Jiminy Peak’s “Zephyr” Wind Turbine

[tjf67]

I also like the idea of attaching turbines to pier post in rivers and oceans and pulling some power from that source as well.

 

[Marc]

When I was there it seemed like there was no wind at all, yet the blades seemed to be moving at a pretty good and even rate. Do you know how that works?

Here is a pedestrian, non technical observation. Every fly a kite? Ever notice how it flies much better./stronger above the treeline? Often there is a lot more wind uppa therea.
p.s., for that reason too, I like skiing below the treeline on a stormy day...

Bill's right, technical or not. Whenever you have fluid flow over a surface (even though not all wind blows parallel to the ground, that is the only kind of wind that can turn a turbine) you can generally model the fluid as having zero velocity infinitesimally close to the surface and the velocity increases as you move further away from the surface until you hit a maximum free stream velocity (for simplified laminar boundary layers, the averages still hold true for turbulent boundary layers however local velocities can vary widely). The thickness of this layer, the distance from the free flowing air to the ground is called a boundary layer. The rougher the surface (things like change in elevation, trees, buildings, etc contribute to surface roughness) the greater the impact on the fluid and the thicker the boundary layer.

Since the turbine is so much further from the surface (ground level) than you, the velocity of the wind was likley higher than where you were standing. Also remember the force of the wind acting on the blades is proportional to the area of the blades. Just like a sail, the more sail area, the greater the force generated for a given velocity. Despite how thin the blades appear to be, they put up a tremendous amount of surface area, so even a light breeze that feels very insignificant to you still has the potential to exert enough force to turn the turbine.

 

[hiroto]

you can generally model the fluid as having zero velocity infinitesimally close to the surface and the velocity increases as you move further away from the surface until you hit a maximum free stream velocity

While skydiving, I have encountered situations when there is 10~20mile/h wind as low as ~150 feet above ground while there is absolute no wind at all on the ground. This can happen in a middle of relatively large open field far away from trees.

 

[Marc]

My example for simplicity was using a constanct velocity fluid flowing over a flat plate. It was just for the ease of understanding the principle of surface roughness and boundary layers.

In real life pressure gradiants, temperature, radiant heating, humidity, coriolis and a multitude of other things affect how the wind blows and there's no practical use of fluid flow over a flat plate beyond understanding how surface roughness affects windspeed, so you won't get far trying to use it for much beyond that.

There are plenty of simple examples to look to (simple model, simple exapmles), however, that are explained by this mechanism... for instance, why the wind over the ocean is often higher than inland, wind at the top of an exposed peak, especially monadnocks is often higher than surrounding areas, why on shore wind typically blows faster than off shore wind, etc. etc.

 

[billski]

wind farms, solar farms BUILD EM'. As many as needed I say.

Yeah, and put restaurants underneath. Open fall and spring, main entree: duck, geese. :smile:

 

[billski]

My example for simplicity was using a constanct velocity fluid flowing over a flat plate. It was just for the ease of understanding the principle of surface roughness and boundary layers.

In real life pressure gradiants, temperature, radiant heating, humidity, coriolis and a multitude of other things affect how the wind blows and there's no practical use of fluid flow over a flat plate beyond understanding how surface roughness affects windspeed, so you won't get far trying to use it for much beyond that.

There are plenty of simple examples to look to (simple model, simple exapmles), however, that are explained by this mechanism... for instance, why the wind over the ocean is often higher than inland, wind at the top of an exposed peak, especially monadnocks is often higher than surrounding areas, why on shore wind typically blows faster than off shore wind, etc. etc.

So Marc, If I understand 5% of what you said, is it fair to say, that just above the surface (not infinitesimally close where wind equals zero), the air is relatively turbulent compared to higher altitude air stream? I would think that will all the irregular surface interference, there must be.

If so, then I finally understand why folks say I have the most to fear during landing and takeoff of aircraft.

 

[Greg]

Why is every thread turning so nauseatingly geeky as of late? uke:

 

[SkiDork]

Yeah, and put restaurants underneath. Open fall and spring, main entree: duck, geese. :smile:

and a village, of course.

 

[billski]

Why is every thread turning so nauseatingly geeky as of late? uke:

without snow, the true fabric of people comes out. If you want to prevent this, get to work on the snow.....

 

[bvibert]

Why is every thread turning so nauseatingly geeky as of late? uke:

What do you expect? This is the internet, the place is crawling with geeks and nerds...

 

[Greg]

What do you expect? This is the internet, the place is crawling with geeks and nerds...

Indeed. But some of Marc's post go well beyond geek or nerd status. I still believe he's an alien.

 

[Marc]

So Marc, If I understand 5% of what you said, is it fair to say, that just above the surface (not infinitesimally close where wind equals zero), the air is relatively turbulent compared to higher altitude air stream? I would think that will all the irregular surface interference, there must be.

If so, then I finally understand why folks say I have the most to fear during landing and takeoff of aircraft.

If the wind is blowing predominately one direction, and we're talking relatively locally, yes, this is correct.

Regarding air planes, typically air fields are big enough areas with smooth ground so the boundary layer is probably fairly laminar. I think the reason to fear landing and takeoff is because that's when you find out how skilled your pilot is Plus it's really hard to do.

Indeed. But some of Marc's post go well beyond geek or nerd status. I still believe he's an alien.

I'm just your average engineer. With too much time on his hands. We haven't even started in on quantum physics yet... :dunce:

 

[billski]

Regarding air planes, typically air fields are big enough areas with smooth ground so the boundary layer is probably fairly laminar. I think the reason to fear landing and takeoff is because that's when you find out how skilled your pilot is Plus it's really hard to do.

Thanks!
Moral of the story: fly your kites over airfields :dunce:

 

[tree_skier]

Yeah, and put restaurants underneath. Open fall and spring, main entree: duck, geese. :smile:

please show me one study showing any bird kill. To me it is just the stuff of all the NIMBY people.

 

[billski]

please show me one study showing any bird kill. To me it is just the stuff of all the NIMBY people.

chill...I'm just joking! See smiley!
I agree with the low-bird-impact posit.
we need to tear down our glass buildings instead (joke, joke, joke)

 

[tequiladoug]

I didnt see any dead birds

 

[SkiDork]

Thanks!
Moral of the story: fly your kites over airfields :dunce:

Lets go fly a kite... Up where the air is light...