Civil Engineering Reference
In-Depth Information
FIGURE 5-5
Tower heights of various capacity wind turbines.
relatively taller than the blade diameter, and generally unattended, requires
low maintenance design. On the other hand, the large machine tends to
optimize the aerodynamic performance for the maximum possible energy
capture. In either case, the blade cost is generally kept below 10 percent of
the total installed cost.
5.1.3
Yaw Control
The yaw control continuously orients the rotor in the direction of the wind.
It can be as simple as the tail vane, or more complex on modern towers.
Theoretical considerations dictate free yaw as much as possible. However,
rotating blades with large moments of inertia produce high gyroscopic
torque during yaw, often resulting in loud noise. Too rapid yaw may generate
noise exceeding the local ordinance limit. Hence, a controlled yaw is often
required and is used.
5.1.4
Speed Control
The wind turbine technology has changed significantly in the last 25 years.
1
Large wind turbines being installed today tend to be of variable speed
