RD2101_R02_20240501

ClassNK Wind Turbine Certification
andRelated Services[Website public version]
01 May 2024
NIPPON KAIJI KYOKAI

＜Attention＞
 This paper is created to inform the policy of wind turbine certification
and related services of ClassNK.
 Please check the latest version on the website because the contentsof this paper will be update.
＜Update history＞
VersionReleased date

RD2101

August 2021

RD2101_R01_20230814

14 August 2023

Updating contents for introducing Registered Conformity
Assessment Body

01 May 2024

 Newly added an overview of the Certification SubCommittee / Section Meeting in the case of onshore
wind farms (p.13) and partially amended theassessment flow for foundations (p.16).
 Reflects changes to the organization of the
Supporting Structures Certification Sub-Committee
in the case of offshore wind farms (p.26 newly
added and part of p.28 amended).

RD2101_R02_20240501

Changes
Newly enacted

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Table of contents
1. ClassNK Wind Turbine Certification
2. Wind Farm Certification [Onshore Wind Farm]
3. Wind Farm Certification [Offshore Wind Farm]
4. Registered Conformity Assessment Body
designated by Electricity Business Act
5. Compliance with laws and regulations foroffshore wind turbines
6. Other related services

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31. ClassNK Wind Turbine Certification

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41. ClassNK Wind Turbine Certification
Type certification
Large wind turbine type certification
Conducts evaluations based on various technical standards related to wind turbines, such as
design conformity assessments and type testing assessments using test units, and ultimately
issues a type certificate.

Small wind turbine type certification
Evaluates the conformity of small wind turbines to the requirements in international anddomestic standards (performance and safety) and issues a type certificate.

Wind farm certification
Wind farm certification
Evaluates the environmental conditions of the site where the wind farm is to be constructed,
evaluates and confirms that the strength and safety of the wind turbine and support structure
are secured in terms of the design based on these environmental conditions, and issues a
Certificate / Conformity Statement.

Wind turbine support structure: Material certification
Certification assumes the wind turbine support structure is made of materials that do NOT fall under any of the following: Building Standards Act, Article 37: “Designated building materials”
 Materials approved by the Minister of Land, Infrastructure, Transport and Tourism
 Materials approved in terms of performance assessments pertaining to technical standards conformity for wind power
generation facilities
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51. ClassNK Wind Turbine Certification
Wind turbine certification [Large wind turbines]
Design conformity assessment
 Assesses whether the wind turbine is designed and documented
according to the design assumptions, specific standards, and othertechnical requirements
Prototype certificationDesign evaluation specialized in verifying safety when constructing test units

Type testing Verifies the output performance and performs an experimental safety
verification through the actual operation of the test unit

Manufacturing evaluation
 Assesses whether the wind turbine is manufactured according to thedesign documents verified during the design evaluation

Wind Turbine Certification
Body Certificate(Japan Accreditation Board)Type certification
 A certificate is granted to wind turbines that satisfy every requirement in the design evaluation, type
test, and manufacturing evaluation
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61. ClassNK Wind Turbine Certification
Wind turbine certification [small wind turbines] Verifies whether the performance and safety of the wind turbine complies with the requirements
specified in the Japan Small Wind Turbines Association Standards (JSWTA0001).
 Certification procedures comply with the “Guidelines for Certification of Wind Turbines and Wind Farms”

Small wind turbine definition
 Output: less than 20 kW

 Swept area: less than 200 m2[Small wind turbine types]

Multi-bladed(horizontal axis)

Darrieus(vertical axis)

Propeller(horizontal axis)

Wind-lens(duct, diffuser)

Savonius(vertical axis)

Helical(vertical axis)

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H-Darrieus(vertical axis)

Wind Turbine Certification
Body Certificate(Japan Accreditation Board)71. ClassNK Wind Turbine Certification
Wind farm certification overview
Evaluates the environmental conditions of the site where the wind farm is to be constructed and verifies that thestrength and safety of the wind turbine and support structure are secured in terms of the design based on theenvironmental conditions. (This certification is unique to Japan and is intended for conformity to the TechnicalStandards for Wind Power Generation Facilities.) In principle, wind farm certification is for wind farms in Japan that have an output of 500 kilowatts or more,consist of one or more wind turbines (RNA) and their support structures (tower and foundation), and are
subject to the Electricity Business Act.
 The purpose of wind farm certification is to assess whether the design for type-certified wind turbines (RNA)and their support structures (tower and foundation) are in conformity with the external conditions and therequirements under the Electricity Business Act.
<Main compliance criteria for wind farm certification>
 Ministerial Ordinance Prescribing Technical Standards for Wind Power Generation Facilities (Ministry of Economy, Tradeand Industry, Ordinance of the Ministry of International Trade and Industry No. 53 of March 27, 1997)
 Interpretation of Technical Standards for Wind Power Generation Facilities (Ministry of Economy, Trade and Industry, No.
20230310, Bureau of Commerce No. 2, March 20, 2023)
 Guidelines for Design of Wind Turbine Support Structures and Foundation (Japan Society of Civil Engineers, 2010)

NIPPON KAIJI KYOKAI is accredited by the Japan Accreditation Board as an
ISO/IEC 17065 (JIS Q 17065) Product Certification Body based on the Board’s“Wind Power Generation System: Windfarm” accreditation criteria.
■ Japan Accreditation Board website, accredited Product Certification Bodies: https://www.jab.or.jp/system/service/product/accreditation/detail/453/

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1. ClassNK Wind Turbine Certification
Wind turbine support structure: Material certification overview
Certification assumes the wind turbine support structure is made of materials that do NOT fall under any of thefollowing: Building Standards Act, Article 37: “Designated building materials”
 Materials approved by the Minister of Land, Infrastructure, Transport and Tourism
 Materials approved in terms of performance assessments pertaining to technical standards conformity for wind
power generation facilities<Review scope> Tower flanges
 Flange joint bolt and nut flat washer sets

 Anchor bolts
 Steel plates<Review criteria>
 The review criteria used in the Ministry of Land, Infrastructure, Transport and Tourism Minister’s
certification process apply mutatis mutandis (in the course of the technical review, a fatigue strength
evaluation, which is important for wind power generation facilities, may be added)<Review details>
 Technical review (statistical assessment)Chemical property value stability (component ratio of present elements, especially weldability, crack sensitivity,
etc.)
Physical property value stability (dimensions, hardness, strength, tolerance, variance, relaxation, delayed
fracture resistance, etc.)

