Design of a Vessel Operating in Offshore Windwflportal.amcplaza.com/System/Lists/SystemProducts/... · 2014. 5. 2. · The missing Link in the Offshore Wind Industry: Offshore Wind

The missing Link in the Offshore Wind Industry: Offshore Wind Support Ship Wilco Stavenuiter

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The missing Link in the Offshore Wind Industry: Offshore Wind Support Ship

Report

Wilco Stavenuiter Version 1.0 Graduation commission consisting of: Prof. Ir. J. Hopman, TU Delft Dr. Ir. H. Boonstra, TU Delft Ir. L. Keuning, TU Delft Ir. M. Ooijen, GustoMSC Report Number: SDPO.09.020.m


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i. Contents i. Contents ................................................................................................................................................. 2 ii. Notations ................................................................................................................................................ 6 iii. List of Figures ................................................................................................................................ 9 iv. List of Tables ............................................................................................................................... 11 v. Axis Convention ................................................................................................................................... 13 vi. Introduction .................................................................................................................................. 14 1. Market Analysis .................................................................................................................................... 15

1.1. Main Components of an Offshore Wind Turbine ......................................................................... 15 1.2. Wind Turbines ............................................................................................................................. 16

1.2.1. Rotor .................................................................................................................................... 17 1.2.2. Nacelle ................................................................................................................................ 17 1.2.3. Tower .................................................................................................................................. 18 1.2.4. Access from the Service Platform to the Nacelle ................................................................ 18 1.2.5. Future Developments .......................................................................................................... 18

1.3. Foundations of Offshore Wind Turbines ..................................................................................... 19 1.3.1. Resonance .......................................................................................................................... 19 1.3.2. Bottom Founded Foundations ............................................................................................. 20 1.3.3. Floating Foundations ........................................................................................................... 21 1.3.4. Sub Conclusion ................................................................................................................... 22

1.4. Offshore Wind Farms .................................................................................................................. 24 1.4.1. The Formation of an OWF .................................................................................................. 24 1.4.2. Operational Offshore Wind Farms ...................................................................................... 24 1.4.3. Offshore Wind Farms Future Outlook ................................................................................. 29

1.5. Life Cycle OWF Cost ................................................................................................................... 31 1.5.1. Energy Balance ................................................................................................................... 31 1.5.2. Life Cycle OWF Cost ........................................................................................................... 31

1.6. Operation & Maintenance ........................................................................................................... 34 1.7. Environmental Considerations .................................................................................................... 37

1.7.1. Waves ................................................................................................................................. 37 1.7.2. Wind .................................................................................................................................... 41 1.7.3. Current ................................................................................................................................ 44 1.7.4. Limiting Waves, Wind & Current ......................................................................................... 45

1.8. The OWF Installation Market ...................................................................................................... 45 1.8.1. Quantitative Analysis of Vessels that have Installed Foundations ...................................... 45 1.8.2. Quantitative Analysis of Vessel that have Installed Wind Turbines .................................... 46 1.8.3. Qualitative Analysis of Jack-ups operating in Offshore Wind ............................................. 47 1.8.4. Qualitative Analysis of Floating Vessels operating in Offshore Wind ................................. 49

1.9. The OWF Maintenance Market ................................................................................................... 50 1.9.1. Vessels Operating in Maintenance Category 1 ................................................................... 50 1.9.2. Vessels Operating in Maintenance Category 2 ................................................................... 50 1.9.3. Vessels Operating in Maintenance Category 3 ................................................................... 51 1.9.4. Vessels Operating in Maintenance Category 4 ................................................................... 51

1.10. Conclusion Market Analysis ........................................................................................................ 52 2. Selection of Subject ............................................................................................................................. 54

2.1. Floating Wind Turbine Installation ............................................................................................... 54 2.2. OWT Feeder................................................................................................................................ 54 2.3. Installation Support ..................................................................................................................... 55 2.4. Personnel Transfer ...................................................................................................................... 55 2.5. Maintenance ................................................................................................................................ 55 2.6. Converge to an ‘Offshore Wind Support Ship’ ............................................................................ 56

3. Functional Description ......................................................................................................................... 57 3.1. Total Systems.............................................................................................................................. 57 3.2. Life Time Scenarios .................................................................................................................... 57


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3.2.1. Scenario 1: OWF Installation Support all Year Around ....................................................... 57 3.2.2. Scenario 2: during Summer OWF Installation Support, during Winter OWF Maintenance 57 3.2.3. Scenario 3: OWF Maintenance all Year Round .................................................................. 58

3.3. Functional Requirements ............................................................................................................ 58 3.3.1. Rules & Regulation.............................................................................................................. 58 3.3.2. Environmental Conditions ................................................................................................... 58 3.3.3. Thruster System .................................................................................................................. 59 3.3.4. Motions ................................................................................................................................ 60 3.3.5. Autonomy, Stores & Capacities .......................................................................................... 60 3.3.6. Accommodation................................................................................................................... 61 3.3.7. Lifting & Handling Systems ................................................................................................. 62 3.3.8. Life Saving Equipment ........................................................................................................ 62 3.3.9. No Helicopter Deck ............................................................................................................. 62

4. Ship Type Concept .............................................................................................................................. 63 4.1.1. Monohull .............................................................................................................................. 63 4.1.2. Catamaran ........................................................................................................................... 63 4.1.3. Semi-submersible................................................................................................................ 63 4.1.4. SWATH ............................................................................................................................... 63 4.1.5. Summary of Ship Type Selection ........................................................................................ 63

4.2. Access Technology ..................................................................................................................... 64 4.2.1. Boat Landing ....................................................................................................................... 64 4.2.2. Helicopter ............................................................................................................................ 64 4.2.3. Transfer System .................................................................................................................. 64 4.2.4. Selection Access Technology ............................................................................................. 64

4.3. Transfer System .......................................................................................................................... 64 4.3.1. Offshore Transfer System (OTS) ........................................................................................ 65 4.3.2. Offshore Access System (OAS) .......................................................................................... 65 4.3.3. Ampelmann ......................................................................................................................... 66 4.3.4. Offshore Wind Access System (OWAS) ............................................................................. 67 4.3.5. Cableway ............................................................................................................................. 67 4.3.6. Motion Compensated Crane (MCC).................................................................................... 68 4.3.7. Selection .............................................................................................................................. 69

5. Main Dimensions ................................................................................................................................. 71 5.1. Example Ships ............................................................................................................................ 71 5.2. Estimation of Main Dimensions ................................................................................................... 71 5.3. Thrusters ..................................................................................................................................... 71

5.3.1. Thruster Requirements by Conditions ................................................................................ 71 5.3.2. Final Thrust System ............................................................................................................ 71

6. Hull Form ............................................................................................................................................. 73 6.1. Mid Shape ................................................................................................................................... 73 6.2. Forward Shape ............................................................................................................................ 73 6.3. Aft Shape ..................................................................................................................................... 73 6.4. Final Hull Form ............................................................................................................................ 74

7. General Arrangement .......................................................................................................................... 75 7.1. Above Main Deck ........................................................................................................................ 75

