Advanced Wind Turbines

Contents
Preface
About the Authors
Chapter 1 Introduction
	1.1 A Case for H-Darrieus Wind Turbine
	1.2 Overview of Floating Offshore Wind Turbine
	References
Chapter 2 State-of-the-art Technologies for Low Wind Speed Operation
	2.1 Types of Wind Turbine
	2.2 Aerodynamics of Darrieus Rotor*
		2.2.1 Tip-speed Ratio and Angle of Attack
		2.2.2 Dynamic Stall
		2.2.3 Aerodynamic Models
			2.2.3.1 Cascade Model
			2.2.3.2 Vortex Model
			2.2.3.3 Single Streamtube Model
			2.2.3.4 Multiple Streamtube Model
			2.2.3.5 Double Multiple Streamtube Model
	2.3 Aerodynamics of Savonius Rotor
		2.3.1 Effect of Aspect Ratio
		2.3.2 Effect of End Plates
		2.3.3 Effect of Overlap Ratio
		2.3.4 Effect of Number of Blades
		2.3.5 Effect of Multi-Staging
		2.3.6 Effect of Accessories
		2.3.7 Effect of Blade Shape
		2.3.8 Effect of Reynolds Number
		2.3.9 Effect of Tip-speed Ratio
	2.4 State-of-the-art Technologies for Starting and Low Wind Speed Operation*
		2.4.1 Airfoil Characteristics
			2.4.1.1 WSU 0015
			2.4.1.2 NACA 00XX
			2.4.1.3 SAND 00XX/XX
			2.4.1.4 TWT 11215-1
			2.4.1.5 NACA 6 Series
			2.4.1.6 ARC Series
			2.4.1.7 DU 06-W-200
			2.4.1.8 LS-0417
			2.4.1.9 S1210
			2.4.1.10 NTU-20-V
		2.4.2 Camber and Symmetric Airfoils
		2.4.3 Solidity
		2.4.4 Helical Blades
		2.4.5 Blade Thickness
		2.4.6 Vortex Generators
		2.4.7 Stepped Airfoils
		2.4.8 Gurney Flaps
		2.4.9 Trailing Edge Flaps
		2.4.10 J-Blade
		2.4.11 Hybrid Savonius-Darrieus Rotor
		2.4.12 Radial Arms with Drag Device
		2.4.13 Double Darrieus Rotor
		2.4.14 Low Resistance Bearings
		2.4.15 Multi-Stage Rotor
		2.4.16 Diffuser-Augmented Turbines
		2.4.17 Generator Starting
		2.4.18 Aspect Ratio
		2.4.19 Circulation-Controlled Blades
		2.4.20 Morphing Blades
		2.4.21 Blade Pitching
		2.4.22 Omnidirectional Guide Vanes
		2.4.23 Trailing Edge Cavity Airfoil
	References
Chapter 3 Feasibility Check on Potential Concepts
	3.1 ERIAN Subsonic Wind Tunnel
		3.1.1 Instrumentation
		3.1.2 Data Reduction and Blockage Correction
	3.2 Airfoil with Step (KF-N-21)*
		3.2.1 Design of KF-N-21 Airfoil
		3.2.2 Computational Optimization of KF-N-21 Airfoil
		3.2.3 Discussion on the KF-N-21 Airfoil Computational Results
		3.2.4 Experimental Setup and Procedure for KF-N-21 Airfoil
			3.2.4.1 Power Coefficient
			3.2.4.2 Static Torque Coefficient
	3.3 Dual Darrieus Rotor
		3.3.1 Description of Dual Darrieus Rotor
		3.3.2 Experimental Setup and Procedure for Dual Darrieus Rotor
		3.3.3 Coefficient of Power
	3.4 Modified Trailing Edge Airfoil
		3.4.1 Design of NACA 0018TC-39 Airfoil
		3.4.2 Computational Optimization of Truncation Parameters
			3.4.2.1 Lift and Drag Characteristics
		3.4.3 Experimental Setup and Procedure for NACA 0018TC-39 Airfoil
			3.4.3.1 Power Coefficient
			3.4.3.2 Static Torque Coefficient
	3.5 Hybrid Darrieus Telescopic Savonius Turbine
		3.5.1 Description of Hybrid Darrieus Telescopic Savonius Turbine
		3.5.2 Analytical Modeling of Telescopic Savonius Turbine
		3.5.3 Computational Optimization of Telescopic Savonius Turbine Buckets
		3.5.4 Discussion on Computational Results of Telescopic Savonius Turbine Buckets
		3.5.5 Experimental Study on Telescopic Savonius Turbine
		3.5.6 Dynamic Performance of Telescopic Savonius Turbine
		3.5.7 Static Performance of Telescopic Savonius Turbine
		3.5.8 Thrust Load
		3.5.9 Experimental Study on Hybrid Darrieus Telescopic Savonius Turbine
		3.5.10 Dynamic Performance of the Hybrid Darrieus Telescopic Savonius Rotor
	Chapter Nomenclature
	References
Chapter 4 Mathematical Modeling of Adaptive Hybrid Darrieus Turbine
	4.1 Introduction to Adaptive Hybrid Darrieus Turbine
