3 ms·

If they do break the sound barrier, that's also when the efficiency drops iirc. So I guess they'll switch it to a heavier load or RPM, or apply the brakes? Not

If they do break the sound barrier, that's also when the efficiency drops iirc. So I guess they'll switch it to a heavier load or RPM, or apply the brakes? Not sure how that works for a wind turbine

pengaru 3y ago
I presume the pitch is adjustable, so unless the mechanism fails you can just relax the pitch like pointing a sailboat directly into the wind to depower the sails.
- bluGill 3y ago
  The mechanism is designed (or at least should be designed) so that if anything breaks the blades rotate to the no power position. There is a lot of engineering and redundancy that i'm only partially aware of.
  - pengaru 3y ago
    I guess the real question is how bad can conditions get before the "no power position" is still too much force for the structure to withstand. You can't escape the fact that the blades are a ton of surface area on a long lever... and if the winds are both forceful and directionally chaotic, there isn't really a "no power position" to be found. Going back to the sailboat metaphor, it's the conditions where you douse the sails entirely. At most flying a little storm jib. Pointing upwind is just to enable doing so.
    - bluGill 3y ago
      The tower catches more wind than the blades and will fail first. And the tower is built dor the force of strong winds with the blades resiting the wind. Though they are built in rural areas and at sea so even in the worst case disaster (manufacturing flaw, not wind) nobody is hurt.
- nuccy 3y ago
  Even if pitch is adjustable the problem is very non-trivial given the size of the blades and different wind speeds and directions on different elevations. Putting the blades in no-power position along the main wind direction, but having small sidewind 200m above the surface would rotate it.
SonicScrub 3y ago
Rotating blades like this should never go beyond the critical Mach number where local airflow on the blade upper surface reaches Mach 1.0 (about Mach 0.8ish). The shockwaves that form are attached to the surface and like to shift around with slight changes in conditions, which cause awful vibrations. I'd expect the blades to be braked in some way to never exceed critical Mach number.
tgv 3y ago
Isn't there a great resistance to overcoming it? So basically it would stop accelerating before ever crossing it. But, AFAIK, windmills wre immobilized when the wind gets too strong, in order to protect them. If the tech allows it, they can also be made to catch less window. Some Dutch wind mills could be rotated, and the cloth covering the arms could cover less surface. Modern windmills adapt their position automatically. Look at [0] and search for "Ten Have / Beckers". [0] https://en.wikipedia.org/wiki/Windmill_sail https://en.wikipedia.org/wiki/Windmill_sail

If they do break the sound barrier, that's also when the efficiency drops iirc. So I guess they'll switch it to a heavier load or RPM, or apply the brakes? Not sure how that works for a wind turbine

pengaru 3y ago

I presume the pitch is adjustable, so unless the mechanism fails you can just relax the pitch like pointing a sailboat directly into the wind to depower the sails.

bluGill 3y ago
The mechanism is designed (or at least should be designed) so that if anything breaks the blades rotate to the no power position. There is a lot of engineering and redundancy that i'm only partially aware of.
- pengaru 3y ago
  I guess the real question is how bad can conditions get before the "no power position" is still too much force for the structure to withstand. You can't escape the fact that the blades are a ton of surface area on a long lever... and if the winds are both forceful and directionally chaotic, there isn't really a "no power position" to be found. Going back to the sailboat metaphor, it's the conditions where you douse the sails entirely. At most flying a little storm jib. Pointing upwind is just to enable doing so.
  - bluGill 3y ago
    The tower catches more wind than the blades and will fail first. And the tower is built dor the force of strong winds with the blades resiting the wind. Though they are built in rural areas and at sea so even in the worst case disaster (manufacturing flaw, not wind) nobody is hurt.
nuccy 3y ago
Even if pitch is adjustable the problem is very non-trivial given the size of the blades and different wind speeds and directions on different elevations. Putting the blades in no-power position along the main wind direction, but having small sidewind 200m above the surface would rotate it.

SonicScrub 3y ago

Rotating blades like this should never go beyond the critical Mach number where local airflow on the blade upper surface reaches Mach 1.0 (about Mach 0.8ish). The shockwaves that form are attached to the surface and like to shift around with slight changes in conditions, which cause awful vibrations. I'd expect the blades to be braked in some way to never exceed critical Mach number.

tgv 3y ago

Isn't there a great resistance to overcoming it? So basically it would stop accelerating before ever crossing it. But, AFAIK, windmills wre immobilized when the wind gets too strong, in order to protect them. If the tech allows it, they can also be made to catch less window. Some Dutch wind mills could be rotated, and the cloth covering the arms could cover less surface. Modern windmills adapt their position automatically. Look at [0] and search for "Ten Have / Beckers". [0] https://en.wikipedia.org/wiki/Windmill_sail https://en.wikipedia.org/wiki/Windmill_sail