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Vortex Generators

Vortex generators and micro-tabs should not be confused. I replaced the microtab references with vortex generators in the "Stall" section of the article. Micro tabs are serrated gurney flaps and not vortex generators. georgepehli (talk) 09:52, 10 February 2010 (UTC)

Stall section needs major re-writing!

I believe that the stall description is very poor and generally inaccurate. Sections like this one:

Stalling is simple because it can be made to happen passively (it increases automatically when the winds speed up), but it increases the cross-section of the blade face-on to the wind, and thus the ordinary drag

should be explained better and in a more accurate way.

Also, what vortex generators do, is that they induce vorticity to the boundary layer thus improving the BL mixing and eventually allow the BL to "stick" to the wall (i.e. airfoil or wind turbine blade) withstanding more adverse pressure gradients. The whole statement:

Vortex generators may be used to control the lift characteristics of the blade. The VGs are placed on the airfoil to enhance the lift if they are placed on the lower (flatter) surface or limit the maximum lift if placed on the upper (higher camber) surface

is completely wrong. First of all these is no "flat" airfoil surface, the terminology is Pressure Side and Suction Side. Then, the installation of VGs on the Pressure Side does NOT increase lift. What usually happens is that trip-stripes (i.e. zig zag tapes) are installed around mid-chord at the Pressure Side in order to fix the Laminar-Turbulent transition location and allow the tripped (i.e. turbulent) boundary layer to attach to the rear part of the pressure side of the airfoil. If this part is cambered (i.e. S shaped trailing edge) then the fact that the BL is attached will lead to a lift increase due to the trailing edge camber.

Regarding the suction side I do not see how the VGs would "limit the maximum lift". What they would do is generally control the stall and the post-stall behavior of the airfoil.

Finally the citation provided by the author of that part does NOT state any of the above (false) statements. georgepehli (talk) 09:52, 10 February 2010 (UTC)

Blade Materials Possible Fallacy

In the section on blade materials there is a piece which states : "One of the most important goals when designing larger blade systems is to keep blade weight under control. Since gravity scales as the cube of the turbine radius, loading due to gravity becomes a constraining design factor for systems with larger blades."

Firstly, I do not think the term "gravity" is correct here. Gravity will not increase or decrease significantly depending on how big wind turbine blades are, it's weight may, yes but it's gravity.... I don't think so. Also, there is mention that it will increase with the cube of the radius however the source cited does not confirm or deny this. —Preceding unsigned comment added by Brokengun (talk • contribs) 01:33, 21 December 2009 (UTC)

This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts, without removing the technical details. (September 2010) (Learn how and when to remove this message)

Can the dynamic braking resistor described in this article be at least partly replaced with ultracapacitors? That sounds like it could keep the energy from being wasted as heat and instead captured and trickled off slowly, still providing the needed braking and giving a boost to the turbine's efficiency and output. Only when the capacitors were topped out (and a great deal of capacitance could be used if wanted) would a resistor be used. Or am I misunderstanding how this works and this is not technically possible?

Wind turbine economics

"Due to the energy required to manufacture, transport, and erect the components of wind turbines it is debated if over the life of the turbine this energy will be recaptured.

Also utility companies rely on government subsidies to offset the cost of building wind farms which are two to three times the cost of equivalent capacity produced by coal fired units. After the subsidies run out the wind facility is normally sold to another utlity who begins to draw the subsidies once more."

These assertions don't seem to be relevant, supported or even referenced further within the article - what utility companies? what government? How does this relate to the topic of wind turbine design? Donquixote2u (talk) 02:08, 13 September 2009 (UTC)

Error in Indiana data

Part of the current article says "Indiana had been rated as having a wind capacity of 30 MW, but by raising the expected turbine height from 50 m to 70 m, the wind capacity estimate was raised to 40,000 MW, and could be double that at 100 m.". The citation does indeed say this but I have to assume that something is wrong here. Obviously, raising the turbine height from 50m to 70m can't give a 1000 fold increase in power. The 30MW figure might be the states current output capacity (although NRELs 2007 report doesn't even provide a figure for Indiana). The 40,000 MW figure might represent a theoretical maximum output capacity but the citation doesn't provide a link to the actual NREL data. Either way, it is at best very confusing and at worst completely wrong.

Emphasis on larger wind turbines

Looking through the article it seems to only include the megawatt class turbines and not anything about kilowatt or even watt class turbines. Could someone try putting in more material on smaller turbines? Aicchalmers 14:46, 2 September 2007 (UTC)

Durability

The "Materials" section of the article briefly discusses materials used for modern wind turbine blades. However the durability (in years) or needed maintenance of the blades, the (steel) tower, or the internal parts is not discussed, but this information would be most welcome. (Any evaluation or cited experiences of the durability/maintenance would be turbine-type specific, so in my understanding this page would be the right place, instead of the more general "Wind turbine" page.) (85.156.172.166 (talk) 20:30, 7 March 2008 (UTC))

More in-depth version of article at powerpedia

See The updated article of wikipedia; more information is available here. Perhaps it may be copied to Misplaced Pages ?

