The Physics of Wind Turbines

This section gives a quick overview of the parts of a wind turbine and how it works. For more information click here or visit the links page.

The Parts of a Wind Turbine

There are four main parts of a wind turbine: the base, the tower, the nacelle and the rotor (hub and blades assembly). The base acts as an anchor that supports the entire assembly so it doesn't fall over, the tower supports the nacelle and rotor and contains the electrical conduits, the nacelle contains the electric generator that makes the electricity, and the rotor assembly converts the energy of the wind to rotational motion.

The Rotor

The blades of modern wind turbines are aerodynamic wings that create lift as wind blows across them. Older wind turbines use the force of the wind pushing against them to turn. This occurs because the wind is deflected by the blades (since they aren't parallel to the wind), and the force the wind exerts on the blades is converted to motion in the opposite direction. Turbines with aerodynamic wings are more complicated, but they work in a similar manner (see section below). The blades are connected to a central cone called the hub, which is in turn connected to an axle that passes into the nacelle.

The Nacelle

The nacelle is a small room at the top of the tower that contains the axle, the gearbox, the generator and other equipment. The axle passes through the front of the nacelle, into a gearbox and then into the generator. The gearbox can be used to adjust the speed of the axle, depending on the wind speed. The generator creates AC power, which is transported from the nacelle by large cables. Other equipment might also be present, depending on the sophistication of the turbine. Some turbines use electronics to adjust the direction in which the nacelle points, or the pitch angle of the blades, in order to increase the amount of wind energy captured. As well, the nacelle can be reached by ladder so that people can access it in case some of the components need repair.

The Tower

The tower usually consists of a hollow steel cylinder that is 40 to 60 metres tall. Some turbines use a different tower design, using a steel lattice or concrete instead. Inside there is a ladder for access to the nacelle, a hoist for moving equipment to the nacelle, and conduits for the electrical cables.

The Base

The base supports the entire wind turbine assembly, and it is essential that it be large enough that the turbine will never blow over. Usually, the base is constructed from concrete, re-inforced with steel bars. It is usually made in the shape of a large cylinder, around 10 to 15 metres in diameter. This cylinder is buried underground so that the turbine assembly is well anchored.
 

How Wind Energy is Converted to Mechanical Energy by the Rotor

This section gives a high level overview of how the blades of the turbine convert energy from the wind into rotational motion of the rotor. For an in-depth description of how this works, click here.

The blades of modern wind turbines are similar to airplane wings, in that they use lift to enhance their conversion of the wind's energy. The way this works is that as air blows across the blades it splits into two parts - some of it goes over the top of the blade (A) and some of it goes under the bottom of the blade (B). The air blowing across the top is compressed into the air above it. As the air travels further across the blade, it begins to decompress and the pressure drops, creating a low-pressure area. This low-pressure area causes the air above it to be sucked down across the rear of the blade. The air blowing across the bottom of the blade also gets compressed as it moves across its width, but not to the same extent as the air above. As the compressed air travels across the blade, its speed and pressure gradually match that of the wind coming over the top of the blade. Together, these two effects create the lift (C) that causes the wind turbine rotor to rotate. Additionally, there is some drag caused by air friction (E) that slows the blade down, so that the force that is actually exerted on the blade is in the direction of D.