# Add a wind turbine to a car?

1. Aug 14, 2007

### The_Thinker

If supposing we were to add a wind turbine connected to a generator to a moving car, would we be able to get the air flowing around the car to turn the turbine and therefore gain some energy? If it is possible, is it economical? if it is, is it practical? would there be a loss? would there be any gain in overall efficiency??

A friend of mine wants to do this project for collage and wants to implement this idea... I just want to know if it is practical or not...

So... what do you guys think?

2. Aug 14, 2007

### MaWM

That depends what you mean by "wind". It is certainly possible to attach a sail to a set of wheels and have the ambient wind blow you around. That would cetainly be efficient.

On the other hand, if you mean the wind generated by the car moving through the air, then the engine creates that motion by moving the car forward. By capturing that wind to extract energy, you are slowing the car down and making the engine work harder. Even using the energy you extract, you will use *more* gas than you do now. That is to say, the system is less efficient than existing cars.

3. Aug 14, 2007

### Averagesupernova

Search the forum on this. There was a lengthly thread about it.

4. Aug 15, 2007

### Staff: Mentor

This is a type 1 perpetual motion machine - it won't work because it violates conservation of energy.

5. Aug 15, 2007

### DaveC426913

The catch is that the wind, acting on the turbine blades, causes drag. The energy you gain from the wind turbine is lost by the increased drag.

But here's a thought to all you who think this is a no-win setup: Who said the addition of a wind turbine has to <I>increase</I> drag? A car already has lots of drag from its forward-facing surfaces. If you punched a hole in one of these surfaces and put a wind turbine in, the overall drag of the vehicle would <I>decrease</I>.

6. Aug 15, 2007

### ank_gl

first u increase the weight, so you need more fuel.
second the turning of blades involves work, which you are to supply with your moving air, ie moving car. hmmm moving car gives energy to turbine and the turbine gives energy back to car!! so cooooool!!!
not much cool;)), you can never get greater or rather equal amount of energy back, that you spend on the turbine

7. Aug 15, 2007

### FredGarvin

You're assuming that the turbine has no induced drag itself. Also you are assuming that there would be no pressure drag created. Simply because you reduce the frontal area of the vehicle by placing a hole in it does not mean you are going to decrease drag.

8. Aug 15, 2007

### dimensionless

This could work if the wind is perpendicular to the motion of the car. It is probably not economical in most regions. There might be exceptions in regions where there is very high wind, although I would expect that it would make the car more difficult to control. It is probably more practical to attach a large sail to the car.

9. Aug 15, 2007

### DaveC426913

I was suggesting that a hole in the front with a turbine behind it would not have any more drag than no hole.

But now I'm questioning even that.

Ignore the turbine turning and ignore air passing through - i.ew. as of the turbine seized. Now you've got the equivalent of a deep, blind pocket on your car. That would be more drag than if you had no pocket.

10. Aug 15, 2007

### Danger

You're reading more into the question than was originally asked. The Thinker didn't ask if the car could be powered by such a device, only if work could be extracted from the windmill. The answer to that is 'yes'. For instance, it could be used to recharge a cell phone or something similar if a 12V outlet wasn't available. It certainly wouldn't be efficient, but it could work.

11. Aug 15, 2007

### ank_gl

the problem is that the energy given to turbine would be greater than the output of turbine. so where is the advantage??? you wont carry a turbine to recharge your phones, would u??

12. Aug 15, 2007

### Staff: Mentor

The math for a turbine producing half the engine's ouput would look like this:

Car engine output: 10kW
Turbine energy production: 5kW

System thermodynamic efficiency (if all pieces were 100% efficient):
(10+5)/10=150%

Still a type 1 pmm.

The key words in the opening post are "gain some energy". Obvously you don't gain anything by doing this and that is what the OP was hoping to do.

Last edited: Aug 15, 2007
13. Aug 15, 2007

### Danger

Who the hell are you talking to that requires 5kW for a cell phone? I think that you're taking this astronomy hobby a tad too far.

Okay, I interpreted that differently. Given your approach, you're absolutely right. I thought that he just wanted to know if anything could be done by the wind.

14. Aug 16, 2007

### caslav.ilic

Just a side note: "put propeller in your own wind" trick is quite a normal feature in airplanes, called the ram air turbine. Of course it's a waste overall, but when other electric generators are shot out and the airplane is left with kinetic energy only, it'll do.

--
Chusslove Illich (Часлав Илић)

15. Aug 16, 2007

### Staff: Mentor

Yeah, if the choices are to have no control of the plane or sacrifice some glide ratio to power your controls and instruments, the choice is easy.

16. Aug 16, 2007

### brewnog

Now charging your battery using a wind turbine while the car is stationary, that's certainly viable.

17. Aug 16, 2007

### ank_gl

having a wind turbine for battery charging is certainly not viable

18. Aug 16, 2007

### The_Thinker

yeah... thats what I felt too actually... it could be done.. but it would be less efficient, so its a non-gain project... thx for the replies guys...

19. Aug 16, 2007

### brewnog

Take a look at the units used on caravans, mobile homes, narrowboats and motor boats.

20. Aug 16, 2007

### kach22i

Along with solar film/paint we are getting somewhere with this idea.