Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Air Car (India)

  1. May 31, 2007 #1

    baywax

    User Avatar
    Gold Member

    :cool:Here's a new form of locomotion using compressed air to turn the engine's pistons. A fill up costs about 2 dollars (2 days wages in India)

    http://green.yahoo.com/index.php?q=node/315
     
  2. jcsd
  3. May 31, 2007 #2

    AlephZero

    User Avatar
    Science Advisor
    Homework Helper

    Hmm... so how big is the air tank? An very efficient IC engine in a small vehicle might use about 1gal of gasoline for that range and performance.

    The volumetric energy density for compressed air is going to be a lot smaller than gasoline, even though the engine might be more efficient at low speed, similar to a positive displacement steam engine - no need for a gearbox, etc.
     
  4. May 31, 2007 #3

    baywax

    User Avatar
    Gold Member

    Pretty wild. I don't have any of these specifications. There may be a website. I thought that perhaps in the future there will evolve a better compression mechanism and that they may also be able to compress on the go and store it in a second tank. This may, however, add more weight. Are there composites that are pretty light that would still hold compressed air?

    http://www.theaircar.com/howitworks.html

    There's a ton of information on this site... this is just a quick quote from "how it works". Of course it is the manufacturer's website!

    edit. Here's and interesting compression industry leader's website with some of the current and expected advances available in air compression explained.

    http://www.plantservices.com/articles/2005/257.html
     
    Last edited: May 31, 2007
  5. May 31, 2007 #4

    NateTG

    User Avatar
    Science Advisor
    Homework Helper

    Compressed gas is a relatively inefficient way to store energy. As a consequence, for net efficiency improvement, the compression plant would have to have some pretty spectacular properties.

    At least in theory, compressed air engines do have the advantages that they can be very inexpensive, and are likely to be much better than 2-stroke engines vis-a-vis polution.

    In practical terms, I'd expect that compressed air cars are going to be an improvement over electrical cars in terms of practicality since they're more conducive to fast refilling, and (hopefully) cheaper, but, at the same time, they're going to be less efficient.
     
  6. May 31, 2007 #5
    From the Yahoo article:
    What would be the point of having a gasoline engine to compress the air which will then run the car? If you are going to be burning gasoline anyways, why not just run the motor on it? The more changes the energy has to go through the less efficiency you are getting, right?
     
    Last edited by a moderator: May 31, 2007
  7. May 31, 2007 #6

    russ_watters

    User Avatar

    Staff: Mentor

    The primary benefit would be to run the gas engine at it's optimal efficiency all the time. But as NateTG said, air is a bad way to store energy, so I don't see that as being a better idea than a gas/electric hybrid.
     
  8. May 31, 2007 #7

    brewnog

    User Avatar
    Science Advisor
    Gold Member

    A gasoline engine could be employed for medium/high speed driving, where it's operating around it's peak efficiency. Round town, and in traffic jams, the compressed air drive could take over, much in the same was as an electric hybrid, thus reducing city pollution.

    Don't really see any huge advantage though.
     
  9. May 31, 2007 #8

    baywax

    User Avatar
    Gold Member

    No need for big batteries may be an advantage over the alternative. Not a complicated engine compared to today's hybrid and fuel cell technologies. But it won't do 120 miles an hour. Not sure what the torque is. Thanks for the input here.
     
  10. Jun 1, 2007 #9
    What are the various alternatives for storing energy efficiently, considering the weight, size and durability of the device? Batteries, for example, are heavy and don't last very long compared to an air tank that lasts until it rusts through. What about mechanical coil springs you find in toy cars? They probably don't scale up to a good weight to energy ratio... What else is there?
     
  11. Jun 1, 2007 #10
    I know flywheels http://en.wikipedia.org/wiki/Flywheel_energy_storage are known for storing energy very good.

    But they might be expensive, or they might be impractical for some other reason.
     
  12. Jun 1, 2007 #11

    baywax

    User Avatar
    Gold Member

    The old 1973 SAAB station wagon had a fly wheel in it. If they don't anymore its because they weren't efficient economically or otherwise. Building and trashing big batteries is environmentally inefficient. Finding and the refining of oil has proven to be environmentally inefficent along with the many inefficent ways it is used in inefficent motors, which maintain its production value. Hydrogen fuel cell engines have yet to prove their worth and I suppose an engine run by compressed air has some proving to do too. Electric cars were crucified but may be resurrected but I have no clue as to how efficient they are. There may be some of the same environmental problems with energy storage as hybrids.
     
