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Structural Enhancements: The Way to lower LCOE
The document summarizes structural enhancements that can be made to wind turbine blades to improve their performance and reduce costs. It describes D-String, X-Stiffener, and D-Stiffener technologies developed by Bladena to address issues like blade panel breathing, twisting, and buckling. Testing and customer cases demonstrate how the retrofit technologies increase blade lifetime by reducing stresses and vibrations. The financial impact is a return on investment of less than two years through reduced maintenance costs and increased turbine uptime.
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Structural Enhancements: The Way to lower LCOE
- 1. 2016 Wind TurbineBlade Workshop Structural Enhancements – The way to lower LCOE CTO and founder: Find Mølholt Jensen, PhD
- 2. 2 Outline 2 1. Introduction andmotivation 2. Breathing – D-String® 3. Twisting - X-Stiffener™ 4. Buckling capacity - D-Stiffener 5. Financial impact of retrofit enhancements
- 3. 3 We are experts in root cause analysis of blades and have specialized knowledge on structural blade failure and knows how to avoid failures on blades. Bladena was foundedin 2011 as a Spin-out from Risø DTU. The company is founded on 7 groundbreaking patents all relatedto structural failures Experts in blades – Structural related topics
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- 7. 7 Motivation – crackswithin the structure Debonding Debonding of the core due to manufacturing flaw and bending of the panels. core laminate Resin debonding Transversal cut in glass layers that lead to transversal crack in blades
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- 10. 10 Root cause: Panelbreathing Deformations Blade panel deformations induced by edgewise gravity induced loads during any operation of any wind turbine makes the panels breath. Peeling There is a direct connection between the breathing and the peeling stresses in the adhesive bond lines: the higher the magnitude of breathing, the higher the peeling stresses.
- 11. 11 More aerodynamic profilesresult in more breathing FEM-model showing that it is the aerodynamic shape which results in out-of-plane deformation
- 12. 12 Transverse cracks onthe trailing edge panels Bending of the TE-panels causes transverse cracks Advanced FEM simulations have confirmed the measurements. 3D longitudinal waves are reduced when the D-Strings® are used. Inside view of the trailing edge FEM illustrating the panel waves when the D-Strings® are not used. With red colour – high magnitude FEM illustrating the reduction of panel waves when D-Strings® are used. With green colour – low magnitude Transverse cracks found during inspection
- 13. 13 Effect of D-String® Breathingdeformations shown before and after D-string installation Peeling stress analysis in trailing edge Withouth D-Strings® installed With D-Strings® installed
- 14. 14 Field installations First kit installed on a Vestas V80 turbine in Tjæreborg Enge in January 2013, followed by severalinstallations on GE, LM, Vestas, etc... blades Almost 4 years of operation Almost 4 years the D-String® has been installed on blades in operation. Recent inspections confirmed that there are no cracks in the TE max chord area and there are no signs of blade damages related to the installation of the D-String® Platform or rope used to access the blades
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- 16. 16 Root-Cause: Twisting Background on loads on blades in operation Loads on wind turbine blades during operation can be split in two main components: • Edgewise loads -dominated by gravity. • Flapwise loads - dominated by aerodynamic forces.
- 17. 17 Root-Cause: Twisting (alsocalled cross-sectional shear distortion) Increased twisting As the new flat-back profiles are more and more used, the twisting becomes higher due to the lack of support in the trailing edge. Hot spots Deformed shape Un-deformed shape Cross-sectional shear deformation generates peeling stresses in the adhesive bond lines. Peeling stresses The effect of the two phenomena is the apearance of peeling stresses in the adhesive bondlines along the blades in certain hot spots.
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- 19. 19 Large scale testing:X-Stiffener enhancement Testing Loads applied in the test creates the same twisting of the blade as seen in the full-scale test and field operation. Different loading configurations The test is carried out at Technical University of Denmark (DTU)
- 20. 20 Large blades havemore twisting Size effects… Deformations increase by 250- 300% when blade is scaled up with a factor of 2. Peeling stresses in the adhesive bondlines follow this increase.
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- 22. 22 Root-Cause: Buckling ofthe TE-panels Premises for failure The bending of the blade due to aerodynamic forces and reduced buckling capacity of the blade in mid span and mid span towards the tip creates premises for failure.
- 23. 23 Root cause: vibrations Design In case of vibrations, such as an earthquake, the blade is loaded in a manner that was not designed for. Aeroelastic and FEM simulations are used in the Root-Case Analysis. Earthquake forcesFEM Transient Response provides accurate results Aero-elastic simulations provides a general blade response Capacity D-Stiffener does not remove the vibrations, however it increases the blade capacity to withstand them.
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- 26. 26 Financial and OperationalImpact, WTO Results • Less maintenance time => reduced cost of energy => higher profit • E.g. D-String® :The cost of one incident repair equals the cost of a D-String® kit for 3 blades (including the installation) • The risk of cracks increases with the age of the blades due to the fatigue loading, bathtub curve • The technologies secures operation of the blade in the anticipated life time of the turbine without added maintenance cost • ROI less than 2 years Owners risk Warranty Years of operation Failurerate
- 27. 27 Design and ManufacturingImpact, OEM Results • Reduced material consumption, thinner panels • Larger manufacturing tolerances • No need for trailing edge over lamination, less work in confined space • Less risk for failurs during full scale test and in operation • Possible option for increased aerodynamic designs, increased AEP
- 28. Contact Ryan Hagelskjær Lauridsen/ ryl@bladena.com Find Mølholt Jensen / fmj@bladena.com Dave Zanier / dz@bladena.com Universitetsparken 7 DK-4000 Roskilde Denmark www.bladena.com © 2016 Bladena. All rights reserved. Reproduction or distribution of this report in any form without prior written permission is strictly forbidden. Violation of the above restrictions will be subjects to legal action under the Danish Arbitration Act. The information herein is taken from sources considered reliable, but its accuracy and completeness are not warranted, nor are the opinions, analyses and forecasts on which they are based. Bladena cannot be held liable for any errors in this report, neither can Bladena be liable for any financial loss or damage caused by the use of the information presented in this report.