Very small wind turbine question

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Could a small ducted fan / wind turbine say 4 -5 inches in diameter placed in the wind stream of a car develop enough energy at freeway speeds ( or less ) to help charge the cars battery at a realistic level say 30 to 75 amps 12v? I am thinking along the line of a duct from the front grill area forcing air through the turbine to spin a generator and provide additional electrical power to help recharge a hybred vehicle thus extending its range.

Zente
 

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  • #2
russ_watters
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No, any energy extracted from the air is provided by the engine. Overall, this will reduce the range of the car.
 
  • #3
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Ok now I really dont understand....

The engine is already pushing the vehicle and a certain amount of air pressure is already being both deverted ( pushed aside by the body of the car ) and also directed through the radiator, the braking system ( for cooling ) , as well as the vents for your flow through ventilation etc. So why is this same air ( non deflected ) putting more power requiremnts on the engine just to be directed into a fan / turbine to spin a generator. How would the internal air flow effect the drag of the vehicle any more than it already is now?

We used to in the 60's and 70's put hood scoops on our street race cars ( which they still do today ) to force more air into the carberator to make the engine breath easier. The hood scoop added drag but the added power output of the engine far more than made up for the drag.

Zente
 
  • #4
russ_watters
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The engine is already pushing the vehicle and a certain amount of air pressure is already being both deverted ( pushed aside by the body of the car ) and also directed through the radiator, the braking system ( for cooling ) , as well as the vents for your flow through ventilation etc. So why is this same air ( non deflected ) putting more power requiremnts on the engine just to be directed into a fan / turbine to spin a generator. How would the internal air flow effect the drag of the vehicle any more than it already is now?
All the stuff that already creates drag is already creating drag, so it isn't the issue here. Anything you add into the airstream will create more drag: Stick your hand out the window of a car and you can feel that it adds drag!
We used to in the 60's and 70's put hood scoops on our street race cars ( which they still do today ) to force more air into the carberator to make the engine breath easier. The hood scoop added drag but the added power output of the engine far more than made up for the drag.
That's a completley different issue as adding airflow into the engine allows you to add more gas and generate more power. It doesn't change the efficiency much except insofar as the efficiency drops off when the power gets high and airflow gets choked (it doesn't increase efficiency at low power, for example).
 
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  • #5
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I think you or I have a different concept .. I do not want the fan / turbine on the outside of the car... I want it inside the body / engine compartment with the duct at the front grill area and everything being enclosed in the existing vehicle. I know if I place it outside the body it effects the drag and thus the power requirement of the engine.

Zente
 
  • #6
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The real World point missed here is the speed at which you travel.IN THE 1950'S YOU COULD EHTER A FREEWAY AND TRAVEL AT 55-60, UNTIL YOU WERE READY TO EXIT. Today I leave on a 34 mile trip to santa monica and expect that trip to take almost two hours. I do not think I could get a fan (that was pushing against a strong magnetic field) to spin much at all in those "stop and go" conditions. You would be better off finding a way to burn the "un-burnt" fuel to generate power we now use platinum to burn. gary.
 
  • #7
russ_watters
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I think you or I have a different concept .. I do not want the fan / turbine on the outside of the car... I want it inside the body / engine compartment with the duct at the front grill area and everything being enclosed in the existing vehicle. I know if I place it outside the body it effects the drag and thus the power requirement of the engine.
Ok, well, it may be possible to put a turbine inside the engine compartment in a way that makes use of wasted airflow, but it would have to be done in a way that doesn't interfere with airflow through the radiator or to the engine. I'm sure it depends on the car, but I doubt there is much truly wasted airflow through the engine compartment.

Doing a quick back of the envelope calc, I don't think there's more than 100W available in a 4" diameter airstream at 75 mph.
 
  • #8
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Thank you for the input ...

Zente
 
  • #9
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A generator that harnesses energy from the air movement will drain the battery of the electric car quicker unless the generator is 100% efficient, in which case it will only break even and that assumes you have a 100% efficient turbine (fan) as well. Since the efficiency will obviously be less than 100% for both, it's a net loss no matter where you place it.
 
  • #10
AlephZero
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It doesn't matter where you put the turbine.

If your turbine is extracting any power form the air, the air will apply a net force trying to push the turbine backwards. This doesn't matter for turbines fixed to the ground, so long as the pole is strong enough to resist it.

But if you put the turbine on a platform on wheels (i.e. a car) the wind would blow it backwards, and you will need more engine power to stop that happening. Because the system is not 100% efficient, you will need more engine power than the useful work you get from the turbine.

The only time you could get a net GAIN of energy from a wind turbine on a car is when it is the car is being braked, not driven by the engine (i.e. stopped, freewheeling down hill, or even being blown along by a strong tail wind!)
 
  • #11
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Try this on for size: If an air duct were to run the length of the cars body with an inlet in the grille and the outlet located somewhere in the rear valance you would have a good solid path for the air to be diverted through. If you inserted a lightweight turbine in the airstream, it would certainly create an obstruction. The trick would be to place the turbine housing at the rear of a long venturi. This will speed up the air as it exits the vortex and run the turbine at high speed. In this case you would want a high voltage/low amperage dc output to minimize torque requirements and keep the turbine from stalling due to magnetic braking caused by the load on the field coils.
 
  • #12
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On another note, forgot to explain the to reason for the air duct exiting in the rear valence. A car traveling at any speed is constantly diverting air and creating pressure differentials. At the rear of the car is an extreme low pressure area which would aid in removing the air flowing through the duct.
 
  • #13
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Don't forget to add the mass of the system into the equation. Although you may get a fairly low mass solution, the car still has to move it about. The moment you increase the mass of the vehicle you lower efficiency by increasing the power required (heavier car = higher fuel consumption).

So not only does the system have to reclaim enough energy to compensate for aerodynamic drag, it also has to recover enough to allow for the additional mass of the car. Which unlike the aerodynamic drag which only really has to be recovered during the higher speed ranges, has to be recovered constantly or during the high speed ranges (which is the only time the generator would work well), you'd have to generate enough to cover the low speed areas.

So from the start you need to generate enough energy to cover:
a) any additional aerodynamic drag on the car.
b) any additional mass added to the car.

And this is all before you get any gain from the system to be of any use to you.
 
  • #14
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Use carbon fiber tubes to build the duct and housing. Saves weight. Aluminum or glass filled nylon would make a nice lightweight turbine. And last but not least, replace that steel rimmed spare tire with an alloy wheel. Besides that, think on this, if you reduce the demand on the engine driven charging system, you free up power to overcome the extra mass.
 
  • #15
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Besides that, think on this, if you reduce the demand on the engine driven charging system, you free up power to overcome the extra mass.
If you reduce the demand on said system, you then also need to compensate for what you lose there. Whether you compensate for the mass or this, either way the amount is the same.
 
  • #16
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If you reduce the demand on said system, you then also need to compensate for what you lose there. Whether you compensate for the mass or this, either way the amount is the same.
I get the idea but the first portion of your statement didn't make a lot of sense. Other than that, here's pro to reducing the ''Engine driven charging system''. You're not using the engine to charge the batteries! That means your reducing the load on the one component in a hybrid that uses a non regenerative energy source.
 
  • #17
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I get the idea but the first portion of your statement didn't make a lot of sense. Other than that, here's pro to reducing the ''Engine driven charging system''. You're not using the engine to charge the batteries! That means your reducing the load on the one component in a hybrid that uses a non regenerative energy source.
So the batteries push the car forward, which turns a wind turbine, which charges the batteries? Is that what you're trying to say?
 

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