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Anemometer measures wind speed. It's shaped with little cups---hollow half-spheres. That looks very logical as the cups grab the wind and the other side is rather streamligned to cut through the air as it spins.

So why are there no wind turbines designed like this? (At least, I've never seen them.)

You could go further and make the cups ellipsoidal (more pointy). You could even add a inner shield, maybe like half a torus, around the inside to further streamlign the cups and help them grab wind.

This would be a vertical axis wind turbine (VAWT). Been looking around at VAWTs on Youtube for a while and found a lot of interesting designs, but never seen one with cups. Why not? I know I've seen anemometers spinning around very rapidly in good winds, so its seems logical.

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    $\begingroup$ Savonius rotor turbines are designed like this. Basic problem is the tip speed ratio is 1, whereas the airfoil blades in HAWTs give tsrs typically 5-10. $\endgroup$
    – user_1818839
    May 19, 2017 at 6:42
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    $\begingroup$ drømstørre.dk/wp-content/wind/miller/windpower%20web/… $\endgroup$
    – mart
    May 19, 2017 at 10:11
  • $\begingroup$ @mart nice link. :) $\endgroup$
    – Solar Mike
    May 19, 2017 at 11:41

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Because the back of the cups create a lot of drag thereby reducing the power produced.

The blade profile used in classic 3-bladed HAWTs is also used in VAWTs and they look like "egg beaters" needing top and bottom bearings. The engineering complications of VAWTs make the 3-bladed HAWT much more popular also due to the power output, rotating mass and visual impact.

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  • $\begingroup$ Could you post a link to a monograph or tutorial on shape vs.drag (as well as tip speed ratio, per a comment above)? $\endgroup$
    – Carl Witthoft
    May 19, 2017 at 14:48
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    $\begingroup$ @CarlWitthoft shape v drag is a huge topic.... Tip speed ratio, NACA profiles, stalling, blade angle and then Betz limit all come to mind straight off... For shape v drag start here : grc.nasa.gov/www/k-12/airplane/shaped.html $\endgroup$
    – Solar Mike
    May 19, 2017 at 14:54
  • $\begingroup$ Can you elaborate on engineering complications of VAWTs? AFAIK you can 3D print "anything" these days. Even helical blades of a Savonious are 3D printed as easily as a straight blade of the same size. VAWTs put all the generator stuff near the ground and usually don't need active wind tracking. Traditional HAWTs do need those things or more complicated versions of those things. (BTW the drag-based VAWTs I imagined in the OP don't need individual blade movement, so the only top/bottom bearings are for the main axis.) $\endgroup$
    – DrZ214
    May 20, 2017 at 0:47
  • $\begingroup$ Do you really believe "you can 3D print anything" ? Print a mirror then. $\endgroup$
    – Solar Mike
    May 20, 2017 at 8:19
  • $\begingroup$ I put "anything" in quotes for a reason. the point was a complex shape (like a helical blade or airfoil blade) is not much different than a simple shape when 3D printing and thus does much affect cost or manufacture time. Anyway, can you elaborate on engineering complications of VAWTs, preferably with a source? $\endgroup$
    – DrZ214
    May 21, 2017 at 3:03
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One other reason is that the propeller-type turbine allows it to be rotated to avoid damage in high winds. When the air is flowing transverse to the axis of the propeller it encounters relatively little drag.

It would be hard to imagine an orientation that would allow the anemometer-type design to avoid this.

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  • $\begingroup$ Good point, also the possible difference in wind speed from top to bottom $\endgroup$
    – Solar Mike
    May 22, 2017 at 5:31
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Usually, the frequency of the ultrasonic anemometer is mainly 200 KHz probe, and there are 4 detectors. Through the description in this paper, it is uncertain whether the wind speed of a large range can be monitored.

Refer to this article:

https://www.weatherstation1.com/what-is-wind-sensor/

This covers almost all the principles of wind monitoring, and I hope it will be helpful to you.

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    $\begingroup$ Was the OP after monitoring or power? $\endgroup$
    – Solar Mike
    Jan 16, 2019 at 6:36
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    $\begingroup$ Yeah, the OP seems to be asking why wind turbines aren't shaped like anemometers, not why anemometers aren't used to monitor "wind speed of a large range". $\endgroup$
    – Wasabi ♦
    Jan 16, 2019 at 13:07

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