offshore wind turbines
Zhiyu Jiang January 18, 2018 Postdoctoral researcher
Department of Marine Technology
Centre for Marine Operations in Virtual Environments (SFI MOVE) Norwegian University of Science and Technology
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Outline
1. Introduction
2. The catamaran installation concept 3. Numerical simulation
4. Conclusion
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Outline
1. Introduction
2. The catamaran installation concept 3. Numerical simulation
4. Conclusion
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Bottom-fixed Floating
Water depth:
<20m<40m 50-70m >50-100m
Background
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Capital expenditure of offshore wind
C. Mone et al. (2015) 2015 Cost of Wind Energy Review, NREL
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Tripod installation using a jack-up vessel (http://worldmartimenews.com)
Jacket installation using a floating vessel (https://www.boskalis.com)
Installation methods - foundation
Monopile installation (www.seawayheavylifting.com.cy)
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Installation methods - rotor blade
Full rotor Dong Energy Bunny ear
Vatenfall
Single-blade installation Fred Olsen Wind Carrier
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Installation methods - full assembly
Saipem 7000 Statoil AS
Novel installation vessel Ullstein AS
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Purpose of numerical simulation
• Design and testing of novel installation methods
• Response-based prediction of limiting operational conditions
• Online decision support for offshore installations
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Outline
1. Introduction
2. The catamaran installation concept
3. Numerical simulation 4.Conclusion
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The catamaran installation concept
L.I. Hatledal et al. (2017)
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Challenges of the concept
• Hydrodynamics
hydrodynamic coupling, sloshing, viscous effect
• Structural dynamics
coupled motion modes, mechanical coupling
• Automatic control
station keeping of the vessel, active ballast system motion tolerance and control, landing force control
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Installation procedure
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Monitoring the relative motions
Mating point
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Properties of the catamaran
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Properties of the spar
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Outline
1. Introduction
2. The catamaran installation concept 3. Numerical simulation
Time-domain simulation Frequency-domain simulation
4. Conclusion
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Time-domain simulation
WADAM: Hydrodynamic analysis of the two-body system
HAWC2: Calculation of the wind forces on the turbine assemblies
SIMO: Time-domain coupled analysis
Catamaran with dynamic positioning system; spar with mooring lines;
sliding grippers between catamaran and spar
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Modelling of the hydrodynamics
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Modelling of the sliding grippers
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Modelling of the mooring system
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Frequency-domain approach
1. Hydrodynamic analysis of the two-body system
2. Short-term motion prediction of the mating point by using Response Amplitude Operators
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Magnitude of the pitch RAOs
Spar Catamaran
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Environmental conditions
Hs=2.0 m Tp Vȕ GHJ
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Results - relative surge motion
2 m OK 2
Hs Pȕ GHJ
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Results - relative roll motion
Hs=2.0 m, ȕ deg
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Conclusion
• A numerical modelling approach of the catamaran installation concept is introduced.
• Future work is needed for implementing the active heave compensator,
dimensioning of the catamaran, active ballast system, etc.
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Acknowledgements
• Zhen Gao
• Karl Henning Halse
• Peter Christian Sandvik
• Zhengru Ren
Instrumenting the Gravity base foundations for the Blyth Offshore Demonstration wind farm
January 2018 Jonathan Hughes and Paul McKeever
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Agenda
• ORE Catapult
• Demowind and the FSFound Project
• The Blyth Offshore Demonstration Wind Farm
• The Project
• Instrumentation in the Marine Environment
• Future Work
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The catapult network:
A long-term vision for innovation & growth
Catapults
• Established by InnovateUK
• Designed to transform the UK's capability for innovation
• Core grant leveraged with industry and other public funding
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ORE Catapult Our Vision:
Abundant, affordable energy from offshore wind, wave and tide
• Reduce the cost of offshore renewable energy
• Deliver UK economic benefit
• Engineering and research experts with deep sector knowledge
• Independent and trusted partner
• Work with industry and academia to commercialise new technologies
80+ technical experts
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ORE Catapult Business Model
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• 5x 8.3MW turbines
• 6.5km off the coast of Blyth
• 191.5m Tip Height (AOD)
• Approx 40m Water Depth
Blyth Offshore Demonstrator Wind farm
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Installation of GBFs at Blyth – Satellite Imagery
NOAH Met Mast 6
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Image from Aeronet-OC Project
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To validate the FS GBF solution as an alternative solution to energy provision by proving that FS GBF performs as intended and can be installed cost-effectively;
• To conduct a range of simulation and modelling studies to minimise the uncertainties and inefficiencies in the deployment process and in various weather windows;
• To compare the actual costs and performance with the cost-benefit analysis performed;
• To assess structural response to extreme and fatigue loads on the FS GBF and compare theoretical loads with real ones;
• To establish the effect of cyclic loadings on the seabed through monitoring and measurement and verify/calibrate models for differential settlements in the soil;
• To establish the optimal seabed preparation requirements (i.e. minimum preparation depth).
