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Fully Electric car with wind generators

  1. Jul 15, 2009 #1
    I'm pretty sure someone somewhere has already built one, i've gone over the concepts involved and it does seem both practical and possible. The idea is this: electric-powered car that is recharged by several wind-generators(essentially fans on the roof) that recharge the batteries once the car is driven up to speed. Yes i do realize that any energy that is being used for recharging the batteries by the generators is how much extra the motor will have to work to overcome the drag(and consequently using battery power), but as long as the generators are generating enough power to equal what the motor is using to sustain constant speed, then the car could in theory run almost forever, right? The only situations where you would be draining the battery and not recovering the charge are: accelerating and going up hills, and of course, any power lost through heat given off through the wires(no electrical system is 100% efficient). Yes the batteries would eventually die, but you could always recharge them and you'd probably get at least hundreds of miles before you ran out. Any ideas why these kinds of cars aren't being marketed?
     
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  3. Jul 15, 2009 #2

    mgb_phys

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    The 2nd law of thermodynamics?

    (in before the lock!)
     
  4. Jul 15, 2009 #3

    negitron

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    Because it won't work, that's why. The only energy the generators will produce is entirely offset by the drag on the fan plus systemic losses, such as friction and generator electromagnetic losses. It's a net loss, overall.
     
  5. Jul 15, 2009 #4
    yes i realize that it's a net loss, but you'd still probably get at least 40 miles or so on it before batteries died, right?
     
  6. Jul 15, 2009 #5

    negitron

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    You don't understand. You will ultimately get FEWER miles out of your batteries with your fan/generator than you would without it, all else being equal.
     
  7. Jul 15, 2009 #6
    allright, thanks for clearing that up for me, another question: could a similiar system work in a hybrid? For example, let's say that you have a generator that produces 5hp at highway speeds to recharge the batteries. 5hp to a 100hp engine is not that much extra power for it to output and therefore doesn't consume too much more gas. Would this be practical or is it subject to the same impracticality?
     
  8. Jul 15, 2009 #7

    negitron

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    Same problem. Ultimately, all the vehicle's forward motion comes from it's engine/motor and anything you do to try to recover that energy, be it a fifth wheel driving a generator or a wind turbine, places an additional drag on the vehicle and results in a net loss due to conversion losses
     
  9. Jul 15, 2009 #8

    Danger

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    Given the malicious perversity of mechanical systems, I suspect that any actual losses would be even greater than those which would be calculated mathematically. Machines are out to screw us any way they can think of. :wink:
     
  10. Jul 15, 2009 #9

    berkeman

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    When I was about 11 years old, my dad found me cutting the bottom off of a coffee can for a project. He asked what I was doing, and I explained how I was going to mount two propellers on a shaft in the can, with the top propeller at one opening, and the bottom propeller at the bottom opening. I was going to put a harness on it so I could wear it like a backpack, and then when I spun up the propellers, the top one would provide the thrust, and the bottom one would recover the thrust and keep the top propeller spinning. I was looking forward to flying around like the jet-pack guy I'd seen on TV (dating myself here).

    My dad sat me down and patiently explained why perpetual motion machines don't work, and how real jet engines do work, etc. I was disappointed, but it sure helped me understand the world better.

    Does that help to answer your questions?
     
  11. Jul 17, 2009 #10
    yeah, thanks. funny story.
     
  12. Mar 7, 2010 #11
  13. Mar 7, 2010 #12

    Buckethead

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    Interestingly enough, I saw an picture in Sci-Am of a proposed ship that had 2 giant wind turbines mounted where sails normally would be, and these would supposedly power a motor directly that turned a propeller, but once the math was worked out it turned out that just using sails would make a much faster ship.
     
  14. Mar 7, 2010 #13

    RonL

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    Until just a few years after 1492 it was a well known fact that the earth was flat.:rofl:

    At some time in the near future, someone that doesn't know any better will likely have an idea that makes use of that mean old friction and law of motion. Behind some brick wall is a better idea.

    I wonder what Columbus would think of the fancy sail boats moving around the ocean today.:rolleyes:
     
  15. Mar 7, 2010 #14

    mgb_phys

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    Sails are very efficent - assuming the wind was in the right direction.
    The wind turbine ship doesn't have to tack to maintain a course, tacking a 400m container ship through the English channel would be interesting.

    There is an intermediate solution that has been tried - a giant parafoil kite deployed in front of the ship.
     
  16. Mar 7, 2010 #15

    mgb_phys

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    No it wasn't, nobody thought the earth was flat since they stopped hitting each other with rocks. The diameter of the spherical Earth was measured 2000 years before columbus.
    The "they thought the Earth was flat" thing was made up by Washington Irvine to show how primitive and superstitious Europeans were compared to educated high tech scientific Americans (how times have changed).
     
  17. Mar 7, 2010 #16

    RonL

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    Thanks, you might have saved my day, learned something not nascar related.:cool:
     
  18. Mar 8, 2010 #17

    MacLaddy

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    11 years old and you thought of that? Plus you could understand the concepts of energy that your dad was telling you? :bugeye:

    I could barely tie my shoes at eleven years old!!!
     
  19. Mar 8, 2010 #18

    vanesch

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    What a terrible experience ! Did you become a terrorist ? :biggrin:
     
  20. Mar 8, 2010 #19

    sophiecentaur

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    Nearly two thousand years before 1492, the Greeks measured the radius of the Earth to within something like 16km.
    (http://en.wikipedia.org/wiki/Spherical_Earth)

    There have been plenty of "idea"s that ignore friction but have there been any proper theories or working inventions?
     
  21. Mar 8, 2010 #20

    Buckethead

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    The parafoil kite is a cool idea, especially since winds tend to be stronger at higher altitudes, but it seems one is limited to the direction of wind travel, or at least close to it. With sails, one can sail in any direction except for about 70 degrees into the wind. Yes, you have to tack to go in certain directions, but not all. A broad reach or a run don't require tacking. With the wind turbine, it doesn't seem likely one could move directly into the wind, as the wind resistance would be stronger than the propeller force so some kind of tacking even with a wind turbine would require tacking.
     
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