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DANSK GEOTEKNISK FORENING Samspil mellem jord og konstruktion
Presented by: Christian Berg Mørch ([email protected])
Torsdag den 20. november 2014
The suction bucket jacket – a new wind turbine foundation concept
2
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
Installation process
1) The suction bucket jacket is lowered to the seabed
2) An under pressure is applied to the buckets by means of individual pumps
3) The hydrostatic pressure difference and the deadweight causes the buckets to
penetrate the soil
4) The suction pumps are recovered to the installation vessel
5) A thin layer of concrete is injected between seabed and bucket lid
3
Introduction to the suction bucket jacket Functionality of the suction bucket jacket
5
Motivations for suction bucket jackets (SBJ)
Strategic rationale
What can the technology do
Introduction
• A 'Suction Bucket Jacket' is a steel jacket foundation
installed with suction pump technology instead of ~50 m
piles driven into the seabed
Key benefits from use of a 'Suction Bucket Jacket'
• Enabler / License to Operate for noise regulated projects
(especially in Germany), as the concept solves noise
regulation issue and associated noise mitigation costs
• Enabler for certain soil conditions
• A cost reduction compared to the current foundation
technology on deeper waters and large WTGs
German cluster offshore wind farm key assumptions
Cost down potential for future wind farms
FID
Foundation installation year
Park capacity
WTG size
No. of positions
Positions suitable for suction buckets
Q3, 2015
2017-2018
576 MW
6MW
96
100 %
Foundation cost reduction potential for German cluster
CAPEX
mEUR / position
Why do we need a full scale test
Be ready for the German cluster projects
• A full scale test is required now to ensure a
proven technology and certification in
Germany for the 'German cluster' projects in
due time
Prove technology for Offshore Wind
• The 'Suction Bucket' technology has been
used for decades within the offshore oil & gas.
The loads from offshore wind turbines differ
significantly from the oil & gas structures and
are more dynamic
• As scaled model test can only verify parts of
the load spectre, a full scale test is required in
order to verify the full concept
wind loads
wave loads
wind loads
wave loads
Vertical
loads
Vertical
loads
Jacket on suction
buckets
Calculations based on GOW weather, water depth and soil conditions
15-20%
Jacket w.
buckets
(DP2)
4.6
3.3
1.3
Jacket w.
buckets
(Jack-up)
5.1
3.3
1.8
Jacket
w. piles
5.3
3.0
2.3
Monopiles
5.6
2.9
2.7
Supply
Installation
6
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
7
Rotor Nacelle and Tower - Confidential part.
Integrated loads and Design Basis
Jacket design and hydrodynamic loads
Geotechnical design
Responsibility split
- Jacket structures for future projects
WTG Supplier
Geotechnical
design
Structural design
WTG Supplier
8
Overall Time Schedule – Result
- Jacket structures for future projects
Approval
• Basic Design approved the 21st of
February 2014
• Duration 8 month
• 2nd BSH release submitted according to
schedule
• 3rd BSH release 21st of May
9
WTG Supplier
Cable protection
Scour protection
Bucket installation
Foundation
installation vessel
WTG installation
Foundation installation
Cable installation
Geotechnical design
Structural design
Jacket
Under lid grouting
Co-funded by
Offshore Wind Accelerator - LOI
Suction Bucket Jacket prototype project Co-funder & Sub-contractors
10
Borkum Suction Bucket Jacket Overview
- Jacket structures for future projects
• Weight
• TP: 130 t
• Jacket: 372 t
• Buckets: 250 t
• Total: 752 t
• Footprint: 23 x 23 m
• Top: 16 x 16 m
• Buckets: 8 x 8 m
• TP b.o.s: + 20.5 m
• TP t.o.s: + 23.5 m
• Interface flange: + 24.7m
• Total height: 56.6 m
11
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
12
BKR01 – Position M05
- Jacket structures for future projects
• Water depth: 24.41 m
• Hmax: 18.3 m
• Mainly sand
Pos. M05
13
BKR01 – Position M05
- Jacket structures for future projects
Main geotechnical data
Lab test overview
• Index tests
• Triaxial
• Static drained and undrained
• Cyclic drained and undrained
• DSS
• Bender element
• Permeability
14
- Jacket structures for future projects
Metrological conditions from Fino mast. Uncomplicated !
Suction Bucket Jacket Design Basis. What was the challenge.
15
Suction Bucket Jacket Design Basis. What was the challenge.
The real challenge was the waves !
• Fino I Waverider. 2003-07-30 - 2011-01-31
• Wamos waveradar 2004-01-27 - 2011-02-27
• Site specific hindcast data,DHI 1994-2007
• Tilo (2007) and Britta (2006)
• Extreme wave height is based on negotiations with DNV
• Largest measured Hs in the area is 11m. Individual waves of up to 18m are recorded
• FINO data was applied for loads and design.
