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A Quantitative Comparison of Three Floating Wind Turbines. AWEA Offshore Wind Project Workshop December 2-3, 2009 Jason Jonkman, Ph.D. Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute • Battelle. Offshore Wind Technology.

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A Quantitative Comparison of Three Floating Wind Turbines


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a quantitative comparison of three floating wind turbines

A Quantitative Comparisonof Three Floating Wind Turbines

AWEA Offshore Wind Project Workshop

December 2-3, 2009

Jason Jonkman, Ph.D.

Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute • Battelle

slide2

Offshore Wind Technology

Onshore

ShallowWater

0m-30m

Transitional

Depth

30m-60m

Deepwater60m+

slide4

Floating Wind Turbine Concepts

  • Design Challenges
  • Low frequency modes:
    • Influence on aerodynamic damping & stability
  • Large platform motions:
    • Coupling with turbine
  • Complicated shape:
    • Radiation & diffraction
  • Moorings, cables, & anchors
  • Construction, installation & O&M
slide5

Modeling Requirements

  • Coupled aero-hydro-servo-elastic interaction
  • Wind-inflow:
    • Discrete events
    • Turbulence
  • Waves:
    • Regular
    • Irregular
  • Aerodynamics:
    • Induction
    • Rotational augmentation
    • Skewed wake
    • Dynamic stall
  • Hydrodynamics:
    • Diffraction
    • Radiation
    • Hydrostatics
  • Structural dynamics:
    • Gravity / inertia
    • Elasticity
    • Foundations / moorings
  • Control system:
    • Yaw, torque, pitch
slide7

Floating Concept Analysis Process

  • Run IEC-style load cases:
    • Identify ultimate loads
    • Identify fatigue loads
    • Identify instabilities
  • Compare concepts against each other & to onshore
  • Iterate on design:
    • Limit-state analysis
    • MIMO state-space control
  • Evaluate system economics
  • Identify hybrid features that will potentially provide the best overall characteristics
  • Use same NREL 5-MW turbine & environmental conditions for all
  • Design floater:
    • Platform
    • Mooring system
    • Modify tower (if needed)
    • Modify baseline controller(if needed)
  • Create FAST / AeroDyn / HydroDyn model
  • Check model by comparing frequency & time domain:
    • RAOs
    • PDFs
slide8

Three Concepts Analyzed

NREL 5-MW on

OC3-Hywind Spar

NREL 5-MW on

ITI Energy Barge

NREL 5-MW on

MIT/NREL TLP

slide10

Normal Operation:

DLC 1.1-1.5 Ultimate Loads

Blade Root Bending Moment

Low-Speed Shaft Bending Moment

Yaw Bearing Bending Moment

Tower Base Bending Moment

slide11

Floating Platform Analysis Summary

  • MIT/NREL TLP
  • Behaves essentially like a land-based turbine
  • Only slight increase in ultimate & fatigue loads
  • Expensive anchor system
  • OC3-Hywind Spar Buoy
  • Only slight increase in blade loads
  • Moderate increase in tower loads; needs strengthening
  • Difficult manufacturing & installation at many sites
  • ITI Enery Barge
  • High increase in loads; needs strengthening
  • Likely applicable only at sheltered sites
  • Simple & inexpensive installation
slide12

Ongoing Work & Future Plans

  • Assess roll of advanced control
  • Resolve system instabilities
  • Optimize system designs
  • Evaluate system economics
  • Analyze other floating concepts:
    • Platform configuration
    • Vary turbine size, weight, & configuration
  • Verify simulations further under IEA OC3
  • Validate simulations with test data
  • Improve simulation capabilities
  • Develop design guidelines / standards

Spar Concept by SWAY

Semi-Submersible Concept

thank you for your attention

Thank You for Your Attention

Jason Jonkman, Ph.D.

+1 (303) 384 – 7026

jason.jonkman@nrel.gov

Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute • Battelle

slide14

Design Load Case Table

Summary of Selected Design Load Cases from IEC61400-1 & -3

slide15

Normal Operation:

DLC 1.2 Fatigue Loads

Side-to-Side

Fore-Aft

Side-to-Side

Fore-Aft

Out-of-Plane

In-Plane

90°

Blade Root Bending Moments

Yaw Bearing Bending Moments

Tower Base Bending Moments

Low-Speed Shaft Bending Moments

slide16

Idling:

DLC 6.2a Side-to-Side Instability

  • Aero-elastic interaction causes negative damping in a coupled blade-edge, tower-S-S, & platform-roll & -yaw mode
  • Conditions:
    • 50-yr wind event for TLP, spar, & land-based turbine
    • Idling + loss of grid; all blades = 90º; nacelle yaw error = ±(20º to 40º)
    • Instability diminished in barge by wave radiation
  • Possible solutions:
    • Modify airfoils to reduce energy absorption
    • Allow slip of yaw drive
    • Apply brake to keep rotor away from critical azimuths
slide17

Idling:

DLC 2.1 & 7.1a Yaw Instability

  • Aero-elastic interaction causes negative damping in a mode that couples rotor azimuth with platform yaw
  • Conditions:
    • Normal or 1-yr wind & wave events
    • Idling + fault; blade pitch = 0º (seized), 90º, 90º
    • Instability in TLP & barge, not in spar or land-based turbine
  • Possible solutions:
    • Reduce fully feathered pitch to allow slow roll while idling
    • Apply brake to stop rotor