Passive Load Control for Large Wind Turbines

Ashwill, Thomas D.

doi:10.2514/6.2010-2577

Cited by 9 publications

(7 citation statements)

References 17 publications

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“…Zayas et al , Berry, Ashwill and Resor describe the design and testing of a 9 m stall‐controlled blade with 20° off‐pitch axis unidirectional carbon fibers in the skin from the 25% span location outward. Results of these efforts showed a reduction in fatigue damage with respect to a baseline model without BTC coupling but also designed for a different maximum tip deflection.…”

Section: Introductionsupporting

confidence: 63%

Optimization‐based study of bend–twist coupled rotor blades for passive and integrated passive/active load alleviation

et al. 2012

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This work is concerned with the design of wind turbine blades with bend-twist-to-feather coupling that self-react to wind fluctuations by reducing the angle of attack, thereby inducing a load mitigation effect. This behavior is obtained here by exploiting the orthotropic properties of composite materials by rotating the fibers away from the pitch axis.The first part of this study investigates the possible configurations for achieving bend-twist coupling. At first, fully coupled blades are designed by rotating the fibers for the whole blade span, and a best compromise solution is found to limit weight increase by rotations both in the spar caps and in the skin. Next, partially coupled blades are designed where fibers are rotated only on the outboard part of the blade, this way achieving good load mitigation capabilities together with weight savings. All blades are designed with a multilevel constrained optimization procedure, on the basis of combined cross-sectional, multibody aero-servo-elastic and three-dimensional finite element models.Finally, the best configuration of the passive coupled blade is combined with an active individual pitch controller. The synergistic use of passive and active load mitigation technologies is shown to allow for significant load reductions while limiting the increase in actuator duty cycle, thanks to the opposite effects on this performance metric of the passive and active control solutions. ABBREVIATIONSADC actuator duty cycle AEP annual energy production BTC bend-twist coupling CAD computer-aided design DEL damage equivalent load DLC design load case EOG extreme operative gust FEM finite element method HAWT horizontal axis wind turbine IPC individual pitch control LQR linear quadratic regulator PID proportional integral derivative SQP sequential quadratic programming

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Section: Introductionsupporting

confidence: 63%

Optimization‐based study of bend–twist coupled rotor blades for passive and integrated passive/active load alleviation

et al. 2012

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“…However, passive morphing is limited to the tailoring of the blade stiffness, as demonstrated by Lobitz et al ., and/or to the shape of the blade, as detailed in Ashwill et al . and Zuteck. In this review, only concepts for active morphing are listed with emphasis given to structural shape changes, noting that a discussion of actuator technology is not the current focus of this article.…”

Section: Introductionmentioning

confidence: 99%

Review of morphing concepts and materials for wind turbine blade applications

2012

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With increasing size of wind turbines, new approaches to load control are required to reduce the stresses in blades. Experimental and numerical studies in the fields of helicopter and wind turbine blade research have shown the potential of shape morphing in reducing blade loads. However, because of the large size of modern wind turbine blades, more similarities can be found with wing morphing research than with helicopter blades. Morphing technologies are currently receiving significant interest from the wind turbine community because of their potential high aerodynamic efficiency, simple construction and low weight. However, for actuator forces to be kept low, a compliant structure is needed. This is in apparent contradiction to the requirement for the blade to be load carrying and stiff. This highlights the key challenge for morphing structures in replacing the stiff and strong design of current blades with more compliant structures. Although not comprehensive, this review gives a concise list of the most relevant concepts for morphing structures and materials that achieve compliant shape adaptation for wind turbine blades.Copyright © 2012 John Wiley & Sons, Ltd.

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“…One should also mention here the concept of bend-twist coupling of wind turbine blades [132,133]. The incorporation of bend-twist coupling into blades realizes the so-called passive load control, i.e., the modification of blade design which should ensure lower loads.…”

Section: Leading Edge Erosionmentioning

confidence: 99%

“…The incorporation of bend-twist coupling into blades realizes the so-called passive load control, i.e., the modification of blade design which should ensure lower loads. This design can be realized as geometric-based coupling, which uses a sweep along the blade to create a moment that induces a twist, or as a material-based coupling, which aligns the primary load-carrying spanwise fibers in an off-axis manner [132]. Ashwill [132] demonstrated a blade, with incorporated off-axis carbon in the blade skin, to ensure bendtwist coupling, and observed enhanced strength of the blade.…”

Section: Leading Edge Erosionmentioning

confidence: 99%

Root Causes and Mechanisms of Failure of Wind Turbine Blades: Overview

Mishnaevsky

2022

Materials

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A review of the root causes and mechanisms of damage and failure to wind turbine blades is presented in this paper. In particular, the mechanisms of leading edge erosion, adhesive joint degradation, trailing edge failure, buckling and blade collapse phenomena are considered. Methods of investigation of different damage mechanisms are reviewed, including full scale testing, post-mortem analysis, incident reports, computational simulations and sub-component testing. The most endangered regions of blades include the protruding parts (tip, leading edges), tapered and transitional areas and bond lines/adhesives. Computational models of different blade damage mechanisms are discussed. The role of manufacturing defects (voids, debonding, waviness, other deviations) for the failure mechanisms of wind turbine blades is highlighted. It is concluded that the strength and durability of wind turbine blades is controlled to a large degree by the strength of adhesive joints, interfaces and thin layers (interlaminar layers, adhesives) in the blade. Possible solutions to mitigate various blade damage mechanisms are discussed.

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Passive Load Control for Large Wind Turbines

Cited by 9 publications

References 17 publications

Optimization‐based study of bend–twist coupled rotor blades for passive and integrated passive/active load alleviation

Optimization‐based study of bend–twist coupled rotor blades for passive and integrated passive/active load alleviation

Review of morphing concepts and materials for wind turbine blade applications

Root Causes and Mechanisms of Failure of Wind Turbine Blades: Overview

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