- Jacket structures for future projects
1 2 5 10 20 50 1006
6.5
7
7.5
8
8.5
9
9.5
10
10.5
Return period [yr]
Hs (
m)
Return period plot
Return period value
95% confidence bounds
Observations
Shiermonnikoog Nord
1979-2010
16
BKR01- Suction Bucket Jacket Design Basis. What was the challenge.
Position M05
yes
- Jacket structures for future projects
17
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
How do we calculate the loads ? Suction Bucket Jacket Integrated loads - methodology
Structural design
19
Suction Bucket Jacket Suction Bucket jacket studies – ROSA
- Jacket structures for future projects
• Rambøll internal software.
• Full ULS and FLS substructure sizing and code check (ROSA)
• Code check for each simulation time step
• Variation in soil conditions – soft, best estimate and stiff
• sadasd
Structural design
20
BKR01- Suction Bucket Jacket Bucket design interface loads
Operational loads – most exposed bucket
Extreme loads – most exposed bucket. Lower bound stiffness
* Dynamic wave excess pressure have not been accounted for
0 100 200 300 400 500 600-2000
-1500
-1000
-500
0
500
Time sec
Vert
ical fo
rce k
N
21
- Jacket structures for future projects
Suction Bucket Jacket Integrated loads – soil degradation and pore pressure from 35 hour storm
• Rayleigh distribution of sea states
• All compass directions
• Isolated wave impact and effect
• Counting and randomization
• Resting period of 70 sec.
22
- Jacket structures for future projects
Suction Bucket Jacket Integrated loads – soil degradation and pore pressure from 35 hour storm
• Counting and randomization are very important
• Resting period between waves will dominate the pore
pressure built up and the effective strength.
NGI demonstrated that
• The soil had undrained behaviour
• No degradation in soil cyclic strength and stiffness
• Accumulated deformation from multiple storms could not
be successfully estimated.
23
- Jacket structures for future projects
Suction Bucket Jacket Integrated loads – ULS secant stiffness evaluation
24
- Jacket structures for future projects
Suction Bucket Jacket Integrated loads – FLS secant stiffness evaluation
25
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program and outlook
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
26
- Jacket structures for future projects
141 sensors, 50 Hz
Wave heights
Pore pressure sensors
Inclinations
Accelerations
Turbine system will be connected
Suction Bucket Jacket Load measuring program
27
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program and outlook
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
Offshore installation of the SBJ Suction in buckets AB and BC as a function of time
Three stages can been identified on figure
<1.8m: Successful start but ending in cycling the flow between 1,5 and 1,8m
1,8-6,4m: 600ton ballast applied. Fast penetration until pressure limited at ~200kPa is reached.
Cycling of suction starts around 6,2m penetration and not very successful.
6,4-6,6m: Pressure up to 320kPa applied on AB and cycled. Installation aborted at 6,6m
30
31
Cycling starts at 1,5m penetration.
Possible piping at this stage but calculated critical suction pressure not exceeded.
A lot of noise in the echo sounder (BC) supports that theory.
No-flow caused by unexpected impermeable layer at 3m penetration?
Offshore installation of the SBJ Suction in buckets AB and BC as a function of penetration and critical
gradient.
Good match between suction pressure and maximum pressure required during no-flow for CPT A
Possible intermediate impermeable layer at 3m
During no-flow case CPT A. Penetration not possible below 6,2m, as is the case for the SBJ.
Possible piston effect around 3m seen on echo sounder (around 800min)
32
Offshore installation of the SBJ Suction in buckets AB and BC as a function of penetration and required
no-flow suction
33
Introduction to the suction bucket jacket
Borkum SBJ Jacket configuration and responsibility split
Introduction to site assessment.
Integrated loads – methodology and results. Suction bucket design challenges
Load Measuring program setup
Suction Installation process predicted and measured.
First results from load measuring program and outlook
Questions
Agenda The suction bucket jacket – a new wind turbine foundation concept
34
Observations from the measuring system First recordings from the system - TP accelerations and inclinations
Observations from the measuring system Transition piece accelerations after accidental boat impact
35
Observations from the measuring system Transition piece accelerations after accidental boat impact
36
Observations from the measuring system Transition piece accelerations after accidental boat impact
37
Eigen frequency design calculation 2.6 Hz
Eigen frequency observed 2.9 Hz
Eigen frequency fixed buckets 4.0 Hz
Observations from the measuring system Comparison between design and observed Eigen frequency
38
Observations from the measuring system Transition piece accelerations after accidental boat impact
39