iea wind task 23 oc3: phase iv results regarding floating wind turbine modeling operated for the...

IEA Wind Task 23 OC3:Phase IV Results Regarding Floating Wind Turbine Modeling

Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by the Alliance for Sustainable Energy, LLC

http://www.sintef.no/Home/Marine/MARINTEK/

http://www.ife.no/index_html-en?set_language=en

EWEC 2010 2 National Renewable Energy Laboratory

Floating Challenges & Phase IV Model

• Low frequency modes:– Influence aerodynamic damping & stability

• Large platform motions:– Coupling with turbine

• Complicated shape:– Radiation & diffraction

• Moorings

• Statoil supplied data for 5-MWHywind conceptual design

• OC3 adapted spar to support the NREL 5-MW turbine:– Rotor-nacelle assembly unchanged– Tower & control system modified

Ch

alle

ng

esO

C3-

Hyw

ind

OC3-Hywind Model


Aero-Hydro-Servo-Elastic Capabilities

FAST Bladed ADAMS HAWC2 3Dfloat Simo SESAM / DeepC

Code Developer NREL GH MSC + NREL

+ LUH Risø-DTU IFE-UMB MARINTEK DNV

OC3 Participant NREL + POSTECH GH NREL + LUH Risø-DTU IFE-UMB MARINTEK Acciona + NTNU

Aerodynamics ( BEM or GDW )

+ DS ( BEM or GDW )

+ DS ( BEM or GDW )

+ DS ( BEM or GDW )

+ DS ( BEM or GDW ) BEM None

Hydrodynamics Airy+ + ME,

Airy + PF + ME ( Airy+ or Stream )

+ ME Airy+ + ME,

Airy + PF + ME Airy + ME Airy + ME Airy + PF + ME Airy+ + ME,

Airy + PF + ME

Control System (Servo) DLL, UD, SM DLL DLL, UD DLL, UD, SM UD DLL None

Structural Dynamics (Elastic) Turbine: FEMP + ( Modal / MBS ), Moorings: QSCE

Turbine: FEMP + ( Modal / MBS ), Moorings: UDFD

Turbine: MBS, Moorings: QSCE,

UDFD

Turbine: MBS / FEM, Moorings: UDFD

Turbine: FEM, Moorings: FEM, UDFD


MBS


FEM

Airy+ – Airy wave theory +) with free surface corrections BEM – blade-element / momentum DLL – external dynamic link library DNV – Det Norsk Veritas DS – dynamic stall

GDW – generalized dynamic wake FEMP – finite-element method P) for mode preprocessing only MBS – multibody-dynamics formulation ME – Morison’s equation MSC – MSC Software Corporation

PF – linear potential flow with radiation & diffraction

QSCE – quasi-static catenary equations SM – interface to Simulink® with MATLAB® UD – implementation through user-defined

subroutine available UDFD – implementation through user-defined force-

displacement relationships


Phase IV Load Cases


Output Parameters (57 Total)

Rotor BladeLoads & Deflections13 Outputs

Drivetrain & GeneratorLoads & Operation

7 Outputs

TowerLoads & Deflections

15 Outputs

EnvironmentWind & Waves4 Outputs

PlatformDisplacements6 Outputs

Mooring SystemFairlead & Anchor

Tensions & Angles12 Outputs

Output Parameters & Results Legend

Results Legend


Full-System Eigenanalysis


Free Decay

Free Decay in Platform Surge

Free Decay in Platform Pitch


Hydro-Elastic Responsewith Regular Waves


Hydro-Elastic Responsewith Irregular Waves


Aero-Hydro-Servo-Elastic Responsewith Regular Waves


Aero-Hydro-Servo-Elastic Responsewith Irregular Waves


Aero-Hydro-Servo-Elastic“Effective RAOs”


• Close agreement was not achieved by all codes:– What was the reason?

• The ”effective RAO” load case was somewhat ”academic”:– What response charateristic is more relevant?– Alternative suggested by IF — RAOs could be derived from irregular

time series & cross spectra between excitation & response

• The stochastic response statistics & spectra are sensitive to simulation length:– What length would be more appropriate?– How can we eliminate start-up transients from the comparisons?

Unresolved Issues of OC3 Phase IV


• OC3-Hywind platform was considered as a rigid body; no hydro-elastic effects

• OC3-Hywind platform is simple in shape; only a single member• Hydrodynamic radiation & diffraction was negligible in the

OC3-Hywind spar buoy• Sea current was never considered• Few sea states were tested; larger waves may be interesting• The relative importance of 2nd versus 1st order hydrodynamics

was never assessed• The relative importance of dynamic versus quasi-static

mooring models was never assessed• The influence of platform motion on rotor aerodynamics was

never looked at in detail

Limitations of OC3 Phase IV

Thank You for Your Attention

Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by the Alliance for Sustainable Energy, LLC

Jason Jonkman, Ph.D.+1 (303) 384 – [email protected]


• OWTs are designed using aero-hydro-servo-elastic codes• The codes must be verified to assess their accuracy

Wind Turbine & Support StructureApplied Loads

External Conditions

Soil

Hydro-dynamics

Aero-dynamics

Waves & Currents

Wind-InflowPower

GenerationRotor

Dynamics

Substructure Dynamics

Foundation Dynamics

Drivetrain Dynamics

Control System

Soil-Struct. Interaction

Nacelle Dynamics

Tower Dynamics

Background


• Discuss modeling strategies• Develop suite of benchmark models & simulations• Run simulations & process results• Compare & discuss results

• Assess simulation accuracy & reliability• Train new analysts how to run codes correctly• Investigate capabilities of implemented theories• Refine applied analysis methods• Identify further R&D needs

Act

ivit

ies

Ob

ject

ives

OC3 Activities & Objectives

The IEA Offshore Code Comparison Collaboration (OC3) is an international forum for OWT dynamics code verification


• All inputs are predefined:– NREL 5-MW wind turbine, including control system– Variety of support structures– Wind & wave datasets

• A stepwise procedure is applied:– Load cases selected to test different model features

• OC3 ran from 2005 to 2009:– Phase I – Monopile + Rigid Foundation– Phase II – Monopile + Flexible Found’tn– Phase III – Tripod– Phase IV – Floating Spar Buoy

• 3-year follow-on project recently initiated:– Phase V – Jacket– Phase VI – Floating semisubmersible

Ap

pro

ach

Ph

asesOC3 Approach & Phases


• OC3 aims to verify OWT dynamics codes• Simulations tested a variety of OWT types &

model features• Code-to-code comparisons have agreed well• Differences caused by variations in:

– Model fidelity– Aero- & hydrodynamic theory– Model discretization– Numerical problems– User error

• Future work will consider offshore jacket & semisubmersible

• Verification is critical to advance offshore windSpar Concept by SWAYSemisubmersible Concept

Summary

iea wind task 23 oc3: phase iv results regarding floating wind turbine modeling operated for the...

Documents

sustainable energy

irregular waves slide

platform pitch slide

servoelastic response

system eigenanalysis

outputs platform displacements

excitation response

outputs environment