 Quality control system reviewA quality management system equivalent to ISO 9001 is in place.
A subcontract management system is in place and properly operated.
A receiving system is in place and an inspection system at each stage within the company has been established.
Testing and inspection equipment are properly managed.
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92. Wind Farm Certification[Onshore Wind Power Plant]

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2. Wind Farm Certification [Onshore Wind Farm]
Guidelines: Wind Farm Certification - Onshore Wind Farm edition
 ClassNK has compiled the requirements as formulated based on a number ofexamples of past wind farm certification reviews for onshore wind farms and issued
this compilation as a new set of guidelines in July 2021. Revised edition was issued in
March 2023.


Since the start of certification services in 2016, ClassNK has issued Wind Farm Certificates for 180
onshore wind farms (as of the end of June 2023).
Registration of wind farm certification (Onshore) :https://www.classnk.or.jp/hp/pdf/authentication/renewableenergy/en/windfarm/RE-081-02_onshore_e.pdf

 The revised edition includes the contents about Registered Conformity Assessment
body designated by revised Electricity Business Act entered force on March 2023.
 In addition to certification review requirements, the guideline’s annexes cover a comprehensive range ofcontent, including details on implementation and verification methods for air flow analysis and windpressure coefficients for the nacelle cover, which are based on the results of independent examinations
by ClassNK.
Guidelines: Wind Farm Certification - Onshore wind farm edition Table of contents
Chapter 1. General
Chapter 2. Site conditions assessment
Chapter 3. Design basis evaluation
Chapter 4. Integrated load analysis evaluation
Chapter 5. Wind turbine (RNA) design evaluation
Chapter 6. Support structure design evaluation

Annex A. Measurement data evaluation methods [normative]
Annex B. Airflow analysis and verification of its validity [normative]
Annex C. Evaluation method for wind conditions [informative/normative]
Annex D. Equivalent wind pressure coefficient for the nacelle cover [informative]
Annex E. Measurement testing for fluctuating pressure characteristics acting on anacelle surface [informative]
Annex F. Design methodologies for tower structures [normative]
Annex G. Design methodologies for foundation [normative]

Download form here : https://www.classnk.or.jp/hp/pdf/authentication/renewableenergy/ja/windfarm/NKRE-GL-WFC01_March2023_Jpn_20230331.pdf

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2. Wind Farm Certification [Onshore Wind Farm]Wind Farm Certification modules [for Onshore Wind Farms][M1] Site conditions assessment (wind conditions)[M2] Wind turbine (RNA) design evaluation(including site conditions assessment, design basis evaluation, and integrated load analysis)[M3] Support structure design evaluation (tower)(including site conditions assessment, design basis evaluation, and integrated load analysis)[M4] Support structure design evaluation (foundation)(including site conditions assessment, design basis evaluation, and integrated load analysis)
 In the case of onshore wind farms, the applicant may specify whether they will implement all modules or only some modules, according
to the applicant’s judgement.
 Considering the application for Registered Conformity Assessment Body, recommend to implement all modules.
 The same as before, different applicants may apply for each module.

※ RNA: Rotor Nacelle Assembly
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2. Wind Farm Certification [Onshore Wind Farm]
Overview of Certification Subcommittee / Section Meeting
Large Wind Turbine Certification Subcommittee
Evaluation items:[M1] Site conditions assessment (wind conditions)[M2] Wind turbine (RNA) design evaluation (including site condition assessment, designbasis evaluation, integrated wind load analysis)

Support Structure Certification Subcommittee / Tower Section Meeting
Evaluation items:[M3] The Support structure design evaluation (Tower) [including site conditions
assessment, design basis evaluation and integrated load analysis] items that deviate fromthe Guidelines for Design of Wind Turbine Support Structures and Foundation (JSCE 2010).

*Among the items to be examined by the Tower Section Meeting as deviations from the Guidelines for Design of Wind Turbine Support
Structures and Foundation(JSCE 2010), the items for which the corresponding design methods have been established are summarized in
Annex F of NKRE-GL-WFC01. If there is deviation in an item not listed in Annex F, or if a method that is different to the methods listed in
Annex F is to be applied, the requirements shall be determined separately by the Tower Section Meeting.

Support Structure Certification Subcommittee / Ground & Foundation Section Meeting
Evaluation items:[M4] The Support structure design evaluation (Foundation) [including site conditions
assessment, design basis evaluation and integrated load analysis] items that deviate fromthe Guidelines for Design of Wind Turbine Support Structures and Foundation (JSCE 2010).

*Among the items to be examined by the Tower Section Meeting as deviations from the Guidelines for Design of Wind Turbine Support
Structures and Foundation(JSCE 2010), the items for which the corresponding design methods have been established are summarized in
Annex G of NKRE-GL-WFC01. If there is deviation in an item not listed in Annex G, or if a method that is different to the methods listed in
Annex G is to be applied, the requirements shall be determined separately by the Tower Section Meeting.

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2. Wind Farm Certification [Onshore Wind Farm]
Review process：[M1] Site conditions assessment (wind conditions)＋ [M2] Wind turbine (RNA) design evaluation[1] Documents submitted by applicants for review are firstly
reviewed by the secretariat.

ClassNK

Applicants Comments for each documents are informed to applicants.
(In some cases, comments is informed after step [2].)Secretariat
Documents

SubmitFeedback

Answers forcomments #1

SubmitDocuments
review
Comments#1[1]

Answers forcomments #2

Submit All comments at the subcommittee are informed to applicants.
Round 1

Comments#2[2]

Documents
review

Evaluation
ReportDraft R01

Conformity
Statement+
Evaluation
Report[3] Based on the answers against comments at step [2], thedraft Evaluation Report is revised. The secretariat explain
the review results of the answers against comments to themembers of the Large Wind Turbine Certification
Subcommittee.
 Go to step [4] if no more additional comments.
 Repeat step [2] and [3] when additional comments are remaining.

Round 2
[3]

Certification
Documents
Issue[2] Based on the answers against comments at step [1], thedraft Evaluation Report is completed. The secretariat
explain their review results to the members of the Large
Wind Turbine Certification Subcommittee.

