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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced rotor technologies' taking place on Tuesday, 11 March 2014 at 11:15-12:45. The meet-the-authors will take place in the poster area.

Tomasz Sieradzan DNV GL- Energy, Denmark
Co-authors:
Tomasz Sieradzan (2) F P Bente Vestergaard (2) Amilcar Quispitupta (2)
(1) DNV, Hellerup, Denmark (2) DNV GL, Copenhagen, Denmark

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Abstract

On certification aspects of wind turbine blade load carrying structure

Introduction

With continuously increasing size of the turbines, the requirements for the blade structure are getting more and more demanding. The energy from wind is to be captured from over 80 meters of blade length and transferred to the rotor hub. As a consequence, functionality of the blades must not only consider aerodynamic efficiency but ensure stable load transfer from the outer parts to high bending moment carrying root section. This publication will provide better understanding of load carrying structure challenges, accounting for utilization of different materials, their interactions and various manufacturing aspects.

Approach

In order to address the challenges of the blade structural design, this paper outlines the latest development within the load carrying structure design and focuses on the complementary character of Design and Manufacturing evaluation. Commonly used certification systems may not always be up-to-date with the latest techniques and processes. The assessment by the certification bodies is no longer bound by strict set of rules; therefore profound understanding of material composition, interaction and manufacturing robustness is required. Study of different designs and consideration of their manufacturability will be conducted in terms of certification aspects and relevant standards.

Main body of abstract

The requirements put ahead of blade designers often necessitate unique, project specific solutions. Variation in structural functionality along the blade’s length needs to be properly addressed and account not only for design requirements, but also for manufacturing capabilities and process robustness. Over the last decade the complexity in the design of the blade internal load carrying structure has evolved from being dominated by thick glass fibre laminate to a hybrid composition of glass and carbon fibre or even sandwich core materials. Significant improvement is noticeable in the quality of the finished parts. This is, to great extent caused by controlled manufacturing processes. Elements of the load carrying structure are often pre-fabricated allowing much more rigorous requirements to be imposed and ensured. Manufacturers put more focus on semi-modular layup, with more and more sub-components assembled off the blade mould and put together in the final assembly process. Availability of high quality materials and innovative solutions for blade construction is no longer in-house advantage of the blade manufacturer alone. Raw material suppliers have been expanding their portfolio by making innovative solutions available for the entire industry.

Along with the material and manufacturing development, the certification procedures and approaches need to be revised and address the relevant issues, which they may have not appeared before. Understanding of various material interactions requires not only standard specified factors, but, involves close cooperation with the customers.


Conclusion

Evaluation of the design needs to be supported by detailed manufacturing considerations on quality and feasibility, involving, if necessary, manufacturing inspections. Higher structure utilization is often accompanied by reduction in partial safety factors applicable with manufacturing techniques. Design Evaluation, Manufacturing Evaluation and Type Testing certification modules are becoming inseparable, as only their interactions give the true picture of the structure performance and robustness.


Learning objectives
Participants attending the presentation can expect the expand their knowledge on following topics:

1. Latest development in blade structural design
2. What are the challenges in hybrid material manufacturing and certification
3. How to make the certification process of blade efficient and where put attention while addressing new concepts