Griffin current status of blade standards

1. DNV GL © 2014 SAFER, SMARTER, GREENERDNV GL © 2014
Wind turbine Blade Standards:
August 31, 2016
ENERGY
19 September 2016
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Current Status and ongoing developments
Dayton A. Griffin

2. DNV GL © 2014
Agenda
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1. Legacy blade standards
2. Introduction to IEC 61400-5
3. Primary Technical Challenges
§ Intro to “Limit States” design methodology
§ Safety factor approach for current existing standards
§ Toward a “physics-based” approach to safety factors
4. Summary

3. DNV GL © 2014
Current / legacy blade standards
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4. DNV GL © 2014
61400-22 (2010)
Wind Turbines – Part 22: Conformity Testing and Certification
61400-1 Ed. 3 (2003)
Wind Turbines – Part 1: Design Requirements
61400-23 Ed.1 (2014)
Wind Turbines - Part 23: Full Scale Structural Testing of Rotor Blades
61400-5 (draft, 2013)
Wind Turbines – Part 5: Design and Manufacturing of Rotor Blades
Legacy IEC Standards for Blade Design, Manufacture and Test
Technical specification
(TS) now revised /
released as standard.
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5. DNV GL © 2014
Legacy Blade Standards
§DNV-DS-J102 Standard (2010)
–Supplements standards in current
IEC system
§GL Guideline for the Certification
of Wind Turbines (2010)
–Used as stand-alone standard, or
with relevant IEC documents
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Current DNV GL Blade Standard
§Published December 2015
§Harmonization of legacy DNV
and GL requirements
§Draws on philosophy / approach
from IEC working group
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Introduction to IEC 61400-5
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IEC Standards for Blade Design, Manufacture and Test
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What were you guys thinking????
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What were you guys thinking????
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Purpose / Scope
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§ Ensure engineering integrity of wind turbine blades
§ Appropriate level of operational safety for design lifetime
§ Requirements for:
– Aerodynamic and structural design
– material selection, evaluation and testing
– Manufacture, including quality management
– Transportation, installation, operation and
maintenance (including repair)
§ Potential uses:
– Technical reference
– Certification

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PT-5 worldwide participation
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13. DNV GL © 2014
IEC61400-5 Document Summary - contents
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IEC 61400-5 Drafting Process
§ 61400-5 approved as new work item by Chinese National
Committee
§ Kick-off October 2009 in Geneva
§ Meetings have alternated between Europe and Asia
§ 16 regular + several “sub-group” meetings to date
§ Due to time taken in drafting, IEC required the standard to be
submitted as new work item proposal (NP)
§ PT5 submitted NP along with Committee Draft (CD) of the
standard June 29, 2016
§ Votes on NP and comments on CD due from National Committees
September 30, 2016
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Primary Technical Challenges
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Current state-of-the-art blade design and analysis
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“Permissible” Methods “State-of-the-Art” Methods
2-D “section” analyses 3-D Finite Element Analyses
Loading in 4 primary directions
(can be decoupled and applied independently)
Loading in at least 12 directions
(i.e. stress/strain response in 12 directions due to
simultaneous application of MFlap, Medge…)
Fatigue using design-equivalent load (DEL) - Markov Matrices
- “Unit stress response function” + time-series
loading
Classical buckling analysis - Linear Eigenbuckling
- Non-linear buckling
Limit States Design method - Probabilistic methods
- Damage tolerant design

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Known shortcomings for current standards / methods
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In principle, partial
safety factors
related to
uncertainties
f
IEC Design Value of Load IEC Design Value of Blade Strength, including partial
factors for materials and consequences of failure
Characteristic Value of Coupon
Strengths (e.g, 95% exceedance)
Coupon Strength
Distribution
Characteristic
Value of Load
Expected Load
Distribution
LOADS (STRESS) STRENGTHS
n* m
Mr

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Known shortcomings for current standards / methods
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In principle, partial
safety factors
related to
uncertainties
In practice, little
relationship to
actual uncertainties

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Known shortcomings for current standards / methods
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In principle, should use
“pyramid” design approach

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Known shortcomings for current standards / methods
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In principle, should use
“pyramid” design approach
In practice, current
methods only use top
and bottom of pyramid

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Partial Safety Factors in Draft 61400-5
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m = m0 m1 m2 m3 m4 m5
Where:
m0 “Base” material factor (to be included in all analyses)
m1 Environmental degradation (non reversible effects)
m2 Temperature effects (reversible effects)
m3 Manufacturing effects
m4 Computation and validation methods
m5 = Resolution of load components

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Example Partial Material Safety Factor (PMSF) Selection –
Laminate Ultimate Strength
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PMSF,

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Summary
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24. DNV GL © 2014
Summary
§ Drafting process has been 6 ½ years
§ CD submitted along with NP June 2016
§ Votes and comments due Sept. 2016
§ Working group has committed to attempt a “physics-based”
approach to partial safety factors
– Intent is to have standard provide a path to reward
“responsible innovation”
– It will be difficult to implement – but we need to try!
– We expect this draft to be very controversial
§ Opportunities for U.S. stakeholder input:
– By email at any point in process
– “Stakeholder Committee” meeting Sept. 1, 8:00–10:00 AM
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+1 425 422 8794
dayton.griffin@dnvgl.com
Dayton A. Griffin