Documents
review

Evaluation
ReportDraft R00

Feedback

Large Wind
TurbineCertification
subcommittee[4] Conformity statement and Evaluation Report are issued
formally.

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2. Wind Farm Certification [Onshore Wind Farm]
Review process：[M3] Support structure design evaluation (tower)[1] Review materials submitted by applicants for review are
first reviewed by the secretariat.

ClassNK

Applicants Comments for each documents are informed to applicants.
(In some cases, comments is informed after step [2].)Secretariat
Materials

Answers forcomments #1

SubmitDocuments
review

Feedback

Comments#1

SubmitFeedback

Answers forcomments #2

SubmitSupport Structure
Certification subcommittee[1]

Documents
review[2]

Evaluation
ReportDraft R00

Round 1

Comments#2
Document
review[3]

Evaluation
ReportDraft R00

Round 2

PrepareChecklist

Certification
Documents
Issue

Tower
Section Meeting

Conformity
Statement+
Evaluation
Report+Checklist[4][2] Based on the answers against comments at step [1], thedraft Evaluation Report is completed. The secretariat
explain their review results to the members of the
Support Structure Certification Subcommittee / Tower.
 This review covers deviated from Guidelines and explanation
for the design of support structures of wind power generation
facilities (Japan Society of Civil Engineers, 2010), and theothers are reviewed by the Secretariat only.
 All comments at the subcommittee are informed to applicants.

[3] Based on the answers against comments at step [2], thedraft Evaluation Report is revised. The secretariat
explain the review results of the answers againstcomments to the members of Support Structure
Certification Subcommittee / Tower.
 Go to step [4] if no comments.
 Repeat step [2] and [3] when additional comments areremaining.

[4] Conformity statement, Evaluation Report and Checklist
are issued formally.
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2. Wind Farm Certification [Onshore Wind Farm]
Review process：[M4] Support structure design evaluation (foundation)
ClassNK

Applicants

Secretariat
Documents

SubmitAnswers forcomments #2

Ground & Foundation
Section Meeting

Round 1

Feedback

Answers forcomments #1

Support Structure
Certification Subcommittee

Comments#1[1]

Documents
review

SubmitFeedback

Comments#2

SubmitDocuments
review[2]

Answers forthe comments
aboutcalculation
documents

SubmitComments
for calculation
documents

Preparechecklist
Evaluation
ReportDraft R00

[3]
Certification
Documents
Issue

Conformity
Statement+
Evaluation
Report+Checklist[1] Based on the documents submitted by the applicants, membersof the Support Structure Certification Subcommittee / Ground &Foundation review with a focus on those items which are
deviated from Guidelines and explanation for the Design of Wind
Turbine Support Structures and Foundations [2010 Edition].
 The Support Structure Certification Subcommittee utilizes a format inwhich the operator, support structure design firm, and wind turbine
manufacturer directly explain the design to the experts in each field thatserve as committee members.

[2] The answers to comments during the step [1] are confirmed bydocument review. Documents review is similarly conducted for
additional study documents and newly added comments.

Documents
review

Feedback

In the design of foundations, if there are any deviations from the Guidelines
for Design of Wind Turbine Support Structures and Foundations [2010Edition], start from [1]. If there are no deviations, start from [3].

[4]Confirm thecontents

 Go to Step [3], when applicants answered against all comments andreceived no more new comment about their answers and additional study
documents.
 Depending on the comments and answers against comments, 2nd
subcommittee will be held instead of documents review.

[3] The secretariat conducts a review of calculation documents andexchanges comments and prepare checklist. Also, reviewed
results at the Support Structure Certification Subcommittee /Ground & Foundation Section Meeting which is mentioned in
the evaluation report is confirmed by its members.
[4] Conformity statement, Evaluation Report and Checklist areissued formally.

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2. Wind Farm Certification [Onshore Wind Farm]Wind Farm Certificate and Certification Assessment Report Issuance System [for Onshore Wind Farms][M1] Site conditions assessment (wind conditions)
Site Conditions Conformity Statement
Evaluation Report (site conditions assessment, wind conditions)[M2] Wind turbine (RNA) design evaluation
RNA Design Conformity Statement
Evaluation Report (wind turbine design evaluation)[M3] Support structure design evaluation (tower) / [M4] Support structure design evaluation (foundation)

Example of a
Conformity Statement

Support Structure Design Conformity Statement
Evaluation Report (support structure design evaluation, tower)
Evaluation Report (support structure design evaluation, foundation)
Checklist

Support Documents for Registered Conformity Assessment Body

Windfarm Certificate
Conformity checklist of technical standards for wind power generation facilities (Article 4,5 and 7)
 Wind Farm Certificate will be issued in case when an application for all of modules ([M1] to [M4]) are submitted.
(This certificate will be issued for power utility operator if applications for review is made separately for each
module.) In case where no application for any of four (4) modules, a checklist with only the items for the modules that havebeen evaluated will be issued. (No Windfarm Certificate will be issued.)

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Example of a Certification
Assessment Report173. Wind Farm Certification[Offshore Wind Power Plant]

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3. Wind Farm Certification [Offshore Wind Farm]Wind Farm Certification module 【Offshore Wind Power Plant】[OM1] Site conditions assessment

 Assess environmental conditions at the construction site (environmental conditions include general weather conditions,such as wind conditions, temperature conditions, and humidity conditions, as well as marine conditions (for offshore windfarms), altitude conditions, landforms, topography, earthquakes, lightning, and changes in operating methods related togrid interconnections)[OM2] Design basis evaluation
 Evaluates whether appropriate design criteria (design policies, etc.) considering the site conditions have been set basedon the design criteria applied at the time of type certification for the purpose of safe design and project execution[OM3] Integrated load analysis evaluation
 Evaluates whether the loads and load effects for thesite-specific environmental conditions on the integrated
wind turbine structure, including the wind turbine,
support structure, and supporting soils, have been
calculated in conformity with the design basis.