7.1.1. Super Structure ................................................................................................................... 75 7.1.2. Motion Compensated Crane ............................................................................................... 75 7.1.3. Free Deck ............................................................................................................................ 75 7.1.4. Aft Structure ........................................................................................................................ 75 7.1.5. Safety Equipment ................................................................................................................ 76

7.2. Below Main Deck ........................................................................................................................ 76 7.2.1. Thruster Rooms ................................................................................................................... 76 7.2.1. Accommodation................................................................................................................... 76 7.2.2. Machine Room (Generators) ............................................................................................... 76 7.2.3. Machine Room (Electrical Equipment) ................................................................................ 77 7.2.4. Crane Room ........................................................................................................................ 77


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7.3. Tank Arrangement ...................................................................................................................... 77 7.3.1. Fuel Oil Tanks ..................................................................................................................... 77 7.3.2. Potable Water Tanks ........................................................................................................... 77 7.3.3. Sewage Water Tanks .......................................................................................................... 77 7.3.4. Ballast Water Tanks ............................................................................................................ 77

8. Weights & Stability ............................................................................................................................... 78 8.1. Light Ship Weight ........................................................................................................................ 78

8.1.1. Allowance ............................................................................................................................ 78 8.1.2. Contingency ........................................................................................................................ 78 8.1.3. Design Margin ..................................................................................................................... 78 8.1.4. Specification of Weight Items .............................................................................................. 78

8.2. Freeboard .................................................................................................................................... 79 8.3. Loading Conditions ..................................................................................................................... 79 8.4. Stability Regulations .................................................................................................................... 80 8.5. Intact Stability .............................................................................................................................. 80

8.5.1. Harbour and Transit Loading Conditions ............................................................................ 81 8.5.2. Lifting Loading Conditions ................................................................................................... 82

8.6. Damage Stability ......................................................................................................................... 83 8.6.1. Harbour and Transit Loading Conditions ............................................................................ 83 8.6.2. Lifting Loading Conditions ................................................................................................... 85

9. Structural .............................................................................................................................................. 86 9.1. Material ........................................................................................................................................ 86 9.2. The Midship Section .................................................................................................................... 86 9.3. The Transverse Deck Girders ..................................................................................................... 87

10. Resistance & Propulsion ............................................................................................................. 90 10.1. Loading Conditions ..................................................................................................................... 90 10.2. Resistance ................................................................................................................................... 90 10.3. Propulsion ................................................................................................................................... 91 10.4. Result .......................................................................................................................................... 92

11. Electrical Power Balance ............................................................................................................ 93 11.1. Power Consumers ....................................................................................................................... 93 11.2. Operating Conditions .................................................................................................................. 93 11.3. Power Generation ....................................................................................................................... 93 11.4. Power Balance ............................................................................................................................ 94 11.5. Key-one-line ................................................................................................................................ 94

12. Motions ........................................................................................................................................ 96 12.1. Loading Conditions ..................................................................................................................... 96 12.2. Environmental Conditions ........................................................................................................... 96 12.3. Calculation Method ..................................................................................................................... 97

12.3.1. AQWA-line ........................................................................................................................... 97 12.3.2. Added Roll Damping ........................................................................................................... 97 12.3.3. Forward Speed .................................................................................................................... 97

12.4. Maximum Motion Amplitudes ...................................................................................................... 98 12.5. Accelerations at Specified Locations .......................................................................................... 98 12.6. Propeller Emergence ................................................................................................................ 100 12.7. Freeboard Exceedance ............................................................................................................. 102

13. Dynamic Positioning .................................................................................................................. 103 13.1. Loading Condition ..................................................................................................................... 103 13.2. Environmental Condition ........................................................................................................... 103

13.2.1. Wave ................................................................................................................................. 103 13.2.2. Current .............................................................................................................................. 103 13.2.3. Wind .................................................................................................................................. 104

13.3. Thruster Configuration .............................................................................................................. 105 13.3.1. Thruster Force ................................................................................................................... 105 13.3.2. Thruster Efficiencies .......................................................................................................... 105 12.3.3. Thruster Power ...................................................................................................................... 106


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13.4. Intact DP-capability Results ...................................................................................................... 107 13.5. DP-capability Results after one Component Failure ................................................................. 108

13.5.1. One Thruster Failure ......................................................................................................... 108 13.5.2. One Generator Failure ...................................................................................................... 108 13.5.3. One Switchboard Section Failure ...................................................................................... 108 13.5.4. Harbour DP-Tracking ........................................................................................................ 110

14. CAPEX ...................................................................................................................................... 111 15. Conclusions & Recommendations ............................................................................................ 112

15.1. Conclusions ............................................................................................................................... 112 15.2. Recommendations .................................................................................................................... 112

16. Bibliography............................................................................................................................... 114


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ii. Notations a) Units

kg Kilogram for mass m Meter for length / distance / displacement N Newton for force and weight s Second for time and period

or rad Degree or radian for angular measurement

b) Constants Hp Horsepower 745.70 W Hz Hertz (rounds / second) s-1 km Kilo meter 1,000 m kn Knots 0.5144 m/s kW Kilowatt (power) 1,000 W MEuro One-Million Euro 1,000,000 Euro MW Megawatt (power) 1,000,000 W nm Nautical mile 1,852 m t Metric ton 1000 kg W Watt (power) kg*m2/s3

c) Physical constants ρsea water Sea water density 1,025 kg/m3 g Standard gravity acceleration 9.81 m/s2 νsea water Kinematic viscosity sea water 1.1833*10-6 m2/s

d) Abbreviations

APP Aft Perpendicular AWL Above Water Line B Greatest moulded Breadth BL Baseline BM Metacentre height CAPEX Capital Expenditures Cb Block Coefficient CL Centreline COG Centre of Gravity Cp Prismatic coefficient D Least moulded Depth DNV Det Norske Veritas DP Dynamic Positioning DWT Deadweight FPP Forward Perpendicular GB Distance between centre of buoyancy and gravity GM Distance between Centre of Gravity and metacentre GMfluid Metacentre height corrected for free surface effects GW Gross Weight GZ Righting lever H&M Holtrop&Mennen HLV Heavy Lift Vessel HLV Heavy Lift Vessel Hs Significant wave height HVAC Heating, Ventilation and Air Conditioning ICLL International Convention of Load Lines ILO International Labour Organisation IMCA International Marine Contractors Association IMO International Maritime Organization


