1 / 17

Optimization of floating support structures for deep water wind turbines

Optimization of floating support structures for deep water wind turbines. EWEA 2011 14-17 March 2011, Brussels, Belgium by Petter Andreas Berthelsen MARINTEK. Background and motivation. Growing interest for floating wind turbines (FWT) Limited access to shallow water areas world wide

selina
Télécharger la présentation

Optimization of floating support structures for deep water wind turbines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Optimization of floating support structures for deep water wind turbines EWEA 2011 14-17 March 2011, Brussels, Belgium by Petter Andreas Berthelsen MARINTEK

  2. Background and motivation • Growing interest for floating wind turbines (FWT) • Limited access to shallow water areas world wide • Can be installed further offshore • in areas with stronger and steadier wind • with less visual impact • Potential is huge provided cost can be brought down to a competitive level • Additional technical challenges for FWT • E.g. exposed to wave induced motions • Conceptual design need to • Limit wave and wind induced motions • Minimize cost There is a need for efficient methods for optimal design of floating offshore wind turbines

  3. Scope of work • Develop a tool for: Optimization of floater and mooring system for a given wind turbine size and given design requirements. Optimization in this context is the same as minimizing the material cost while satisfying functional and safety related design requirements • Based on existing software tools • Consider optimization of Spar type floaters only

  4. Design tool • WINDOPT • Efficient design tool for minimum cost design offloatingsupport structures, includingmooring system and cable connection • Spar type concepts • Building block for WINDOPT • MOOROPT – Optimization tool for mooring- and riser systems • MIMOSA 6.3 – Response analysis in frequency domain • WF+LF motion • Mooring and power cable forces • WAMOF 3 – Hydrodynamic response analysis of slender structures • NLPQL – Nonlinear optimisation with arbitrary constraints • Usefultoolfor conceptual design and parametric studies

  5. Problem formulation • 3 key items for optimization • Objective function Cost function to be minimized: Spar buoy cost + mooring line cost • Constraints Design requirements: Floater motions, heel angle, nacelle accelerations, capacity (safety factors), offset limitations, etc… • Variables Design parameters influencing the objective function and/or constraint related responses: Spar diameter and length, mooring line diameter, lengths, pretension, etc…

  6. Parameterizations and cost model • Need a simplified representation of the spar buoy • Assume that a representative mass and cost figure for an initial structure is available • Mass per unit length governed by depth and diameter • Spar buoy cost • Mooring line cost Diameter dependency Depth dependency

  7. Constraints • Spar buoy: • Maximum spar draught • Maximum tower inclination • Max/min requirements on heave and pitch period • Maximum nacelle acceleration • Mooring lines: • Maximum mooring line tension • Maximum allowable horizontal offset • Minimum static horizontal pretension (for minimum yaw stiffness) • …

  8. Variables • Spar buoy • Cylinder variables • Height and diameter • Diameter of footing • Vertical positionof fairleads • Mooring system • Line direction • Pretension or distance to anchor • Segment length • Segment diameter • Tower and turbinearefixed Col 1 Water plane section Col 2 Transition section Col 3 Main buoyancy section Col 4 Heavy ballast section Footing, Bottom plate Mooring lines Power export cable

  9. Analysis option • Extreme response analysis • Repeated NCASE times, each one with NENV different environments. • Typical cases • Operational (rotor running) • Survival (passive rotor) • Damage (line break, etc…) • Check for design constraints • Fatigue response calculation • Check for fatigue life constraints (mooring lines only) (not included in present work)

  10. Example • Water depth is 320 m • Extreme conditions: Reference case based on: NREL/IEA OC3 5MW turbine

  11. Example: Floater definitions • Initial data: • Material mass- and cost assumption • Consider three different design options

  12. Example: Performance • Constraints Max allowable draught is 120 m • Results

  13. Example: Spar shape

  14. Example: Cost Mooring lines:

  15. Concluding remarks • Useful tool for finding improved solutions for floating support and mooring system • Efficient for parametric studies and valuable for early evaluations of spar concepts • (not intended as detailed simulation tool) • Weight and cost models can be further improved • Realistic design constraints need to be obtained • Further development to be considered are: • Fatigue life constraints (completed, but not included in present work) • Optimize power cable (completed, but not included in present work) • Include tower design • Other types of floaters • Improved description of wind loads

  16. Acknowledgement • This work has been carried out as part of NOWITECH (Norwegian Research Centre for Offshore Wind Technology) which is co-funded by the Research Council of Norway, and participating industrial companies and research organisations (www.nowitech.no)

  17. References • Fylling and Berthelsen (2011), WINDOPT – An optimization tool for floating support structures for deep water wind turbines, OMAE 2011

More Related