[OM4] Wind turbine (RNA) design evaluation
 Evaluates whether the type-certified wind turbine(RNA) has structural integrity against theenvironmental conditions of the construction site
*RNA: Rotor Nacelle Assembly[OM5] Support structure design evaluation

 Evaluates the structural integrity of the support
structure against the environmental conditions of*In the case of offshore wind farms, only the power utility operator can apply for review.
the construction site
(Applications for review cannot be made separately for each module)
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3. Wind Farm Certification [Offshore Wind Farm][OM1] Site conditions assessment [1] Evaluates whether the following value settings for environmental and external conditions at theconstruction site as provided by the operator are valid.
ClassificationWind
conditions

Marineconditions

Item (examples)

Setting methods, etc. (examples)[1] Wind conditions during wind turbine operations (wind turbine
position and hub height)- 10-minute average wind speed, turbulence intensity, wind
shear exponent, air density, etc.

[1] Wind conditions during wind turbine operations−Calculate values at each wind turbine positionand hub height based on observation data at
the site and simulations[2] Wind conditions during wind turbine storm standby (wind turbine
position and hub height)[50-year recurrence periods]- 10-minute average wind speed, turbulence intensity, 3-second
average wind speed, wind shear exponent, air density, etc.

[2] Wind conditions during wind turbine storm
standby−Calculate values at each wind turbine positionand hub height based on the reference windspeed under the Building Standards Act orother simulations[1] Marine conditions during normal states (during wind turbine
operations) (wind turbine position)- Significant wave height, significant wave period, tide level,
currents, etc.

[1] Marine conditions during normal periods−Calculate values at each wind turbine position
based on observation data at the site andsimulations[2] Marine conditions during storm waves (wind turbine position)[50-year recurrence interval]- Significant wave height, significant wave period, tide level,
currents, etc.

[2] Marine conditions during storm waves−In addition to existing wave observation andwave prediction data, calculate the values at
each wind turbine position with reference todesign values for nearby port and coastal
protection facilities

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3. Wind Farm Certification [Offshore Wind Farm][OM1] Site conditions assessment [2] Evaluates whether the following value settings for environmental and external conditions at theconstruction site as provided by the operator are valid.
Classification

Soil andgeology

Item (examples)[1] Submarine topography of the sea area

[1] Conduct a submarine topography survey[2] Soil composition, structure, and properties at the windturbine position (physical properties, mechanicalproperties, etc.)[2] Set the required values for the design at each windturbine position based on the results of geophysicalexploration, ground boring and sampling, field tests, andlaboratory tests

Seismic waves at the wind turbine position[1] Spectrally matched waves[2] Observed waves[3] Site waves

Set [1] and [2] as rarely occurring earthquake groundmotions and extremely rarely occurring earthquake groundmotions specified in “Interpretation of Technical Standards
for Wind Power Generation Facilities”

Earthquake

Other
environmental
conditions

Setting methods, etc. (examples)Set [3] as Port and Harbor Level 1 earthquake groundmotions specified in the Technical Standards for Port andHarbor Facilities in Japan (consideration should also begiven to Port and Harbor Level 2 earthquake groundmotions as necessary)
Tsunamis, snow cover, sea ice and ice accumulation,
marine growth, temperature and humidity, sea water
density, lightning

Set site-specific values based on relevant laws andregulations, local ordinances, and observation data at thesite, etc.

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3. Wind Farm Certification [Offshore Wind Farm][OM2] Design basis evaluation
 Assesses whether the design criteria considering the site conditions (design policies, etc.), as indicatedbelow, have been appropriately set based on the design criteria applied at the time of type certification forthe purpose of safe design and project execution.
Design Criteria Part A
Site conditions(Examples)

Design Criteria Part B
Wind turbines and towers(Examples)

Design Criteria Part C
Foundation(Examples)

Prepared by: Operator

Prepared by: Wind turbine manufacturer

Prepared by: Foundation designer

1) Wind turbine installation
location
2) Wind conditions
3) Wave conditions4) Other marine conditions
5) Soil and geologicalconditions
6) Seismic conditions7) Other environmental
conditions8) Constraints, etc.

1) Applicable criteria and standards2) Site conditions
3) Wind turbine and tower specifications4) Design policy (required performance,
reference items, materials used, etc.)
5) Design parameters related to the load
calculations, and the validity of the applied load
analysis method
6) Load case table
7) Partial safety factor
8) Overview of the load analysis model
9) Simulation details
10) Extreme and fatigue design loads andresponse analysis11) Materials and welds12) Coatings and corrosion prevention systems

1) Applicable criteria and standards2) Site conditions3) Support structure specifications (including
additional installations)4) Design policy (required performance, reference
items, materials used, etc.)
5) Design parameters related to the load
calculations, and the validity of the applied load
analysis method
6) Load case table
7) Partial safety factor
8) Overview of the load analysis model
9) Simulation details
10) Extreme and fatigue design loads and response
analysis11) Materials and welds12) Coatings and corrosion prevention systems*Includes items that overlaps
with the site conditions
assessment

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3. Wind Farm Certification [Offshore Wind Farm][OM3] Integrated load analysis evaluation
 Assesses whether the loads and load effects for the site-specific environmental conditions on the
integrated wind turbine structure, including the wind turbine, support structure, and supporting soils, havebeen calculated in conformity with the design basis.
<Main assessment items>
1. Combinations of external and design conditions
 Wind turbine in operation (wind conditions + normal
marine conditions during wind turbine operation)
 Wind turbine during storm standby (wind conditions
during wind turbine storm standby + marine
conditions during storm waves) During an earthquake (during wind turbine
operations/wind turbine emergency shutdown/wind
turbine standby)
2. Design load cases defined with reference to site
conditions, as well as to wind turbine operational andsafety systems
3. Partial safety factor
4. Calculation methods (simulation procedures, numberof simulations, and combinations of wind and wave
loads, etc.)
5. Analytical model employed as the integrated load
analysis and validation outcome for its results

Analysis Concept for a Wind Turbine During Operations(analysis is conducted in consideration of the effects of windturbine operations, wind, waves, flow, and soil at the same time)

Source: Wind Energy Engineering, A Handbook for Onshore and Offshore Wind Turbines, P. 276