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ISO International Standard Organisation Ixx Moment of inertia in roll Iyy Moment of inertia in pitch Izz Moment of inertia in yaw KG Distance between baseline and Centre of Gravity KGfluid Distance between baseline and Centre of Gravity, corrected for free surface effects KM Distance between Keel and Metacentre kxx Radius of gyration for roll kyy Radius of gyration for pitch kzz Radius of gyration for yaw LCB Longitudinal Centre of Buoyancy LCG Longitudinal Centre of Gravity LO Lubrications Oil LOA Length Over All LPP Length between perpendiculars LSW Light Ship Weight Lwl Length of the Waterline LWT Light Ship Weight MCC Motion Compensated Crane MDO Marine Diesel Oil MDO Marine Diesel Oil NMD Norwegian Maritime Directorate NW Net Weight O&M Operation & Maintenance OAS Offshore Access System (product of Offshore Solutions) OPEX Operational Expenditures OTS Offshore Transfer System (product of Offshore Solutions) OWAS Offshore Wind Access System (product of Reflex Marine) OWF Offshore Wind Farm OWF Offshore Wind Farm OWSS Offshore Wind Support Ship OWT Offshore Wind Turbine OWT Offshore Wind Turbine PS Portside PTB Personnel Transfer Bridge PW Potable Water RAO Response Amplitude Operator RMS Root Mean Square SB Starboard SOLAS Safety of Life at Sea SPC Special Purpose Code SWAMH Small Waterline Area Mono Hull SWATH Small Waterline Area Twin Hull SWL Safe Working Load t Trim T Mean moulded draft t Thrust deduction factor T&I Transport & Installation TCG Transverse Centre of Gravity TLP Tension Leg Platform Tp Wave peak period Vc Angle of capsizing Vc Current speed VCG Vertical Centre of Gravity Vfl Angle of downflooding Vh Angle of heel


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Vm Angle of maximum stability Vs Angle of second intercept Vs Ship speed Vw Wind Velocity W Wake factor WB Water Ballast WT Wind Turbine WT Wind Turbine WTI Wind Turbine Installation γ Peak enhancement factor Δ Displacement [t] ρ Density ς Wave Amplitude ω Circular wave frequency [rad/s]


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iii. List of Figures Figure 1: Axis Convention ........................................................................................................................... 13 Figure 2: Main Components of an Offshore Wind Turbine ......................................................................... 15 Figure 3: Offshore Wind Turbine ................................................................................................................. 15 Figure 4: Nacelle OWT (Vestas V90-3MW) ................................................................................................ 17 Figure 5: Foundation ................................................................................................................................... 19 Figure 6: Excitation Frequencies OWT ....................................................................................................... 19 Figure 7: Floating Foundations Types ........................................................................................................ 21 Figure 8: Triangle of Stable Floating Foundations ...................................................................................... 22 Figure 9: Overview of Foundation Types (Vries, 2007) .............................................................................. 23 Figure 10: Cost of Foundation Types (Musial, Butterfield, & Ram, 2006) .................................................. 23 Figure 11: Offshore Wind Energy Market Development in Europe (OWF-database, 2009) ...................... 24 Figure 12: Operational Offshore Wind Farms end 2009 (OWF-database, 2009) ....................................... 25 Figure 13: Operational Offshore MW / Offshore Wind Turbine (OWF-database, 2009)............................. 26 Figure 14: First and Latest Year of Installation / Offshore Wind Turbine (OWF-database, 2009) .............. 26 Figure 15: Hub Height / WT (OWF-database, 2009) .................................................................................. 27 Figure 16: Water Depth / Year (OWF-database, 2009) .............................................................................. 27 Figure 17: Water Depth / Foundation Type (OWF-database, 2009) .......................................................... 28 Figure 18: Installed Foundations (OWF-database, 2009) ........................................................................... 28 Figure 19: Distance to Shore (OWF-database, 2009) ................................................................................ 29 Figure 20: Offshore Wind Power Scenarios to 2030 (EWEA-PP, 2008) .................................................... 29 Figure 21: Planned Offshore Wind Farms for 2015 (EWEA, 2009) ............................................................ 30 Figure 22: European Offshore Wind Energy Map (Van Oord, 2009) .......................................................... 31 Figure 23: Offshore Wind Farm Level 1 Cost Breakdown of 1 WT of 5MW ............................................... 32 Figure 24: Offshore Wind Farm Level 2 Cost Breakdown of 1 WT of 5MW ............................................... 33 Figure 25: Offshore Wind Farm Level 3 Cost Breakdown of 100 WT’s of 5MW ........................................ 34 Figure 26: Failure Rate Statistics ................................................................................................................ 35 Figure 27: Failure Distribution per System LWK & WMEP Statistics (69-368 turbines, year 1998-2000).. 36 Figure 28: Corrective Maintenance Distribution by Maintenance Category (ECN-DOWEC, 2002) ........... 37 Figure 29: Map of Measurement Locations (List: Table 5) ......................................................................... 38 Figure 30: Measured Wave Data near the Netherlands (planned) OWF’s (Rijkswaterstaat, 2009) ........... 39 Figure 31: Measured Wave Data near German (planned) OWF’s (BSH, 2009) ........................................ 39 Figure 32: Measured Wave Data near West Coast England (planned) OWF’s (Shell&Fugro, 2002) ........ 40 Figure 33: Measured Wave Data near Dutch OWF’s by Season (Rijkswaterstaat, 2009) ......................... 40 Figure 34: Estimates of 50-year Return Significant Wave Heights, Hs50 ................................................... 41 Figure 35: Wind Resources over Open Sea (Risø, 1989) .......................................................................... 42 Figure 36: Wind Speed Distribution, at 10 m Height, according an Assumed Weibull (μ=7.5, λ=8.46, k=2) Distribution .................................................................................................................................................. 43 Figure 37: Estimates of 50-year Return Omni-directional Hourly-mean Wind Speeds at 10 m above Still (BOMEL, 2002) ........................................................................................................................................... 43 Figure 38: Estimates of Maximum Depth-averaged Flow of a Spring Tidal Current (m/s) (BOMEL, 2002)44 Figure 39: Assumed Sinusoidal Tidal Current Behaviour (period 12 hrs) .................................................. 44 Figure 40: Foundation Installation Units (OWF-database, 2009) ............................................................... 45 Figure 41: Type of Foundation Installation Units (OWF-database, 2009) .................................................. 46 Figure 42: Wind Turbine Installation Units (OWF-database, 2009) ............................................................ 46 Figure 43: Type of Wind Turbine Installation Units (OWF-database, 2009) ............................................... 47 Figure 44: Jack-ups Crane Capacity and Leg Length ................................................................................ 49 Figure 45: Fob Jr. ........................................................................................................................................ 51 Figure 46: Windcat 11 (Windcat Workboats) and Offshore Performer (South Boats) ................................ 51 Figure 47: Personnel Transfer Units ........................................................................................................... 52 Figure 48: Offshore Transfer System .......................................................................................................... 65 Figure 49: Offshore Access System ........................................................................................................... 66 Figure 50: Ampelmann ................................................................................................................................ 66 Figure 51: FROG ......................................................................................................................................... 67