Thanks. 87.64.203.222 (talk) 16:47, 4 April 2008 (UTC)

Rotation control

"High efficiency 3-blade-turbines have tip speed/wind speed ratios of 6 to 7" is ambiguous: does the ratio range from 6.0 to 7.0 or is it 6/7? —Preceding unsigned comment added by 71.205.58.127 (talk) 04:24, 4 July 2008 (UTC)

• I assume it means between 6:1 and 7:1. Rocketmagnet (talk) 22:32, 19 May 2009 (UTC)

A dumb question (or two)

This keeps coming up on the Science Refdesk, so I'm going to try to figure it out.

If a three-blade turbine is good, why isn't a six-blade turbine twice as good? Is the only point of a wind turbine to turn the generator at a certain speed? Doesn't the electrical load on the turbine slow the blades down? If that was the case, one would think that twice as many blades would push the electrons through twice as hard (as it were), i.e. you could put twice the load on the generator.

I'm sure I'm missing something here, but it's not completely clear from reading the article so I appreciate any explanation. Thanks! Franamax (talk) 06:15, 22 July 2008 (UTC)

Your first question is in Wind_turbine_design#Blade_count "Increasing the number of blades from one to two yields a six percent increase in aerodynamic efficiency, whereas increasing the blade count from two to three yields only an additional three percent in efficiency. Further increasing the blade count yields minimal improvements in aerodynamic efficiency and sacrifices too much in blade stiffness as the blades become thinner." Mion (talk) 06:29, 22 July 2008 (UTC)

Yes, that's where my dumb questions multiply.

• What does that mean, a six percent increase in aerodynamic efficiency - 6% of what? Where is "aerodynamic efficiency" defined?
• And more, sacrifices too much in blade stiffness as the blades become thinner - I told you to add more blades, I never asked you to make them thinner. What happens when they stay thick?
• And what does thick/thin refer to - length of the blade (trailing not radial)? profile presented to the wind? aerodynamic thickness of the blade itself?

Thanks for the quick response so far! Franamax (talk) 12:46, 22 July 2008 (UTC)

here Drag (physics) you improve the aerodynamic efficiency by lessening the friction forces (mostly), and looking at your other question, this was my last answer on this page. Cheers Mion (talk) 13:01, 22 July 2008 (UTC)

OK, so where do the friction forces lessen? Does that mean there is better balance on the central bearings?

And I'm not sure what you mean by my last answer on this page - an archived answer? Franamax (talk) 13:10, 22 July 2008 (UTC)

"I told you to add" , i'm not your dog, so please mind your language. Mion (talk) 13:20, 22 July 2008 (UTC)

Ohh, finally I get it - you're taking things personally. No, that was a figure of speech, a rhetorical formulation or what have you. Not a personal comment to you, not at all. The comments were actually directed to the disembodied voice of the article text (and if you wrote that text, then sorry again I guess :), asking the article to make itself more clear. I apologize for any misunderstanding, I'll plead the fact it took me this long to figure it out as evidence of my sincerity. Sorry :)

I try to approach technical questions directly, it's often the best way to get direct answers. Hopefully someone will tackle the questions because it's just not clear to me. Thanks. Franamax (talk) 19:13, 22 July 2008 (UTC)

he, no hard feelings, Cheers Mion (talk) 20:07, 22 July 2008 (UTC)

I must agree that I don't feel that this article has answered the question fully: Why not have 6 blades? Indeed, small turbines seem to have more blades. Also, the bit about aerodynamic efficiency could be explained a little better I think. What exactly is the input power in this case? Thanks Rocketmagnet (talk) 22:38, 19 May 2009 (UTC)

The 3rd paragraph in the Blade Count section especially needs more clarification. Quantalume Wanderer (talk) 04:26, 5 January 2010 (UTC)

Reference on the increased aerodynamic efficiency

It would be a good idea to have a reference for the increase in the aerodynamical efficincy of the wind turbine with the increasing number of blades —Preceding unsigned comment added by 193.190.163.52 (talk) 09:29, 19 August 2008 (UTC)

How is the electricity from the head mounted Generator transmitted to the tower as the head yaws?

Surely if it was hard wired the wires would tangle? Some sort of slip ring to allow the transfer of power must exist, but not mentioned in the article. How about transferring the rotation of the power shaft through a crown gear - ie rotate 90 so as to be inline with the tower. then mount the genny on the tower vertically, and wire it up? —Preceding unsigned comment added by 82.30.126.139 (talk) 13:56, 24 February 2009 (UTC)

When the turbine controller detects that the power cables have been twisted by three rotations, it shuts the machine down and untwists them. --24.65.122.222 (talk) 02:50, 2 March 2009 (UTC)Wally Flint

The generator section is unclear

The generator explanation changes back and forth from asynchronous to synchronous machines and merges explanations from several different technologies. We should clearly define the different methods. —Preceding unsigned comment added by 74.98.33.199 (talk) 20:50, 13 June 2009 (UTC)

Induction Generator

This is NOT correct:

"Older style wind generators rotate at a constant speed, to match power line frequency, which allowed the use of less costly induction generators."