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3. Wind Farm Certification [Offshore Wind Farm][OM4] Wind turbine（RNA）design evaluation
 Assesses whether the type-certified wind turbine (RNA) has structural integrity against the environmental
conditions of the construction site
<Main assessment items>
 Closely examines the following items to verify whether the wind turbine is structurally safe against thesite-specific load based on the site conditions obtained from the integrated load analysis[1] Comparison of the design load set at the time of type certification (certified design load), and thesite-specific load obtained from the integrated load analysis[2] Detailed calculation/analysis results for each component when the site-specific load exceeds thedesign load set at the time of type certification (certified design load)[3] Specifications and the validation results for any parts and systems that are NOT fully covered bytype certification and that have been newly modified or reinforced for the site Assesses connection part between tower top and RNA
 Closely examines strength evaluation results for tower top load receiving from RNA
 Strength assessment of nacelle cover Closely examines whether the nacelle cover has been satisfied with requirements as Wind Farm
Certification
 Assesses the natural frequency
 Confirm whether the resonance is correctly prevented by comparing natural frequency including
support structure and modal frequency with operating wind turbines Assesses corrosion prevention (Assesses about corrosion measures for RNA) The protection design for the power cable (that passes from the seafloor surface into the wind turbine
foundation)
 Closely examines parts to protect the power cable (In addition, closely examine the adjustment withsupport structure design evaluation)
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3. Wind Farm Certification [Offshore Wind Farm][OM5] Support structure design evaluation
 Assesses whether the support structure has structural integrity against the environmental conditions of theconstruction site
<Main assessment items>
 Closely examines the following items to verify whether the support structure (including tower / substructureand foundation / floating structure and mooring equipment / each connecting system) is structurally safe
against the site-specific load based on the site conditions obtained from the integrated load analysis[1] Closely examines validation of drawing and detailed strength calculation statement for the support
structure Strength evaluation for the limit states (ULS/FLS/SLS/ALS) associated by designer[2] Closely examines validation of drawings and calculation statements for additional installations(such as landing facilities, ladders, platforms, the power cable protection)
 Strength evaluation for the limit states (ULS/FLS/SLS/ALS) associated by designer
 Strength detail evaluation for the connection to support structures
 SLS evaluation for support structures
 Evaluation for wind turbine limitation, such as the residual rotation argument of foundation andnatural frequency
 Design for scour protection (if necessary) Evaluation for location and required volume of bagged compaction materials and edge settlement
at the location
 Evaluation for the validation of associated design and inspection / maintenance plan
 The protection design for the power cable (that passes from the seafloor surface into the wind turbine
foundation)
 Evaluation for such as location and required volume of pouched foot protection works which fix thepower cable and edge settlement at the location
 Evaluation for the conformity and validation of associated design and inspection / maintenance plan
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3. Wind Farm Certification [Offshore Wind Farm]
Overview of Certification Subcommittee / Section Meeting
Large Wind Turbine Certification Subcommittee
Evaluation items:[OM4] Wind turbine (RNA) design evaluation (common to both offshore bottom fixed typeand offshore floating type)* Includes the part of [OM1] Site condition assessment / [OM2] Design basis evaluation / [OM3] Integrated
load analysis related to [OM4].

Support Structure Certification Subcommittee / Offshore Bottom Fixed Type Section Meeting
Evaluation items:[OM5] Support structure design evaluation ( Offshore Bottom Fixed Type )* Includes the part of [OM1] Site condition assessment / [OM2] Design basis evaluation / [OM3] Integrated
load analysis related to [OM5].

Support Structure Certification Subcommittee / Offshore Floating Type Section Meeting
Evaluation items:[OM5] Support structure design evaluation ( Offshore Floating Type )* Includes the part of [OM1] Site condition assessment / [OM2] Design basis evaluation / [OM3] Integrated
load analysis related to [OM5].

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3. Wind Farm Certification [Offshore Wind Farm]
Review process: [OM4] Wind turbine (RNA) design evaluation(including RNA-related items of [OM1] Site conditions assessment , [OM2] Designbasis evaluation and [OM3] Integrated load analysis evaluation)[1] Documents submitted by applicants for review are firstly
reviewed by the secretariat.

ClassNK

Applicants Comments for each documents are informed to applicants.
(In some cases, comments is informed after step [2].)Secretariat
Documents

SubmitFeedback

Answers forcomments #1

SubmitDocuments
review
Comments#1

Answers forcomments #2

Submit[2] Based on the answers against comments at step [1], thedraft Evaluation Report is completed. The secretariat
explain their review results to the members of the Large
Wind Turbine Certification Subcommittee.

Documents
review

Evaluation
ReportDraft R00

Feedback[1]

Large Wind
TurbineCertification
subcommittee All comments at the subcommittee are informed to applicants.
Round 1

Comments#2[2]

Documents
review

Evaluation
ReportDraft R01

[3] Based on the answers against comments at step [2], thedraft Evaluation Report is revised. The secretariat explain
the review results of the answers against comments to themembers of the Large Wind Turbine Certification
Subcommittee.
 Go to step [4] if no more additional comments.
 Repeat step [2] and [3] when additional comments are remaining.

Round 2
[3]

Finishthe review
Assemble Evaluation Report[4][4] The review will be finished when no additional comments
are received from the subcommittee. In addition, theEvaluation Reports of each module are assembled .
(confirm the adjustment with support structure design
evaluation)

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3. Wind Farm Certification [Offshore Wind Farm]
Review process: [OM5] Support structure design evaluation(including Support structure-related items of [OM1] Site conditions assessment ,[OM2] Design basis evaluation and [OM3] Integrated load analysis evaluation)

Secretariat
Explanation
Documents• Answers forcomments #1• Explanation
Documents• Answers forcomments• Explanation
Documents
Calculation
Documents

Answers forcomments
againstcalculation
documents[1] Based on the documents submitted by the applicants,
members of the Support Structure Certification.

ClassNK

Applicants

SubmitFeedback

Round 1
Comments#1[1]

SubmitFeedback

Support Structure
Certification subcommittee
Offshore Bottom Fixed/ Floating Type
Section Meeting

Round 2
Comments#2

SubmitFinal Round[2]

SubmitDocuments
review

Feedback

Comments
for calculation
documents

SubmitDocuments
review[3]
Finishthe review[2] At the after second subcommittee meetings, theresponses to the comments in [1] and other new items
shall be reviewed. This process is repeated until all items
to be reviewed are completed and there are no morecomment.
 subcommittee meetings will be set according to the progress of thedesign and the wishes of the applicant for review.
 Go to Step [3], when applicants answered against all comments
and received no more new comment.

