wind turbine types
Wind turbines have two main design categories: horizontal and vertical axis. The horizontal-axis turbine typically has a three-blade vertical propeller that catches the wind face-on. The vertical turbine has a set of blades that spins around a vertical axis. Each type has its advantages and disadvantages and is suited to different environments.
Wind Direction and Speed
To work properly, the horizontal-axis turbine needs the wind to flow at a right angle to the blades. If it blows from a different direction than the blades are facing, the turbine gets much less energy from the wind. To accommodate changes in wind direction, the turbine has a yaw drive that rotates the unit’s direction. However, the drive adapts slowly to changing directions because it must turn the entire turbine and propeller assembly. By contrast, a vertical turbine runs well regardless of wind direction, making it better-suited to urban areas with tall buildings where wind turbulence is a given. The vertical-axis design allows it to operate on lower wind speeds than is possible with the horizontal turbine.
Wind Energy Efficiency
Horizontal-axis turbines convert more of the wind’s energy into useful mechanical motion because the blades are perpendicular to wind direction, and the blades pick up the energy throughout their range of movement. By comparison, the blades on a vertical-axis turbine suffer an efficiency disadvantage, capturing energy from the wind only on the front side; at the rear part of their rotation, they drag on the system.
Mechanical Complexity and Stress
Because it requires a yaw mechanism to adjust to changing wind direction, the horizontal-axis turbine is mechanically more complex than the vertical design. The gyroscopic action of the spinning blades of a horizontal-axis turbine produce stress when the yaw mechanism turns to catch the wind. Over time, the stress can crack the turbine blades and hub. The vertical-axis turbine does not experience this stress.
The horizontal turbine’s tall tower and long blades work well only in wide-open spaces. Vertical turbines are generally much more compact and can be placed on building rooftops and other urban locations with fewer restrictions. The vertical unit’s low height also makes it suitable for areas where wind picks up speed between buildings or over hilltops.
Although the vertical-axis turbine has some advantages over the horizontal design, more large-scale energy developers have chosen the horizontal-axis layout, leaving vertical-axis generation to small commercial operators or individuals. The horizontal axis is simpler to understand and meets the expectations of what a wind turbine should look like. Vertical-axis generators have historically been the object of exaggerated claims, causing skepticism for potential investors of the technology.