not liquid) air, more like 4000 psi ! No, it can’t compete with a sailboat or a solar PV electric vehicle, only with gasoline, diesel, CNG. It will go 50-60 miles easy (at 65 mph), refuels (haha) in about 3-5 minutes at any station with a large-ish diving tank-type compressor. Yes, you can buy one, but you wouldn’t because you don’t believe me. Your loss.
    And you’re making a lot of logic mistakes along the way, talking about perpetuum mobiles, etc. – apples to oranges, my friend.
    Trust me, I’m an experienced automotive engineer, and although a 100% electric is even better, the battery problem kills it. Here you carry several cylindrical carbon-fibre tanks, which do not explode BTW. They are hardly heavier than a tank of gasoline.
    Take care and check your sources.

  18. Ben - September 18, 2008

    Air compressors are loud, and they will probably be run in neighborhoods… at night.
    Things are going to get noisy

  19. Craig Hunter - September 18, 2008

    For those who want to know the truth about the air powered vehicle.
    From the designers own page;
    http://www.aircarcatvolution.com/air-car-performance/index-eng.php
    the original article from Pop Mechanics;
    http://www.popularmechanics.com/automotive/new_cars/4217016.html?series=19
    and on the braking;
    http://www.aircarcatvolution.com/air-car-technology/braking-eng.php
    13% is a long way from 90 or even 80%

  20. autoidea - September 18, 2008

    Ben, air stations are not going to be in your backyard ! And if you do not re-air at night, there is no reason for them to run at night, either.
    I hope you don’t live at a gas station now ?
    m

  21. Tim - September 20, 2008

    Atleast someone is thinking along paths away from petroleum.

  22. autoidea - September 21, 2008

    Yes, we are making biofuels (ethanol, diesel).

  23. vortiz - September 26, 2008

    Thought went through my mind to legislate that all cars in city limits must be this vehicle. Otherwise, those big steel monsters gonna be crushing those styrofoam wonders.
    Also, do you seriously think GM will grow a brain and have a competitive car to this that soon? More scary is what those bigs corps might do to ZPM like they did to Tucker.
    I am game for a car like this if it can be made road-survivable.

  24. Tiffany - November 29, 2008

    This car is even better than an electric car and why is this, because this car is a none polluter and does not waste energy and can keep on being used and used with no problems at all.WE do not have to worry about pricey gas,this car i would suggest is very well being used and we should have these cars on our streets than our traditional ones or even electric cars!!!

  25. Douglas Hvistendahl - January 12, 2009

    One problem in this discussion is not noting the difference between the usual isentropic air compression and expansion, and isothermal. Isentropic wastes energy on compression by heating the air, and on expansion by cooling it. Nobody has been able to make pure isothermal (best I’ve read about is 95%, and that isn’t portable), but if they could, efficiency would be as high as battery. MDI has maybe 80% isothermal equivalent. The key is the lower price. I’m cheering them on! and hoping they make the business side work out.

  26. Homer Ferguson - February 1, 2009

    I am intrigued by the idea of a compressed air car, but can see potential pitfalls when it comes to efficiency vs. weight. I used to have a Mazda 323 and even it was light enough to get a little shaky going 75 MPH on the highway on an especially windy day. Perhaps other technologies can be integrated to allow for more weight for control, crash test performance, etc.
    For example, if air is being moved within the engine, air-lines, exhaust system, as well as an air intake design, the basics of wind power are present to turn mini-turbines for power production to be used in recharging the battery, heating the air, etc.
    Furthermore, if only air is emitted, why not look into the recirculation of these emissions back into the tanks for reuse? Also, an air intake system can bring in more air for use. In a sense, one could be refueling and recharging while one drives.
    I make no claims of being an expert, although even they seem to seldom agree with each other