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Clean Power how wind turbines work

Published on March 1st, 2012 | by Charis Michelsen

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How Wind Turbines Work



 
Wind-generated electricity is one of the first images that comes to mind when someone says “renewable energy.” New wind farms—both massive and not so much—are under construction all over the world. But do you know how wind turbines work? It’s actually very cool.

how do wind turbines work

The image of a wind turbine is pretty familiar—it’s basically a massive three-bladed pinwheel on top of a huge stalk (in most cases). I’ve seen dozens of clusters while driving south through Illinois, and I’m sure most people have similar experiences. The blades turn (slowly) as the wind blows, generating electricity.

The Visible Bits

The pole supporting the moving parts of the wind turbine is called the “tower” (surprise, surprise). Directly on top of the tower is the nacelle, which is the housing for all the parts of the wind turbine that aren’t the giant blades.

Outside the nacelle is the most recognizable part of a wind turbine, the three blades attached to the hub in the middle. In slightly more technical terms, this assembly is called a rotor. Pitch motors in the hub allow the angle of the blades to be changed so that they can meet the wind.

Also outside the nacelle are the anemometers (wind vanes), which tell the turbine control system how fast the wind is and in what direction it’s blowing (no use in being able to adjust the blades if something isn’t telling them how to be adjusted).

The Inside Parts

Inside the tower are ladders for (relatively) easy access, and cables to export the electricity. Since the height of a wind turbine can range anywhere from 315’ to 540’, that’s not a ladder I’d want to climb (although better the ladder than attempting to scale the outside of the tower).

Inside the nacelle, the main shaft of the hub connects to a gearbox and a brake. Since rotor speeds are usually around 10-20rpm, which is utterly useless for generating any kind of power, the gearbox is responsible for converting that speed to something like 1,500rpm—much, much better for generating electricity.

The final component inside the nacelle is the generator, which is connected to the gearbox and the brake. It takes the 1,500rpm rotational energy and converts it into electrical power. The power is then sent out of the turbine through the cables running down the length of the tower.

It All Comes Together

how wind turbines work

A wind turbine can start producing power at wind speeds of 7-11 mph, but it reaches its full output at wind speeds of around 29mph. If it’s been appropriately placed, the turbine will generate over 40% of its maximum capacity over the course of each year it’s operational.

Questions or comments? Let us know below.

Source: The Guardian | Images: Wikimedia Commons

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About the Author

spent 7 years living in Germany and Japan, studying both languages extensively, doing translation and education with companies like Bosch, Nissan, Fuji Heavy, and others. Charis has a Bachelor of Science degree in biology and currently lives in Chicago, Illinois. She also believes that Janeway was the best Star Trek Captain.



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  • Dave2020

    Hi Bob,

    “30 meters is not a vertical mill sitting on the ocean surface.”

    Nobody’s ever suggested “sitting on”. Where did that come from? Look at the wind gradient graph.

    The point is, the heavy ‘nacelle’ is 90m lower down! A huge difference in C of G.

    The VAWTs pictured in the links I gave are obviously mounted clear of anything other than a freak wave.

    • Bob_Wallace

      Strength of tower and foundation/ballast is going to be determined by highest wind conditions.

      If you can’t reduce the wind resistance of a VAWT in heavy storm conditions then you’re going to have to make one strong/steady base for it.

      Have you seen anyone build a great big (comparable to current offshore HAWTs) several meters off the ocean surface?

      • Dave2020

        My floating design can’t possibly overturn and as I’ve said, the VAWT would be of a size and robustness to suit the operating conditions. It would obviously move under a high side load, but that’s a good thing isn’t it?

        Unlike the VAWTs I linked to, which I assume are designed to survive being parked in a storm, mine would still rotate (so one blade doesn’t have wind loading concentrated on it) and pump up the hydro accumulator.

        The VertAx is rated at 10MW. Maybe it’s designed for low-cost blade replacement?

