Presentations

Abstract

As wind turbine blades have grown larger to capture more wind energy, their bending stiffness has decreased, making them more susceptible to deformations, failure, and damage during their lifetime. Consequently, it is important to monitor the structural health of wind turbine blades to improve operational safety and prevent failures. In this study, we propose an innovative method to use automotive lidars to inspect the deflections and twisting of full-scale wind turbine blades. These parameters are typically measured with traditional sensors that are embedded inside the blades, including optical or electrical strain gauges and optical fibers. However, some accurate sensors can be expensive, time-consuming to install, and impossible to repair if malfunctioning. An alternative technique is photogrammetry, which uses multiple cameras to observe the markers attached to the turbines. Nevertheless, the application and precision of this method are quite limited. Thanks to the massive development in automotive lidars, they are now capable of mapping the surroundings of a driving car in real-time, the three-dimensional (3D) positions and velocity, with camera-level resolution. Our experiment investigates the Livox Avia 3D lidar, a fairly compact and lightweight instrument (498 g) with a detection range of up to 450 m and a range precision of 2 cm. Therefore, we install three lidars on the wind turbine spinner to observe deformations throughout the three blades under different environmental conditions. For data validation, measured results will be compared carefully with reference sensor data and model simulations from HAWC2. The lidars also record reflectivity, which might be used to inspect insects accumulated on the blade surface, blade erosion due to precipitation, and leading-edge icing. Insects and rain erosion lead to a rough surface and reflect more laser light. Combined with the 3D positions, the location of insects and rain erosion could be identified. The application of such automotive lidars in wind energy would accelerate the development of wind energy technology, especially for the improvement of non-destructive testing techniques. Before we mounted the lidars on the wind turbine spinner, we performed a proof-of-concept trial with one 3D Avia lidar at the Technical University of Denmark (DTU) Large Scale Facility. The Avia lidar provides repetitive and non-repetitive scanning modes. Especially the repetitive line scanning mode offers a 70.4 degree x 4.5 degrees field-of-view (FOV) with a repeat cycle of 0.1 s, making it suitable for measuring low-frequency blade deflections. The tested blade is the DTU01 blade, about 12.6 m long. A total of 1350 kilograms of loads were loaded at three different places on the blade, and an exciter was located at 5.2 m from the blade root. Lidar measurements over two hours show that flatwise deflection can be accurately observed, while edgewise deflection and twisting seem to be biased.  Based on the promising results of this trial, we developed the methodology to install three Avia lidars on the DTU V52 wind turbine spinner. A field experiment campaign is scheduled to begin late in February 2025.