T echnische U niversität M ünchen W ind E nergy I nstitute Integrated Design Optimization of Wind Turbines: Challenges, Methods, Applications Carlo L. Bottasso Technische Universität München Funktionsleichtbau für die Windkenergie – Anforderungen, Möglichkeiten, Nutzen DLR, Braunschweig, 20 September 2016
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Design Optimization of Wind Turbines Carlo L. Bottasso ... · Integrated Design Optimization of Wind Turbines: Challenges, Methods, Applications Carlo L. Bottasso Technische Universität
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Integrated Design Optimization of Wind Turbines:
Challenges, Methods, Applications
Carlo L. BottassoTechnische Universität München
Funktionsleichtbau für die Windkenergie – Anforderungen, Möglichkeiten, Nutzen DLR, Braunschweig, 20 September 2016
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Motivation: the Need for Design Tools
Size
Weig
ht (C
ost)
Cubic law of growth
Technological innovation
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Motivation: the Need for Design Tools
Active and passive load
reduction techniques
(source: Timber Tower)
(source: Alstom)
Electromechanical conversionRotor aerodynamics
Materials and structural design
Sensing &
advanced controls
Construction technology
(source: Risø-DTU)
Each innovation will come with pros and cons
Crucial role of design -the final judge-: “Nice idea, but does it reduce the CoE?”
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Pitch-torque control laws:- Regulating the machine at different set points depending on wind conditions- Reacting to gusts- Reacting to wind turbulence- Keeping actuator duty-cycleswithin admissible limits- Handling transients: run-up, normal and emergency shut-down procedures- …
- Annual Energy Production (AEP)- Noise- Transportability-…
- Loads: envelopecomputed from large number of Design Load Cases (DLCs, IEC-61400) - Fatigue (25 year life), Damage Equivalent Loads (DELs)- Maximum blade tip deflections - Placement of natural frequencies wrt rev harmonics- Stability: flutter, LCOs, low damping of certain modes, local buckling- Complex couplingsamong rotor/drive-train/tower/foundations (off-shore: hydro loads, floating & moored platforms)- Weight: massive size, composite materials (but shear quantity is an issue, fiberglass, wood, clever use of carbon fiber)- Manufacturingtechnology, constraints
Pitch-torque control laws:- Regulating the machine at different set points depending on wind conditions- Reacting to gusts- Reacting to wind turbulence- Keeping actuator duty-cycleswithin admissible limits- Handling transients: run-up, normal and emergency shut-down procedures- …
- Annual Energy Production (AEP)- Noise- Transportability-…
- Loads: envelopecomputed from large number of Design Load Cases (DLCs, IEC-61400) - Fatigue (25 year life), Damage Equivalent Loads (DELs)- Maximum blade tip deflections - Placement of natural frequencies wrt rev harmonics- Stability: flutter, LCOs, low damping of certain modes, local buckling- Complex couplingsamong rotor/drive-train/tower/foundations (off-shore: hydro loads, floating & moored platforms)- Weight: massive size, composite materials (but shear quantity is an issue, fiberglass, wood, clever use of carbon fiber)- Manufacturingtechnology, constraints
• Dynamic wake model (Peters-He, yawed flow conditions)
• Efficient large-scale DAE solver with index 3 pre-conditioning
• Non-linearly stable time integrator₋ Energy decaying/preserving scheme₋ Zero-work constraints
• Rigid body
• Geometrically exact beam
• Revolute joint
• Flexible joint
• Actuator
Multibody Dynamics Technology
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• Rigid body
• Geometrically exact beam
• Revolute joint
• Flexible joint
• Actuator
ANBA (Anisotropic Beam Analysis) cross sectional model (Giavotto et al., 1983):• Evaluation of cross sectional stiffness (6 by 6 fully populated) • Recovery of sectional stresses and strains
Optimal blade design with Bend-Twist Coupling (BTC) by spar cap offset
Coupling coefficient 𝜶 =𝑲𝒇𝒍𝒂𝒑−𝒆𝒅𝒈𝒆𝟐
𝑲𝒇𝒍𝒂𝒑𝑲𝒆𝒅𝒈𝒆
Note: all designs satisfy exactly the same requirements
Flap up –> bend edgewise back (sweep)
Optimal offset: 20 cm
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Applications: Passive Load Alleviation
Optimal combination of spar fiber rotation and offset
Note: all designs satisfy exactly the same requirements
Optimal combination: offset 20 cm + angle 5 deg
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Optimal combination of spar fiber rotation and offset
Rotor resizing:
◀ Significant benefits
Applications: Passive Load Alleviation
Optimum: R+5%(similar hub loads as baseline)
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Composite Optimization
Automatic selection of composite laminates along the blade for the different structural components (in collaboration with Owens Corning)
Material catalogue: Multi-parametric composite material model(e.g. fiber fraction, technological parameter, etc.)
