Dave Corbus, Craig Hansen Presentation at Windpower 2005 Denver, CO May 15-18, 2005 Test Results from the Small Wind Research Turbine (SWRT) Test Project

2 SWRT Project SWRT Test Background SWRT Test Supply data for model validation of small furling wind turbines Increase understanding of furling and small wind turbine dynamics Further state-of-the- art test procedures for small wind turbines

3 SWRT Project SWRT Testing and Model Development SWRT Test Three different turbine configurations tested Most comprehensive small turbine test Upgrade FAST model to include furling Perform model comparisons between SWRT FAST and ADAMS models and FAST and SWRT Models often break down more for small turbine conditions In and out of stall more More yawed flow conditions Dynamically active turbine

4 SWRT Project SWRT Test Description Yaw slip rings and encoder Furl Sensor Sonic anemometer junction box Shaft sensor Flap and edge blade strain gages Tower leg load cell “washers” Rotor slip ring, encoder, and amplifiers

5 SWRT Project SWRT shaft sensor - first accurate small turbine thrust measurements  Measures Shaft 0/90 bending, torque, thrust on fixed frame  4 by 4 cross-talk matrix  Critical path load is the shaft bending from gyroscopic loads

6 SWRT Project Pre-testing Turbine Characterization Data for modeling included: –Tail assembly and main frame: Weight, Cg, bi- filar, moment of inertia about yaw axis –Magnet can Cg and moment of inertia –Tail damper properties –Exact turbine geometries –Blade modal test

7 SWRT Project Max and Mean Furl vs. Mean Wind Speed

8 SWRT Project Yaw Rate vs. Mean Wind Speed

9 SWRT Project Rotor Speed vs. Mean Wind Speed

10 SWRT Project Furl vs. Thrust

11 SWRT Project SWRT Furling Event – Time Series Plot

12 SWRT Project Furling and Center of Thrust

13 SWRT Project SWRT Test Configurations  All configurations tested with inverter load –Total of minute records  A few resistor load files taken for each configuration –Some scatter in rpm- torque curve from inverter controller hysteresis SWRT Configuration ABC Airfoil SH3052 SH3055 Lateral shim 4 degree none Swept Area/Rotor Diameter 26.4 m 2 / 5.8 m 35.3m 2 / 6.7 m Blade pitch

14 SWRT Project Furl vs. Wind Speed for Different Configurations

15 SWRT Project Thrust vs. Wind Speed for Different Configurations

16 SWRT Project Ratio of Tail/Met Wind Speed vs. Wind Speed

17 SWRT Project Power/Thrust Ratio for Configurations A and C

18 SWRT Project Furling and Inflow  Use sonic anemometer and meteorological data  Correlate inflow parameters and furling  Shows significance of vertical wind component and coherent turbulent kinetic energy

19 SWRT Project Furling and Richardson Number

20 SWRT Project - CoTKE and vertical gust variance for two files with same wind speed and different furl

21 SWRT Project SWRT Test & Simulation Models SWRT FAST Model  Extensive turbine properties provided by NREL  12 degrees-of-freedom (DOFs) used –Blade flexibility2 flap and 1 edge mode DOF per blade –Drivetrain1 variable generator speed DOF with torque-speed look-up table –Nacelle yaw 1 yaw DOF –Tail-furl 1 tail-furl DOF with nonlinear damper  Aerodynamics –Used dynamic stall and dynamic inflow options in AeroDyn –Original airfoil data based upon Selig wind tunnel tests Tapered tip section airfoil data based upon XFoil predictions by Tod Hanley –Airfoil data “tuned” after comparing with measured Cp-TSR data (very limited range)  Dynamics verified via comparisons with ADAMS

22 SWRT Project Model & Test Comparisons Configuration A Statistics (Inverter Load)

23 SWRT Project Model & Test Comparisons Configuration A Statistics (Cont’d.)

24 SWRT Project Model & Test Comparisons Configuration A Statistics (Cont’d.)

25 SWRT Project Model & Test Comparisons Configuration A Statistics (Cont’d.)

26 SWRT Project Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s

27 SWRT Project Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s

28 SWRT Project Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s

29 SWRT Project Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s

30 SWRT Project SWRT Summary  Most comprehensive small turbine test data set  Better understanding of small wind turbine dynamic behavior, including thrust and furling  SWRT test data and modeling effort will help make furling design efforts for small wind turbines easier, but furling remains a challenge!  Better test procedures for small turbine testing  Inflow analysis shows effects of turbulence  Fundamental shortcomings in aerodynamic modeling are the main reason for test data and model disagreements –3-D stall effects (i.e., rotational augmentation) –Uncertainties in skewed wake correction for yawed flow