FSFound Project Aims
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1. Validation of the design, including input to verifying simulation models 2. Providing feedback to the design limits of the structure, such that an updated
life expectancy can be calculated (if required) 3. Understanding the interaction between:
GBF and Seabed (e.g. settlement)
GBF and WTG (e.g. modal interaction, load transfer) GBF/WTG combination and the Environment (e.g. wind/wave misalignment loads)
Effect of internal divisions on the displacement of the caisson outer walls 4. Provide inputs to the design of a Structural Health Monitoring system for GBF
system
5. Provide inputs to the cost model, in the form of estimated O&M OPEX costs 6. Provide a platform for the development of a prognostic methodology for
NDT of GBFs
Aims of the measurement campaign?
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Caisson Pressure Sensors
• Upper sensor mounted near vent (sea reference)
• Lower sensor mounted near top of slipform
• 3 sets of 2 mounted at 120˚ spacing
• 4Hz sample rate
Upper Pressure Sensor
& Electronics JB
Lower Pressure Sensor Vent Hatch
Wet Joint • Indirect measurement of depth
• Also can calculate period
• Triangulation may permit direction measurement
• Comparison after calculation with other wave data on site.
• Data corrected for Atmospheric variation
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• High stability servo inclinometers
• Measurement range of +/-14.5˚
• Resolution of 0.001˚
• Positioned to match ANSYS AQWA modelling nodes
• Positioning is critical to interpretation of data
Inclination and Mode Shapes
Inclinometer
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• Initially aimed to installed SGs into Concrete, however not possible
• Structure can be analysed through load paths rather than direct loads
• Bending, Compression and Torsion are independently assessed
• Loads measured above and below “Wet Joint” – calculation of loads into caisson roof
• Loads measured at field weld to establish effect of loads from turbine and torsional loads
Load Paths
Strain Gauges (Below Wet Joint)
Strain Gauges (Above Wet Joint)
Strain Gauges (Above Wet Joint)
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• Structures are filled ballasted with sand and seawater flooded below LAT
• Water is expected to have slow transit rate through structure, leading to oxygen depletion
• Dissolved Oxygen sensors are installed to monitor
• Water level in shaft is monitored for comparison
• DO Sensors use dynamic luminescence quenching rather than an EC sensor
Corrosion
From AADI 4330 manual
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• Instruments are useless if they don’t work or give questionable data
• Welding and Bolting were not permitted by the designer
• All instruments are permanently bonded, but need a temporary method of attachment until the adhesive “grabs”
• Protection needed against ballasting force
• Protection against settlement
• Subsea-grade cables and connectors
• Full epoxy fill to instrumentation systems
Connection and Protection
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• Vertical installation requires significant additional time and risk management
• Installing delicate sensors; to fine tolerances; in the wet; hanging from a rope…
• Horizontal installation challenging without the ability to roll or traverse
Installation Challenges
• Location Referencing
• Novel and Evolving design
• Fitting research into a complex and time-critical construction project
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How close are models to their physical counterparts?
