solar/wind powered buggy

Discussion in 'The Projects Forum' started by ilovelamp, Dec 7, 2011.

  1. ilovelamp

    Thread Starter New Member

    Dec 7, 2011
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    Hi,
    For a project I need to combine solar and wind power to drive a buggy on a 7m course into oncoming wind.

    Before the race we have 5 minutes solar charging time with 2 panels either in series or parallel under 1x 100W lamp. This energy can be stored in any arrangement of capacitors that we desire.

    During the race, we must have a wind turbine fixed to the buggy which is capturing the energy from the oncoming wind and combines with the energy stored in the capacitor to drive the motor.

    I was wondering what our different options are in terms of how we actually combine the voltages from the capacitor and the wind turbine?? I.e. how we would design a combinational circuit which uses both power sources. Or a microcontroller which uses both.

    Any help would be kindly appreciated.

    Many thanks.
     
  2. wayneh

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    Sep 9, 2010
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    Any turbine driven into a headwind will accomplish nothing except add drag. There's no way you'll harvest enough out to make up for the drag losses, and in reality the loss will be much larger than the small gain.

    So, requiring a turbine could be a trick, the answer to which is to make the turbine as small and drag-free as possible.

    Seems to me a single pump of a solenoid - firing all the accumulated solar energy - could fling your buggy the full 7 meters in one shot. Maybe that's not allowed?

    [UPDATE] Oh wait, I'm sorry, I was thinking of calm air with any "wind" being from movement of the buggy. If you've got enough natural headwind, you can get plenty of power. At the minimum all you need is a blocking diode (or rectifier) on the wind generator and feed its output into the capacitor, same as the solar. But this won't give you any power until the wind generator can overcome the voltage on the cap, plus the diode voltage drop. Being able to harvest wind energy at low voltage is a challenge. The most efficient approach is to wind the generator coils to provide higher voltage directly. Basically this means using narrow gauge wire, more loops. Any transformer outside of the generator will introduce losses, no matter how good.
     
    Last edited: Dec 7, 2011
  3. strantor

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    Oct 3, 2010
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    What? I think you had it right in the beginning.
    Any headwind, whether from the car cutting throught still air, or from natural souces + the car cutting through the air, applies the same drag force to the car as it does to the turbine. the turbine cannot harvest enough energy to overcome the additional drag caused by its presence in either case. it is more of a hindrance than a help, any way you cut it.

    @ilovelamp What kind of school are you going to where they require you to build overunity projects? The only point I can see, is to illustrate how well this doesn't work, which is even quite silly to me.
     
  4. strantor

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  5. strantor

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    This has gotten me thinking though; what if you put a turbine under the hood of a car, behind the front grille? you wouldn't be adding any drag would you? I consider this like a turbocharger in how it improves efficiency; a turbocharger, even though it is powered by the engine (exhaust), is not an overunity machine because itutilizes otherwise wasted energy. A turbine behind the grill is utilizing waste as well, since that area of the car is (in my theory) already wasting as much energy as it can (you can't add any additional drag by putting a turbine there).
     
  6. wayneh

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    No, think of it this way: Picture a large VAWT sitting on a dolly with the wheels locked. The VAWT spins in the wind and collects energy with no movement of the dolly. Then you use the collected wind energy to move the dolly forward. The collected power could be much larger than the small amount needed to overcome drag and move the turbine forward.

    The wind is doing work on the turbine blades - force times distance - and is slowed in the process. There's no energy created or lost, just a portion transferred from the wind to the turbine blades.
     
  7. wayneh

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    Actually I think you would. Race car designs work very hard to avoid air moving through the vehicle, you want it to go around and minimize any transfer from air to car.

    Air resistance and fluid viscosity are essentially momentum transfer phenomenon; the net result of zillions of collisions at the molecular level.
     
  8. strantor

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    Ok, so you're referring that energy which is captured by the turbine during 5min solar chargin period, and not the energy captured while the car is transporting the turbine down the track? I can agree with that, but that's not how OP made it sound. The way it was described makes it sound like it is indoors, and that the car is capturing it's own wind.
     
  9. strantor

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    yeah but thats my point; the air is already moving through the vehicle. the front grille is just a big open wind scoop, gobbling up all the air in front of it and cooling the engine. Why not send all that gobbled up air through a turbine before it cools then engine?
     
  10. strantor

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    Oh I think I understand; the air is already moving through the vehicle, but the more things you put in its path, the more drag?
     
  11. wayneh

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    That's what I pictured initially, and of course that's useless, but I think if there's a substantial natural wind, a turbine could contribute.
     
  12. John P

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  13. wayneh

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    Very cool. Looks like the power transfer is purely mechanical, which makes sense. A gearbox will be more efficient than just about any electrical approach.
     
  14. strantor

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    hey cool! Seems like the same principle as a sailboat or sail car, the way it can cruise into the wind with the blades at the right angle. I guess this lends some credibility to the idea of putting a turbine on a car, and to what wayneH said at the beginning about natural wind. Sorry wayneH I didn't get your point at first but now I do; had to see it to understand it. these cars are using natural wind, and not harvesting their own wind. this would not power itself indoors, or on a calm day, just like a sail boat wouldn't.
     
  15. wayneh

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    Right, and your challenge would be easier if you could tack into the wind at some angle, not directly into it. A good sail can propel you upwind at a decent tack angle, with no moving parts. But NO sail will take you into the eye of the wind.

    But I suppose your class is not about making you a better sailor. ;)
     
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