1. EWEC 2009 Marseille, France Design of Wind Turbine Passive Smart Blades ©University of Bristol Department of Aerospace Engineering Slide 1 Design of Wind Turbine Passive Smart Blades Department of Aerospace Engineering University of Bristol, Bristol, UK Alireza.Maheri@bristol.ac.uk Askin.T.Isikveren@bristol.ac.uk European Wind Energy Conference and Exhibition EWEC 2009 18 March 2009, Marseille, France European Wind Energy Conference and Exhibition EWEC 2009 18 March 2009, Marseille, France A. Maheri, A.T. Isikveren

2. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 2 EWEC 2009 Marseille, France Overview Problems with adopting traditional design approach in design of bend-twist blades New design approach, variable-state design parameters Case studies Summary

3. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 3 EWEC 2009 Marseille, France Aeroelastic Tailoring Aerodynamic force Operating condition Corrected blade topology Inertia force

4. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 4 EWEC 2009 Marseille, France Material/Structural design parameters Aero Analysis Aerodynamic performance evaluation Structural performance evaluation Overall performance evaluation Aerodynamic design parameters Design space search Analysis Design candidate assessment Structural Analysis Aero load Induced twist Applying Traditional Design Approach

5. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 5 EWEC 2009 Marseille, France New Design Approach-Induced Twist a Variable-State Design Parameter

6. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 6 EWEC 2009 Marseille, France Blade topology Aerodynamic analyser New Design Approach-Decoupled Simulation Iteration Loop Reference induced twist Unloaded topology Aerodynamic load Aerodynamic performance Topology corrector State parameters

7. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 7 EWEC 2009 Marseille, France Iterative coupled aero- structure analysis Iterative aero analysis Structural analysis New Design Approach-Decoupled Simulation Aerodynamic load Structural analyser Material/ Structural characteristics Blade topology Structural performance

8. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 8 EWEC 2009 Marseille, France Material/Structural design parameters Structural analysisLoad Structural performance evaluation + check for constraint satisfaction Design space search Analysis Design candidate assessment Iterative aerodynamic analysis Aerodynamic performance evaluation Aerodynamic design parameters VSDP (Induced twist at a reference state) Overall performance evaluation New Design Approach

9. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 9 EWEC 2009 Marseille, France Reduced Structural Design Space For a given material/structural configuration, once normalised induced deformation has been calculated it is valid for all states as well as all values of material/structural properties Maximum value at the tip Span-wise trend Induced twist (VSDP ) at a reference state

10. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 10 EWEC 2009 Marseille, France New Design Approach in Practice Rotor speed loop Wind speed loop Pitch loop

11. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 11 EWEC 2009 Marseille, France Design Parameters Rotor radius Elastic coupling Chord distribution Pre-twist distribution – Dependent approach – Independent approach Blade pitch angle and rotor speed

12. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 12 EWEC 2009 Marseille, France Design Case 1  Design case:  An approximation of a pitch-control 3-blade V52- 850 with a rotor radius of 25 m running at 26 rpm.  It is assumed that the blades are made of NACA 63-415  Control modification:  None  Constraint:  Power  Topology and size modification:  None  Material modification :  Elastic coupled material, Tip induced twist of at wind speed of

13. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 13 EWEC 2009 Marseille, France Design Case 2  Design case:  An approximation of a pitch-control 3-blade V52- 850 with a rotor radius of 25 m running at 26 rpm.  It is assumed that the blades are made of NACA 63-415  Control modification:  Pitch control  Stall regulated  Constraint:  Power  Topology and size modification:  Rotor radius (R=25 m  R=26.2 m)  Pre-twist  Material modification:  Elastic coupled material, Tip induced twist of

14. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 14 EWEC 2009 Marseille, France Design Case 3  Design case:  An approximation of a pitch-control 3-blade V52- 850 with a rotor radius of 25 m running at 26 rpm.  It is assumed that the blades are made of NACA 63-415  Control modification:  Pitch control  Semi-activated pitch control  Constraint:  Power  Flap bending  Topology and size modification:  Rotor radius (R=25 m  R=26.2 m)  Pre-twist  Material modification:  Elastic coupled material, Tip induced twist of

15. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 15 EWEC 2009 Marseille, France Design Case 4  Design case:  300 KW stall-regulated constant speed AWT-27 with a rotor radius of 13.7 m running at 53 rpm.  Control modification:  None  Constraint:  Power  Topology and size modification:  Rotor radius (R=13.7 m  R=14.45 m)  Pre-twist  Material modification:  Elastic coupled material, Tip induced twist of (Graphite epoxy ply angle of 21 degrees and shell thickness of 6 mm)

16. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 16 EWEC 2009 Marseille, France Summary Traditional design methods are not efficient enough for performing optimal design of passive smart blades – Simulation of wind turbines utilising adaptive blades is an iterative coupled aero-structure process – High fidelity structural analyser (FEA) is required to obtain reliable induced twists Introducing the induced twist as a VSDP decouples the aerodynamic and structural analyses – Dependency of the induced twist on the material/structural characteristics of the blade is taken into account by imposing a proper constraint in structural design phase – Using a reduced structural design space, situations in which the imposed constraint is impossible to be satisfied are avoided Presented design tool can be used to investigate the potential benefits of converting conventional blades into adaptive ones

17. ©University of Bristol Department of Aerospace Engineering Design of Wind Turbine Passive Smart Blades Slide 17 EWEC 2009 Marseille, France Questions?