Application
INNWIND 10 MW wind turbine, equipped with E-GFRP
Costs estimated from SANDIA model
Blade cost breakdown
Blade materials cost breakdown
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Composite Optimization
Redesign of the spar caps laminate
Redesign of the shell skin laminate
The optimum laminate is between H-GFRP and CFRP
The optimum laminate is between Bx-GFRPand Tx-GFRP
Combined optimum: Blade mass -9.3%, blade cost -2.9%
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POLITECNICO di MILANO POLI-Wind Research Lab
Case Study Results: Optimal blade 3D
Three-dimensional view with detail of thick trailing edge and flatback airfoils.
Free-Form 3D Aero-Structural Optimization
Design airfoils together with blade:
• Bezier airfoil parameterization
• Airfoil aerodynamics by Xfoil + Viterna extrapolation
Additional constraints:
• CL max (margin to stall), geometry
Automatic appearance of flatback airfoil!
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Some ReferencesP. Bortolotti, A. Croce, and C.L. Bottasso: Combined preliminary–detailed design of wind turbines. Wind Energ. Sci., 1, 1–18, 2016, doi:10.5194/wes-1-1-2016
C.L. Bottasso, P. Bortolotti, A. Croce, and F. Gualdoni: Integrated Aero-Structural Optimization of Wind Turbine Rotors. Multibody Syst. Dyn., doi: 10.1007/s11044-015-9488-1
C.L. Bottasso, F. Campagnolo, A. Croce, S. Dilli, F. Gualdoni, M.B. Nielsen: Structural Optimization of Wind Turbine Rotor Blades by Multi-Level Sectional/Multibody/3DFEM Analysis, Multibody System Dynamics, 32:87-116, 2014
C.L. Bottasso, F. Campagnolo, C. Tibaldi: Optimization-Based Study of Bend-Twist Coupled Rotor Blades for Passive and Integrated Passive/Active Load Alleviation, Wind Energy, 16:1149-1166, 2013
C.L. Bottasso, A. Croce, F. Campagnolo: Multi-Disciplinary Constrained Optimization of Wind Turbines, Multibody System Dynamics, 27:21-53, 2012
O.A. Bauchau, A. Epple, C.L. Bottasso: Scaling of Constraints and Augmented Lagrangian Formulations in Multibody Dynamics Simulations, ASME Journal of Computational and Nonlinear Dynamics, 4:021007, 2009
• P. Bortolotti, G. Adolphs, C.L. Bottasso: A methodology to guide the selection of composite materials in a windturbine rotor blade design process
• A. Croce, L. Sartori, M.S. Lunghini, L. Clozza, P. Bortolotti, C.L. Bottasso: Lightweight rotor design by optimalspar cap offset
• L. Sartori, P. Bortolotti, A. Croce, and C.L. Bottasso: Integration of prebend optimization in a holistic windturbine design tool
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Conclusions
• Strong couplings between aero and structural design variables
• Multi-level approach to marry high fidelity and computational effort
• Integrated design optimization allows for fast exploration of design space, leading to potential significant CoE improvements
Open issues/outlook:• CoE: solutions are highly sensitive to cost model, need detailed
reliable models that truly account for all significant effects, problem partially alleviated by Pareto solutions (in progress)
• Uncertainties everywhere (aero, structure, wind, …), move away from deterministic design (but what about certification standards?), currently working on UQ and robust design P
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Acknowledgements
Work in collaboration with:
• Pietro Bortolotti (TUM)
• Alessandro Croce, Luca Sartori (Politecnico di Milano)