Advances in Wind Turbine Blade Design and Materials

Advances in Wind Turbine Blade Design and Materials
Copyright
Contributors
1. Introduction to wind turbine blade design
1.1 Introduction
1.1.1 State of the art—Blade design
1.2 Design principles and failure mechanisms
1.2.1 Design principles
1.2.2 Failure mechanisms
1.2.2.1 Failure in the cap(s) caused by brazier loads
1.2.2.2 Buckling
1.2.2.3 Cross-sectional shear distortion
Fatigue problem at the root transition area
1.2.2.4 Failure in the adhesive bondlines
1.2.2.5 Buckling driven delamination
1.2.2.6 Shear web failure
1.2.2.7 Flutter
1.2.2.8 Impact of torsional loads
1.3 Challenges and future trends in wind turbine blade design
1.3.1 Testing approach
1.3.2 Development of more advanced test methods
1.3.3 Testing parts of blades
1.3.4 Building block approach
1.3.5 Certification and standards
1.3.6 Owners' requirements
1.3.7 Finite element approach
1.3.8 Digital twin technology
1.4 Retrofit solutions
1.4.1 D-string
1.4.2 D-stiffener
1.4.3 X-stiffener
1.4.4 Floor
References
Further reading
2. Loads on wind turbine blades
2.1 Introduction
2.2 Types of load
2.2.1 Global loads
2.2.2 Local strains and stresses
2.2.3 Deflection and deformation
2.3 Generation of loads
2.3.1 Aerodynamic loads in operation and at idling or standstill
2.3.2 Inertia, gravitational and gyroscopic loads
2.3.3 Actuation loads
2.4 Fatigue and extreme loads
2.4.1 Assessment of ultimate loading
2.4.2 Assessment of fatigue loads
2.5 Design verification testing
2.5.1 Design verification process
2.5.2 Instrumentation
2.5.3 Calibration of global bending moment measurements
2.6 Challenges and future trends
2.6.1 Design options
2.6.1.1 Aeroelastic tailoring
2.6.1.2 Vortex generators
2.6.2 Operation strategies to mitigate loading
2.6.2.1 Individual pitch control
2.6.3 Materials issues
References
Sources of further information and advice
3. Aerodynamic design of wind turbine rotors
3.1 Introduction
3.1.1 State-of-the-art rotor design
3.1.2 Models and elements used in the rotor design process
3.2 The blade element momentum method
3.2.1 One-dimensional momentum theory
3.2.2 Blade element momentum theory
3.3 Important parameters in aerodynamic rotor design
3.3.1 Airfoil performance
3.4 Particular design parameters
3.4.1 Tip speed ratio
3.4.2 Size of rotor/generator
3.4.3 Rotor control
3.4.4 Design constraints
3.4.5 Choice of number of blades
3.4.6 Evaluation of the rotor design
3.5 An example of the rotor design process
3.5.1 Step 1: wind climate
3.5.2 Step 2: size of rotor/generator
3.5.3 Step 3: rotor control
3.5.4 Step 4: design constraints
3.5.5 Step 5: choice of number of blades
3.5.6 Step 6: choice of design lift and airfoils
3.5.7 Step 7: choice of design tip speed ratio
3.5.8 Step 8: one point design of blade
3.5.9 Step 9: evaluation of the blade design
3.6 Future trends
3.7 Sources of further information and advice
Appendix: nomenclature
Acknowledgments
References
4. Aerodynamic characteristics of wind turbine blade airfoils
4.1 Introduction
4.2 Computational methods
4.2.1 Panel codes, XFOIL and RFOIL
4.2.2 Computational fluid dynamics
4.2.2.1 Investigation of airfoil contour
4.2.2.2 Mesh generation
4.2.2.3 Inspection of mesh
4.2.2.4 Boundary conditions
4.2.2.5 Turbulence model
4.2.2.6 Computing
4.2.2.7 Inspection of results
4.2.3 Panel codes versus Navier–Stokes codes
4.2.3.1 Computational speed
4.2.3.2 Time for preparation
4.2.3.3 Computational details
4.2.3.4 Comparisons to measurements
4.2.3.5 Summary
4.3 Desired characteristics
4.3.1 The velocity and forces on a blade element
4.3.2 Outboard airfoils
4.3.3 Inboard airfoils
4.4 The impact of leading edge contamination, erosion and Reynolds number
4.4.1 Effects of roughness
4.4.2 The effect of the Reynolds number
4.5 Noise
4.6 Airfoil testing
4.6.1 Setup and testing equipment
4.7 Airfoil characteristics at high angles of attack
4.8 Correction for centrifugal and Coriolis forces
4.8.1 Existing 3-D correction models
4.8.2 An example of the application of 3-D models to a wind turbine rotor with stall control
4.9 Establishing data for blade design
4.9.1 Available airfoil data
4.9.2 Establishing the data
4.10 Future trends
Appendix: Nomenclature
References
5. Aeroelastic design of wind turbine blades
5.1 Introduction
5.1.1 Aeroelasticity
5.1.2 Natural modes
5.2 Wind turbine blade aeroelasticity
5.2.1 Wind turbine blade modes
