recent activities to develop guidelines for offshore...
TRANSCRIPT
![Page 1: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/1.jpg)
Recent Activities to Develop Guidelines for
Offshore Turbines Applicable to US Waters
DOE-BOEM Workshop on Offshore Wind Energy Standards and Guidelines
Qing YuManaging Principal Engineer, Offshore Renewables
Arlington, VA17 June 2014
![Page 2: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/2.jpg)
2
ABS Offshore Renewables R&D Group
2010
Offshore Renewables Group formed
Studies performed since 2007; AWEA RP; BSEE TAP 669 & 670 grants
2011
ABS BOWTI Guide
Two DOE grants in collaboration with TAMU and U. Michigan
2012
ABS FOWTI Guide
BSEE TAP 705 & 706 grants; IEA Wind Task 30 (OC4) Phase I
2013
ABS Guidance Notes on FOWT Global Performance Analysis
IEC 61400-3-2;IEA Wind Task 30 (OC4) Phase II; MHK energy converters
![Page 3: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/3.jpg)
3
Technical Basis of the ABS Guides for Offshore Wind Turbines
ABS BOWTI Guide
& FOWTI Guide
IEC 61400
In-house research
Existing ABS Rules & Guides
Offshore industry best practice (API, in particular)
Project experience
and industry feedback
![Page 4: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/4.jpg)
4
Planned Updates for the ABS Guides
� Bottom-Founded Offshore Wind Turbine (BOWTI) Guide
� Further clarifications for the Design Load Case (DLC) definitions
� Appendix on the hurricane wind modeling
� Appendix on the fatigue analysis method
� Floating Offshore Wind Turbine (FOWTI) Guide
� Safety factor for “damaged condition with one broken line”
� Further clarifications for the DLC definitions
� Additional guidance on global performance analysis
� Updates to the FOWT on-boarding machinery and systems
� Appendix on the fatigue analysis method
![Page 5: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/5.jpg)
5
Hurricane Wind Models
� API and ISO adopted the NPD wind model, which is derived using the wind measurements (Frøya Database) on the Norwegian coast – there are no hurricanes in Norway
� The maximum measured wind speed at the reference height is about 25 m/s
� The NPD wind model was extrapolated to model hurricanes with much higher wind speeds (50-year return 10-minute mean wind speed at 10 m elevation is about 40~50 m/s in the GoM)
![Page 6: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/6.jpg)
6
Hurricane Wind Models
� Hurricane wind measurements at the GoM and other locations now support a critical revisit to the current practice
� Main References:
� Analysis of the Structure of hurricane Winds near Shore and
Offshore, DeepStar Report, 2012 (Vickery, Giammanco and
Schroeder)
� Guidelines for Converting between Various Wind Averaging Periods
in Tropical Cyclone Conditions, World Meteorological Organization
(WMO) Report, 2010 (Harper, Kepert and Ginger)
� Reduced Drag Coefficient for High Wind Speeds in Tropical
Cyclones, Nature, Vol. 422, 2003 (Powell, Vickery and Reinhold)
![Page 7: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/7.jpg)
7
Hurricane Wind Models
� Current edition of the ABS Guides address the hurricane design requirements through the requirements in the design load cases and design criteria in addition to those from IEC 61400-3. The hurricane wind model is still based on API Bulletin 2INT-MET.
� An appendix to the ABS BOWTI Guide is currently under development based on available information to address some of the key features of hurricane wind on the open ocean
� Surface drag coefficient leveling off at high wind speeds
� Steeper wind speed profile than those based on the NPD wind model
� Smaller turbulence intensity insensitive to the mean wind speed
� Higher gust factors with less sensitivity to the mean wind speed
![Page 8: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/8.jpg)
8
Hurricane Wind Models
� Hurricane wind spectrum and coherence function need further development – the DeepStar report seems to be pointing development in the right direction
� Some of the issues that need to be addressed include
� Wind spectrum for three directions (isotropic versus anisotropic)
� Measurements to support the better understanding of the coherence
![Page 9: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/9.jpg)
9
Format of Strength Design Criteria for Hurricane Prone Areas
Normalized Hazard Curve
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
10 100 1000 10000
Return Period (Years)
(Ws90 /
Ws90_50yr)
2
Southern North Sea
GoM Central West
50 500 – Robustness Check
![Page 10: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/10.jpg)
10
Design Criteria vs. Robustness Check
� Robustness check can be used to verify whether a design has achieved an intended safety level
� Robustness check should not play the role of design criteria
Design Environmental Conditions + Design
Safety Factors �Local/Global Strength
Robustness Check Conditions + Reduced
Safety Factors �Global Strength
![Page 11: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/11.jpg)
11
Challenges in the Robustness Check
� Robustness check in API RP 2A (WSD) Ed 22 is for the global strength (i.e. base shear and overturning moment) with a prescribed RSR. Local member or joint overstress is allowed.
