A. L. Hopstad, K. Ronold, C. Sixtensson, J. Sandberg 2013-02-07
Standard Development for Floating Wind Turbine Structures EWEA
2013
Slide 2
Standard Development for Floating Wind Turbine Structures
2013-02-07 Outline of presentation Development of a standard for
design of floating wind turbine structures Certification process
for floating wind turbines 2 HywindWindFloDIWETWindSea Statoil
Norway Future Emerg. Tech. EU Blue H Netherlands WindSea AS
Norway
Slide 3
Standard Development for Floating Wind Turbine Structures
2013-02-07 Joint Industry Project (JIP) Objective: Develop a (DNV)
standard for design of floating wind turbine structures 10
participants from the industry - Statoil - Navantia - Gamesa -
Alstom Wind - Iberdrola - Sasebo Heavy Industries - Nippon Steel -
STX Offshore & Shipbuilding - Glosten Associates - Principle
Power Kick off: September 2011 External/internal hearing:
tentatively March/April 2013 Expected release: Q2 2013 3
Slide 4
Standard Development for Floating Wind Turbine Structures
2013-02-07 Why develop a standard for floaters? Until recently
existing standards have been restricted to bottom-fixed structures
only: - IEC61400-3- DNV-OS-J101 - GL (IV Part 2)- ABS #176 This
forms the background for the new floater standards issued by ABS,
NKK, GL and for the standard to be issued by DNV later in 2013 The
standard will contain normative requirements that shall be
satisfied in design of tower and support structure Development of
this standard will lead to: - Expert / industry consensus on design
principles - Experience from the industry reflected in the contents
- Innovative designs and solutions - Economically optimized designs
4 Courtesy: Principle Power WindFloat, Principle Power
Slide 5
Standard Development for Floating Wind Turbine Structures
2013-02-07 Three main technologies: Spar buoys, Semi-submersibles,
Tension leg platforms (TLP) Weight-buoyancy stabilized structure
with large draught + Simple, inherently high stability substructure
+ Proven technology - Substructure weight - Draught implication on
site flexibility 5 Tension restrained structure with relatively
shallow draught + Low steel weight + Small seabed footprint -
Sensitive to soil conditions - Stability in intermediate phases
Free-surface stabilized structure with relatively shallow draught +
Simple transport & installation + Flexible design with respect
to site - Substructure weight and complexity - Motions in extreme
wave conditions Spar Semi- submersible TLP
Slide 6
Standard Development for Floating Wind Turbine Structures
2013-02-07 Technical issues covered by the standard SSafety
philosophy and design principles SSite conditions, loads and
response MMaterials and corrosion protection SStructural design
DDesign of anchor foundations SStability SStation keeping CControl
system MMechanical system TTransport and installation IIn-service
inspection, maintenance and monitoring CCable design (structural)
GGuidance for coupled analysis 6 Photo: Knut Ronold
Slide 7
Standard Development for Floating Wind Turbine Structures
2013-02-07 Safety philosophy The safety class methodology is based
on the failure consequences The safety class is characterized by a
target annual failure probability Safety class LOW => target
annual probability of failure of 10 -3 Safety class NORMAL =>
target annual probability of failure of 10 -4 Safety class HIGH
=> target annual probability of failure of 10 -5 In DNV-OS-J101
and IEC rules: safety class Normal Requirements for load factors to
be used in design depend on the target safety level of the
specified safety class 7 Hywind Photo: C.F. Salicath
Slide 8
Standard Development for Floating Wind Turbine Structures
2013-02-07 What shall the safety level be in large floating wind
farms? The current safety class NORMAL was originally developed for
small, individual turbines on land and has been extrapolated to be
used also for: 1.Larger MW size turbines on land 2.Offshore
turbines 3.Support structures for offshore turbines 4.Many large
turbines in large offshore wind farms Is it possible to reduce the
target safety level based on having large wind farms with many
turbines offshore? The consequence of failure is primarily a loss
of economic value => cost-benefit analysis 8 Kabashima
demonstration turbine Photo: Knut Ronold, DNV
Slide 9
Standard Development for Floating Wind Turbine Structures
2013-02-07 Cost benefit analysis Establish which safety level is
necessary / acceptable in design of floating support structures
Find optimum between choice of safety class in design and net
present value (NPV) for a wind farm development The analysis is to
be used as part of the basis for selecting target safety level
Input: - Insurance companies estimated maximum loss philosophy -
Cost data for CAPEX and OPEX - Cost data for replacing turbines and
support structures - Cost differences when applying different
safety classes - Electricity prices 9
Slide 10
Standard Development for Floating Wind Turbine Structures
2013-02-07 Cost benefit analysis example of results 10 Optimum Low
CAPEX, low safety level High CAPEX, high safety level
Slide 11
Standard Development for Floating Wind Turbine Structures
2013-02-07 Structural design Special provisions for the different
floater types and for floater specific issues Design rules and
partial safety factors for structural components - Ultimate Limit
State (ULS) - Fatigue Limit State (FLS) - Accidental Limit State
(ALS) Existing design standards from oil & gas industry has
been capitalized on: - DNV-OS-C101 for offshore structures -
DNV-OS-C105 for tendons - DNV-OS-E301 for mooring lines Design
Fatigue Factors (DFFs) specific for floating support structures and
station keeping system have been established 11 Kabashima
demonstration turbine Photo: Knut Ronold, DNV Kabashima
demonstration turbine Photo: Knut Ronold, DNV
Slide 12
Standard Development for Floating Wind Turbine Structures
2013-02-07 Station keeping Develop design rules and requirements
for station keeping of floating wind turbines The JIP has received
data on load/response from three developers: - Hywind (full-scale
data, mooring lines) - Pelastar (analysis data, tendons) -
WindFloat (analysis / full scale data, mooring lines) Load factors
for tendons and mooring lines for different safety classes are
established - Capitalize on PosMoor rules (DNV-OS-E301) -
Reliability-based calibration for validation has been performed
based on received data 12 Demonstration turbine in Japan Photo:
Knut Ronold, DNV
Slide 13
Standard Development for Floating Wind Turbine Structures
2013-02-07 Project Certification for Offshore wind farms Provide
evidence to stakeholders that a set of requirements laid down in
standards are met during design and construction and maintained
during operation DNV-OSS-901 Project Certification of Offshore Wind
Farms (2012) - developed for DNV service for bottom-fixed wind
farms Phases: - Phase I Verification of Design Basis - Phase II
Verification of design - Phase III Manufacturing Survey - Phase IV
Installation Survey - Phase V Commissioning Survey - Phase VI
In-Service 13
Slide 14
Standard Development for Floating Wind Turbine Structures
2013-02-07 Project Certification for Floating Wind Farms DNV is
currently in the process of extending the project certification
service to also cover floating wind farms Extended scope for Phase
II Design verification: - Floater stability - Station keeping -
Validation of software - Verification by model testing Current
floating wind turbine concepts capitalize on novel technology to
various degrees Technology items not covered by any standards may
need to be taken through a technology qualification process to
obtain documentation required for certification 14
Slide 15
Standard Development for Floating Wind Turbine Structures
2013-02-07 Type Certification Type certification of floating units
for a specific environmental class is foreseen as a possible new
service in the case of mass-produced floater units The station
keeping system including anchor design would need to be qualified
for each site 15 WindFloat Photo: Principle Power
Slide 16
Standard Development for Floating Wind Turbine Structures
2013-02-07 16 Thank you Thank you for your attention
Slide 17
Standard Development for Floating Wind Turbine Structures
2013-02-07 www.dnvkema.com