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Figure 52: OWAS ........................................................................................................................................ 67 Figure 53: Cableway ................................................................................................................................... 68 Figure 54: MCC Operation Steps ................................................................................................................ 68 Figure 55: Lifting Capacities (Luff angles @ 60,45,30,0 degrees) ............................................................. 69 Figure 56: Thruster Lay Out ........................................................................................................................ 72 Figure 57: Lines Plan OWSS ...................................................................................................................... 74 Figure 58: Allocation of Main Components (side view) ............................................................................... 76 Figure 59: Print-screen of Seasafe ............................................................................................................. 81 Figure 60: KG Limiting Curves based on IMO A167&A562 ........................................................................ 82 Figure 61: KG Limiting Curves based on DNV Lifting Criteria .................................................................... 83 Figure 62: Side view Frame 60 - 80 ............................................................................................................ 86 Figure 63: Cross Sections ........................................................................................................................... 87 Figure 64: Transverse Deck Girders Construction ..................................................................................... 88 Figure 65: Girders Plate Flange Width ........................................................................................................ 88 Figure 66: Built Section ............................................................................................................................... 89 Figure 67: Ship Resistance ......................................................................................................................... 91 Figure 68: Propeller Operation at Design Speed ........................................................................................ 92 Figure 69: Key-one-line ............................................................................................................................... 95 Figure 70: Mesh OWSS .............................................................................................................................. 97 Figure 71: Convention of Propeller Emergence ........................................................................................ 100 Figure 72: Axis Convention DP-Capability Plot......................................................................................... 103 Figure 73: Current Coefficients ................................................................................................................. 104 Figure 74: Geometry in Windos ................................................................................................................ 104 Figure 75: Wind Coefficients ..................................................................................................................... 105 Figure 76: Thruster Interference, T1 to T2 ................................................................................................ 105 Figure 77: Efficiency, T1 ........................................................................................................................... 106 Figure 78: Intact DP Capability Plot .......................................................................................................... 107 Figure 79: DP Capability Plot after a Switchboard Section Failure .......................................................... 109


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iv. List of Tables Table 1: Wind Turbines used Offshore ....................................................................................................... 16 Table 2: Bottom Founded Foundations ....................................................................................................... 20 Table 3: Public Announced Commercial Floating Foundations .................................................................. 22 Table 4: Annual Installation of Offshore Wind Farms (EWEA-PP, 2008) ................................................... 30 Table 5: Measurement Points of Wave Data (Locations: Figure 29) .......................................................... 38 Table 6: Environmental Availability Limits of the NG5300HPE ................................................................... 45 Table 7: Jack-ups operating in Offshore Wind ............................................................................................ 48 Table 8: Picture of Jack-ups operating in Offshore Wind ........................................................................... 48 Table 9: Floating Vessels operating in Offshore Wind ................................................................................ 50 Table 10: Functional Requirements ............................................................................................................ 58 Table 11: Estimation of Needed Containers for Maintenance .................................................................... 60 Table 12: MDO Capacity ............................................................................................................................. 61 Table 13: Potable Water Capacity .............................................................................................................. 61 Table 14: Work during Maintenance ........................................................................................................... 61 Table 15: Comparison of Ship Types .......................................................................................................... 63 Table 16: OTS Technical Specification ....................................................................................................... 65 Table 17: OAS Technical Specification ....................................................................................................... 66 Table 18: Ampelmann Technical Specification ........................................................................................... 67 Table 19: MCC Technical Specification ...................................................................................................... 69 Table 20: Summary of Transfer Systems ................................................................................................... 70 Table 21: Main Dimensions......................................................................................................................... 71 Table 22: Tank Summary ............................................................................................................................ 77 Table 23: Light Ship Weight ........................................................................................................................ 78 Table 24: Specific Densities ........................................................................................................................ 79 Table 25: Loading Conditions ..................................................................................................................... 80 Table 26: Basic Hydrostatics....................................................................................................................... 80 Table 27: Hydrostatics by Loading Conditions............................................................................................ 81 Table 28: Hydrostatics by Lifting Loading Conditions ................................................................................. 82 Table 29: Required Subdivision Index ........................................................................................................ 83 Table 30: Fictive Loading Conditions .......................................................................................................... 84 Table 31: Damage Zones ............................................................................................................................ 84 Table 32: Permeability of the Living Compartment ..................................................................................... 84 Table 33: Attained Subdivision Index .......................................................................................................... 84 Table 34: Design Loads to Midship Section ................................................................................................ 86 Table 35: Required Section Modulus .......................................................................................................... 87 Table 36: Hull Girder Strength Summary .................................................................................................... 87 Table 37: Required Section Modules of Transverse Deck Girder .............................................................. 88 Table 38: Effective Flange of Girder ........................................................................................................... 89 Table 39: Section Modules of the Transverse Deck Girder ........................................................................ 89 Table 40: Vessel Description for Resistance Calculation ........................................................................... 90 Table 41: Propulsion Efficiencies ................................................................................................................ 91 Table 42: Propeller (B4-70 in 19A) ............................................................................................................. 91 Table 43: Power Consumers....................................................................................................................... 93 Table 44: Consumers at Different Loading Conditions ............................................................................... 93 Table 45: Power Generation ....................................................................................................................... 94 Table 46: Power Balance ............................................................................................................................ 94 Table 47: 100% CON-RDL in AQWA .......................................................................................................... 96 Table 48: Added Damping .......................................................................................................................... 97 Table 49: 3hours Maximum Motion Amplitudes .......................................................................................... 98 Table 50: Locations at which 3hour Maximum Accelerations are Determined ........................................... 98 Table 51: 3hour Maximum Accelerations at Specified Locations ............................................................... 98 Table 52: Criteria for Accelerations and Roll (Faltinsen, 1990) .................................................................. 99 Table 53: RMS Accelerations at Specified Locations ................................................................................. 99 Table 54: RMS Accelerations at Specified Locations ................................................................................. 99


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Table 55: Locations and Dimensions of Propellers (Station Keeping)...................................................... 100 Table 56: 3hour Maximum Propeller Emergence (Station Keeping) ........................................................ 101 Table 57: DNV Steepness Criteria (Hs=3m) ............................................................................................. 101 Table 58: Emergence Occurrence by Rayleigh Distribution (Station Keeping) ........................................ 102 Table 59: 3hour Maximum Freeboard Exceedance (Station Keeping) ..................................................... 102 Table 60: Thrust ........................................................................................................................................ 105 Table 61: Thruster Efficiencies ................................................................................................................. 106 Table 62: Resulting Power for Thrusters after Generator Failure ............................................................. 108 Table 63: Thruster Designation (based on the Key-one-line) ................................................................... 109


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v. Axis Convention The origin of the coordinate system is as follow, Figure 1:

At the mirror1

At CL (centre line)

At BL (base line level)

Figure 1: Axis Convention

The origin of the axis system of ship motions is at centre of gravity.

1 APP is not used because neither a thruster or frame is at this position


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vi. Introduction During the upcoming decennia many offshore wind farms are planned to be built. The offshore wind industry is a young growing market. Therefore, the maritime logistics in this industry have not been stabilized yet. Opportunities to sell new type of vessels in this market are the interest of the company Gusto. The offshore design and engineering company Gusto is already present in the offshore wind market with several of its designs for wind turbine installation jack-ups. This report is a representation of the graduation project to finish the master study ‘Design of Ships’ at the faculty of Maritime technology at the TU-Delft, the Netherlands. The master thesis is executed in collaboration with Gusto. The two goals of this research are:

1. Define the most interesting vessel to develop for the offshore wind industry 2. Select a concept that meets the criteria

The body of this report can be split in three parts. The first part describes the offshore wind market, chapter 1. The second part describes the selection of an offshore wind support ship, chapter 2. The third part describes the offshore wind support ship structured by technical subjects, chapter 3 to 14. The last chapter contains conclusions and recommendations.