5.2.2 Wind turbine blade instabilities
5.2.2.1 Stall-induced instabilities
5.2.2.2 Idling and parked instabilities
5.2.2.3 Classical flutter
5.3 Blade design
5.3.1 Avoidance of resonance
5.3.2 Structural pitch angle
5.3.3 Bend twist coupling
5.3.4 Analysis
5.3.5 Aerofoils
5.4 Complete turbine design
5.5 Challenges and future trends
5.6 Sources of further information and advice
References
6. Micromechanical modeling of wind blade materials
6.1 Introduction
6.2 Analytical methods of micromechanical modeling of fiber-reinforced composites: an overview
6.2.1 Analytical models of damage and strength of fiber-reinforced composites: tensile loading
6.2.2 Modeling of compressive failure of composites
6.3 Unit cell modeling of fiber-reinforcedcomposites
6.4 3D modeling of composite degradation under tensile loading
6.5 Carbon fiber-reinforced composites: statistical and compressive loading effects
6.6 Hierarchical composites with nanoengineered matrix
6.7 Conclusions, challenges, and future trends
6.8 Sources of further information
Acknowledgments
References
Further reading
7. Fatigue as a design driver for composite wind turbine blades
7.1 Introduction
7.2 Materials in blades
7.3 Blade structure and components
7.3.1 Load-bearing components
7.3.1.1 Root and blade joint connections
7.3.2 Aerodynamic shell
7.3.2.1 Skin
7.3.3 Cost
7.4 Fundamentals of wind turbine blade fatigue
7.4.1 Significance of fatigue loading on blades
7.5 Rotor blade tests at Delft University of Technology in 1984 ()
7.5.1 Number of load cycles
7.5.2 Variability of cycles
7.5.3 Contribution of each load cycle to fatigue damage
7.5.4 Need for design optimization
7.5.5 Fundamentals of fatigue modeling
7.6 Research into wind turbine blade fatigue and its modeling
7.6.1 Empirical and phenomenological fatigue modeling
7.6.2 Micromechanical modeling
7.6.3 Thick laminates
7.6.4 Extreme conditions
7.6.5 Bondlines
7.6.6 Leading- and trailing-edge reinforcement
7.7 Future trends
7.7.1 Significance of material models for blade tests
7.7.2 Probabilistic modeling
7.7.3 Structural health monitoring
7.7.4 Sustainability
7.7.5 Testing
7.7.6 Reaching the limits
7.7.7 Redundancy of supply
7.7.8 Automated production
7.7.9 Repair
7.7.10 Subcomponent research
7.8 Conclusion
7.9 Sources of further information and advice
References
Further reading
8. Effects of resin and reinforcement variations on Fatigue resistance of wind turbine blades
8.1 Introduction
8.2 Effects of loading conditions for glass and carbon laminates
8.3 Tensile fatigue trends with laminate construction and fiber content for glass fiber laminates
8.3.1 Materials
8.3.2 Fatigue parameters for different laminate types
8.3.3 Effects of fiber content
8.4 Effects of resin and fabric structure on tensile fatigue resistance
8.4.1 Effects of resin on multidirectional (MD) laminates
8.4.2 Effects of resin on unidirectional (UD) fabric laminates
8.4.3 Effects of resin on UD aligned strand (AS) laminates compared to UD fabric laminates
8.4.4 Effects of resin on biax laminates
8.4.5 Effects of fabric weight and structure on epoxy resin MD laminates
8.5 Delamination and material transitions
8.5.1 Ply drops in carbon and glass prepreg laminates
8.5.2 Infused complex structured coupons with ply drops
8.6 Comparison of fatigue trends for blade materials
8.7 Conclusion
8.8 Future trends
8.9 Sources of further information and advice
Acknowledgments
References
9. Fatigue behavior and life prediction of wind turbine blade composite materials
9.1 Introduction
9.2 Fatigue behavior of laminates under complex loading profiles
9.2.1 Fatigue experiments
9.3 Fatigue life modeling and prediction
9.3.1 Macroscopic failure theories
9.3.1.1 S–N curve formulations
9.3.1.2 Constant life diagrams
9.3.2 Strength and stiffness degradation fatigue theories
9.3.3 Fracture mechanics fatigue theories
9.3.3.1 Manipulation of fracture mechanics data
9.4 Case study: phenomenological fatigue life prediction
9.5 Summary and future trends
References
10. Probabilistic design of wind turbine blades
10.1 Introduction
10.1.1 Overview of probabilistic design
10.1.2 Uncertainty modeling
10.2 Structural analysis models
10.3 Failure definition
10.3.1 Lamina failure probability
10.3.2 Laminate failure probability
10.3.3 Failure probability of the blade section
10.3.4 Failure probability against buckling
10.4 Random variables