Pipe B
Pipe A
Brackets Sensor Axis
CP String A
Pipe C
Pipe D Pipe E CP String B
CP String C
CP String D
CP String E Pipe F Hardware Driver
Created
VOB Server OPC Connection Software Unit Test
Unit to Main Integration
Core Main Software (Logging and Communication)
Software Unit Test
Server-side software for OPC
Software Unit Test
Software
Cabling Verification, Interconnects
Hardware Acceptance Test
Encapsulation
Installation into Foundation
Site Acceptance
Test Replication of PC for
Backup
Test ODSL File Server
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Example Data – Inclinometer Profile
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Planning for Analysis
• Flowcharts convert theory into algorithm for processing
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Commercial Ideals
• Strong “proven” technical solution
• Warrantable performance allowing for “tight” contracts
• No unexpected outcomes Research Ideals
• Cutting Edge “novel” technical solution
• Project technical output comes before programme
• Unexpected outcomes are interesting (isn’t that why we do it?)
The best common outcomes only come through
• Close collaboration between practical and theoretical work
• Novel techniques but proven technologies and strong theoretical base
• Trial and error (more trials, fewer errors!)
Why is Research in a Commercial Project so challenging?
Ballast Pipe
Test Rod (same dimension as widest part of plug)
Pipe Aperture
Shaft
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BLYTH ORE Catapult National Renewable Energy Centre Offshore House Albert Street Blyth, Northumberland NE24 1LZ
T +44 (0)1670 359 555 F +44 (0)1670 359 666 GLASGOW
ORE Catapult Inovo
121 George Street Glasgow G1 1RD
T +44 (0)333 004 1400 F +44 (0)333 004 1399
LEVENMOUTH ORE Catapult Fife Renewables Innovation Centre (FRIC) Ajax Way
Leven KY8 3RS
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Contact us
Integrated design optimization of jackets and foundations for offshore wind turbines
Kasper Sandal Chiara Latini Varvara Zania Mathias Stolpe
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ABYSS– Advancing BeYond Shallow waterS funded by Innovation Fund Denmark
DTU Wind Energy, Technical University of Denmark 06 October 2017
This is how optimization can become a valuable tool for structural engineers in offshore wind
minimize ݂(࢞) subject to ࢞ െ ࢈
࣌ ࣌ ࢞ ࣌
࣓ ࣓ ࢞ ࣓
Design considerations Optimal design problem
Design trends
2
DTU Wind Energy, Technical University of Denmark 06 October 2017
This is how optimization can become a valuable tool for structural engineers in offshore wind
minimize ݂(࢞) subject to ࢞ െ ࢈
࣌ ࣌ ࢞ ࣌
࣓ ࣓ ࢞ ࣓
Design considerations Optimal design problem
Design trends
3
minimize ݂(࢞) subject to ࢞ െ ࢈
࣌ ࣌ ࢞ ࣌
Design considerations Optimal design problem
Design trends
࣌ ࣌ ࢞ ࣌
࣓࣓ ࢞ ࣓
DTU Wind Energy, Technical University of Denmark 06 October 2017
minimize ݂(࢞) subject to ࢍ ࢞
Objective function
How to formulate a numerical optimization problem:
Let xbe a vector of variables, where we want to minimize f(x)
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Constraint functions
DTU Wind Energy, Technical University of Denmark 06 October 2017
minimize ݂(࢞) subject to ࢍ ࢞
࢞= design variables:
1. Diameters &
wall thickness 2. Diameters, wall
thickness, &
length ŽƐƚу:ĂĐŬĞƚнĨŽƵŶĚĂƚŝŽŶŵĂƐƐ
Engineering limits:
1. Fatigue limit state 2. Ultimate limit state 3. Soft-stiff frequency range
How to design a jacket and its foundation with optimization:
Let xdescribe the design, f(x) the cost, and g(x) the engineering limits
5
DTU Wind Energy, Technical University of Denmark 06 October 2017
minimize ݂(࢞) subject to ࢍ ࢞
The optimization problem has very few design variables, but a high number of nonlinear constraints
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o 24 design variables for the jacket o 3 design variables for the foundation o 7k constraints for each static load
¾Stress along all tubular welds
¾Shell buckling & column buckling
¾Foundation capacity o 2 frequency constraints
DTU Wind Energy, Technical University of Denmark 06 October 2017
:KW
Mesh Loads Finite Element
ŶĂůLJƐŝƐ Sensitivity
analysis WŽƐƚ
processing Interfacing scripts
