Abstract
Sectional wind turbine blades, by dividing an intact blade into multiple segments, have the advantage of being easy to handle and transport. To determine a suitable blade division location, this study was performed to clarify some crucial aspects and challenges for sectional blades. This paper proposes a method to estimate the effects of the location of the blade division on structural, manufacturing, and assembling performance of sectional blades. The advantage of this method is the ease of the assessment process, since it can be performed at an early stage of blade design, where only the aerodynamic profile, mass density and stiffness distribution, and service fatigue loads of original blades are essential. A case study with the proposed method was carried out based on a 38-meter commercial blade. Results show that the best position for the division of sectional blades is located 20% from the blade root by balancing the three aspects listed above. The key approaches to reduce additional increases in stiffness and weight of sectional blades are related to improving the fatigue strength and the choice of low-modulus materials for connecting bolts. The effects of the division location on assembling accessibility and natural frequencies of scaled sectional blades are consistent with the basic sectional blade. Unfavorable effects occur when up-scaling the diameter of the bolts; and, harsh external loads on the connections have negative effects on the application of sectional blades with larger wind turbines. In this regard, lightweight design is indispensable to reduce bolt stress.
Highlights
Amongst all the clean and renewable energies, wind energy has been a promising candidate to replace conventional fossil energy, due to availability and relative low cost
Based on previous studies and our experience with designing and manufacturing sectional blades [19], our work presents a brief method for determining the division location for sectional blades by evaluating the effects of the following three aspects on connection performance of sectional blades: natural frequencies, connection strength, and assembling accessibility
Literature review reveals that a mechanical connection with a bolted joint dominates the load transfer for sectional review reveals that a mechanical connection with a bolted joint dominates the load transfer for blades, and bolt failure is the key challenge of sectional blade applications [10,13,15,17,20,23,24,25]
Summary
Amongst all the clean and renewable energies, wind energy has been a promising candidate to replace conventional fossil energy, due to availability and relative low cost. Vionis et al [11,15] first studied sectional blades based on a MW-class blade whose length was 29.65 m, without considering the 4.5 m tip section used for braking; the rest of the inner section was designed to be nearly divided so that the final division location was 12.4 m from the blade root. Based on previous studies and our experience with designing and manufacturing sectional blades [19], our work presents a brief method for determining the division location for sectional blades by evaluating the effects of the following three aspects on connection performance of sectional blades: natural frequencies, connection strength, and assembling accessibility. Larger WTs are evaluated using an analytic upscaling principle and by examining the constraints on transportation vehicles
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