[3] The secretariat will conduct a document review of thecalculation documents, exchange comments, andcomplete the review when there are no additionalcomments.

Confirm thecontents

Preparation and finalization of
the Evaluation Report The Support Structure Certification Subcommittee utilizes a format
in which the operator, support structure design firm, and windturbine manufacturer directly explain the design to the experts ineach field that serve as committee members.
 When the design is not yet complete, the review can be
accelerated to the extent possible as a preliminary review.
 Preliminary review is not mandatory. (Preliminary review isconducted upon the request of the applicant.)[4][4] Prepare and finalize the Evaluation Report for each
module. (The consistency with the RNA side evaluation
results shall be checked.) The contents of the Evaluation Report will also be reviewed by themembers of the Supporting Structures Certification Subcommittee.

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3. Wind Farm Certification [Offshore Wind Farm]
Windfarm Certification Assessment Report Issuance System [for offshore farms]
Windfarm Certificate
Site Condition Conformity Statement
Evaluation Report (site conditions evaluation)
Design Basis Conformity Statement
Evaluation Report (design basis evaluation)
Integrated Load Analysis Conformity Statement
Evaluation Report (integrated load analysis)

Example of a Conformity
Statement

RNA Design Conformity Statement
Evaluation Report (wind turbine design evaluation)
Support Structure Design Conformity Statement
Evaluation Report (support structure design evaluation)
Support Documents for permits and approvals, such as Registered Conformity Assessment Body, etc.
Conformity checklist of interpretation of technical standards for offshore wind power generation facilities
Conformity checklist of technical standards for wind power generation facilities (Article 4,5 and 7)
RD2101_R02_20240501

Example of a Certification
Assessment Report29

4. Registered Conformity Assessment Body
designated by Electricity Business Act

RD2101_R02_20240501

30

4. Relationship between Registered Conformity Assessment Body andWind Farm Certification

New procedure at ClassNK
Operator
Manufacture
EPC

ClassNK
Certificate Body

Wind Farm
Certification

Strength calculation
document
Application• Wind Turbines• Support Structures

Certification
document

Issue
certification＋

Certification
document
Statement

Construction
Plan＋
Statement

Start
Construction• Continue former
process• Add some items
contribute toconstruction plan
review

ClassNK

Operator
Construction
Plan

Optional
service(on demand)

Application

METI

Submit Construction Plan

Response WFC is not mandatory requirement by the Electricity
Business Act.
 In the case of WFC, ClassNK can flexibly review suchas implementing each module before completing windturbine and support structure site –specific designs.
 Conformity assessment for Technical Standards forwind power generation facilities article 4,5 and 7 iscompleted at the review of WFC.

Registered Conformity Assessment Body

Registered Conformity
Assessment Body

Issue
Review asstatement Registered Conformity
Assessment Body

Wind Farm Certification (WFC)

Regional Bureau
Review forConstruction Plan・secure smoothelectrical supply chain
・reflect environmental
assessment
・conformity totechnical standards

Confirm
statement In case where WFC has been acquired in advance, it
is basically treated as the conformity assessment forTechnical Standards for wind power generation
facilities article 4,5 and 7 has been already completed.
 Further information about Registered Conformity
Assessment Body is Registered Conformity
Assessment Body on the website and refer to thefollowing materials ;<references> Outlines and explanation of Registered Conformity
Assessment Body
 Business regulations of Registered Conformity Assessment
Body [NKRE-SP-0009]* These reference documents are Japanese Version only.

RD2101_R02_20240501

315. Compliance with laws and regulations foroffshore wind turbines

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32

5. Compliance with laws and regulations for offshore wind turbines
Outlines of laws and regulations applied to the safety of wind power generation facilities Wind turbine and entire power generation facility：Electricity Business Act
 Offshore wind turbine (fixed bottom and floating type) : Port and Harbor Act
 Tower, Floating structure and Mooring systems (floating type) : Ship Safety Act
Onshore wind turbine

Offshore wind turbine(fixed bottom type)

Offshore wind turbine(fixed bottom type)

From 1st July, 2019
Offshore wind turbine(floating type)*Offshore wind turbine has been subject to the conformity assessment by Technical Standards for Portand Harbor Facilities due to small change of Port and Harbor Act from 14th February, 2020.

Electricity Business Act(entire power generation facility)

Act on Promoting the Utilization of Sea Areas forthe Development of Marine Renewable Energy
Power Generation Facilities / Port and Harbor Act(entire power generation facility)

Ship Safety Act(Tower, Floating structure,
Mooring systems)

source: : NEDO, Renewable Energy White Paper

RD2101_R02_20240501

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5. Compliance with laws and regulations for offshore wind turbines
Electricity BusinessAct (present)

Port / Harbor Act

Ship Safety Act

Onshore wind farm

Applied

N/A

N/A

Offshore wind farm
(fixed bottom type)

AppliedAppliedN/A

Offshore wind farm
(floating type)

AppliedAppliedAppliedApproval format

Construction Plan Notification[directly reviewed by
Japanese Government]＋[Registered Conformity
Assessment Body]

Conformity Verification by CDIT,
a confirmation agency
registered with the Minister ofLand, Infrastructure, Transport
and Tourism

Classification Survey byClassNK, a classification society
registered with the Minister ofLand, Infrastructure, Transport
and Tourism

Refer to review resultsof WFC by ClassNK

 ClassNK continues the jointly review about the same items of the support structure ofoffshore wind farms and their additional installations for Wind Farm Certification underconformity assessment with CDIT.
 The results of this joint review are effective even after ClassNK applied as RegisteredConformity Assessment Body. (no additional joint review is required.)
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34

5. Compliance with laws and regulations for offshore wind turbines
Electricity Business Act regulation
 When a person intends to implement a construction project to install or modify wind power generation
facilities for business use, the person must notify the competent minister of plan for the construction
project. (Article 48)
 When a person installs special electric facilities for business use must be confirmed Order for Conformity
to Technical Standards by Registered Conformity Assessment Body. (Article 48)• When a person intends to construct wind farm that have an output of 500 kilowatts or more , theperson must submit prior notification. (Appended table 2 , Electricity Business Act Enforcement
Regulations)• Special electric facilities are defined as wind turbine and support structures of wind power generation
facilities.
 A person that installs electric facilities for business use must maintain the electric facilities for business
use to ensure that they conform to the technical standards established by order of the competent
ministry. (Article 39)• In case of wind power generation facilities : Technical Standards for wind power generation facilities
established by order of the competent ministry. (Ordinance of Ministry of International Trade andIndustry No. 53 of 1997)• In case of floating offshore wind turbine : support structures of wind power generation facilities (floating
structure, mooring system, tower) must be conformed Ship Safety Law due to the following regulations;<Technical Standards for Wind Power Generation Facilities>(Structure to support the wind turbine)
Article 7. The structure supporting the wind turbine shall be structurally safe against its own weight, loading capacity, snow and windpressure, and against earthquakes and other vibrations and impacts.