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1. Market Analysis The main part of this market analysis is an overview of the offshore wind industry. The focus of this market analysis is based on the offshore logistics. At the beginning of this project it was undecided what type of vessel would be designed. Therefore an intensive and broad analysis has been done. The main questions to be answered are:

What are the dimensions of equipment to cope with?

What is the development of the offshore wind market?

What are the types of (offshore) units operating in the offshore wind industry?

1.1. Main Components of an Offshore Wind Turbine The main components of an OWT are the wind turbine and the foundation, Figure 2. These main components are similar for all existing OWT’s and designs.

Figure 2: Main Components of an Offshore Wind Turbine

Figure 3 gives an overview of an OWT. At the right side of the figure the split of the foundation and wind turbine can be seen. On the left side, the main components of the wind turbine are noted: rotor, nacelle and tower. The wind turbine and its components will be discussed in paragraph 1.2. and the foundations will be mentioned in paragraph 1.3.

Figure 3: Offshore Wind Turbine

OWT

FoundationWind turbine

and

Fou

nd

atio

nW

ind

Tu

rbin

e

Ro

tor

Tow

er

Nacelle


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1.2. Wind Turbines The wind turbines are produced in series. Wind turbines from the same type are build at different locations with different site conditions. The foundation will be adapted to the site circumstances. The different designs used offshore can be summarized, see Table 1: Wind Turbines used Offshore. All designs noted in Table 1 have been built. An extensive list of the technical specifications of wind turbines used offshore can be seen in appendix A. The foundations noted in Table 1 have the preferences of the WT manufactures. The OWF’s which use the WT’s from Table 1 will be mentioned in paragraph 1.4.

Table 1: Wind Turbines used Offshore

In the following subsections the main components of the wind turbines will be described.

Wind Turbine V80-2MW Siemens 2.3 Nordex N90 V90-3MW Siemens 3.6 GE 3.6 REpower5M M5000 Bard 5.0

Rated power MW 2 2.3 2.5 3 3.6 3.6 5 5.315 5.27

First operational year year 2002 2003 2009 2005 2007 2003 2007 2009 2009

Nr. up to 2009 nr 200 221 21 156 77 7 20 27 5

Component weight

Tower (all between trans and nacelle)t 160.00 98.00 178.80 120.00 160.00 160.00 350.00 267.44 400.00

Nacelle t 79.00 82.00 91.00 88.00 125.00 290.00 214.50 280.00

Generator t 10.00 8.50 10.00 17.00

Gearbox t 18.50 23.00 42.00 63.00

Rotor t 37.00 60.00 55.60 41.00 95.00 120.00 120.00 155.50

Hub t 17.50 24.00 25.00 21.20 52.60 60.00 75.50 70.00

Blade t 6.50 12.00 10.20 6.60 17.20 17.74 16.50 28.50

Nacelle + rotor t 116.00 142.00 234.40 129.00 215.00 295.00 410.00 310.00 435.50

Nacelle + hub t 96.50 106.00 203.80 120.00 182.00 340.00 290.00 350.00

Bunny Ear t 109.50 130.00 224.20 120.00 87.00 375.48 323.00 407.00

Component sizes

Hub height WT specification m 80.00 80.00 80.00 80.00 77.30 73.50 106.68 102.16 99.00

Hub height OWF data m 66.00 73.25 90.00 73.75 93.33 74.00 100.50 116.00 122.00

Average hub height m 73.00 76.63 85.00 76.88 85.32 73.75 103.59 109.08 110.50

Average hub height/rotor dia % 91% 82% 94% 85% 80% 71% 82% 94% 91%

Tower m 60.00 60.00 80.00 60.00 60.00 70.50 90.00 97.00 75.00

Dia transistion/tower m 4.00 4.00 5.00 5.00 6.00 6.00 5.50

Dia tower/nacelle m 2.30 2.30 3.12 3.00 5.49 4.01 4.50

Nacelle L m 13.25 13.20 18.00 12.00 20.00

Rotor Dia m 80.00 93.00 90.00 90.00 107.00 104.00 126.00 116.00 122.00

Blade L m 39.00 45.00 43.00 44.00 52.00 50.50 61.50 56.50 59.40

Accessibility

Service lift t 1 0.24 1

Internal cranes Gantry+6.4 build on Gantry + 10t build on Gantry Arm Arm/tele Gantry

Service crane t 0.80 0.60 0.25 0.80 0.60 6.31

Big crane / build on t 6.4 10 40 20

Technical

Rated wind speed m/s 15.00 13.50 14.00 15.00 13.00 14.00 13.00 12.00 12.50

Min rotor speed rpm 9.00 6.00 9.60 8.60 5.00 8.50 6.90 5.90

Nominal rotor speed rpm 16.70 16.00 16.80 16.10 13.00 15.30 12.10 14.80 12.50

Max rotor speed rpm 19.00 16.00 16.80 18.40 13.00 15.30 13.92 14.80 12.50

Power Regulation Pitch Pitch Pitch Pitch Pitch Pitch Pitch Pitch Pitch

Generator 50 Hz Asyn Asyn Dbl fd asyn Asyn Asyn Dbl fd Asyn Dbl fd 6-pole asynSyn, PM Dbl fd Asyn

Gearbox ratio - 100.50 91.00 77.40 104.50 119.00 97.00 9.90 97.00

Foundation Monopile Monopile Monopile Monopile Monopile Monopile Jacket/gravityTripod Tripile


17

1.2.1. Rotor

All of the available wind turbines have an upwind facing rotor. The rotors are all three bladed. The shaft power is regulated by pitching the blades. The dimensions of the different rotors are not the same; the rotor diameters vary from 80 to 126 meter. The lightest rotor weighs 37 ton and the heaviest 180 ton.

1.2.2. Nacelle

The rotor of the wind turbine is connected to the nacelle. The nacelle is positioned on top of the tower where it can rotate around its vertical axis. The nacelle contains the power drive train. All of the existing WT’s contain the conventional drive train. The conventional drive train has the following typical components:

A main shaft which is directly connected to the rotor

A gearbox which increases the rotational speed of the main shaft

A high speed generator

Electronic equipment to obtain the wanted frequency and voltage The main technical components of a nacelle with the conventional drive train can be seen in Figure 4.

Figure 4: Nacelle OWT (Vestas V90-3MW)

Most of the WT’s have electronic equipment in the nacelle. The latest designs M5000 and Bard 5.0 have the converter positioned in the tower instead of the nacelle. That results in a lower centre of gravity. This replacement has influence on the natural frequency of the OWT as will be mentioned in paragraph 1.3.1.


18

All of the models have space inside the nacelle for workers. From the existing WT’s the heaviest nacelle weighs 290 ton.

1.2.3. Tower

The dimensions of the tower depend on the site parameters. Therefore, most WT designs have two or three optional towers. The heaviest tower which has been built weighs 400 ton. The longest tower designed is 100 meter long.