  • Pingback: Floating Wind Turbines May Be Coming Soon to a Beach Near You

  • Dave2020

    In response to idyl:

    Sure thing, and as the wind speed rises above 15m/s you have to modulate the turbine by adjusting the blade pitch, otherwise it will over-speed. So, there’s more energy available, but it can’t be utilized. Then above 25m/s the turbine is usually stopped, with blades furled.

    At sea, the winds are evidently strong enough closer to the surface. HAWTs would still fail to capture all the potential energy above 15m/s – they’d still be furled in gales. Advanced VAWTs with rotation controlled by pump displacement could do better. The choices are – a power output that varies with the weather, or certain, constant MWs from storage at the flick of a switch.

    300 tons 90m above the sea is OK if it has a sea-bed foundation, but on a floating platform it needs a huge volume of superstructure just to stabilize it. That’s wasteful and expensive, unless you put it to good use by adding wave power AND storage.

    • Bob_Wallace

      ” At sea, the winds are evidently strong enough closer to the surface ”
      Got data?

      • Dave2020

        Still looking for precise data, but here is another factor that affects HAWTs, but is not an issue with VAWTs:

        “The reduced wind gradient over water means shorter and less expensive wind turbine towers can be used in shallow seas.” – Wikipedia, wind gradient.

        • Bob_Wallace

          I haven’t been able to find anyone claiming that locating turbines close to the surface is ‘best practice’. I find papers where wind speeds are collected at a lower altitude, say 10 meters, and then speeds at higher altitudes (80 meters) are calculated.

          If you’re on land and have a lot of “disturbances” on the surface then you have to move higher to get to less turbulent air. You’d need to increase your hub height considerably if your were just down wind of a city with a lot of tall buildings as opposed to being on a expansive, smooth plain.

          Think about wind close to the water. Wind traveling over the water, in contact with the water is loosing energy to friction. That energy makes waves. Some energy is used up at the water’s surface.

          Additionally that frictional interact is almost certainly to cause turbulence. The wind closest to the water is being slowed by friction. That’s going to disrupt the wind just above.

          In the meantime, the wind higher up continues along, suffering none or only very little of the disruption.

      • Dave2020

        This CHINA-US ECOPARTNERSHIP has broken ranks with the majority view.

        http://floatingwindfarms.com/projects.html

        Looks like the ideal air starts at 50m. But they don’t seem too concerned. Maybe it’s good enough at 30m? They show a graph of the wind gradients on land and offshore, argue their case and have money!

        http://floatingwindfarms.com/swas.html

        VertAx have a different approach.
        Their generator runs at 4 r.p.m!

        http://vertaxwind.com/technology.php#electrical

        VertAx Wind Limited was formed in 2007 out of Eurowind Developments Ltd with the objective of developing a multi-megawatt wind turbine generator for use specifically offshore. The company’s aim is to substantially reduce the cost of offshore wind energy whilst re-establishing a wind turbine manufacturing activity within British industry and thus creating new ‘Green Jobs’ within the United Kingdom.

        The company’s strategy is to develop a design that is simple, robust and cost effective, whilst moving away from traditional supply chains. Longevity, reliability and low maintenance costs are key areas of consideration.

        • Bob_Wallace

          30 meters is not a vertical mill sitting on the ocean surface.

          So let’s go back to my original criticism. Put all that hardware up in the air, hardware that can’t be furled, and you’ve got to engineer a lot of resistance to storm winds.

          VAWTs might have an advantage in lower speed, fluky winds but the idea is to install turbines where the winds are most often strong and steady. There’s a chance that VAWTs might be better for things like the tops of buildings, but that a small niche market.

  • Dave2020

    Thanks Bob, this is a useful exchange of views.

    “Every VAWT I’ve seen has been mounted very close to the ground. I’ve never seen one mounted 80 meters in the air, where the cleanest wind tends to start.”

    This was Hywind project manager Sjur Bratland’s view on the standard HAWT in 2009.

    “For the purposes of floating wind farms, such turbines are not light enough, they are too tall and the rotor blades are too small, according to Mr Bratland’s early assessments, made even before the 2.3MW turbine started delivering electricity through the sea-bed cable connecting it to the Norwegian national grid.”

