challenges in the construction of offshore wind structures · pile . transition piece - solutions...
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Challenges in the Construction of Offshore Wind Structures
Dr Ned Minns IT Power UK
Foundations - Options
Gravity Monopile Jacket Tripod
Floating
<40m <40m <60m <60m
>60m
Shallow Intermediate Deep
Floating Wind Foundations
Tested Prototypes
100m
HyWind – 2.3MW WindFloat – 2MW
BlueH – 80 kW
Challenges
• Not just installing onshore WT at sea. – Specialist skills required. – Marinisation. – Maintenance. – Supply chain. – Cables
Installation
• Typical offshore works process for monopile foundation
Start Finish
Approximately 4 – 10 days
Vessels
• Small survey boats required for initial work
Vessels
• Aura and Toisa Sonata - Transport of monopiles from the Netherlands
• Carry two monopiles per voyage
~100m long vessels
Vessels
• Oleg Strashnov – Installation of 1,000 tonne substations and 88 monopiles
• Four piles per voyage cycle
5,000 tonne crane, 183 m long vessel
Vessels
• Three Jack Up Barges to install turbines and towers – two turbines at a time
GMS Endeavour Leviathan SEA JACK
All +90m long vessels, with ~90m long legs
Vessels
• Team Oman – Cable laying vessel – transport of cable from Norway and installation of infield and export cable
Vessels
• Toisa Warrior – infield and export cable burying using an ROV trencher
Vessels
• Rock dumping for scour protection of turbines and cable • Larger rocks to protect underlying layers
Jan Steen Four foundations per day
HAM 602 Two foundations per day
Vessels
• Regina Baltica - Personnel accommodation “Floatel” • Temporary living for 100 workers • Former cruise ferry
Vessels
• Windcat – Operations and maintenance vessels for transportation of personnel
Vessels
• Helicopter – expensive but quick
Transition Piece
• Transition piece between tower and monopile • Grouted to compensate imperfection in pile verticality
to ensure turbine tower will be vertical
Grout
Transition Piece
Monopile
Export Cable
J Tube
Scour Protection
Supports for installation
Transition Piece - Solutions
Conical Joint • Allows and expects failure in the grout • Shape of tapered interface causes recompression to a
stable condition • Quality is key as any “ovality” of either component will
affect the locking together of the two
Used on the recently completed London Array
Transition Piece - Solutions
Shear Keys • Circumferential rings on the outside of
the monopile and inside of the transition piece
• Increase the sliding resistance between the grout and steel
• Requires more fabrication and cost but benefits outweigh cost of offshore repair
Transition Piece
Grout Pile
Transition Piece - Solutions
Elastomeric Bearings • If slippage occurs, bearings gradually take load to
assist grout
Used on: Sheringham Shoal, Belwind (BE), Greater Gabbard, Gwynt y Môr & Rhyl Flats
Top of pile wall
Grout
Transition piece wall
Compression jack
Elastomer bearing
Bearing units
Challenges
• Not just installing onshore WT at sea. – Specialist skills required. – Marinisation. – Maintenance. – Supply chain. – Cables.
• Learn from worldwide experience and mistakes.
Offshore Wind in the UK Offshore Wind Resource UK wind farms
Practical OSW Resource of ~ 400 TWh/yr
IT Power Marine Energy Group
Supporting the emergent marine energy industry Covering the following technologies • Tidal stream • Tidal barrages • Wave power • Hydropower • Offshore wind
Marine - Long Track Record
Courtesy Severn Tidal Fence Group
Support Services to: Investors
Project developers Venture capital companies
Public Sector National & regional government Resource owners Research organisations
Developers & Utilities Site developers Resource owners Grid operators Power purchasers
Industry Device developers Component or system suppliers Integrators
Supporting Information
OSW – Vessel Costs
• Jack-up - £100 - 150k/day • Floating crane ships – £200 - 270k/day • Trenching vessel - £75 - 90k/day • Export cable laying vessel - £75 - 125k/day • Array cable laying vessel - £65 - 95k/day • Ornithological survey vessel - £8 - 10k/day • Coastal survey vessel - £4 - 6k/day • Geophysical survey vessel - £14 - 16k/day • Geotechnical survey vessel - £40 - 70k/day • Windcat workboat - £1,500/day
Monopiles
Jackets
Tripods
Alpha Ventus, Germany
Narec, UK
Gravity Foundations
Suction Caisson
Floating Wind Foundations Spar Buoy (Ballast
Stabilised)
Semi-Submersible (Buoyancy Stabilised)
Tension Leg Platform (Mooring Stabilised)
Conclusions
‐ Many challenges and important lessons are still
being learned
‐ A variety of expensive, specialist vessels are
required for installation
Offshore Wind Turbines – Growing!
