BMT Nigel Gee Ltd

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BMT Nigel Gee Ltd

• The Transport and Installation of Concrete Wind
  Foundations
• European Offshore Wind 2009, Stockholm
• Mark Willbourn
• Marketing Director

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BMT Nigel Gee

• Specialised in Naval Architecture and Marine
  Engineering Design Consultancy part of BMT
  Group
• Particular expertise in specialised vessels
  high speed, low wash and vessels with excellent
  seakeeping characteristics
• Experience in innovative new designs 80m high
  speed catamaran for US Navy and patented 220m
  Pentamaran hull form
• gt150 vessels built to BMT NG designs up to 220
  LOA
• BMT can provide not only design consultancy,
  structural and seakeeping analysis, etc. but also
  full construction detailed design packages for
  operators and shipbuilders and ship repair yards
  worldwide

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Study Background

• Gifford approached BMT NG to assist in Concrete
  Foundations study following earlier feasibility
  study on suitability for wind farm foundations.
• BMT NGs specific task was to provide innovative
  but workable solutions to task of moving large
  foundations to wind farm sites.
• Study work included review of
• Structural requirements for vessel
• Stability assessments
• Latching mechanism
• Towing requirements
• Seakeeping assessments
• Logistics analysis

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Study Objectives

• To provide an integrated systems approach to the
  tasks
• Coordinate design and construction of foundation
  and installation methodology for efficient
  production
• Use conventional concrete construction
  technology onshore
• Maximise operational weather window for offshore
  transit and installation
• Minimise reliance on expensive offshore heavy
  lift equipment
• Use relatively simple barge concept for
  transport and installation

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Concrete Foundation Design

• Pre-stressed concrete
• Slipformed stem
• Reduced stem diameter at sea bed level

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Onshore Construction Site
Offices / Workshops
Building Pads
Load Out Quay
TIB
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Launch of Foundation
Vertical Launch Platform
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TIB Connected Over Foundation
TIB
Base Unit
Vertical Launch Platform
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TIB Features, for 3600 Te Foundation

• LOA 34 m
• Beam 32 m
• Minimum Draft 6.2 m
• Operating Draft 9.0 m
• Required Water Depth with Foundation
• Unit 11.3 m

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TIB Features

• Dumb barge, power only for ballast and latching
  systems
• Unmanned barge for normal operations
• Simple for remote operation
• High lift and transport capacity
• Relatively fast system

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TIB Under Tow
Maximum Hs 3.0m
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Operating Context
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Seakeeping Analysis

• Undertaken using VERES programme in-house by BMT
• Operating criteria based on forces and motion
  limits that foundation could reasonably expect to
  withstand and safety margins
• Motion criteria for placement of foundation on
  sea bed are significantly more restrictive
  then for transit
• Impact force on sea bed
• Risk of foundation bouncing on sea bed
• Risk of distortion of prepare bed
• Transit criteria no significant restrictions up
  to 3m significant wave height
• Placement criteria limited to 1.25m significant
  wave height, depending on water depth

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TIB and Foundation Placed on Sea Bed

• TIB ballast tanks flooded under control to place
  Base Unit onto sea bed
• Maximum significant wave height Hs 1.2m

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TIB Disconnected

• TIB disconnects from Base Unit
• TIB deballasted with compressed air and towed off

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Manoeuvring Simulations

• Not yet completed but BMT has PC Rembrandt to
  undertake bespoke simulations to enable
  operations and tow masters to
• Establish safe operating limits
• Investigate tow and handling strategies
• Assess risks for tows
• Assess marine issues for installation and
  de-comissioning
• Assess mooring arrangements

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Conclusion

• Adaptation of existing technologies can provide
  low cost solution to transport and installation
  of concrete foundations
• Seakeeping analysis has determined that
  transport is feasible in up to 3m significant
  wave height
• Installation is possible in up to 1.25m
  significant wave height, depending on water depth
• Use of TIB concept could enable installation
  operations in wider weather windows
• As foundations get larger, operating window
  extends

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Thank You