IEC 61400-3-2: Technical Specification for Floating Offshore

Wind Turbines (FOWTs) Workshop on Offshore Wind Energy Standards and Guidelines June 17-18, 2014 Arlington, VA Jason Jonkman, Ph.D. Senior Engineer, NREL

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Workshop on Offshore Wind Energy Standards and Guidelines 2 National Renewable Energy Laboratory

Outline

• Introduction & Background: – FOWT Concepts – Industry Status – Objectives, Approach, & Outcome – Participants – Coordination with Related Projects

• Key Features: – Scope – External Conditions & Assessment – Design Load Cases – Simulation Requirements – Stationkeeping System – Floating Stability – Other

• Schedule & Status

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Introduction & Background FOWT Concepts

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Introduction & Background Floating Wind Industry Status

Developer • Statoil, Norway • PPI & EDP, Portugal • METI, Japan • MOE, Japan

Platform • “Hywind” spar buoy with catenary moorings

• “WindFloat” semi-submersible with catenary moorings

• Mitsui semi-submersible with catenary moorings

• Spar buoy with catenary moorings

Wind Turbine

• Siemens 2.3 MW • Vestas V80, 2 MW • Hitachi 2-MW downwind

• Hitachi 2-MW downwind

Status • $70M demonstration project in North Sea

• First PoC installed in Summer 2009

• More optimized demonstrator under development

• $25M demonstration project in Portugal

• First PoC installed Fall 2011

• EU FP7-funded “Demofloat” testing & validation project

• US project underway

• Installed in Summer 2013 near Fukushima

• Part of the $189M “Fukushima Forward” project in 2011-2015, which will also have two 7-MW turbines

• 2-MW full-scale system installed in Fall 2013 in Kabashima, Japan

• Followed 100-kW half-scale system

• Testing & validation underway

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• Objective: Develop a Technical Specification (TS) for ensuring the engineering integrity of FOWTs

• Approach: Develop a document that is as aligned with the -3 as much as possible, but with differences where needed

• Outcome: Depending on the differences in the end, the new requirements could become: – Merged into the -3 – An appendix to the -3 – An entirely new standard

Introduction & Background Objectives, Approach, & Outcome

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• Convener: Lars Samuelson – ABS (USA) Hyun Kyoung Shin – University of Ulsan (Korea) • Secretary: Denis Matha – University of Stuttgart (Germany) • Doc Master: Jason Jonkman – NREL (USA)

Introduction & Background Participants

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• MT1 for land-based wind • MT3-1 for fixed-bottom offshore wind • AWEA Recommended Practice • BSEE Technology Assessment & Research (TA&R)

project 669 on FOWTs • DNV JIP for FOWTs • GL Offshore Wind Guideline 2012 • ABS Guide for Building & Classing FOWTs • IEC TC-114 for Marine Energy Converters

Introduction & Background Coordination with Related Projects

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• Primarily applicable to: – One single HAWT – Unmanned units – Spar buoys, TLPs/TLBs,

semi-submersibles, or hybrids

• Additional requirements may be needed for: – Multi-turbine units – VAWTs – Units with permanent

personnel – Wind/wave-combined

units

Key Features Scope

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• Wind gusts (EOG, EDC, ECD): – Durations corresponding

to FOWT natural frequencies

• New appendix for seismic analysis (especially for TLP/TLB)

• New appendix for tsunami analysis (high surge & strong current)

Key Features External Conditions & Assessment

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Key Features Design Load Cases

• Operational sea-state limits (modified 1.6; new 2.5 & 4.3) • Redundancy check (after line loss):

– Transient situation & afterword – Neglected for non-redundant stationkeeping system, but higher safety

factors then required – During both

power-production & parked/idling

• Damage stability (flooded compartment): – During both

power-production & parked/idling

Design Situation DLC Wind Condition

Wave Condition

Directionality Other Conditions

Type of Analysis

Power production 1.x

Power production plus occurrence of fault

2.x

Start up 3.x

Normal shut down 4.x

Emergency shut down 5.x

Parked 6.x

Parked with fault 7.x

Transport, assembly, and maintenance

8.x

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• Modeling requirements: – 6 DOF floater motion – Stationkeeping system – Radiation/diffraction

(where applicable) – Second-order hydro.

• Strongly recommended for model validation: – Tank testing for floater – Prototype of turbine onshore

• Limitation of aerodynamic models with large floater motion • Frequency-domain analysis permitted only when shown to

achieve equal or higher level of safety

Key Features Simulation Requirements

External Conditions

Applied Loads

Wind Turbine

Hydro-dynamics

Aero-dynamics

Waves & Currents

Wind-Inflow Power Generation

Rotor Dynamics

Platform Dynamics

Mooring Dynamics

Drivetrain Dynamics

Control System

Nacelle Dynamics

Tower Dynamics

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• Treatment of wind/wave directionality: – Importance of potentially large motions &

little damping side-to-side

• Longer simulation length: – Importance of low-frequency floater motion

& slow-drift effects – Use of periodic wind data is recommended

• Longer start-up transients & better initial conditions

Key Features Simulation Requirements (cont)

50-yr Load Roses for Tower- Base FA (Top) & SS (Bottom)

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• Basically design in accordance to ISO 19901-7

• Loads from DLC simulations • Non-redundant systems allowed

via an increase in safety factors

Key Features Stationkeeping System

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• Intact static stability criteria following IMO code • Alternative intact stability criteria based on dynamic response • Damage stability:

– Flooding of any single watertight compartment – Not required if there is no danger for human safety or damage to the

environment & neighboring facilities – Local authority requirements may supersede

Key Features Floating Stability

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• Design methodology: – Rigorous description of limit states (ULS, FLS,

& SLS) – WSD method allowed as alternative to LRFD

• Control & protection systems: – Turbine operational controller shall not bring

about instability of low-frequency floater motions

– Protection system activated for excessive motions of tower & floater

• Assembly, transportation, & installation – ISO 19901-6 for floating-specific items

• Commissioning, operation, & maintenance – ISO 19901-6 for floating-specific items

Key Features Other

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• Mechanical systems – Must be able to support heel angles (especially lubrication)

• Materials – Of floater & stationkeeping system to follow 19904-1

• Marine support systems – Generally follow ISO 19901-4

Key Features Other (cont)

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• New work proposal (draft standard) from Korea • Kicked-off WG in September 2011 • Major revision of Korean draft proposed by Japan • Rewrote entire document within WG • Most controversial topics:

– Use of the term “scantling” – Loss of floating stability – Corrosion protection

• CD to be submitted June 2014 • Final to be published after national comments in 2015

Status Schedule & Status

Questions?

Jason Jonkman, Ph.D. +1 (303) 384 – 7026 jason.jonkman@nrel.gov

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.