� Robustness check in the proposed IEC 61400-3, Annex J deals with local structural strengths of, for instance, tubular members – should the global strength be checked as well or instead?
� The reduced return period (75 years?) of hurricane conditions for the abnormal DLC with turbine yaw control malfunction may not be justifiable – can the designer takes credit of the turbine yaw control or, perhaps, its malfunction is a sure thing during hurricanes?
![Page 12: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/12.jpg)
12
Example of Hurricane Wind Direction Change
200o
300o
100o
0o
100 sWind
Direction
Hurricane Katrina Landfall Wind (Schroeder, et al., 2009)
![Page 13: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/13.jpg)
13
Hurricane Design Criteria in the ABS BOWTI Guide
� Focuses on the integrity of the support structures and foundation
� Assumes that wind loads are governing or at least a significant part of the total loads
� The design criteria are based on 100-year return hurricane conditions for the support structures with:
� Normal yaw misalignment
� Abnormal yaw misalignment (-180o-180o, unless the effectiveness of
yaw control can demonstrate its capacity for a smaller range)
� Alternative methods such as the following are acceptable but need further justifications
� Using 50-year return hurricanes with higher safety factors suitable for
the site; or
� Robustness check with a longer return period (normally 500 years)
![Page 14: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/14.jpg)
14
Hurricane Design Criteria in the ABS FOWTI Guide
� Focuses on the integrity of the floating support structures and stationkeeping systems
� The design criteria are based on 50-year return storm conditions
� Robustness check is required for the integrity of the stationkeeping systems when the FOWT is subjected to 500-year return storm conditions
� Robustness check for structures is optional – the global strength of the hull structure is mostly governed by wave loads in a similar way to traditional floating platforms
![Page 15: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/15.jpg)
15
Fatigue Analysis for Bottom-Founded OWTs
� Spectral fatigue analysis method recommended in API RP 2A is found not applicable to bottom-founded OWTs
� Time-domain dynamic analysis is preferred as it can provide a more rational representation of nonlinear responses and actions of the turbine’s control and protection systems
� Scatter diagram lumping may be used to reduce the number of seastates for which time-domain dynamic analyses are needed
� Extensive studies on the applicability of various scatter diagram lumping methods using both monopile and jacket supported OWTs were conducted
� An appendix will be included in the 2014 revision of the ABS BOWTI Guide to provide the guidance
![Page 16: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/16.jpg)
16
Fatigue Analysis for FOWT Support Structures
� Spectral-based fatigue analysisfor fatigue damage of floating hull structures due to:
� Low frequency motions
� Wave frequency responses
� High frequency responses
� Combination of broadband fatigue load spectra
� Time-domain fatigue analysis for structural components subject to strong nonlinear loading
� Tower
� Heave plates
� An appendix is under development for the 2014 revision of the ABS FOWTI Guide
![Page 17: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/17.jpg)
17
ABS Guidance Notes on FOWT Global Performance Analysis
� Partially based on the outcome of BSEE TAP 705
� Extensive literature review
� Evaluation of critical design parameters
� Case study using representative conceptual designs and the US OCS environmental conditions (GoM Central, OR and ME)
ABS Case Study Model – SEMI FOWTABS Case Study Model – TLP FOWT
ABS Case Study Model – SPAR FOWT
![Page 18: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/18.jpg)
18
ABS Guidance Notes on FOWT Global Performance Analysis
� Objectives
� Bridge gaps in global performance analysis methods for traditional
floating offshore platforms and FOWTs
� Recommend practical analysis procedures and methods
� Main Contents
� Global response parameters
� Environmental load calculation
� Global motion analysis
� Air gap analysis
� Mooring strength analysis
� Mooring fatigue analysis
![Page 19: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/19.jpg)
19
Summary
� Hurricane wind model needs a critical revisit
� Second thought on the robustness check for offshore wind turbines in hurricane-prone areas
� Global strength versus local strength
� The occurrence of losing power grid connection may not be relevant
to the robustness check
� A review of ABS hurricane design criteria for OWTs
� Fatigue analysis
� Relatively well established for bottom-founded OWTs, but only
having limited experience with FOWTs
� ABS is developing guidelines for fatigue analysis of support
structures – designer’s feedback is important for further improvement
� New ABS guidance on global performance analysis for FOWTs
![Page 20: Recent Activities to Develop Guidelines for Offshore ...usmodcore.com/content/file/Yu-Qing_ABS-OffshoreTurbineGuidelines.pdf · Recent Activities to Develop Guidelines for Offshore](https://reader031.vdocuments.us/reader031/viewer/2022020315/5aedf4947f8b9aa17b8ba667/html5/thumbnails/20.jpg)
www.eagle.org