ライブラリー Annual Energy Outlook 2000

Wind energy is the fastest growing alternate source of energy in the world since its purely economic potential is complemented by its great positive environmental impact. The wind turbine, whether it may be a Horizontal-Axis Wind Turbine (HAWT) or a Vertical-Axis Wind Turbine (VAWT), offers a practical way to convert the wind energy into electrical or mechanical energy. Although this book focuses on the aerodynamic design and performance of VAWTs based on the Darrieus concept, it also discusses the comparison between HAWTs and VAWTs, future trends in design and the inherent socio-economic and environmental friendly aspects of wind energy as an alternate source of energy.

Wind turbine design with emphasis on Darrieus concept Ion Paraschivoiu

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Formulas For Natural Frequency And Mode Shape

Review of performance optimization techniques applied to wind turbines

Low Speed Aerodynamics

Sandia National Laboratories (SNL) Wind Energy Technologies Department, as part of its ongoing R&D efforts, creates and evaluates innovative large blade concepts for horizontal axis wind turbines to promote designs that are more efficient aerodynamically, structurally, and economically. Recent work has focused on the development of a 100-meter blade for a 13.2 MW horizontal axis wind turbine, a blade which is significantly longer than the largest commercial blades of today (approximately 60 meters long). This report documents the development of the Sandia 100-m All-glass Baseline Wind Turbine Blade, which employs conventional architecture and fiberglass-only composite material reinforcement. Follow-on studies for this baseline will include a variety of innovations targeting reductions in weight and improvements in structural and aerodynamic performance. The report begins with a review of several large utility-grade machines (3-6 MW). Available 5 MW turbine models (with 61.5 meter blades) are identified and described. Geometric scaling of these models is performed to produce aeroelastic turbine models with 100-meter blades, which are analyzed to demonstrate the important effects of scale for large blades. Based on these preliminary analyses, we proceed to develop the Sandia 100-m all-glass baseline blade model. A detailed composite layup and geometry are provided. Analyses of the baseline model for design loads from international standards are presented to demonstrate acceptance of the design with respect to strength, fatigue, deflection, and buckling. In future work, it is envisioned that this model will provide a starting point for consideration of blade innovations with potential performance and cost improvements and will be targeted toward the offshore environment.

https://energy.sandia.gov/wp-content/gallery/uploads/113779.pdf

The Sandia 100-meter All-glass Baseline Wind Turbine Blade: SNL100-00

https://onlinelibrary.wiley.com/doi/pdf/10.1002/we.2661

The effect of resin uptake on the flexural properties of compression molded sandwich composites

Experimental and numerical study of high-order complex curvature mode shape and mode coupling on a three-bladed wind turbine assembly