	4.2 Analytical Model of Adaptive Hybrid Darrieus Turbine in Open Configuration (Open Savonius)
		4.2.1 Wake of Savonius Rotor in Open Configuration (Conventional Two-Bucket Savonius Rotor)
			4.2.1.1 Analytical Model
	4.3 Analytical Model of Adaptive Hybrid Darrieus Turbine in Closed Configuration (Cylinder)
		4.3.1 Wake of Savonius Rotor in Closed Configuration (Cylinder)
			4.3.1.1 Analytical Model
	4.4 Discussion on Analytical Predictions
		4.4.1 Parametric Study
		4.4.2 Blade Torque and Rotor Torque
		4.4.3 Power Coefficient and Torque Coefficient
	Chapter Nomenclature
	References
Chapter 5 Computational Study of Adaptive Hybrid Darrieus Turbine
	5.1 Mathematical Formulation of the Computational Fluid Dynamics
		5.1.1 Reynolds-Averaged Navier Stokes Model
		5.1.2 Turbulence Model
	5.2 Computational Domain and Meshing
		5.2.1 Numerical Model Validation
	5.3 Discussion on Computational Results
		5.3.1 Torque Coefficient Comparison for Different DR /DT
		5.3.2 Power Coefficient Comparison for Different DR /DT
			5.3.2.1 Power Coefficient Comparison for Rotor Solidity (s = 0.5)
			5.3.2.2 Power Coefficient Comparison for Rotor Solidity (s = 0.75)
		5.3.3 Comparison of DR /DT for Various Re
			5.3.3.1 At Rotor Solidity of σ = 0.5
			5.3.3.2 At Rotor Solidity of σ = 0.75
		5.3.4 Discussion on Flow Physics of Adaptive Hybrid Darrieus Turbines
	Chapter Nomenclature
	References
Chapter 6 Experimental Optimization of Adaptive Hybrid Darrieus Turbine
	6.1 Experimental Setup and Wind Tunnel Models
	6.2 Adaptive Hybrid Darrieus Turbine in Closed Configuration — Two-Bladed (σ = 0.5)
	6.3 Adaptive Hybrid Darrieus Turbine in Closed Configuration — Three-Bladed (σ = 0.75)
		6.3.1 Cp Comparison of Savonius Rotor for Various DT
		6.3.2 Cp Comparison of Adaptive Hybrid Darrieus Turbine in Open Configuration for Various DR/DT
		6.3.3 Cp Comparison of DR/DT = 3.5 for Various Configurations
		6.3.4 Cp Comparison of DR/DT = 3 for Various Configurations
	6.4 Starting Torque Comparison of Optimum Adaptive Hybrid Darrieus Turbine with H-Rotor
	Chapter Nomenclature
Chapter 7 Overview of Floating Offshore Wind Turbines
	7.1 Floating Offshore Wind Turbine
		7.1.1 Overview of Wind Energy
		7.1.2 Offshore Wind Energy
		7.1.3 Floating Offshore Wind Sector Forecast
		7.1.4 Floating Platform Configuration
			7.1.4.1 Spar-Type Floating Wind Turbine
			7.1.4.2 Tension-Leg Platform Type
			7.1.4.3 Semi-Submersible Type
	7.2 Prediction of Aerodynamic Performance of Floating Offshore Wind Turbines
		7.2.1 Aero-Servo-Elastic Method
			7.2.1.1 BEM Method
			7.2.1.2 Tip-Loss Model
			7.2.1.3 Glauert Correction
		7.2.2 Computational Fluid Dynamics
			7.2.2.1 Turbulence Model for Reynolds-Averaged Navier-Stokes Equations
			7.2.2.2 Standard k−ε Model
			7.2.2.3 Re-Normalization Group k−ε Model
			7.2.2.4 Realizable k−ε Model
			7.2.2.5 Shear Stress Transport k−ω Model
			7.2.2.6 Discretization Methods
		7.2.3 Vortex Lattice Method
	7.3 Scaled Rotor Design and Unsteady Experimentation
		7.3.1 Floating Offshore Wind Turbine Scaled Model Evaluation
		7.3.2 Floating Offshore Wind Turbine Rotor-Scaling Methodology and Application
			7.3.2.1 Direct Aerofoil Replacement Methodology
			7.3.2.2 Geometrically Free Rotor Design Methodology
			7.3.2.3 Scaling Methodology Evaluation
	7.4 Remaining Useful Life Prediction of Floating Offshore Wind Turbine Power Converter
		7.4.1 Wind Farm Operation and Maintenance
		7.4.2 Why Predictive Over Condition-Based Maintenance?
		7.4.3 Power Converter
		7.4.4 Investigation on Converter Failures
		7.4.5 Studies Pertaining to Temperature-Related Failures in Power Converters
		7.4.6 Proposal Summary: Remaining Useful Life Estimation Model of Power Converter