1.2.4. Access from the Service Platform to the Nacelle

The service platform is the platform near sea level where workers can enter the tower of the wind turbine. Personnel climbs a stair inside the tower or, especially in the latest designs, go up with a lift. All wind turbines have a service crane inside the nacelle to handle material. This service crane can lift from the service platform to the nacelle. The capacity from the service cranes in the different designs varies from 0.25 to 6.31 ton. Some wind turbines have other possibilities to handle material. This can be a lift or a built up crane. An alternative access is to use a helicopter to enter directly to the nacelle. There are wind turbines fitted with a deck special for winching operations, the Vestas V80-2MW in Table 1 has one.

1.2.5. Future Developments

There are many developments going on at the manufactures of wind turbines. Only developments with major influence are noted in the following sub sections a,b,c and d.

a) Power drive train Wind turbines with the conventional drive train have been failed often by the failure of the gearbox. There is a development going on to make use of a direct drive train instead of the conventional drive train. In a nacelle, with a direct drive train, the rotor and generator are connected to the same (low speed) shaft. Dutch company Darwind designed a 5MW direct drive wind turbine. Siemens announced to develop a 3.6MW direct drive WT.

b) New manufactures There are some wind turbine manufacturers potentially entering the offshore wind market which are: Clipper, Scanwind, Win Wind, 2B Energy, Acciona, Mitsubishi, Gamesa and Enercon. These manufacturers all have an onshore wind turbine design. These designs have a similar concept as described above except that some onshore WT- designs are already equipped with a direct drive train.

c) Large WT’s Adrew Garrad, of wind energy consultancy Garrad Hassan presented at the Offshore Wind Conference Den Helder February 2009 that in 2020 they expect WT’s with a capacity over ten MW. According Garrad Hassan the WT design will be with a downwind facing rotor which contains two blades. According Garrad Hassan and Gijs Hulscher from Siemens (appendix J) a larger wind turbine has a relative lower operations & maintenance, foundation and installation cost. The implementation should come from the manufactures, but none of the current manufactures did announce at the Offshore Wind Conference Den Helder February 2009 that they design a larger WT. In this thesis the dimensions of only existing designs will be taken into account.

d) Vertical axis turbines Next to horizontal axis wind turbines various types of vertical axis wind turbines exist. An advantage of this type is that the generator can be placed on base level. However, this type is not often seen in practice, probably because of worse efficiency and durability (Wikipedia, 2009).


19

1.3. Foundations of Offshore Wind Turbines All beneath the tower of the wind turbine is named the foundation, Figure 3. The function of the foundation is to keep the wind turbine in place, create an access point on the sea level and guide the cable to the sea bed. This function of the foundation can be fulfilled by a bottom founded or floating structure, Figure 5.

Figure 5: Foundation

The foundation of the OWT has static and dynamic loads. The dynamic loads on the OWT play a large role in dimensioning the structure. The mechanics of dynamics are explained in the next paragraph.

1.3.1. Resonance

The excitation frequencies of an OWT are mainly driven by the rotor and waves. The rotor frequencies are named 1P and 3P. The 1P excitation frequency describes one rotation of the rotor and the 3P excitation frequency describes a blade passing by the tower. The variations of 1P between the OWT models are between 0.2 to 0.3 Hz. Most of the WT have a constant rotor speed. With a constant rotor speed the 1P and 3P frequencies are independed from the wind speed. All used WT’s are three bladed, so the fixed relation between 1P and 3P is 3P=3*1P. The frequency excitations by waves are site depended. To illustrate an overview of the excitation frequencies wind waves and swell have an assumed value. A visualization of the excitation frequencies can be seen in Figure 6. The figure is based on an explanation of Piet Chevalier from Siemens wind power, appendix J.

Figure 6: Excitation Frequencies OWT

To avoid resonance of the OWT the total structure needs a specified natural frequency. There are three frequency ranges where the natural frequency of the OWT is not in resonance by the excitations in Figure 6.

1. A natural frequency of 0.8 Hz or higher, above all excitation frequencies in Figure 6 2. A natural frequency around 0.45 Hz, in between the 1p and 3P excitation frequencies in Figure 6 3. A natural frequency of 0.05 Hz or lower, below all excitation frequencies in Figure 6

Foundation

FloatingBottom founded

or

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 5 10 15 20 25

Fre

qu

ancy

(H

z)

Wind speed (m/s)

3P-constant speed

3P-variable speed

1P-constant speed

1P-variable speed

Wind waves

Swell-13 seconds


20

1) The natural frequency is a function of the OWT’s stiffness and mass. With the weight and dimensions of wind turbines given in the previous paragraph it is unrealistic to built a structure stiff enough to obtain a natural frequency of 0.8 Hz or higher.

2) All operational offshore wind turbines have a natural frequency around 0.45 Hz. The natural frequency of the OWT is usually too low if one only takes static loads into account. To obtain a higher natural frequency the OWT needs to be stiffer. Therefore the structure design is partly driven by dynamic loads.

3) It is possible to build a very flexible construction (compliant tower) with a natural frequency below the excitations mentioned in Figure 6, but it is never done or proposed for an offshore wind turbine. The designs of the most floating foundations do have natural frequencies below all excitation frequencies in Figure 6.

1.3.2. Bottom Founded Foundations

Foundations are generally produced in small series; often for one particular offshore wind farm. The main bottom found foundation types are presented in Table 2, where a brief description and overview of weights and sizes are mentioned.

Table 2: Bottom Founded Foundations

a) Gravity based The gravity based foundation is a simple concept. The overturning stability is covered by the weight of the foundation. However, the gravity based foundation has its limitations. The weight of gravity based foundations becomes very high in combination with high turbines in deep water. The lightweight of the heaviest gravity based foundation, the Thornton bank, is 3,000 ton and weighs in total 10,000 ton. The weight of gravity based foundation makes this simple foundation difficult to install.

b) Drive pile based All other foundations than the gravity foundation mentioned in Table 2, monopile, tripile, tripod and jacket have a construction technique in common. Their bottom foundations are base on driven piles into the sea bottom. This technique, the driven piles in the sea bed, cannot be fixed to the OWT by bolts because:

The driven pile is slightly damaged by the hammer

The driven pile does not meet the accuracy requirements Therefore the driven piles are connected to the foundation structure by grouting.

Gravity Monopile Tripile Tripod Jacket

In water depths of 1-25 m, a

gravity based foundation have

been used. The gravity based

foundation is made of concrete

with steel additions.

The gravity foundation

dimensions for a Vestas 2MW

OWT at Middelgrunden OWF are

about:

- 1800 ton A transition piece balances

the topside. The transition

piece weighs 50 - 430 ton. - Box size= 11*18 m

The gravity foundation

dimensions for a Repower 5MW

OWT at the Thornton bank OWF

are about:

The tri-transition piece

dimensions for a Bard 5MW

OWT at Bard Offshore OWF are

about:

The tripod dimensions for a

Multibrid 5MW OWT foundation

at Alpha Ventus OWF are about:

The jacket dimensions for a

Repower 5MW OWT at Beatrice

OWF are about:

- Empty 3000 ton, filled 7000 ton - 490 ton - 800 ton - 700 ton

- Box size 40*26 m - Box size of 20*20*20 m - Box size of 20*20*20 m - Box size 60*30*30 m

The foundation total weight is

about 7000 ton


about 1500-2000 ton.


about 1200 ton


about 1200 ton

In water depths of 30-40 m,

tripiles have been used. A tripile

is a combination of 3 monopiles

connected to one (tri-)transition

piece. A series produced

transition piece can be combined

with site dependent monopiles of

a diameter about 4.5m. The

advantage of this is to obtain a

stiffer foundation without needing

an very large pile drive hammer.