50 kW Ø 15 m
100 kW Ø 20 m
500 kW Ø 40 m
600 kW Ø 50 m
2000 kW Ø 80 m
5000 kW Ø 125 m
1980 1985 1990 1995 2000 2010
Name Operation date Size, MW Turbine Distance to Shore km Water Depth, m Foundation Type Cost, million
£
Barrow 03/2006 90 Vestas V90 3MW 7.5 12–16 Steel Monopile 139.5
Beatrice 07/2007 10 REpower 5MW 23 45 Steel Quadropod 35
Blyth 11/2000 4 Vestas V66 2MW 1 6-11 Steel Monopile 4
Burbo Bank 07/2007 90 Siemens SWT 107 3.6MW 6 0-8 Steel Monopile 181
Gunfleet Sands I + II 01/2010 172.8 Siemens SWT 3.6MW 7 2-15 Steel Monopile 420
Inner Dowsing 10/2008 97.2 Siemens SWT 107 3.6MW 5 6-18 Steel Monopile 300
Kentish Flats 08/2005 90 Vestas V90 3MW 9 3-5 Steel Monopile 105
Lynn 10/2008 97.2 Siemens SWT 107 3.6MW 5 6-18 Steel Monopile 300
North Hoyle 03/2004 60 Vestas V80 2MW 7 7-11 Steel Monopile 80
Ormonde 03/2012 150 Repower 5MW 10 17-22 Jacket 500
Ryhl Flats 12/2009 90 Siemens 3.6MW 8 6-12 Steel Monopile 198
Robin Rigg 04/2010 180 Vestas V90 3MW 11 4-13 Steel Monopile 396
Scroby Sands 12/2004 60 Vestas V80 2MW 3 0-8 Steel Monopile 75.5
Thanet 09/2010 300 Vestas V90 3MW 12 14-23 Steel Monopile 900
Walney Phase 1 04/2011 183.6 Siemens SWT 107 3.6MW 14 19-28 Steel Monopile 183.6
Walney Phase 2 04/2012 183.6 Siemens SWT 120 3.6MW 14 25-30 Steel Monopile 183.6
Greater Gabbard 09/2012 504 Siemens SWT 107 3.6MW 36 20-32 Steel Monopile 1,300
Sheringham Shoal 12/2012 316.8 Siemens SWT 107 3.6MW 23 15-22 Steel Monopile 1,100
Gwynt y Mor Under construction 576 Siemens SWT 107 3.6MW 13 12-28 Steel Monopile 1,600
Lincs Under construction 270 Siemens SWT 120 3.6MW 8 10-15 Steel Monopile 725
London Array Ph 1 Under construction 630 Siemens SWT 120 3.6MW 20 0-25 Steel Monopile 2,200
Teeside Under construction 62.1 Siemens SWT 93 2.3MW 2 7-15 Steel Monopile
Turbine Failures
• Electrical control, gearbox, yaw system, generator,
hydraulic, grid and blades are rated (60% of the total
failures)
Turbine Failures
• Yaw Control - cracking of yaw drive shafts, fracture of
gear teeth, pitting of the yaw bearing race and failure
of the bearing mounting bolts
• Gearbox – wear and tooth breakage due to particle
contaminations, frequent stoppage and starting and
high loaded operation conditions
Turbine Failures
• Hydraulics – leakages in the pitch, yaw, braking system
and gearbox lubrication system. Failure due to high/low
temperature, corrosion, vibration and improper
installation
• Blades - turbulent wind, out-of-control rotation,
lightning and production defects.
Turbine Failures
‐ Lightning Damage to Transformer
Vessel Failures
• Failure of jacking mechanisms on installation vessels
Vessel Failures
• Foundation failure below legs – feet pierce the sea bed
causing the platform to list
Met Mast Failures
• Failure of met mast structures due to fatigue
O&M Access
• Windcat – cheaper but can be slow travel and limited by
sea conditions
UK Offshore Wind - Rounds
Sheringham Shoal
Greater Gabbard
Robin Rigg
Ormonde
Sheringham Shoal - Information
Sheringham Shoal - Information
OSW – Vessel Costs
• Jack-up - £100 - 150k/day • Floating crane ships – £200 - 270k/day • Trenching vessel - £75 - 90k/day • Export cable laying vessel - £75 - 125k/day • Array cable laying vessel - £65 - 95k/day • Ornithological survey vessel - £8 - 10k/day • Coastal survey vessel - £4 - 6k/day • Geophysical survey vessel - £14 - 16k/day • Geotechnical survey vessel - £40 - 70k/day • Windcat workboat - £1,500/day