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A simple calculation shows the power $P$ you can get from wind at speed $v$ passing through an area $A$ is (in Watts) $$P = 1.23\,v^3 \frac{A}{2}.$$

Using the above equation and taking the Venturi Effect in a very simple way, we know that half the area would produce wind with twice the speed i.e. if you collect the fluid at $v_1$ through a tube of cross-section area $A_1$, then you get $2v_1$ if the cross-section area is reduced to $A_1/2$.

So instead of collecting from an area A, you could divide the area by ten for example, and get a 10 times faster wind speed. From there and the power get from wind you have infinite power :D. A fan could be an infinite source of energy (after it has been initiated).

So I suppose I am missing a point. My question is what am I misssing?

(I guess the pressure needed to "push" the air through a tunnel would be so much that the fan would just do nothing or you would need that much energy to fight that.)

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  • $\begingroup$ Wind speed is an independent variable for a wind turbine, meaning that you have no control over it, and you can't arbitrarily increase it with the geometry of the device that you are using. $\endgroup$
    – David White
    Commented Aug 27, 2019 at 17:04
  • $\begingroup$ I don't want to increase the wind speed of the device. I want to "push" the air trough a tunnel. And i want to know why the gain of speed from that cannot be a way to produce energy. (And i know it cant cause it would violate all the law of normality). And thanks @ohneVal for the edit, this post looks so beautiful). $\endgroup$
    – PauZen
    Commented Aug 28, 2019 at 10:53
  • $\begingroup$ @PauZen "So instead of collecting from an area A, you could divide the area by ten for example, and get a 10 times faster wind speed." Why? $\endgroup$
    – Guimoute
    Commented Aug 23, 2023 at 9:30
  • $\begingroup$ Your final remark is correct - you would have to expend more energy to press the air through the smaller hole. As you shrink the hole, more of this energy is actually lost to friction, so that you would indeed lose energy, and physics still works. $\endgroup$
    – paulina
    Commented May 2 at 7:32

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Yes, it can be done and it's already under research. Just google with "application of venturi effect in wind turbines" and you can see a lot of papers there. It's an accepted fact that the velocity of wind increases when a venturi is used. Papers with experimental results are already available.

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