When modal testing a structure for model validation, free boundary conditions are frequently approximated in the lab to compare with free boundary-condition analyses. Free conditions are used because they are normally easy to simulate analytically and easier to approximate experimentally than boundary conditions with fixed conditions. However, the free conditions can only be approximated in the lab, because the structure must be supported in some manner. This article investigates and quantifies the effects of the support conditions on both the measured modal frequencies and damping factors. The investigation has determined that the measured modal damping is significantly more sensitive to the support system (stiffness and damping) than the measured modal frequency. Included in the article are simple formulas that can be used to predict the effect on measured modal parameters given the support stiffness and damping. Modal testing is frequently used to validate the accuracy of structural dynamic models. Modal tests are performed on a structure to measure the modal frequencies, damping factors, and mode shapes. However during the modal test, a structure must be supported in some manner by the surrounding environment. Very frequently, free boundary conditions are the desired support conditions for comparison with computational results. Free conditions can only be approximated in the lab using soft supports, but the stiffness and damping of these added supports will affect the modal parameters of the combined structural system. A required part of pre-test planning is to design the support system to minimally affect the modal parameters. Obviously, one can include a model of the support system as part of the overall system model, and sometimes that is required due to compromises involved in the support system design. But one would like to be able to calculate the effects of the support system on the modal parameters to determine whether the effects are negligible or need to be accounted for. One of the primary objectives of this article is to derive fairly simple formulas and rules of thumb by which one can calculate the effect of the support conditions on the measured modal frequencies and damping factors so that appropriate support design can be performed before the test. The formulas and the effects of poor support conditions are also illustrated with results from two different modal tests. Historically, there has been concern for support stiffness and its effect on measured modal frequencies. Bisplinghoff, Ashley and Halfman 1 discuss the effects of support stiffness and mass on the modal frequencies, based on results of Rayleigh. 2 Wolf 3 discusses the effects of support stiffness with regard to modal testing of automotive bodies. He reports that the rule of thumb to simulate free boundary conditions is to design the support system so that the rigid-body modes, that is, the modes that would be at zero frequency except for the support conditions, are no more than one-tenth the frequency of the lowest elastic mode. But it is seldom possible to achieve this separation for vehicle tests. He states that test engineers frequently use a 1:3 to 1:5 separation ratio between the rigid-body modes and the lowest elastic mode. Wolf shows that such stiff supports can lead to significant errors in the measured modal frequencies. One of the current authors discussed support conditions in an earlier work, 4 and this article expands on that work with additional theoretical results and illustrates the theory with experiments and modeling. In his second edition of Modal Testing, 5 Ewins briefly discusses the issue of location of suspen sions for free boundary conditions in the test planning chapter. More recently, Brillhart and Hunt presented an exposition of many of the practical difficulties involved in designing good fixtures for a modal test, 6 and Avitabile briefly discussed this issue in a “Back to Basics” article. 7 In this article our primary emphasis here was to develop some quantitative measures of the effect of the support conditions on the modal frequencies and the modal damping ratios. Most finiteelement models could include the support stiffnesses and masses in the model, thus taking into account those effects. However, structural dynamic models often do not initially include damping, but use the measured modal damping ratios from a test to create a model, including damping. There is typically no validation of the damping model; it is taken directly from the test with the support conditions included. Consequently, one must be concerned with how the support conditions affect the measured damping. The remainder of this article is divided into four primary sections. In the first section, simple formulas are derived for a two degree-offreedom system. These formulas are simplistic, but can be used to derive rules of thumb and also easily illustrate the severity of the problem. The next section develops approximate formulas for the multi-degree-of-freedom problem that can be used for general structures. The last two sections further illustrate both the problem and the theory with some example modal tests, first from a very lightly damped uniform beam and second with a wind turbine blade that required a modal test for model validation and damping determination.

Support Conditions for Experimental Modal Analysis

Offshore wind turbines are an attractive source for clean and renewable energy for reasons including their proximity to population centers and higher capacity factors. One obstacle to the more widespread installation of offshore wind turbines in the USA, however, is that recent projections of offshore operations and maintenance costs vary from two to five times the land-based costs. One way in which these costs could be reduced is through use of a structural health and prognostics management (SHPM) system as part of a condition-based maintenance paradigm with smart loads management. This paper contributes to the development of such strategies by developing an initial roadmap for SHPM, with application to the blades. One of the key elements of the approach is a multiscale simulation approach developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. A case study of a trailing edge disbond is analysed to demonstrate the multiscale sensitivity of damage approach and to show the potential life extension and increased energy capture that can be achieved using simple changes in the overall turbine control and loads management strategy. The integration of health monitoring information, economic considerations such as repair costs versus state of health, and a smart loads management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit. Copyright © 2013 John Wiley & Sons, Ltd.

D. Todd Griffith

Papers

The Sandia 100-meter All-glass Baseline Wind Turbine Blade: SNL100-00

The effect of resin uptake on the flexural properties of compression molded sandwich composites

Experimental and numerical study of high-order complex curvature mode shape and mode coupling on a three-bladed wind turbine assembly

Support Conditions for Experimental Modal Analysis

Structural health and prognostics management for the enhancement of offshore wind turbine operations and maintenance strategies