As odd as this might seem, a Tesla motor/generator (so-called squirrel cage rotor) does not need to run at a constant speed. It does need to run at a narrow speed range to function as a generator. It has a synchronous speed (ω) which is a function of the AC frequency (f) and the number of poles (n): ω = 120f/n. When used as a motor, it runs at less than that speed. The difference is usually called slip. As slip increases, the motor will produce more and more torque till the maximum is reached. If connected to a load, the motor will then stall. When used as a generator, it must be driven at a speed greater than the synchronous speed. As with use as a motor (but in reverse), the power produced increases as the slip increases until it reaches a peak. If that slip rate is exceed, the generator will produce less power. If slip continues to increase, a point will be reached where no power is produced and if that slip is exceeded, it will start absorbing power from the grid.

Tyrerj (talk) 22:38, 31 July 2010 (UTC)

Image

Can someone take over the picture at http://express.howstuffworks.com/gif/wind-power-horizontal.gif for the construction and design section ? Upload at wikimedia commons and show image here —Preceding unsigned comment added by 91.176.215.15 (talk) 10:49, 12 September 2009 (UTC)

No, because it is copyrighted, and belongs to the website... - Adolphus79 (talk) 13:08, 12 September 2009 (UTC)

I already took over the image myself, legally. Perhaps that the EERE_Illust_large_image may be imbedded to the image; the image I draw thus being the larger whole, and the with the EERE image as magnification of the head of the turbine (as it contains more info). The large picture has added info as it mentions the nacelle, rotor blades, rotor hub and transformer. See

91.182.191.178 (talk) 17:04, 12 September 2009 (UTC)

Image 2

Added this image, needs CGI'ing dough

Blade Shape

My 81-yr old mom asks a very elementary and important question, "What was wrong with the 4-arm dutch windmills of the 1800's ?? Why do modern wind turbines have such a different shape?" We should try to address this question early in the subsection about blade shape.

Also, from a cursory reading of the article, I cannot figure out what are the primary, secondary, and tertiary design criteria for a windmill blade design. Thus, this article fails to address a fundamental question about turbine design. For example, what's more important to efficient power generation, torque (which probably implies large blades), blade speed (which probably implies small blades), or availability (which probably implies lowering the stall windspeed, and thus blade mass and generator resistance and having variable pitch, so the turbine can generate power all the time)? SystemBuilder (talk) 18:55, 27 February 2010 (UTC)

Qn: mathematical analysis of the cyclic stresses in the blade root while rotating

Dear All,

When wind turbine rotor rotates it's blades especially blade roots undergo cyclic stresses. These stresses are due to gravitation forces and inertial forces.

Could any body of you explain me how these cyclic forces vary? I am interested to know the basic mechanics of these forces for example what would be the stress level in a blade root when the blade is perpendicular to group (pointing towards ground or sky), or the stress level when a blade is horizontal etc....(I am not much interested in Aerodynamics forces, since for steady mean wind flow they are constant)

Apart from basic mechanics of these stresses I would also like to go in the details of mathematical analysis of this phenomenon. So could you please suggest me some good reference book, lecture notes or any other written material.

thanks a lot in advance,

regards, Milind. —Preceding unsigned comment added by Milindashokshende (talk • contribs) 14:08, 26 May 2010 (UTC)

ARTICLE has focus challenge per title

The title would invite consideration of design of any type of wind turbine, not just the towered HAWT. VAWT and other types ...belt, airborne are neglected. So, the sentence :"This article covers the design of horizontal axis wind turbines (HAWT) since the majority of commercial turbines use this design" is POV on "commercial" and does not count well, as VAWT and other sorts have a count that might be more than the count of the HAWTs.

WP:Notability and WP:SPLIT applies here. This article already has a reasonable size, and additions about VAWT, small or non-commercial types could be mentioned here but is best expanded upon in the relevant articles Unconventional wind turbines, Vertical axis wind turbine, Darrieus wind turbine, Savonius wind turbine, Small wind turbine and the like. The vast majority of wind energy production is made from large grid connected commercial HAWTs (as per and maybe ), they happen to be commercial because that is what is feasible. As for a non-commercial wind turbine, see free to copy I guess, but so far feasibility seem to overwhelmingly prefer commercial solutions. TGCP (talk) 13:18, 18 December 2010 (UTC)

Wind Turbine Noise

I would question the statement in the current version (May 9) that the noise varies with the 5th power of the tip speed. If that were true the Vestas V47 (229 fps at nominal rotational speed) would be noisier than the Vestas V82 (202 fps at nominal rotational speed). There seems to be broad agreement that the reverse is true. —Preceding unsigned comment added by Carlfoss (talk • contribs) 22:43, 9 May 2011 (UTC)

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