Wind Turbine Reliability：

IET-CAS’s Perspective

National Energy Wind Turbine Blade R&D Center

Institute of Engineering Thermophysics (IET)

Chinese Academy of Sciences (CAS)

Dr. Xiao Chen

chenxiao@iet.cn

Presentation at 2014 Sandia Blade Workshop, A2E Reliability Meeting

Albuquerque, NM

28 August, 2014

Introduction of IET Wind Energy Group

IET Wind: National lab for R&D of MW WT blades

Director: Prof. J.Z. Xu

Profs.: 7 Asso. Profs.: 8 Ass. Profs.: 14

Other staffs and engineers: 13

Phd and Msc Students: 30+

Aerodynamics

Aero-elasticity

Structures

Materials

Designing

Manufacturing

Testing

Simulation

Aero-acoustics

Components NDT

Consulting

Xiao Chen @IET since 2013

D.Eng.@ Nagoya Univ. Japan

Postdoc.@ NWEC, UHouston

Research fields: Nonlinear buckling/post-buckling

behavior and multiple failure mode

interaction of large WT blades;

Composite material and structural

testing and modeling;

Repair of offshore FRP composite and

steel structures.

Industrialization

Fundamental

research

By 2013:

In total: 91 GW

Offshore: 0.39 GW

China’s target:

By 2020:

In total: 200 GW

Offshore: 30 GW

Cumulative

Facilities and Equipments

- 2 wind tunnels: 0.5x0.5x5 m, 2.5x0.8x6 m

3x4x20 m (under construction)

- PIV experimental system

- Pressure Scanner

- Constant temperature anemometer system

- Computational cluster: 38 cpus, 200 cores

- Commercial and in-house CFD codes

Aerodynamics & Aero-elastics & Aero-acoustics (3As)

Structures & Materials

Manufacturing

Field Testing and Validation

- MTS bi-axial static/fatigue testing platform (up to100m) (under construction)

- Bending-Torsion component testing rig

- Material and components fatigue testing machine

- Lightning test equipment

- FORCE AMS-64 blade defect scanner

- 100kW WT blade testing platform

- 3As/structure/power output testing

- New design concept validation

- Blades up to 70 m

Collaborative Opportunities

International Science and Technology Cooperation Program of China (ISTCP) Ministry of Science and Technology (MOST) $0.5~1M per program International Energy Research Cooperation Program National Energy Administration (NEA) $~0.5M per program International Scientific Research Cooperation Program National Natural Science Foundation of China (NSF) $~0.5M per program

NSF5%

NEA59%

CAS13%

Int.5%

MOST16%

MOF2%

Total: $26.4M

Int’l

IET Wind and DTU shared $1.28 M research funds provided by

Chinese MOST through 1 research program from 2011 to 2013.

Fund share: IET Wind $0.71M, DTU $0.57M

Take Away Messages:

The IET wind group has been awarded $26.4M

funding in total during the National 12th 5-year Plan.

Only 5% is for international research collaboration.

We are looking forward to increasing collaborative

scales and numbers of partners in the National 13th

5-year Plan (2015~2019)

Writing proposal starts at the early months of

2015. We now call for international partners!

Comments to the Existing A2e Proposal

- Ensuring WT plant reliability become more challenging as turbine sizes

get larger and their working environments become harsher.

- In-depth understanding of reliability/integrity of WT components by

clarifying, quantifying and ultimately reducing uncertainties of external and

internal factors is essential to overcome these challenges.

- Needs for industry standards are urgent, recommendations and/or

modifications to the current design practices and standards should be

formulated as soon as possible and should be included as one of desired

outcomes.

- Experience and lessons learned from other countries could be helpful to

better achieve objectives set by the project. International collaboration

may be necessary.

Important Questions for the Future

With increase of blade sizes and more

installation of WTs in the harsh environment:

Thin-walled Thick-walled shell

2D in-plane stresses 3D stresses

Known failure modes Unexpected failure modes

Single mode Competing/interactive mechanisms

Reliability decrease due to environmental effects

Cost-effective O&M considering life cycles

Reliability & Cost

Material

Structure Load

-New materials

-Environmental effects

-Material defects, etc.

-Failure mechanisms

-Manufacturing flaws

-Repair methods, etc.

-Uncertainty of extreme weather

-Bending-torsion combined loading

-Realistic load assessment, etc.

Research Proposal #1 for A2E Project

Reliability of Large Offshore Wind Turbine Blades

The goals of this research are to increase structural reliability of offshore WT

blades while reducing their cost to a competitive level.

Emphasis need to be placed on:

• Failure mode change and multiple failure mode interaction of thick-walled

blade structures under complicated/combined bending-torsion loading;

• Critical damage detection and performance evaluation after extreme wind

events such as typhoon and hurricane;

• Cost-effective in-field repair methods and evaluation of upgraded

performance.

To achieve this, failure testing on component and full-scale structure level are

necessary but usually very expensive. Computational models capable of

capturing multiple failure modes and their interaction need to be established.

Research Proposal #2 for A2E Project

Environmental Effects on Blade Reliability and Integrity

The goals of this research are to characterize and quantify the effects of

environmental parameters on blade reliability and structural integrity, and to

establish the corresponding standards/guidelines for wind energy industry.

The critical environmental parameters include not only icing, lightning, erosion,

but also corrosion, moisture, and heat. In many cases, multiple parameters

adversely affect blade performance simultaneously.

To achieve this, massive high-quality experimental tests on material,

components, and structural levels are necessary in order to obtain reliable

database. Meanwhile, NDI and post-mortem observation are also important to

gain insights into environmental effects .

