About Modeling Examples

A new hub design has been developed that enables teetering for horizontal axis wind turbines.  The design is flexible in that it allows for attachment of any number of blades greater than one.  The design is also flexible in that it can be used for both small and large wind turbines and can be modified to fit hubs of wind turbines currently in operation.  The new hub design provides a number of performance and competitive advantages to wind turbine manufacturers.

This website is designed to compare existing a three-bladed turbine with a rigid hub to a three-bladed turbine with a teetering hub.  Modeling was performed by modifying FAST software to enable the two additional degrees of freedom provided by the teetering hub.  A description of the modifications is presented in the FAST Modifications tab.  FAST software and the modeled wind turbines are available from the National Renewable Energy Laboratory in Golden, CO.  Overall, modeling data show significant reductions in some loads on the blades, bearings, main shaft and the tower in comparison to a fixed-hub, three bladed turbines.  A software program entitled Turbsim was used to generate all wind profiles.

The "Modeling Examples Demonstrating Reduction in Fatigue" section accessible from the home page provides modeling comparisons of wind turbines under typical conditions.  Results from three wind turbines (AWT-27, WP 1.5 MW and NREL 5 MW) with fixed and teetering hubs are provided.  Additionally, the NREL 5 MW wind turbine was modeled with three platforms (onshore, offshore in a fixed-bottom tripod, and offshore on a floating, semi-submersible platform).  Comparisons were made with a mean wind speed of 12 m/s, normal turbulence and no skew.  The same shaft tilt (-5°) was used for teetering and rigid hubs.  This wind speed was chosen because wind speeds below and above the rated wind speed will be shown.  Presentations link together a series of slides displaying many FAST output values.  Most of the slides have notes at the bottom providing a comparison of the fixed and teetering hubs.  Some of the slides are designated highlight slides and demonstrate the reduction in fatigue provided by the teetering hub.  By clicking the appropriate button at the bottom of any slide, one can view either all slides or highlight slides only.  One can also change the timeframe with choices of 30 seconds, 1 minute, 2 minutes, 3 minutes and all data.  Additionally, one can use the slider at the bottom of the graph to modify the timeframe to any desired range. 

The "Extensive Modeling" section is accessible from the home page after registering and logging in.  Here modeling studies were performed to assess the impact of various wind turbine stresses such as wind shear, turbulence, misalignment, and impact of other wind turbines in a wind farm.