Venturi effect or Coanda effect or a combination of both in this windmill?

[T C]

TL;DR Summary

Recently I have come up with a new kind of concentrated wind turbine and I just want to know the basic principle behind this new kind of windmill. I want to know whether this is Venturi effect or Coanda effect or a combination of both.

I have recently find this video and just curious about the working principle behind this concentrated windmill. Apparently it seems that the basic principle is Venturi effect but the shape of the entry point is more suitable for Coanda effect with its curved surface at the entry. And it's also highly possible that this is a combination of both. Want to know others opinion regarding this matter especially from those who has ever tried to build something similar.

 

[russ_watters]

I don't see that it has anything to do with the coanda effect. It kind of uses the Venturi Effect, but it's not exactly or all.

There's a lot of sources online for how wind concentrators work.

 

[T C]

The entry point has curved surface. Doesn't that related to Coanda effect?

 

[russ_watters]

The entry point has curved surface. Doesn't that related to Coanda effect?

Not if the surface is pointed into the airflow.

 

[boneh3ad]

Focus less on the names of phenomena and more on physical principles. I agree this has nothing to do with Coanda and seemingly nothing to do directly with Venturi, so the real question here is what principles were actually intended to be described when using those two names.

 

[berkeman]

You got to love their hillbilly wind tunnel testing...

 

[cjl]

I have to admit I'm curious what the goal here is. It's almost never worth the effort (actually, it's never worth the effort in my experience, but I am always hesitant to make absolute statements) to duct or concentrate wind on a wind turbine, because for the same amount of extra material and expense, you could just make the rotor larger and gain far more energy than you will ever get from a concentrator.

 

[T C]

@ cjl, kindly look at this video and see how the RPM dramatically increased after introduction of a venturi. And here is one more example and see by yourself the difference between having a venturi and not having it. Just search youtube with "venturi turbine" and you can see tons of examples.

 

[cjl]

So a couple of comments there.

That first one is really basically irrelevant to any practical wind turbine design. Sure, it's great as a basic science demo for learning, but if you want to talk about maximizing efficiency and output, you really have to start with a design using lifting blades rather than cups (since you sacrifice so much with the cups that it's basically never worth it except at very small scale if you just want a simple design).

As for that second video, I'm amused by the claim that palm springs is the wind turbine capital of the US. In reality, northwest Texas and Iowa are the leaders in US wind generation, and it isn't close (I worked in wind turbine design for a number of years). Everything about that video just screams that they have no idea about modern wind turbine design though. Maximizing efficiency and output is all about going big, so contrary to their claim at 42s in that video that a standard turbine spins 800rpm, a typical onshore wind turbine with 50-75m blades spins more like 11-13 RPM. Generally the more powerful they are, the slower they go too, since you want to keep a fairly constant tip speed (usually ~75-90m/s) and more power means a larger turbine.

Next, I'm confused why they have what look like repurposed fans or blowers as their turbines. The dense mesh around the blades is going to kill their efficiency, since it's obstructing a lot of flow and it's also going to cause a ton of turbulence. There's a reason why all actual professional wind turbine designs are completely out in the open air. Their blade design is awful too. They also don't show any power measurements, and I get the feeling they aren't even applying a load, but rather they're just letting them spin freely. Electric generators have more resistance when they're actually, well, generating, so freewheeling tests tell you very little. That having been said, I'm sure their concentrator does better than their other one, but they're both awful.

Also, again, I didn't say it doesn't increase the output to add a concentrator or duct, I said it's generally not worth the expense, materials, cost, and structure, since you'll get a greater increase in output by just making the rotor bigger. For the same amount of materials and cost as the concentrator, you could just make the blades on the other one twice as long, and you get far more energy that way.

For some evidence that I know what I'm talking about, here is a turbine I did some design work on (I was in the blade design department). I guarantee you that it's vastly more efficient and powerful than anything in that video above.

Also, interestingly, efficiency isn't even necessarily what you want. The maximum theoretical efficiency of a wind turbine is around 59%, and we can actually get darn close to that, but it turns out that if you back that off to 45-50% instead, it substantially reduces the loads on the blades, which then enables you to make the blades longer for the same strength and actually makes more power than you would get with the smaller, higher efficiency design (with no more structural load). At the end of the day, the most important thing isn't efficiency, it's annual energy production, cost per kWh, and capacity factor.

(There's also considerations about where the turbines will be installed, what kind of conditions it'll need to endure, what storms you want it to handle, etc, but this post is getting long enough already)

 

[T C]

That first one is really basically irrelevant to any practical wind turbine design. Sure, it's great as a basic science demo for learning, but if you want to talk about maximizing efficiency and output, you really have to start with a design using lifting blades rather than cups (since you sacrifice so much with the cups that it's basically never worth it except at very small scale if you just want a simple design).

This video is just to show that how venturies can drastically increase output of a wind turbine. What you are telling is the next step, that's another matter.

As for that second video, I'm amused by the claim that palm springs is the wind turbine capital of the US. In reality, northwest Texas and Iowa are the leaders in US wind generation, and it isn't close (I worked in wind turbine design for a number of years). Everything about that video just screams that they have no idea about modern wind turbine design though. Maximizing efficiency and output is all about going big, so contrary to their claim at 42s in that video that a standard turbine spins 800rpm, a typical 50-75 meter onshore wind turbine spins more like 11-13 RPM. Generally the more powerful they are, the slower they go too, since you want to keep a fairly constant tip speed (usually ~75-90m/s) and more power means a larger turbine.