			7.4.6.1 FAST Capabilities — Generator Model in FAST
			7.4.6.2 Squirrel Cage Induction Generator
			7.4.6.3 Wind Turbine Specification
			7.4.6.4 Power Converter as Integrated Power Modules
			7.4.6.5 Thermal Analysis of Power Semiconductor Converters
	References
Chapter 8 Aerodynamic Analysis of Floating Offshore Wind Turbine
	8.1 NREL 5MW Wind Turbine Details
	8.2 General Aerodynamic Analysis of Floating Offshore Wind Turbines
	8.3 OC3 Phase IV Case 5.1 — with Normal Sea State
		8.3.1 Benchmark Simulation Scenarios for FAST
		8.3.2 Methodology
		8.3.3 Induction Factors
		8.3.4 Elemental Torque and Thrust
		8.3.5 Computational Fluid Dynamics- and FAST-Based Induction Factors
		8.3.6 Computational Fluid Dynamics Simulation Scenarios
		8.3.7 Results and Discussion
			8.3.7.1 Comparison of Axial and Tangential Induction Factors
	8.4 OC3 Phase IV Case 5.1 — with Theoretical Sea State for Turbulent State Operating Condition Assessment
		8.4.1 Introduction
		8.4.2 Methodology and Approach
		8.4.3 FAST Simulation Scenario for Computational Fluid Dynamics Simulation
		8.4.4 Coupled Dynamic Mesh Motion in Computational Fluid Dynamics
		8.4.5 Transient Motion Pitching Results
		8.4.6 Comparison of Rotor Power in High Wave Elevation Pitching
	References
Chapter 9 Numerical Validation of Floating Offshore Wind Turbine Scaled Rotor for Surge Motion
	9.1 Introduction
	9.2 Scaled Rotor for Unsteady Aerodynamic Experiments
		9.2.1 Experimental Design of Surge Motion
	9.3 Numerical Methodology
		9.3.1 Computational Fluid Dynamics Model
		9.3.2 LR-AeroDyn Model for Unsteady Experimental Scenario
			9.3.2.1 FAST Model Settings
		9.3.3 LR-uBEM Model for Unsteady Experimental Scenario
	9.4 Results and Discussion of Unsteady State Test Cases
		9.4.1 Hydrodynamic Thrust
		9.4.2 Hydrodynamic Torque Comparison
		9.4.3 Evaluation of Wind Turbine Operating State
	References
	Appendix A1
	Appendix A2
Chapter 10 Remaining Useful Life Prediction
	10.1 Introduction
	10.2 Offshore Wind Turbine Power Converter — Thermal Fatigue Loading Cycle-Based Remaining Useful Life Prediction
		10.2.1 Thermal Loads due to Environmental Conditions
		10.2.2 Thermal Loads due to Mechanical Systems of Wind Turbine
		10.2.3 Thermal Loads due to Electrical Systems of Wind Turbine
	10.3 Physics-based Remaining Useful Life Prediction Methodology
		10.3.1 Integrated LR-Aerodyn and LR-uBEM Elastic Servo Control Code
		10.3.2 Python-based Induction Generator Model
		10.3.3 Python-based Power Loss Prediction Model
		10.3.4 Python-based Thermal Model for Junction and Case Temperature Prediction
		10.3.5 Python-based Rain Flow Counting Method
	10.4 Digital Twin Platform
	References
Chapter 11 Concluding Remarks
	11.1 Summary of Darrieus Rotor Characteristics
		11.1.1 Feasibility Check on Four Innovative Concepts
		11.1.2 Computational and Experimental Studies
		11.1.3 Analysis on Discrepancies between Computational Predictions and Experimental Measurements
	11.2 Potential Progress of Darrieus Turbines
		11.2.1 Design Feasibility of 1 kW Hybrid Darrieus Telescopic Savonius Rotor
		11.2.2 Field Test Comparison of Adaptive Hybrid Darrieus Turbine Configuration
		11.2.3 Optimization of Darrieus and Savonius Rotors for Adaptive Hybrid Darrieus Turbines
	11.3 Recommendations
		11.3.1 Improvements on Aerodynamic Model
		11.3.2 Three-dimensional Computational Study
	11.4 Summary of Floating Offshore Wind Turbines
	11.5 Aerodynamic Analysis of Full-Scale 5MW NREL-Based Floating Offshore Wind Turbine
	11.6 Numerical Validation of Scaled Floating Offshore Wind Turbine Rotor
	11.7 Methodology Development and Implementation of Remaining Useful Life for Floating Offshore Wind Turbine Power Converter
Index