Anatomy of a Wind Turbine


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

For thousands of years, people have been harnessing the energy of the wind. A fascination for wind energy has driven both of us to build, buy, install, and maintain our own machines for the last three decades. Chances are that the first wind-energy users were driven by the same maniacal glee that we experience when we grab energy out of thin air.

The design of home-scale wind-electric generators has been through many permutations and variations, with lots of circles and dead ends. But most of today’s modern wind-electric generators are surprisingly similar. This article will help you understand each part of a typical wind generator, and how it functions in the overall design.

Rotor (Blades & Hub)

“Rotor” is just a fancy word for a wind turbine’s blade assembly—the part that rotates. (There are actually two rotors—the blade rotor, and the magnet rotor in the alternator or generator, which is driven by the blade rotor.) The wind generator’s blades are the energy collectors. After the wind itself, the circular area that the rotor sweeps is the most important factor in determining how much power the machine can generate. The swept area of the rotor depends on the square of the diameter. Compared to a 5-foot-diameter rotor, a 10-foot one will be twice as wide, and twice as high. Doubling the diameter gives access to four times as much wind, and usually results in four times as much power.

Most modern wind turbines have three blades. Blades are usually made of plastic, often in a composite with fiberglass, or sometimes out of wood. Rotors with more than three blades have more start-up torque, but actually produce less power at high speeds. Two-bladed rotors can work at even higher speeds than their three-bladed counterparts, but can be noisy and also vibrate when the wind changes.

Mechanical power is a combination of speed and torque. Wind-electric generators need to spin at relatively high rpm and at low torque, unlike water-pumping wind machines, which need low rpm and high torque. 

For home-scale wind generators, the blade rotor drives the magnet rotor directly. This design is the simplest and most efficient way to collect the wind’s energy. Adding belts, pulleys, gearing, or any other indirect transmission will incur losses, as well as require more maintenance.


Most modern small-scale wind turbines employ permanent magnet alternators (PMAs). Electricity is generated when a magnetic field passes a wire. In a PMA, magnets move relative to coils of wire (windings). In one popular configuration (as shown in the diagram above), the magnet rotor is a rotating “can” that spins outside the coils. The magnets are on the inside (facing the coils) and the blades attach directly to the front of the can. These PMAs usually generate wild three-phase AC, which is not usable by appliances directly. Instead, this energy is rectified (converted to DC electricity). After that, it can be used as DC or inverted to AC electricity for AC appliances. Traditionally, the energy has been stored in batteries, but in many modern wind-electric systems, it is fed straight into the household grid supply.

Tail Boom & Vane

The tail of a wind generator orients the turbine into the wind. When the wind changes direction, it pushes on one side of the tail, swinging the turbine around to face and collect wind energy. In tail-furling designs, the tail is also involved in protecting the turbine from high winds (see Governing Systems), and tail and boom length are designed carefully for weight and area. Changing these parameters can change the way the machine operates—so don’t do it.

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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