Optimisation of Wind Turbine Blade Structural Topology

N. Buckney, A. Pirrera and P. M. Weaver

www.bris.ac.uk/composites

16th April 2012

Introduction

• Wind turbine blades

– Current blade designs

– Square-cubic law between power and mass

– Lightweight blades

Aims and Objectives

The overall aim is to reduce the cost of wind energy by increasing blade structural efficiency (reduce mass)

• Investigate alternative structural layouts using topology optimisation

• Evaluate and understand these layouts in terms of structural efficiency using shape factors

0

10

20

30

35 45 55 65

Mass [

10

3 k

g]

Blade Length [m]

2 MW

3 MW

4 MW

5 MW

Optimisation of Wind Turbine Blade Structural Topology

Topology Optimisation

• Topology optimisation

– Gives optimal material distribution

– Provides non-intuitive solutions

– Topology is altered by changing a fictional element density

– This modifies element stiffness

• Optimisation problem

– Seven key load cases

– Large model size

-1 -0.5 0 0.5 1-0.8

-0.4

0

0.4

0.8

Flapwise Moment

Edgew

ise M

om

ent

Critical Load Case

Objective: min(max) compliance Subject to: vf < 0.125 δtip < 9m θ < 2°

Optimisation of Wind Turbine Blade Structural Topology

Topology Optimisation

Trailing edge (TE) Reinforcement Offset Spar Caps

Optimisation of Wind Turbine Blade Structural Topology

Structural Efficiency

• Shape Factors

– Determines the efficiency of material usage in a structure

– Account for complex bending

– Deflection and stress

– Depend only on the direction of loading

Offset spar caps

Conventional

Conventional

TE reinforcement

Medge α = 90°

Mcrit α = 33°

Mflap α = 90°

M

α (°)

Optimisation of Wind Turbine Blade Structural Topology

Deflection Shape Factor

Radius = 25% Radius = 75%

Optimisation of Wind Turbine Blade Structural Topology

Stress Shape Factor

Radius = 25% Radius = 75%

Optimisation of Wind Turbine Blade Structural Topology

Conclusion

From this, two observations are made:

1. Alternative layouts could be used to reduce blade weight

2. It is crucial to consider asymmetric bending in wind turbine blades

• An alternative structural layout was found using topology optimization

• The new layout is more efficient in terms of minimizing deflection and stress

Optimisation of Wind Turbine Blade Structural Topology

Questions