09 Nov 2022
09 Nov 2022
Status: this preprint is currently under review for the journal WES.

Assessing the rotor blade deformation and tower-blade tip clearance of a 3.4 MW wind turbine with terrestrial laser scanning

Paula Helming1, Alex Intemann1, Klaus-Peter Webersinke2, Axel von Freyberg1, Michael Sorg1, and Andreas Fischer1,3 Paula Helming et al.
  • 1University of Bremen, Bremen Institute for Metrology, Automation and Quality Science, 28359 Bremen, Germany
  • 2LASE Industrielle Lasertechnik GmbH, 46485 Wesel, Germany
  • 3BEST Bremen Research Centre for Energy Systems, University of Bremen, 28334 Bremen, Germany

Abstract. Wind turbines have grown in size in recent years, making an efficient structural health monitoring of all of their structures ever more important. Wind turbine blades deform elastically under the loads applied to them by wind and inertial forces acting on the rotating rotor blades. In order to properly analyze these deformations, an earthbound system is desirable that can measure the blade deformation, as well as the tower-blade tip clearance from a large measurement working distance of over 150 m and a single location. To achieve this, a terrestrial laser scanner (TLS) in line-scanning mode with vertical alignment is used to measure the distance to passing blades and the tower for different wind loads over time. In detail, the blade deformations for two different wind load categories are evaluated and compared. Additionally, the tower-blade tip clearance is calculated and analyzed with regard to the rotor speed. Using a Monte-Carlo simulation, the measurement uncertainty is determined to be in the mm-range for both the blade deformation analysis and the tower-blade tip clearance. The in-process applicable measurement methods are applied and validated on a 3.4 MW wind turbine with a hub height of 128 m. As a result, the deformation of the blade increases with higher wind speed in wind direction, while the tower-blade tip clearance decreases with higher wind speed. Both relations are measured not only qualitatively but also quantitatively. Furthermore, no difference between the three rotor blades is observed, i.e. each of the three blades is shown to be separately measurable. The tower-blade tip clearance is compared to a reference video measurement, which recorded the tower-blade tip clearance from the side, with validated the novel measurement approach. Therefore, the proposed setup and methods are proven to be effective tools for the in-process structural health monitoring of wind turbine blades.

Paula Helming et al.

Status: open (until 21 Dec 2022)

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Paula Helming et al.

Paula Helming et al.


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Short summary
Using renewable energy such as wind energy is vital. To optimize the energy yield from wind turbines, they have increased in size leading to large blade deformations. This paper measures these deformations for different wind loads as well as the distance between the blade and the tower from a distance of 170 m away from the wind turbine. The paper proves that the blade deformation increases in wind direction with increasing wind speed, while the distance between the blade and the tower decreases.