Anatomy of a Wind Turbine: Page 3 of 3


Inside this Article

Turbine head
Rotor, stator, diode rectifier, slip rings, and bearings exposed on a Bergey XL.1 1 KW generator.
Blade's airfoil
A cross-section of an extruded carbon-fiber blade shows the airfoil shape.
The stator from a 10 KW Bergey Excel showing multiple windings. A bearing in the center supports the rotor.
Slip rings, brushes, bearing
Slip rings and brushes, and yaw bearing assembly from an ARE wind turbine.
One feature of Southwest Windpower’s controller is to rectify the turbine’s AC output to DC for battery charging.
Before regulating
As the wind approaches this turbine’s rated speed for maximum power, the rotor begins to swivel out of the wind to prevent overspeed. (Before)
As the wind approaches this turbine’s rated speed for maximum power, the rotor begins to swivel out of the wind to prevent overspeed. (After)
Turbine head
Blade's airfoil
Slip rings, brushes, bearing
Before regulating

Governing System

To a novice, high winds seem like a bonus. But to seasoned wind-energy users and turbine designers, once the wind turbine is already going flat out, stronger winds become a cause for concern. Doubling the wind speed makes eight times as much power available, and also increases the thrust force on the turbine and tower by a factor of four.

A turbine should be able to shed excess force, or it will overspeed, burn out, or self-destruct in some way. Protection from strong winds, called governing, can be accomplished either by furling or by blade pitch-control. The most common governing system is a furling tail that steers the rotor out of the wind. Some machines twist the angle (pitch) of their blades toward stalling, which decreases their efficiency and prevents overload. Both of these systems are passive, in the sense that they are driven by the force of the wind, or by the speed of the blade rotor. Very recently, electrical braking also has been introduced to automatically control a turbine’s speed.

Putting It All Together

In an effective wind generator design, all of these systems and components are carefully matched to each other. For example, the alternator must produce power at the best rotational speed (rpm) to get the most power from the blade rotor. Too slow and the rotor will stall; too fast and the machine will be noisy and ineffectual in low-speed winds.

Of course, a complete wind-electric system is much more than just the turbine. Other major components are the tower, rectifier, charge controller and dump load, battery bank (if needed), inverter, and metering. Several of these components can be more expensive than the turbine, and all of them need to be considered as you design a complete system.

The bottom line is to buy a turbine that is robust, simple, low speed, and reliable. Talk with experienced wind-energy users to find out which turbines stand the test of time. Heavier wind turbines with larger swept areas are usually more expensive, but more durable.

Focus on the energy the turbine makes, not its peak power. The energy will depend on the swept area and the average wind speed at the tower top. A small rotor on a short tower will not generate much energy. Remember that low and medium wind speeds are the most frequent, and therefore the most important. Do it right and you can share our glee in wind energy.


Ian Woofenden, PO Box 1001, Anacortes, WA 98221 •

Hugh Piggott, Scoraig Wind Electric, Dundonnell, Ross Shire, Scotland, IV23 2RE • 44-018-54-633-286 • Fax: 44-018-54-633-233 •

Major U.S. Turbine Manufacturers/Importers:

Abundant Renewable Energy • 503-538-8298 •

Bergey WindPower Co. • 405-364-4212 •

DC Power Systems • 800-967-6917 • 

Pine Ridge Products LLC • 406-738-4283 •

Southwest Windpower • 866-807-9463 •

Wind Turbine Industries Corp. • 952-447-6064 •

Additional Reading:

“Apples & Oranges: Choosing a Home-Sized Wind Generator,” by Mick Sagrillo in HP90

“Wind Generator Tower Basics,” by Ian Woofenden in HP105

“Wind-Electric Systems, Simplified,” by Ian Woofenden in HP110

Wind Power: Renewable Energy for Home, Farm, and Business, by Paul Gipe, 2004, Paperback, 496 pages, ISBN 1-931498-14-1, $50 from Chelsea Green Publishing Co. • 800-639-4099 or 802-295-6300 •

Comments (6)'s picture

The most efficient wind device ever conceived is the Mag Lev Vertical

Ian Woofenden's picture

I'm guessing that this idea/device is most efficient at separating dollars from investors (and perhaps homeowners) wallets.

The physics of vertical designs is not promising -- see and .

In addition, it's a mistake to put much focus on "efficiency" with wind turbines. They capture a free and abundant resource -- not a resource you have to pay for. So while capturing it more efficiently is useful, it's not as important as capturing it cost effectively. Hitting a specific efficiency number doesn't matter compared to what you pay for your kilowatt-hours over the lifetime of the machine.

And in the end, _reliability_ is the key measure of wind turbines. The "most efficient" wind turbine will make _very_ expensive energy if the machine only lasts a few months or years. The goal of wise wind turbine owners is a machine that reliably pumps out the kWh for years and decades. History shows that vertical designs and companies to not give this satisfaction. I recommend looking for products with a long track record, substantial warranty, and stable company that supports them.

Ian Woofenden, Home Power senior editor, and author of Wind Power for Dummies's picture

So do you even know What Vertical Axis Magnetic Levitation actually means?
cause if you did you know your statement is categorically wrong...
When you remove the bearings that ware out overtime, as well as the friction they intern create...
Why you can blow on the turbine with your own breath and make it spin...


Ian Woofenden's picture

There are many "brilliant ideas" that don't actually pan out in the real world of physics and business. While reducing bearing friction may be useful (though a minor factor), the bigger question is at what cost, and with what reliability. My experience -- and that of most long-time wind energy observers -- is that keeping it simple actually ends up making more kWh over the life of a machine.

A broken or very expensive machine that is "much more efficient" is actually not too useful. The bottom line is the cost per delivered kWh over the life of a real machine, not something that sounds like a good idea, but can't actually be purchased and operate for decades, providing energy to real people.

I'll continue to recommend tried and true machines from long-term manufacturers with warranty, support, and track record. The wind industry is full of distracting, time-and-money-wasting ideas and schemes. The real companies, products, and ideas last for decades and don't rely on hype or hyper marketing.'s picture

Oh I see.... it is that exact narrow mined thinking that has lead to no R&D into the subject matter in over 15yrs...
except one... little outfit not very well known Advanced Technology Industries (plural more than one Industry)
we have a 10mw system that will be deployed on the top of landfills as the "new standard" 4way hybrid Renewable Generation stations
worldwide starting July 2016

Shinning example of your defeatist attitude:
the electric car would have been the over welling car of choice on the highways today if what happened in 1992
never happened....i believe you get the picture...
Had Columbus listened to all those others saying you idiot...your gonna fall off the earth and never be heard from again...

Michael Welch's picture

Hi Solar Man. I suppose you are right, after many decades of either failed R&D involving vertical axis wind generators or the final products just not making it in the market for whatever reasons, my own views on the issue have been narrowed similar to Ian Woofenden's.

Home Power is not against research, but what we are against is touting technologies that aren't going to do what the customer needs. It's great to be excited about new possibilities, and that IS important to bringing new and successful technology to market.

But as a promoter of and a consumer of renewable energy technology, I flat out want stuff to work.

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