10.4.1 Material properties under static conditions
10.4.2 Material strength properties for fatigue conditions
10.4.3 Loads
10.5 Probabilistic methods and models
10.5.1 Monte Carlo simulation method
10.5.2 Edgeworth expansion method
10.5.3 First-order reliability method
10.5.4 Response surface method
10.6 Application examples and discussion of techniques
10.6.1 Reliability under extreme loading
10.6.2 Reliability against buckling
10.6.3 Reliability against fatigue
10.7 Challenges and future trends
10.8 Sources of further information and advice
References
11. Biobased composites: materials, properties, and potential applications as wind turbine blade materials
11.1 Introduction
11.2 Biobased fibers and matrix materials
11.2.1 Biobased fibers
11.2.2 Biobased matrix materials
11.3 Biobased composites
11.3.1 Glass fiber/bioresin composites
11.3.2 Bamboo fiber/epoxy composites
11.3.3 Jute fiber/bioresin composites
11.4 Case study: comparison between cellulose and glass fiber composites
11.5 Special considerations in the development and application of biobased composites
11.5.1 Fiber defects
11.5.2 Variability in fiber properties
11.5.3 Interface properties
11.5.4 Other issues
References
Sources of further information and advice
12. Surface protection and coatings for wind turbine rotor blades
12.1 Introduction
12.2 Fundamentals of surface protection for wind turbine blades
12.2.1 Adhesion of surface coatings
12.2.2 Selection criteria for coatings
12.2.3 Particular coating materials
12.2.3.1 Unsaturated polyesters
12.2.3.2 Epoxies
12.2.3.3 Acrylates
12.2.3.4 Vinylesters
12.2.3.5 Polyurethanes
12.3 Protection from blade icing, lightning and air traffic
12.3.1 Wind turbine blade icing
12.3.2 Lightning protection
12.3.3 Protection from air traffic
12.4 Performance testing of protection layers: an introduction
12.4.1 Performance testing considerations
12.4.2 Degradation of polymers
12.4.2.1 Weathering
12.4.2.2 Sunlight
12.4.2.3 Oxygen and humidity
12.4.2.4 Degradation mechanisms
12.4.3 Measuring the degradation of polymer systems
12.4.4 Accelerated testing: an introduction
12.4.4.1 UV tests and xenon light tests
12.4.4.2 Ozone
12.4.4.3 Combined influences
12.5 Accelerated testing of the surface coatings of wind turbine blades in practice
12.5.1 Standards
12.5.2 Selected test methods
12.5.2.1 Norsok test
12.5.2.2 Wear test
12.5.2.3 Humidity test
12.5.2.4 Chemical attack
12.5.2.5 Results of tests
12.6 Conclusions, challenges, and future trends
12.6.1 Advantages and limitations of different protection technologies
12.6.2 Challenges and future trends
12.6.2.1 New materials
12.6.2.2 Protection of the surroundings
12.6.2.3 Working environment
12.6.2.4 Test methods
References
Further reading
13. Design, manufacture, and testing of small wind turbine blades
13.1 Introduction
13.1.1 Background
13.1.2 Key differences between small and large blades
13.1.3 Scope and layout
13.2 Requirements for small wind turbine blades
13.3 Materials and manufacture
13.3.1 Timber
13.3.2 Fiber-reinforced composites
13.3.3 Rapid prototyping and low-volume production methods
13.4 Blade testing
13.4.1 Static testing
13.4.2 Small blade fatigue
13.4.3 Quality control
13.5 Installation and operation
13.6 Challenges and future trends
Acknowledgments
References
14. Wind turbine blade structural performance testing
14.1 Introduction
14.2 Test program
14.3 Types of tests
14.3.1 Static tests
14.3.2 Fatigue tests
14.3.3 Ultimate tests
14.4 Test loads
14.4.1 Static test
14.4.2 Fatigue test
14.4.2.1 Sequential single-axial, single location
14.4.2.2 Multiaxial, single location
14.5 Test details
14.5.1 Load introduction
14.5.2 Blade root clamping
14.5.3 Instrumentation
14.5.3.1 Applied force
14.5.3.2 Strains
14.5.3.3 Displacements
14.5.3.4 Accelerations
14.5.3.5 Environmental conditions
14.5.3.6 Electrical conductivity of lightning protection system
14.5.4 Conclusion
References
15. Maintenance and repair of wind turbine blades
15.1 Introduction
15.2 Structural health monitoring: main approaches
15.3 COST evaluation of repair technologies
15.4 Repair technologies of wind turbine blades
15.5 Computational modeling of patch repair of wind turbine blades
15.6 Conclusions, challenges, and future trends
15.7 Sources of further information
Acknowledgment
References
Index
A
B
C
D
E
F
G
H
I
J
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y