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Universal Foundation A novel wide‐ranging substructure installation concept Søren A. Nielsen, Nielsen, MBD, CPO. CPO. Lars Bo Ibsen, Aalborg Aalborg University, University, Research Professor.
MBD introduction The Universal Foundation Framework The prototypes The supply chain Conclusion 1 1 0 2
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MBD Offshore Power A/S R&D company founded in 2001 Shareholders: • DONG Energy, >50% • Aalborg University • Novasion
Primary cooperation: • Aalborg University • Dong Energy • NearshoreLAB • Fred. Olsen Group
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Universal Foundation Concept: A framework for industrialization A concurrent process, adding new processes and experiences to a database, used by a configuration methodology to produce the required documentation in each step of the wind farm projects focusing on: • The optimal foundation for each turbine position • Design is parameter driven
Database
• Structure based on scaleable modules and elements
Configurator
Standard output
• Production based on series or mass production Feasibility studies
• Installation in widest possible weather window • Installation based on common available vessels Principles, Owner
Feedback
Consultant
Feedback
Construc -tion
Feedback
Installati on
Feedback
Site data
methodes, procedures, expirences
Sales
Engineering
Feedback Development
Production
Installation
n o i t a r u g i f n o c t c u d o r P
t n e m s e s s a t s o c / k s i R
Conseptual design Tender design Detail design Construction documentation Operation documentation
Feed back
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Main focus area:
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The bucket foundation technology as large diameter monopile Concept advantages: • Reduced use of steel compared to any other substructure solution. • Use of simple geometric welded steel structures. The structure is omni‐ directional symmetrical with respect to the vertical axis. • Few offshore operations, with utilizing smaller equipment/vessels during installation. • No seabed preparation and no or reduced need for scour protection. • Adjusting the upper part of the shaft to fit the standard wind turbine tower. • Simple decommissioning. Installation advantages: • Minimum noise impact. No pile driving hammers or drill drives are used. • No grouted connections. • Minimum disturbance to the existing seabed. • The use of excess material for scour protection is reduced or not necessary. • All steel materials can be recovered from the seabed and reused / recycled when the foundation is decommissioned
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Offshore wind turbine foundations The flexibility of the bucket foundation gives wider range of application. Sites with complex geotechnical properties can be cover by a single foundation concept 1 1 0 2
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Platform
Bucket
Mono pile
Tripod
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Basic geotechnical design principles
Bracings
Skirt
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Basic steel structure design
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Steel structure: • Coned platform • Standardized upper structure • Internal J‐tupe • Guides for pump unit • Steel quality: 355 • Plates 40 – 75 mm
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Basic steel structure design
Structure analyzes: • Ultimate load • Fatigue load • Eigenfrequen
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The prototype for Pos. 1, Frederikshavn The Ø12x6 m prototype bucket foundation was designed for a Vestas V90 3MW turbine placed on 4 m of water. The design is certified by DNV. The bucket was installed in late 2002 and is in normal operation. The structure/soil interaction has been investigated with sophisticated modal analyse equipment.
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The Mobile Met‐Mast "The Mobile Met Mast" is a prototype of a bucket foundation designed as support structure for a metmast.
Specification
Purpose: To gain confidence that a monopod bucket foundation can be successfully installed offshore.
Fabricated in Aalborg in August 2008.
Total height: 34 m Weight: 165 tones Skirt length: 6 m Skirt diameter: 12 m
Installed at Horns Rev 2 Offshore wind farm in March 2009.
To obtain a movable metmast, which can be used in several offshore wind farms.
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Installation
A penetration velocity of 2 m/hour was obtained. After 2.5 m penetration, the foundation started tilting. At 4 m penetration, the process was reversed until 3 m penetration. Then the penetration process was repeated without tilting problems. The tilt problem was properly caused by a stone along the skirt circumference. The flow induced in the soil was blocked, indicating that a clay layer was present. Installation continued. The foundation was successfully installed with a 0.1 degree inclination out of vertical.
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Universal foundation solutions Variation in water depth 0 - 60 m
Variation in seabed properties Hard clay, soft clay, sand, silt
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Logistics
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Transport: • Production in Northern Europe, facilities placed by a harbour. • Transport to interim harbour nearby site on barge
Installation: • Foundation is launched in horizontal position, and is trimmed with ballast water • Buoyant towing to site by tug boat • Clip‐on pump unit conneted • The structure is upended by manipulating ballast water • Crane is hooked on to stabilize touch down • After initial penetration, suction is applied
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Supply Chain
The implementation of the concept is conducted by a facilitator organization (solution provider) with access to the IP‐rights of the bucket concept. • Close cooperation with the project developer/owner of the wind farm project. • The functions of the facilitator are to the ensure that the technology, methodologies and procedures is optimized throughout the entire supply chain as well as ensure that the contract relations in‐between the different stakeholder is managed to utilize the full potential of the concept.
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•
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Conclusion
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Universal Foundation is found to be: • Applicable in a wide range of offshore conditions water depth / soil conditions • A focused concept development and design procedures • A cost effective fabrication / installation concept ‐> reduced cost of energy • Environmental feasible ‐ no noise impact and seabed disturbance Plan for commercialization and further development: One package complying of: • Geotechnical calculation / design manual • Production basis • Transport concepts • Installation manual • Decommission concepts • Concurrent concept development Next step: • Prototype reference full scale implementation • 2 Ph.D.s working on steel/concrete composites and soil/structure interaction in clay • Development of click‐on pump unit and soil investigating equipment
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