NDI, Performance Evaluation of Full-Scale Large Composite Blades

The Goal is to standardize methods for evaluating & improving integrity and

reliability of large blades through NDI and/or systematic testing.

Emphasis is placed on:

a)Evaluation of fatigue and ultimate performance of large blades with initial flaws;

b)Effective repair methods for different in-service damage.

c)Modifications and/or revisions of the existing standards .

Desired outcomes:

a)Methods to evaluate fatigue/ultimate performance of large WT blades through

full-scale bi-axial test;

b)Methods for life extension and performance improvement of wind turbines.

c)Standards to assess blade integrity and reliability considering manufacturing

defects, design misses and environmental effects;

Research Proposal #3 for A2E Project

Research Proposal #4 for A2E Project

Life Cycle Analysis (LCA) of WT Blades and Rotors

The goals of LCA are to establish methodologies to evaluate possible

reliability improvement and cost reduction by deploying inspection, maintenance,

and repair strategies over the blades and rotors’ lifetime.

Using LCA (cost, performance, management), the overall cost associated with

a certain strategy can be analyzed and the optimal management of wind turbine

plants can be expected.

To achieve this, outcomes from Research Proposal #2 and #3 are needed as

inputs considering performance degradation due to environmental effects and

performance enhancement after repair. The introduction of probability analysis is

necessary to take into account statistic nature of both externalities and

internalities of wind turbine plants.

Appendix-1: Current R&D Work @ IET Wind

Aerodynamics & Aero-elastics & Aero-acoustics (3As)

CAS-W1 Airfoil Family with t/c up to 60%

High lift/drag ratio；

Stable stall

characteristics；

Insensitive to the

roughness at LE

Flow control by vortex generators

Improved actuator model

2

2

1i i ij i

j i i

V V VpV f

t x x x

Appendix-1: Current R&D Work @ IET Wind

Aerodynamics & Aero-elastics & Aero-acoustics (3As)

Aero-acoustic measurement on multi-MW Turbines

Terrain effect on wind farm and micro-siting

Bionics based techniques

Higher lift @ large AoA

Appendix-1: Current R&D Work @ IET Wind

Innovative blade design

Structures and Materials

Failure mechanisms of large WT blades

52.3m

Appendix-1: Current R&D Work @ IET Wind

Multiple-axial strength and fatigue properties of blade materials and components

Modular blade design Bending-torsion loading of components

Structures and Materials

Appendix-1: Current R&D Work @ IET Wind

Field testing and post-marketing study

NDT, defect inspection/evaluation, blade repair 100kW WT testing platform

Aerodynamics

Aero-elasticity

Structures

Aero-acoustics

LE cracks

LE

erosion

Appendix-2: Suggested Areas for Int’l Collaboration #1

Large Offshore Wind Turbine Blades and Supporting Structures

The Goal is to develop analysis & design methods for offshore WTs with high

efficiency and competitive cost at Chinese southeast coast.

Emphasis is placed on:

a)Aerodynamic, aero-elastic modeling and testing of offshore WTs considering

Chinese coastal and metocean conditions;

b)Interaction in wind-rotor-supports-wave system and among turbines;

c)Failure mechanisms and prevention of blade and supporting structures under

typhoon and hurricane loading.

Desired outcomes:

a)Integrated methodologies to improve efficiency of offshore WTs with substantial

reduction of the CoE;

b)Understanding of offshore WT failures and methods for failure prevention;

c)Demonstration projects at a moderate water depth.

Appendix-2: Suggested Areas for Int’l Collaboration #2

Numerical & Experimental Study on Slender Blades with Flatback

and Large Thick Airfoils

The Goal is to develop and validate computational model for aero-elstic

analysis of slender blades with flatback and large thick airfoils with t/c up to 60%.

Emphasis is placed on:

a)Aero-elastic modeling of the blades considering 3D full coupling of elasticity;

b)Parameter optimization for significant weight reduction.

c)Field testing and model validation using IET testing platform;

Desired outcomes:

a)Efficient computational models for the coupled aero-elastic analysis;

b)Optimization methods for slender blades with flatback and large thick airfoils;

c)Demonstration and testing.

Appendix-2: Suggested Areas for Int’l Collaboration #3

NDI, Performance Evaluation of Full-Scale Large Composite Blades

The Goal is to standardize methods for evaluating & improving integrity and

reliability of large blades through NDI and/or systematic testing.

Emphasis is placed on:

a)Evaluation of fatigue and ultimate performance of large blades with initial flaws;

b)Effective repair methods for different in-service damage.

c)Modifications and/or revisions of the existing standards .

Desired outcomes:

a)Methods to evaluate fatigue/ultimate performance of large WT blades through

full-scale bi-axial test;

b)Methods for life extension and performance improvement of wind turbines.

c)Standards to assess blade integrity and reliability considering manufacturing

defects, design misses and environmental effects;

Appendix-2: Suggested Areas for Int’l Collaboration #4

Other Forms of Energy Conversion using Wind Power

The Goal is to develop cost-effective energy conversion systems other than

the wind-electricity ones to meet the demands of energy in various forms

especially for local regions.

Emphasis is placed on:

a)Innovative forms of energy conversion powered by wind;

b)New systems for energy storage;

c)Combined wind-marine power systems.

Desired outcomes:

a)Innovative and efficient energy conversion systems to meet particular demands

of energy at utility scale;

b)New concepts and modeling of combined wind-marine power systems.

We are always open to other opportunities for

R&D collaboration in wind energy.

Thank you!

IET Wind