<Interpretation of Technical Standards for Wind Power Generation Facilities>(Ministerial Ordinance Article 7) Article 16(2) The structure supporting the wind turbine (limited to those structures subject to the provisions of Article 2, Paragraph 1 of the
Ship Safety Act) shall conform to the provisions of the same paragraph.
•

Further detailed information about Registered Conformity Assessment Body is written in p.11 or refer to Registered Conformity Assessment Body on the website.

RD2101_R02_20240501

355. Compliance with laws and regulations for offshore wind turbines
Port and Harbor Act compliance The NK Support Structure Certification Subcommittee and CDIT Offshore Wind
Power Subcommittee hold joint sessions
Note: In case of a dispute over translation, Japanese text shall prevail
Unified review system overview〇 Standardizing the review documents for offshore wind farm support structures and submitting the same
documents to both organizations reduces the burden on power utility operators.
〇 Unifying the process through a joint review shortens the review duration.
Past

Present
Power utility operator

Power utility operator

Site conditions documentation
Design policy documentation
Integrated load analysis documentation(wind turbine)

Integrated load analysis documentation(support structure)

Support structure design documentation

Documents associated with support
structures (tower, foundation, andadditional installations)- Location map

Nippon Kaiji Kyokai
Product certification body accredited by the Japan
Accreditation Board■ Project Certification Committee- Support Structure Certification
Subcommittee- Large Wind Turbine Certification
SubcommitteeWind turbine design
documentation- Structural elements and required
performances- Site conditions documentation ◎ Standardized review documents- Design policy documentation- Integrated load analysis documentation (support structure)- Support structure design documentation- Documents associated with support structures (additional
installations)- Basis for functions and settings- Inspection methodology

Third-party certification bodyWind turbine design documentation

Third-party certification body

Integrated load analysis
documentation (windturbine)Registered confirmation agency

Nippon Kaiji Kyokai

Coastal Development Institute ofTechnology

Product certification body accredited by the Japan
Accreditation Board

Agency registered by the Minister of Land, Infrastructure,
Transport and Tourism

Registered confirmation agency
Coastal Development Institute ofTechnology
Agency registered by the Minister of Land, Infrastructure,
Transport and Tourism■ Compliance Review Committee- Offshore Wind Power Subcommittee(Review based on the Port andHarbor Act)

■ Project Certification
Committee- Large Wind Turbine
Certification
Subcommittee

RD2101_R02_20240501◎ Joint review■ Project Certification
Committee- Support Structure
Certification
Subcommittee■ Compliance Review
Committee- Offshore Wind Power
Subcommittee(Review based on the Portand Harbor Act)36

5. Compliance with laws and regulations for offshore wind turbines
Ship and Safety Act regulation
Ship Safety Law

Article 2 Ships shall be outfitted pursuant to the provisions of ordinances of the Ministry ofLand, Infrastructure, Transport and Tourism (ordinances of the Ministry of Land, Infrastructure,
Transport and Tourism and ordinances of the Ministry of Agriculture, Forestry and Fisheries
only with regard to fishing vessels) with regard to the following matters:(i) Hull(ii) to (xiii) (omitted)[Reference] Public Notice Establishing Vessels with Special Structures or Equipment
under Article 1, Paragraph 4 of the Ordinance for Enforcement of the Ship Safety Act
Ships with special structures or equipment as established in the Public Notice under Article
1, Paragraph 4 of the Ordinance for Enforcement of the Ship Safety Act are as follows:(i) to (iii) (omitted)(iv) Floating offshore wind power facilities

Technical Standards for Floating
Offshore Wind Power Facilities

Kokkaian No. 194 dated April 23, 2012
Partially Amended Kokkaian No. 286 dated March 3, 2020

Technical standards establishing the requirements
for structures and facilities based on the Ship
Safety Act

Ministry of Land, Infrastructure, Transport and Tourism website: Promoting the use of floating offshore wind power facilities- Establishing technical standards for ensuring safety https://www.mlit.go.jp/maritime/maritime_fr6_000006.html

RD2101_R02_20240501

375. Compliance with laws and regulations for offshore wind turbines
Ship and Safety Act regulation
Ship Safety Law

Article 8
Under Article 25-47 applied mutatis mutandis pursuant to Article 23-69 and Article 25-72, shipout of passenger ship (the capacity is over 12 people ; hereinafter the same as) that have beensurveyed by ClassNK ,“Classification Society authorized by the Minister of Land, Infrastructure,
Transport and Tourism” (hereinafter the “Classification Society”), and that have registered asclassification are regarded as having undergone inspection about what is listed in the Article 2
Cause 1 each number, such as load line / radio telegraph, and to have passed such by themaritime authorities excluding inspection established by order of the Minister of Land,
Infrastructure, Transport, and Tourism during having effective certification.

 ClassNK is a “Classification Society authorized by the Minister of Land, Infrastructure,
Transport and Tourism” as prescribed in Article 8 of the Ship Safety Law.
 Floating offshore wind power facilities that have been surveyed by ClassNK, a“Classification Society authorized by the Minister of Land, Infrastructure, Transport andTourism,” and that have registered as classification are regarded as having undergone
inspection and to have passed such by the maritime authorities.
*maritime authorities : the headquarter of Transport Bureau or Maritime Bureau dealing with ship register
RD2101_R02_20240501

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5. Compliance with laws and regulations for offshore wind turbines
Classification Survey (as a Classification Society authorized by the MLIT)

Design Review

 Review designs for floating structures, towers, and mooringlines based on the Guidelines for Floating Offshore Wind
Power Facilities.
 Review site condition (wind conditions,marine conditions, etc.) settings, wind turbine
and floating structure coupled analyses, andsupport structure design evaluations at thesame time as wind farm certification.
 Confirm that the steel plate and fittings to be
used are approved by NK.