I am not interested about what is the wind turbine capital of US. In the video, you can see two same wind turbines rotating side by side, one with a venturi and the other one without. The difference in RPM is clearly visible.
You have asked "why venturi" and i have posted this videos. Kindly Google with "concentrated wind turbine" and you can see some interesting new developments in this regards.

 

[boneh3ad]

For some evidence that I know what I'm talking about, here is a turbine I did some design work on (I was in the blade design department). I guarantee you that it's vastly more efficient and powerful than anything in that video above.

Sure it's big enough, but look at the location!

 

[boneh3ad]

This video is just to show that how venturies can drastically increase output of a wind turbine. What you are telling is the next step, that's another matter.

I am not interested about what is the wind turbine capital of US. In the video, you can see two same wind turbines rotating side by side, one with a venturi and the other one without. The difference in RPM is clearly visible.
You have asked "why venturi" and i have posted this videos. Kindly Google with "concentrated wind turbine" and you can see some interesting new developments in this regards.

Did you read anything else @cjl said or did you just take a few sentences you didn't like, ignore the rest, and then claim he didn't understand your point? You have a history of dismissing sound science and engineering on these boards. Responses like that are why you usually don't get detailed responses anymore.

 

[anorlunda]

For some evidence that I know what I'm talking about, here is a turbine I did some design work on (I was in the blade design department). I guarantee you that it's vastly more efficient and powerful than anything in that video above.

Yes indeed. Here is a web page with some more information. The page says 14 MW nominal, but 15 MW with power boost. What is power boost?

As an interesting milestone. Here is a PF thread from 2019. Skeptics back then doubted that GE could actually deliver a 12 MW wind turbine. Now 3 years later, despite the pandemic, we see Siemens delivering a 14 MW wind turbine.

That is a 20% improvement in only 3 years. Lightning fast by engineering standards. Kudos to you and other developers.

 

[cjl]

Yes indeed. Here is a web page with some more information. The page says 14 MW nominal, but 15 MW with power boost. What is power boost?

As an interesting milestone. Here is a PF thread from 2019. Skeptics back then doubted that GE could actually deliver a 12 MW wind turbine. Now 3 years later, despite the pandemic, we see Siemens delivering a 14 MW wind turbine.

That is a 20% improvement in only 3 years. Lightning fast by engineering standards. Kudos to you and other developers.

So, for what it's worth, you'll notice a fair amount of that skepticism came from me. The reason for my disclaimer at the time is that I was actually working on this 222m 14MW turbine when that thread was active, so I was trying not to say too much. Obviously, I believed 12MW 220m was totally possible (we were working on a bigger one anyways), it's more just that it was surprising that GE made such a large jump. I can say that when I was working for Siemens, we had a lot of learnings from the 6MW 154m up to the 8MW 167m, then the 10MW 193m, and then we finally had the confidence to jump to the 14MW 222. The reason I was so skeptical wasn't so much that I didn't think it was possible, more just that GE had never been an offshore powerhouse, and even the 6MW turbine they had was basically just purchased from Alstom and not their own design. It's tremendously impressive that they jumped up to a 12MW with no steps in between.

As for power boost? Basically, the turbine has a whole bunch of sensors onboard, including windspeed, direction, blade strain sensors, nacelle accelerometers, etc. Based on all those sensors, we can judge not just windspeed, but things like turbulence, consistency of wind direction, shear profile, etc. Power boost is basically a capability where we are able to increase power generation from 14 up to 15MW if the conditions are just right. The reason the turbine is rated at 14MW is because that's what is guaranteed across a range of turbulence values, windspeeds, etc, but it turns out that in certain conditions, if the windspeed is high but there is minimal variability in wind direction and low turbulence, there's actually quite a lot of margin in the design. Powerboost attempts to utilize this margin to give a bit of extra power if the conditions are ideal, and it allows the turbine to generate an extra megawatt if it's safe to do so.

And yes, the rate of development in wind turbines is truly impressive. I can't wait to see what's coming next, now that I'm no longer in the industry and privy to the latest info.

 

[cjl]

This video is just to show that how venturies can drastically increase output of a wind turbine. What you are telling is the next step, that's another matter.

I am not interested about what is the wind turbine capital of US. In the video, you can see two same wind turbines rotating side by side, one with a venturi and the other one without. The difference in RPM is clearly visible.
You have asked "why venturi" and i have posted this videos. Kindly Google with "concentrated wind turbine" and you can see some interesting new developments in this regards.

You have failed to address any of my actual points, and you're completely ignoring my explanations and expertise.

I'm happy to answer any good faith actual questions, but you need to actually read and understand my points for it to be worth my time to answer.

Again, concentrators do increase power, but for the same money and excess materials, it's basically always better to just make the turbine bigger. This will be my last reply to you unless you actually make a good faith effort to understand my whole post, and not just minor excerpts.

 

[cjl]

Sure it's big enough, but look at the location!

Yeah, if you ever happen to be in northern Denmark, visit the Osterild test center for wind turbines. It's ridiculously impressive, and completely open to the public. As impressive as these turbines look on video, it's a totally different thing to see them in person.

 

[berkeman]

I'm happy to answer any good faith actual questions, but you need to actually read and understand my points for it to be worth my time to answer.

That probably won't happen in this thread. @T C has been thread banned, and since he is the OP this thread is closed for now. Thanks for the impressive posts, @cjl