fmincon ' /WKWd W>y Built-in solvers
The problem is implemented in the special purpose software JADOP (Jacket Design Optimization)
7
DTU Wind Energy, Technical University of Denmark 06 October 2017
We make assumptions in the structural analysis which are suitable for the conceptual design phase
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o Timoshenko beam elements for the support structure
o Linear 6-dof responsefor each foundation o 4 Damage equivalent loads for the fatigue limit state o 3 Extreme static loads for the ultimate limit state o Conservative analysis of column buckling o Stress concentration factors in welded tubular joints No safety factors are applied in the following examples
DTU Wind Energy, Technical University of Denmark 06 October 2017
For a given design problem (10 MW turbine, 50 m depth, piles), the total mass was minimized to 631 tons (in 5 minutes on a laptop)
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Piles in sand Diameter: 1.41 m
Length: 50 m
Mass: 140 tons
Jacket
Mass: 491 tons
Soil: Medium stiff sand
Foundation: Wiles Design procedure: W/
32 m
DTU Wind Energy, Technical University of Denmark 06 October 2017
JADOP has a parameterized mesh which makes it a quick task to modify for example the leg distance
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DTU Wind Energy, Technical University of Denmark 06 October 2017
When support structures with different leg distance are optimized, jacket mass and foundation mass show opposite design trends
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Medium stiff sand
DTU Wind Energy, Technical University of Denmark 06 October 2017
The optimal leg distance will depend on for example the soil stiffness
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Medium stiff sand
DTU Wind Energy, Technical University of Denmark 12
Very stiff sand
DTU Wind Energy, Technical University of Denmark 06 October 2017
But several other aspects of the anchoring will also influence the design problem
We have looked at:
• WŝůĞƐΘƐƵĐƚŝŽŶĐĂŝƐƐŽŶƐ
• Sand & clay
• Varying soil stiffness
• Different design procedures for piles
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Source: SPT Offshore
Suction caisson
Source: 4coffshore
WŝůĞƐ
DTU Wind Energy, Technical University of Denmark 06 October 2017
The design considerations are “translated” into an optimization problem, and it is now a quick task to generate design trends
minimize ݂(࢞) subject to ࢞ െ ࢈
࣌ ࣌ ࢞ ࣌
࣓ ࣓ ࢞ ࣓
Design considerations Optimal design problem
Design trends
14
DTU Wind Energy, Technical University of Denmark 06 October 2017
The figure below shows how jacket mass and foundation mass change as functions of both leg distance and soil stiffness (A=stiff, D=soft)
xº F
Fz
ªux
uz
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Soil = sand
Foundation = piles
DTU Wind Energy, Technical University of Denmark 06 October 2017
The preferred leg distance now depends on the soil stiffness, and perhaps also the desired fundamental frequency
º Fx
Fz
ªux
uz
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Soil = sand
Foundation = piles
DTU Wind Energy, Technical University of Denmark 06 October 2017
Structural optimization is used to automate the “well-defined”
engineering tasks of conceptual support structure design
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࢞= design variables Cost function
Engineering limits:
1. Fatigue limit state 2. Ultimate limit state 3. Soft-stiff frequency range
minimize ݂(࢞) subject to ࢍ ࢞
DTU Wind Energy, Technical University of Denmark 06 October 2017
With a tool like JADOP it is then quick & easy to investigate how input conditions influences the design
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minimize ݂(࢞) subject to ࢍ ࢞
F) Wind farm optimization
The DIMSELO Project (Dimensioning Sea Loads for Offshore Wind Turbines), F. Pierella, IFE
A savings procedure based construction heuristic for the offshore wind inter-array cable layout optimization problem, S. Fotedar, University of Bergen
Calibration and Initial Validation of FAST.Farm Against SOWFA, J.Jonkman, National Renewable Energy Laboratory
An Experimental Study on the Far Wake Development behind a Yawed Wind turbine, F. Mühle, NMBU