    “He wants turbine manufacturers to produce lower turbines, to take advantage of winds blowing strongly and steadily close to the surface of the sea.”

    “Lower turbines should, together with clever design and material selection, help reduce the turbines’ weight, and thus their need for ballast, which in turn should reduce sub-sea costs.”

    “At the same time, Mr Bratland wants the power output of each turbine to be raised to perhaps 6MW, and he wants it all to be cheaper than it is today.”

    Seems to me, some of his “wants” are mutually exclusive, perhaps unattainable.

    “Technip was previously involved in the design and development of the floating structure for the Hywind project in Norway.”

    Technip say – “An offshore VAWT has the main advantage over horizontal axis turbines in that it doesn’t require a foundation upon which to be installed.”

    Which suggests to me that their experience with Hywind led them to conclude that HAWTs are best mounted on sea-bed foundations and VAWTs are much better for floaters.

    “(VAWTs) leave some parts of the blades exposed to all wind.” Yes, but if it’s rotating a strong gust of wind is dissipated better. After all, energy is being transferred into storage.

    “A couple of organizations have talked about building some of these puppies.” I’d like a link to them please.

    “Any storage that can serve more than one function is going to pay for itself quicker than single use storage.”

    Yes, you’re right. That is just ONE basic premise of the design. It stores energy from wind and wave directly, and also serves as negative reserve, taking surplus power off the grid. When you plan to deploy several thousand installations, even a modest 10MWh capacity per unit soon adds up to an efficient grid-smoothing facility, which could obviate the need for HVDC interconnectors to new (or existing) pumped storage, or grid batteries, in future. Dispersed negative reserve is more dependable too.

    Predictions by UK National Grid in 2009, on the assumption that new energy storage has not been built:-

    “Interconnectors are used by market participants to export excess generation.”

    “Our negative reserve requirement increases to 2,600MW to cater for the loss of an exporting interconnector.” (all your eggs in one basket?)

    “We need to curtail wind for 4 hours on average a night.”

    “Costs to pull back wind and place on response are estimated at around £1.6m per occasion in 2020.”

    Maybe NOT investing in storage now would be a false economy?

    High wind events are predictable hours or even days in advance, so the stores would be run down in readiness. Instead of shutting down turbines for safety or curtailment, surplus power is stored, which prevents surges on the grid. Tackle the problem at source, I say. If you generate electricity, store it, then put it back in the grid, it is an inefficient round trip.

    • Bob_Wallace

      “He wants turbine manufacturers to produce lower turbines, to take advantage of winds blowing strongly and steadily close to the surface of the sea.”

      Think about it. Why would several different companies (and countries) put their offshore turbines 80 or so meters in the air above the ocean’s surface if the wind blows strongly and steady close to the surface of the sea? Do you really think all those (probably hundreds) of engineers didn’t study wind speed and variability prior to committing to that height?

      You think the bean counters let them spend those extra billions if they could have produced the same power with a much shorter tower or egg-beater turbines?

      Clearly this guy got it wrong – “Technip say – “An offshore VAWT has the main advantage over horizontal axis turbines in that it doesn’t require a foundation upon which to be installed.””

      We’ve got floating HAWTs.

      ““A couple of organizations have talked about building some of these puppies.” I’d like a link to them please.”

      One was in Texas and the other in the Midwest. I didn’t save the links, so
      you’ll have to Google. The Texas plan was a CAES system, if I remember
      correctly. Rather than generators behind the blades it had an air
      compressor.

      If you think about it, that’s a lot of extra gear. An air compressor and
      air storage facility. Needs gas to heat the air up before it feeds into
      the generating turbine.

      ““(VAWTs) leave some parts of the blades exposed to all wind.” Yes, but if
      it’s rotating a strong gust of wind is dissipated better. After all, energy
      is being transferred into storage. ”

      If you can’t “park” the blades in very high wind the rigs tear themselves
      apart. I seem to remember that happening to a turbine in the UK recently.
      There was a failure of the blades to align with the direction of the wind
      and the system was overloaded.