In water depths of 30-40 m a

tripod have been used. A tripod

is a triangle structure installed at

the seabed suitable for large

wind turbines. The tripod is

founded with three piles

(diameter = 3m) driven through

the corners of structure. One

design of a tripod is applicable in

a narrow range of water depth

and turbine weight.

In water depths of 30-50 m a

jacket have been used. The

jacket is an open frame steal

structure which is fixed on the

seabed with driven piles.

In water depths of 1-30 m, a

monopole foundation have been

used. A monopile is a circular

tube driven in the sea bed. The

diameter of the monopile is

currently limited by the capability

of pile drive hammers. ton.

Dimensions of monopiles applied

for a 3.6 MW Siemens wind

turbine are about:

Water

depth

(m)

Weight

(ton)

Diameter

(m)

0-10 150 4

10-20 300 5

20-30 750 6


21

The monopile is a simple foundation where only one pile is driven in the sea bed. A transition piece is connected on the driven pile by grouting. The grouting process takes place above water. Pictures from transition pieces can be seen in appendix B. The tripile uses a similar technique as the monopile. The only difference is that the transition piece is connected to three piles driven in the sea bed. The tripod and jacket are connected to slightly smaller piles. The connection of the piles is at the sea floor. Therefore grouting process also occurs under water.

c) Suction bucket based The Dutch companies Sea of Solutions and SPT-Offshore both designed foundations which are connected to the sea bed by suction buckets. However, these concepts have not been seen in offshore wind farm plans so far. Therefore these concepts have not been taken into account into this research.

d) Selection process For a monopole, the stiffness becomes a problem in deeper water. The enlargement of the diameter increases the stiffness, but the following disadvantages occur:

The wave excitation forces increase

Limitation of pile driving (the largest available hammer now, is from IHC and has a diameter of 5.1 meter)

Local strength is limiting

The wall thickness must be very large The heaviest monopile foundation ever, is the one to be constructed at the Greater Gabbard, which is a tapered monopile to maximum 6 meter diameter and weights 750 ton. The tripile, tripod and jacket, summarized by space frame foundations, are relative stiff constructions. In deeper water and with heavy weight wind turbines, space frame foundations become competitive with monopiles.

1.3.3. Floating Foundations

The first requirement of the floating foundation is that it must be able to carry the weight of the OWT. Secondly the floating foundation must have sufficient stability. The required stability is significant caused by the high static moment (VCG*weight) and overturning moment. Floating foundations are stabilized by one or more of the following principles:

A: Spar stabilized by the geometric difference between centre of buoyancy and mass (negligible BM), GB = VCB – VCG

B: Barge stabilized by the geometric difference between metacentre and centre of mass, GM = VCB + BM – VCG

C: Tension leg stabilized by the anchoring system A visualisation of type A,B and C can be seen in Figure 7.

Figure 7: Floating Foundations Types

A stable foundation can also be a combination of the floating foundation types. There are many designs for floating OWT from several companies. Public announced commercial designs are set in the triangle of stability, Figure 8, and are briefly described in Table 3.

A: Spar B: Barge C: Tension leg


22

Figure 8: Triangle of Stable Floating Foundations

Table 3: Public Announced Commercial Floating Foundations

The Hywind, Trifloater and Wetcop design intend to use an existing wind turbine while the Sway concept is designed with non-existing downwind rotor. All of the floating foundation designers have the intention to install the wind turbine on the foundation in a protected area. After the installation the entire OWT will be towed offshore. From all the concepts in Table 3, scaled prototypes have been built. Only the Hywind OWT is build in full scale.

1.3.4. Sub Conclusion

To identify what foundations will be installed in the upcoming years Figure 9 has a considered overview based on detailed grading of four experts2 (Vries, 2007) in offshore wind. One can conclude from Figure 9 that as long as offshore wind farms are built in water depths up to 80 meter bottom founded foundations have the highest score. An absolute cost comparison could give a better answer to that question.

2 J. van der Tempel (Delft University of Technology)

K. Argyriadis (Germanischer Lloyd) H. Carstens (Rambøll) P. Passon (Universität Stuttgart)

A: Spar

B: Barge C: Tension leg

Sway

Trifloater

Hywind

Exhbit-a

Wetcop


23

Figure 9: Overview of Foundation Types (Vries, 2007)

Figure 10, (Musial, Butterfield, & Ram, 2006), shows that floating foundations are expected to be more expensive compared to bottom founded foundations. The cost is a dominant factor in offshore wind farm design. Therefore it is logical that possible OWF’s will be located in relative shallow waters. It will depend on the demand of offshore wind power versus available “shallow water” sites if floating foundations will be used. For this moment, none of the contracted sites have water depths of more than 50 meters. For this reason this project will focus only on bottom fixed foundations.

Figure 10: Cost of Foundation Types (Musial, Butterfield, & Ram, 2006)


24

1.4. Offshore Wind Farms In the 90’s the installation of wind turbines in water started. One can hardly speak about offshore wind farms because the wind turbines were:

Located in calm water

Located in shallow water

Located close to the shore (some turbines had an onshore accessibility, by a small bridge)

The wind turbines were in a small group (about 5 WT’s) The first offshore wind farms are built since the year 2000. In this project the WT’s in water are called an OWF if they meet the following requirements:

These offshore wind farms are at least 1 km offshore at sea

The nominal power of the wind turbine is at least 1 MW

1.4.1. The Formation of an OWF

The main reason why wind turbines offshore are bundled to one location is to reduce the cost of cables. The group of WT’s (OWF) is connected with one high voltage cable to the shore. The high voltage cable is connected to an offshore substation near the OWF. The high voltage cable has a voltage of about 150 kV. At the substation the medium-voltage electrical net of the wind turbines is converted to high voltage. A substation can be seen in appendix C. The medium voltage electrical net, where wind turbines are connected on, has a voltage of usually 30kV. The groups are allocated in a (curved) line or a matrix with spare distances of about 5 times the rotor diameter.

1.4.2. Operational Offshore Wind Farms

There are lists of offshore wind farms available from wind energy associations. These lists give an overview of the number of OWT’s and their powers, but the technical data is limited. Therefore an intensive offshore wind farm database was created for this project of the European OWF’s. The database is created in March 2009. The database contains OWF’s which are already built and those which are planned to be build before the end of the year 2009. The sources of OWF-database are several wind energy associations and websites from offshore wind farms. The OWF-database can be seen in appendix D: OWF-database (from now on it will be called “OWF-database, 2009”). The analysis on this database will be discussed in this paragraph.

a) Market development The size of offshore wind is analyzed by the total operational power in Figure 11. The cumulative installation from 2000 to 2003 shows an extreme growth. However, in 2004 and 2005 the cumulative installation where limited to 90 MW. From 2006 to 2009 the cumulative installation growth is increasing again. The exact reason for the fluctuation in cumulative growth is unknown, but it is probably driven by politics.

