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Abstract:There is a trend to increase the length of wind turbine blades in an effort to reduce the cost of energy (COE). This causes manufacturing and transportation issues, which have given rise to the concept of segmented wind turbine blades. In this concept, multiple segments can be transported separately. While this idea is not new, it has recently gained renewed interest. In this review paper, the concept of wind turbine blade segmentation and related literature is discussed. The motivation for dividing blades into segments is explained, and the cost of energy is considered to obtain requirements for such blades. An overview of possible implementations is provided, considering the split location and orientation, as well as the type of joint to be used. Many implementations draw from experience with similar joints such as the joint at the blade root, hub and root extenders and joints used in rotor tips and glider wings. Adhesive bonds are expected to provide structural and economic efficiency, but in-field assembly poses a big issue. Prototype segmented blades using T-bolt joints, studs and spar bridge concepts have proven successful, as well as aerodynamically-shaped root and hub extenders.

Abstract:A novel approach for creating highly detailed finite element models of wind turbine blades is presented. The approach is implemented as a software tool which handles all the different steps of the model creation process. The novel approach considers the blade to consist of a collection of parametric predefined blocks. This allows wind turbine blade models consisting of shell elements, solid elements or combinations to be created. By including the tools to accurately partition the outer mold layer, create the required offset surfaces and calculate accurate element-wise material orientations, a high level of detail and fidelity can be achieved.Keywords: wind turbine blade, finite element modelling, solid mesh IntroductionWind turbine blade designs have been increasing in size during the last decades. They are complex structures, both in terms of shape and layup of composite materials. The rotor is at the very beginning of the energy conversion chain, turning airflow into mechanical energy. Consequently, the blades are at the beginning of a cost cascade system. For example, reducing the blade mass allows for cost savings in many other turbine components. Meanwhile, the aerodynamic performance directly contributes to the overall cost of energy (COE) of the turbine. As a result, there is great value in optimizing blades. Nevertheless, current wind turbine blades are often designed with relatively high safety factors. However, relatively large

A commercial 43 m wind turbine blade was tested under static loads. During these tests, loads, displacements, and local strains were recorded. In this work, the blade was modeled using the finite element method. Both a segment of the spar structure and the full-scale blade were modeled. In both cases, conventional outer mold layer shell and layered solid models were created by means of an in-house developed software tool. First, the boundary conditions and settings for modeling the tests were explored. Next, the behavior of a spar segment under different modeling methods was investigated. Finally, the full-scale blade tests were conducted. The resulting displacements and longitudinal and transverse strains were investigated. It was found that for the considered load case, the differences between the shell and solid models are limited. Thus, it is concluded that the shell representation is sufficiently accurate.