      “Maybe NOT investing in storage now would be a false economy?”

      From what I’ve read we just aren’t there yet. We’ve got a lot of
      dispatchable power already built and most of the time we just turn some of
      it off when cheaper wind is available. Battery storage is approaching a
      profitable price point and utilities are starting to experiment with it,
      but I’ve seen no one claim that it is now cheaper than alternatives. My
      guess is that prices will fall enough in the next couple of years to allow
      batteries to start replacing gas peakers. What we’re investing in right
      now, and what makes the most sense to invest in, is battery development.
      Sodium-ion batteries look very promising. They are built with inexpensive
      materials and it looks like they will have long cycle lives.

      Battery storage closer to point of use has all sorts of advantages over
      pump-up hydro, CAES /’underwater bladders’. Getting storage close to point
      of use means that transmission needs are lessened. Grid disruption is less
      of a problem in the event of damaging weather, etc. Batteries are
      extremely quick to react. And they can store electricity from any source.

      I don’t have a crystal ball, so I try to use “crowd sourcing” as a
      predictive tool. I’m hearing more and more about batteries and very little
      about new pump-up or CAES. Seems to me that the folks with the best access
      to inside information are heading toward batteries.

  • Bob_Wallace

    Since the wind industry put up some VAWTs several years ago and went pretty much 100% to HAWTs I sort of think they’ve figured out HAWts work better.

    Better performance in variable wind is not a particular advantage. Variable winds are generally not very strong.

    What might seem intuitively correct to you doesn’t seem to have proven itself to the many engineers who design and test turbines.

    • Dave2020

      Hi Bob,

      Thanks for your reply. I agree with what you say about variable wind. I know that’s the most insignificant of the points I raised. What about all the other design changes? (and still running in gales) I was specifically dealing with floating designs, you understand, which is why C of G should be factored in.

      None of the “many engineers” you mention has built a turbine that feeds power direct to storage, instead of to the generator, so what can they “have proven”?

      I would welcome your views in greater detail, addressing all the issues. Dispatchability becomes ever more useful as the market penetration of every type of ‘intermittent’ renewable energy increases.

      • Bob_Wallace

        Since turbine designers put offshore turbines way up in the air rather than down low where it would be cheaper/easier to install and service I’m going to guess that the wind up high is better than the wind close to the surface. Just like it generally is on land. (There are some rare exceptions on land.)

        Every VAWT I’ve seen installed or in an illustration has been mounted very close to the ground. I’ve never seen one mounted 80 meters in the air, where the cleanest wind tends to start.

        Is there any information that shows that a VAWT has less mass than a HAWT, equated for output? Unless the VAWT is significantly lighter then ‘center of gravity’ doesn’t matter.

        Has anyone designed a VAWT that can be furled in extremely high winds. The designs I’ve seen leave some parts of the blades exposed to all wind
        directions. It’s not just center of gravity considerations, it’s also amount of force on the tower/base in heavy storm conditions.

        Feeding wind power straight to storage. At least a couple of organizations have talked about building some of these puppies. But so far as I know no one has gone forward with this idea. Storage adds cost and at this point the grid can incorporate the wind generation we have plus some more without the expense of storage.

        My guess is that we won’t go to direct storage of wind energy. Almost all the activity I see is aimed at large scale battery storage. Batteries, as opposed to dedicated wind storage, are indifferent as to the electricity source. If there’s extra solar on the grid or extra hydro on the grid or even extra fossil/nuke on the grid batteries can tuck that power away and spit it out when needed.

        Any storage that can serve more than one function is going to pay for itself quicker than single use storage.

      • idyl

        Power output rises as a cube of the wind speed. If wind speed doubles, power output increases by factor eight. You get far better performance with higher hub heights (where wind speeds are faster) than lower to the ground (trying to capture wind variability using turbines that are very efficient).

  • Anumakonda Jagadeesh

    Good illustration on Wind Turbines for general reading.
    Dr.A.Jagadeesh Nellore(AP),India
    E-mail: anumakonda.jagadeesh@gmail.com

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