  13. Jun 3, 2007 #12
    An extremely interesting idea which I suppose wasn't feasible until the development of the more efficient compressed-air engine. We'll see if this picks up and I do have to say, its a great way to get pollution out of the cities.
     
  14. Jun 3, 2007 #13

    russ_watters

    User Avatar

    Staff: Mentor

    Thermodynamics puts hard and fast limits on the efficiency of compressors and compressed-air engines. It isn't ever going to be an efficient way to store energy.
     
  15. Jun 5, 2007 #14

    baywax

    User Avatar
    Gold Member

    Here is a link to a good study out of Switzerland with some more facts concerning the "Thermodynamic Analysis of Compressed Air Vehicle Propulsion"


    (pdf)
    ......continued.......

    http://www.efcf.com/e/reports/E14.pdf

    This is an excellent analysis of the whole idea. There are several comparisons of various compression techniques with graphs showing the thermodynamic efficiency of each method.

    I'm not sure if this study was written before or after Tata Motors of India came up with their little car with an air compression engine that can do approx. 68 m per hour for approx. 184 m until requiring a re-fill of...... air.
     
  16. Jun 5, 2007 #15

    russ_watters

    User Avatar

    Staff: Mentor

    I only skimmed it, but it seems like a good analysis and the bottom line is a thermodynamic efficiency of 40% using a four-stage compressor with intercooling and 4 stage turbine to recover the energy. The efficiency of a generator -> battery-> motor system in a conventional hybrid is upwards of 80%. So I don't see how this could be considered a viable technology.
     
  17. Jun 6, 2007 #16

    baywax

    User Avatar
    Gold Member

    The Air Car has obviously been considered efficient enough to build 6000 of them. Here's a page on the company website with some of the early test results of the prototype "Taxi". There seems to be room for improvement in terms of energy efficiency. Just look at how gas vehicles have changed over the decades.

    This page has specs on energy, amount of compression, size of tanks etc... Also, weight has been reduced by using carbon fiber air tanks that meet safety specs.

    http://www.theaircar.com/tests.html

    Here's their page on thermodynamics and mileage:

    http://www.theaircar.com/data_sheet.html

    Here are the press-releases on the Air Car found in many major news sources but not really heard about in NA.

    http://www.theaircar.com/media_articles.html
     
    Last edited: Jun 6, 2007
  18. Jun 6, 2007 #17

    russ_watters

    User Avatar

    Staff: Mentor

    That doesn't mean anything at all.
    You're basically saying that you don't accept that the laws of thermodynamics are real. And no, while gas vehicles have changed a lot over the decades, the thermodynamic efficiency has not increased substantially. The fact that a 2007 Honda Civic gets better fuel economy than a 1970 Chevelle has very little to do with the thermodynamics of an Otto cycle engine.
     
  19. Jun 6, 2007 #18

    baywax

    User Avatar
    Gold Member

    I admit that I don't know enough about the laws of thermodynamics.
    What I'm pointing out is that the car maker is working with what they can get out of the available energy efficiency that comes with compressed air. Isn't that what technology is all about? Doing more with less and that sort of thing.
     
  20. Jun 6, 2007 #19

    wolram

    User Avatar
    Gold Member

    A big problem with compressed air is keeping it dry, free of water, also seals
    degrade, a typical linear cylinder is due for refurbishment after about 2 million cycles, beyond that the performance can not be guaranteed.
     
  21. Jun 6, 2007 #20

    AlephZero

    User Avatar
    Science Advisor
    Homework Helper

    If I understand that page right, they actually managed to travel 7.22 km before they ran out of air. Then they thought of a list of reasons why the 7.22 km was really 242.10km, honest. That's quite an impressive extrapolation!

    The term do describe this sort of thing in aviation is "a paper aeroplane".

    The other "technical" web pages are fairly content-free, as well.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: The Air Car (India)
  1. New car (Replies: 7)

  2. Future Cars? (Replies: 26)

  3. Driverless cars (Replies: 0)

  4. Robot Car (Replies: 2)

Loading...