Coupled Analysis Model Example

 Conduct a witness survey for the following items:
Inspection of
construction
and on-site
workCompletion
Survey•••Witness survey during floating structure andtower manufacturing
Shipment survey for chains, anchors, etc.
used in mooring lines
Attendance at manufacturing plant tests(water pressure tests, etc.) and installation
work tests (holding capacity tests, etc.)

 After installation at the site is complete, ClassNK will attend
verification tests of wind turbine control systems and floating
structure ballast systems, etc.
RD2101_R02_20240501

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6. Other related services

RD2101_R02_20240501

406. Other related services
Wind turbine support structure: Manufacturing evaluation
 This service covers wind farms that are subject to the Electricity Business Act and that have an output of 500kW
or more, where one or more wind turbines are installed. The scope of this service includes manufacturing
evaluation for the wind turbine support structures (tower and foundation) as required for acceptance of theConstruction Plan Notification for such wind farms.
 This service assumes that the wind turbine support structures to be evaluated have been appropriately designed
based on the local site conditions of the planned construction location, and have either obtained a Wind Farm
Certificate from ClassNK regarding the details or have satisfactorily undergone design evaluation by a third party.

Design evaluation(1) Kick-off-Meeting (KOM) [manufacturing plant](2) Document review(3) Inspection and Test Plan approval(4) Witness testing and witness inspection [manufacturing plant](5) Manufacturing records review

Certificate issuance

Certificate Example

Evaluation Module and Flowchart

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416. Other related services
Wind turbine support structure: Manufacturing evaluation [for onshore wind farms]
Note

4
Requirement items for support structuresof onshore wind farms 【NKRE-GL-WFC01, March 2023】

6.1.1 GeneralStart-1. The structural integrity of the support structure for the site conditions is confirmed by using integrated load analysis to indicatethat there is sufficient strength against the site-specific loads. In addition, for the tower of the support structures, the prerequisites
are that the design has obtained type certification, and that the tower has been manufactured at a manufacturing site specified in
the certification documents pertaining to the type certification.

<Tower design> When the tower is included in type certification:• Evaluate through wind farm certification (verify that the design approved during type certification isappropriate for the site conditions).
 When the tower is NOT included in type certification:• Evaluate through WF certification (verify that the tower design for the site is appropriate for the site
conditions).
Rejectconstruction
plan<Tower manufacturing evaluation>
 When the tower is included in type certification:• No specific requirements. However, this is limited to the case where the tower is manufactured by amanufacturer authorized during type certification.
 When the tower is NOT included in type certification:• Add the tower to type certification or conduct a “Wind turbine support structure manufacturing
evaluation” .
→After WF Certification is issued, manufacturing evaluation should be conducted until the authorized
date in the certificate document.

Note 1
Note 2

Note 4Note 5RD2101_R02_20240501

426. Other related services
Wind turbine support structure: Manufacturing evaluation [for onshore wind farms]
Manufacturing evaluation by type certification
Evaluates whether units are manufactured according to the design documents verified
during design evaluation in terms of the following items:
1.Quality system evaluation
2.Manufacturing inspection (representative unit check) This evaluation covers the manufacturing plant, and the actual manufacturing of the towers to be delivered is
NOT inspected.

Wind turbine support structure: Manufacturing evaluation
Evaluates whether units are manufactured according to the design documents verified
during design evaluation in terms of the following items:
1.Quality system evaluation
2.Manufacturing inspection
 Evaluated items are the same as those under manufacturing evaluation by type certification.
 Evaluates individual manufacturing processes based on the results of the design evaluation for the site.
 Conducts witness inspections during the manufacturing processes for the towers to be delivered to the site.

As part of the wind turbine support structure manufacturing evaluation, a witness inspection is carriedout during the manufacture of the towers to be actually constructed at the site, thereby acting asverification by a third party and creating a record trail that includes inspection reports.
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436. Other related services
Wind turbine support structure: Manufacturing evaluation [for offshore wind farms]
 In the case of offshore fixed-bottom wind farms, the wind turbine tower is also designed for each site andthe foundation is generally made of steel. Under the Electricity Business Act, operators are responsiblefor quality control related to power plant construction.
 If an application is submitted for an offshore fixed-bottom wind farm, ClassNK conducts a manufacturing
evaluation of the wind turbine tower and foundation (monopile/jacket).
 The “Wind turbine support structure manufacturing evaluation” for offshore fixed-bottom wind farms
conducted by ClassNK is limited to a third-party assessment based on a private-sector contract. As athird party, ClassNK basically conducts its evaluation from the viewpoint of whether units are
manufactured according to the order specifications.
<Application reasons assumed with offshore fixed-bottom wind farms>[1] When a developer / operator requires explanations to the lender from the viewpoint of project financing, or requires
the EPC or contractor manufacturing the tower/foundation to undergo a third-party evaluation from the perspectiveof avoiding risks related to licensing.
[2] When the lender requires the developer / operator to undergo a third-party evaluation related to tower/foundation
manufacturing from the perspective of project financing.
[3] When the EPC intends to acquire a third-party evaluation related to tower/foundation manufacturing from theperspectives of providing explanations to developer / operator and of avoiding various risks.
[4] When the tower/foundation manufacturer intends to acquire a third-party evaluation from the perspective ofproviding explanations to the ordering party and of avoiding various risks.

 In the case of offshore floating wind farms, an inspection equivalent to “Wind turbine support structure
manufacturing evaluation” as part of classification inspection is carried out on the support structures(Tower, Floating structures, Mooring systems).
RD2101_R02_20240501

44

For the most recent information:

ClassNK

Click “ClassNK Renewable
Energy” under Quick Links on
the website.

<Inquiries regarding wind power>
Renewables and Environment Department
NIPPON KAIJI KYOKAI (ClassNK)
E-mail: re@classnk.or.jp
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