Dave Corbus, Dan Prascher Presentation at the 24 th ASME Wind Energy Symposium

1. Analysis and Comparison of Test Results from the Small Wind Research Turbine (SWRT) Test Project Dave Corbus, Dan Prascher Presentation at the 24th ASME Wind Energy Symposium January 10-13, 2005

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

5. SWRT shaft sensor - first accurate small turbine thrust measurements

6. Shaft Sensor • 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 • During high yaw rate events and high rpm

7. 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

8. Data Analysis – Edge Correction 3 edge summation in-plane did not equal torque • About 3-5x higher due to centrifugal loading! • But slow rolls validate calibrations • Moment arm created • Blade Cg minus centerline of rotation • Difference in edge gage neutral axis and blade Cg

9. Moment Arm for Edge Correction

10. Edge Corrected by Unloaded Correlation

11. Max and Mean Furl vs. Mean Wind Speed

12. Yaw Rate vs. Mean Wind Speed

13. Electrical Power vs. Mean Wind Speed

14. Rotor Speed vs. Mean Wind Speed

15. Thrust vs. Mean Wind Speed

16. Furl vs. Thrust

17. SWRT Furling Event – Time Series Plot

18. Furling and Center of Thrust

19. SWRT Test Configurations All configurations tested with inverter load Total of 514 10-minute records A few resistor load files taken for each configuration Some scatter in rpm-torque curve from inverter controller hysteresis SWRT Configuration

20. Furl vs. Wind Speed for Different Configurations

21. Thrust vs. Wind Speed for Different Configurations

22. Ratio of Tail/Met Wind Speed vs. Wind Speed

23. Power/Thrust Ratio for Configurations A and C

24. Power vs. Wind Speed for Configuration A and C

25. Shaft tilt moment vs. wind speed for different configurations

26. Shaft yaw moment vs. wind speed for different configurations

27. 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

28. Furling and Richardson Number

29. - CoTKE and vertical gust variance for two files with same wind speed and different furl

30. 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 • Data will be available on NREL Website and final technical report available soon • SWRT FAST modeling results presented tomorrow morning