Performance Advantages

Computer modeling shown in this website demonstrate the advantages of teetering in reducing fatigue on blades, main shaft, main shaft bearing, gearbox and yaw bearing. The modeling also shows less impact of wind shear, turbulence, wind skew, and waves in offshore platforms.  These performance advantages will lead to competitive advantages because replacement of the blades, main shaft, main shaft bearing, gearbox and yaw bearing would all require a crane and lead to significantly higher maintenance costs over the lifetime of the wind turbine.  Other performance advantages include reduced power needed for yaw rotation and less likelihood of resonance.

Blades

Modeling shows reduced cyclic stresses on blades as demonstrated with the output profiles of the out-of-plane tip deflection (OoPDefl1, OoPDefl2, OoPDefl3) and the out-of-plane moment at the blade root (RootMyC1, RootMyC2, RootMyC3).  In 2015, A. Ramsland  published a paper in Journal of Solar Energy Engineering entitled "Description and Computer Modeling of a Ball-and-Socket Hub that Enables Teetering for Three-Bladed Wind Turbines".  The paper described a blade fatigue study using rainflow counting of multi-axial torque contributions of the blade root that showed very substantial reductions in lifetime fatigue of a three-bladed wind turbine with a teetering hub in comparison to a three-bladed turbine with a rigid hub and a two-bladed turbine with a teetering hub.  It should be noted that the new hub design no longer uses a ball-and-socket design, however the modeling data remain valid. 

Main Shaft and Main Shaft Bearing

Significantly reduced loads on main shaft and main shaft bearing as demonstrated with the output profiles of the bending moments at the shaft tip (LSSTipMya and LSSTipMza) and the bending moments at the location of the main shaft bearing (LSSGagMys and LSSGagMzs). Output parameters presented as charts in the four modeling presentations for the 1.5-MW wind turbine and the four modeling presentations for the 5-MW wind turbine.  

Gearbox

Reduced loads on gearbox would be realized if the loads (LSSGagMys and LSSGagMza ) are transferred through main shaft bearing(s) to the gearbox. It would be expected that gearbox noise would also be reduced with less loads.  Future plans include a study to assess the difference in impact upon the gearbox between a teetering hub and rigid hub.

Yaw Bearing

Significantly reduced loads on yaw bearings and tower as demonstrated with the output profiles of the tower top yaw bearing moments (YawBrMyn and YawBrMzn).

Reduced Power Needed for Yaw Rotation

A three-bladed teetering hub requires less power to rotate than does a three-bladed rigid hub. This is because wind forces, rather than yaw motors, cause yaw rotation of the rotor. The Yaw Mechanism section explains how.

Reduced Possibility of Resonance

The Resonant Teetering section provides a rationale as to why a three-bladed teetering hub is much less likely to cause resonance than is a three bladed rigid hub.