Figure 11: Offshore Wind Energy Market Development in Europe (OWF-database, 2009)

0

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tio

nal

po

we

r (M

W)

Year

Cummulative

Operational


25

An overview of offshore wind power per country can be seen in Figure 12.

Figure 12: Operational Offshore Wind Farms end 2009 (OWF-database, 2009)

b) WT-designs The distribution of wind turbines designs in European waters can be seen in Figure 13. Behind the name of the WT design, see the x-axis in Figure 13, the nominal power of the turbine is mentioned in mega watts. For example the “Siemens 3.6” is a wind turbine design from Siemens producing maximal 3.6 MW. The WT designs: General Electric 1.5 (MW), Neg Micon3 2.0 (MW) and Bonus4 2.0 (MW), have been grouped by “Other < 2.0”. These wind turbines have not been installed after 2001. The resulting nine wind turbine models mentioned in this figure have had a thorough analysis. Of the wind turbines in Figure 13 a detailed description is presented in paragraph 1.2. In this figure it can be seen that the most offshore WT’s come from Vestas and Siemens.

3 The Neg Micon WT manufacturer is overtaken in 2003 by Vestas. 4 The Bonus WT manufacturer is overtaken in 2004 by Siemens.

Belgium 60MW 3%

Denmark 597.6MW 29%

France 105MW 5%

Germany 137.5MW 7%

Ireland 25.2MW 1%Netherlands 228MW 11%

Sweden 130.9MW 6%

United Kingdom 785.2MW 38%


26

Figure 13: Operational Offshore MW / Offshore Wind Turbine (OWF-database, 2009)

The date of first and latest installation is presented in Figure 14. The Vestas and Siemens turbines have been installed during a couple of years. The GE 3.6 has been installed only in the year 2003.

Figure 14: First and Latest Year of Installation / Offshore Wind Turbine (OWF-database, 2009)

c) Specifications The hub height above the water line is an important parameter because it has a correlation with the hoisting height for installation. In comparison with onshore wind profile, the offshore wind profile contains a higher wind speed near the surface. Therefore an offshore hub height is usually below 1 times the rotor diameter, while onshore the hub height is usually over 1 times the rotor diameter. The hub height by offshore wind turbine is presented in Figure 15. The spreading of the hub height for the same OWT-design is significant. The reason for that could be optimization to site conditions. However, it can be the result of a different in hub-height definition. The hub-height definition was absent at a number of sources from the OWF-Database.

0

50

100

150

200

250

Oth

er

< 2

.0

Ve

stas

2.0

Sie

me

ns

2.3

No

rde

x 2

.5

Ve

stas

3.0

Sie

me

ns

3.6

GE

3.6

REp

ow

er

5.0

Mu

ltib

rid

5.0

Bar

d 5

.0

Nr.

of

win

d t

urb

ine

s

2002

2003

2004

2005

2006

2007

2008

2009

Ve

stas

2.0

Sie

me

ns

2.3

No

rde

x 2

.5

Ve

stas

3.0

Sie

me

ns

3.6

GE

3.6

REp

ow

er

5.0

Mu

ltib

rid

5.0

Bar

d 5

.0

Ye

ar

Latest installation

First installation


27

Figure 15: Hub Height / WT (OWF-database, 2009)

One can see in Figure 16 that in the last ten years the average and maximum water depth of operational offshore wind farms has increased. The minimum and maximum water depth in this figure are the mean water depth including tide.

Figure 16: Water Depth / Year (OWF-database, 2009)

The waterdepth is a parameter influencing the foundation. The range of water depths where the foundation types are used are illustrated in Figure 17.

0

20

40

60

80

100

120

140

Ve

stas

2.0

Sie

me

ns

2.3

No

rde

x 2

.5

Ve

stas

3.0

Sie

me

ns

3.6

GE

3.6

REp

ow

er

5.0

Mu

ltib

rid

5.0

Bar

d 5

.0

Hu

b h

eig

ht

(m)

Max

Average

Min

0

5

10

15

20

25

30

35

40

45

50

20

00

20

01

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02

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05

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06

20

07

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08

20

09

Wat

er

de

pth

(m

)

Year

Max

Average

Min


28

Figure 17: Water Depth / Foundation Type (OWF-database, 2009)

The number if installed foundations from one foundation type is plotted in Figure 18. Of the foundations in the OWF-database 2009, 75% is a monopile foundation. The gravity based foundation has a contribution of 20%. Only 5% is left over for the tripile, tripod and jacket foundation.

Figure 18: Installed Foundations (OWF-database, 2009)

The distance from shore to the OWF has increased accoring Figure 19. The extreme increasing maximum distance from shore to the OWF is driven by Germain OWF’s.

05

1015202530354045

Gra

vity

Mo

no

pile

Trip

ile

Trip

od

Jack

et

Wat

er

de

pth

(m

)

Foundation type

Max

Average

Min

Gravity 152WTs 20%

Monopile 579WTs 75%

Tripile 5WTs 1%

Tripod 27WTs 3% Jacket 8WTs 1%


29

Figure 19: Distance to Shore (OWF-database, 2009)

1.4.3. Offshore Wind Farms Future Outlook

In 1997 the EC (European Commission) set a goal of 40 GW wind power (onshore!) in 2010. Already in 2005, 40 GW of wind power (onshore!) was installed, so 5 years earlier than of the EC 40 GW target. It seemed that the installation of wind power (onshore!) in the last decennia has been growing faster as it was prospected. Offshore wind power does not necessary follow the same growth as onshore wind power, but it illustrates the possible developments.

a) Market On 9 March 2007 the EC decided to extensive support renewable energies. The European Heads of State unanimously agreed on a binding target of 20% renewable energy of the total energy used by 2020. Wind energy is expected to play a key-role in the renewable energies. In what extend wind energy will be installed, is mentioned in prospective scenarios from the EWEA (European Wind Energy Association), the IEA (International Energy Agency) and the EC. These are all mentioned in the report Pure Power (EWEA-PP, 2008). Both prospects of the EC and IEA are in between of the low- and reference-scenario from the EWEA. In the report of (EWEA-PP, 2008) only the EWEA scenarios are specified with offshore wind power. Only the offshore prospects of the EWEA are presented Figure 20.

Figure 20: Offshore Wind Power Scenarios to 2030 (EWEA-PP, 2008)

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2007 2010 2015 2020 2025 2030

Off

sho

re w

ind

po

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r (G

W)

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Offshore wind power scenarios to 2030

Low

Reference

H

Documents

Design of a Vessel Operating in Offshore Windwflportal.amcplaza.com/System/Lists/SystemProducts/... · 2014. 5. 2. · The missing Link in the Offshore Wind Industry: Offshore Wind