Figure Mean yaw error for Configuration A

Time series comparisons for the SWRT modeled with FAST showed results similar to the summary statistics shown above rotor RPM was severely over predicted at higher wind speeds but thrust was modeled accurately. This modeling was conducted for all three turbine configurations with the same results. Various approaches were tried to understand why the FAST model predicts rotor speeds much higher than measured in high winds. In low winds, the predictions were quite good. Both the airfoil tables and...

Tail Wind Speed

A sonic anemometer is located on the tail of the wind turbine just upwind of the tail fin at approximately 3.26 m 10.7 ft. from the rotor plane at the centerline of the shaft. Specifications for the sensor may be found in Appendix C. A sonic anemometer was located at hub height 24.4 m 80 ft on a meteorological tower Figure 11 located 19.8 m 64.9 ft upwind from the turbine and at a height of 24.4 m 80 ft . The distance from the sonic anemometer to the turbine was 3.5 rotor diameters for...

Turbine Configurations

Sh3052 Airfoil

Data were collected for three turbine configurations, A, B, and C, as summarized in Table 5 8 . Configuration A and B differ by the lateral offset distance between the rotor centerline and the yaw axis, which was 0.106 m in Configuration A and 0.083 m in Configuration B a 22 change . The change in the lateral offset for Configuration A was implemented by placing a 4-degree shim between the alternator and the shaft sensor. Figure 13 shows a schematic of the shim and the change in the lateral...

Yaw Position and Velocity

Yaw position and velocity were also measured using a high-speed, optical shaft encoder. The encoder is smiliar to the rotor speed and azimuth encoder and comes mounted on a slip ring that was used to get the signals from the rotating nacelle frame to the tower. The encoder outputs 512 pulses per rotor revolution. The yaw position signal is an analog signal. Yaw position is defined as positive in a counterclockwise direction from true north as shown in Figure 10. Specifications for the sensor...

Test Turbine Description

Sh3055 Airfoil

The SWRT is a modified Bergey EXCEL 10-kW turbine that furls horizontally out of the wind. The tail boom attaches with a hinge and bumper arrangement to the rotor generator main-frame assembly, and there is a lateral offset between the yaw axis and the rotor axis. The axis of the hinge pivot joint is inclined laterally at a small angle to the vertical yaw axis and produces a gravity restoring moment. A main-frame stop keeps the tail boom from furling more than about 68 degrees. There is a...

Calibration Procedures

The test engineer must follow defined procedures to perform calibrations. Whenever possible, the measurement chain from the sensor output through the data acquisition system is calibrated by generating known sensor outputs and recording the corresponding readings in the data acquisition system, i.e., an end-to-end calibration. Several points provide data for linear interpolation, and the slope and offset values of a linear transducer can then be determined. This form of calibration is used for...

Figure PSD of blade edge and flap moments

-Torque -Thrust-Shaft Tilt-Shaft Yaw-blade 3 flap-Blade 3 Edge Figure 16. PSD at 17.3 m s showing the effects of blade flutter at 34 hz Figures 17 through 20 show scatter plots of furl, yaw rate, electrical power, and rotor speed for Configuration A. The data show mean, maximum, and minimums plotted against mean wind speed. The average yaw error for Configuration A is between 15 and 20 degrees depending on wind speed. Because of space limitations, only scatter plots for Configuration A are...

Fast Furling Model

Example Moment Inertia

Jason Jonkman of NREL recently upgraded the FAST code to include furling effects 6 . The upgrades include a lateral thrust offset and skew angle of the rotor shaft from the yaw axis, rotor-fUrling and tail-furling degrees-of-freedom DOFs , up- and down-furl stops, and tail fin aerodynamics and inertia. The location and orientation of the new furling DOFs are completely user-specified, making the simulator flexible enough to model many furling wind turbine configurations. For example, to model a...