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Research articles 21 Feb 2018

Research articles | 21 Feb 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Wind Energy Science (WES).

Extreme fluctuations of wind speed for a coastal/offshore climate: statistics and impact on wind turbine loads

Ásta Hannesdóttir, Mark Kelly, and Nikolay Dimitrov Ásta Hannesdóttir et al.
  • DTU Wind Energy Dept., Technical University of Denmark, Roskilde, Denmark

Abstract. For measurements taken over a decade at the coastal Danish site Høvsøre, we find the variance associated with wind speed events from the offshore direction to exceed the prescribed extreme turbulence model of the IEC 61400-1 Ed.3 standard for wind turbine safety. The variance of wind velocity fluctuations manifested during these events is not due to extreme turbulence; rather, it is primarily caused by ramp-like increases in wind speed associated with larger-scale meteorological processes. The measurements are both linearly detrended and high-pass filtered in order to investigate how these events – and such commonly-used filtering – affect the estimated 50-year return period of turbulence levels. The impact of the observed events on a wind turbine are investigated using aeroelastic simulations, that are driven by constrained turbulence simulation fields. Relevant wind turbine component loads from the simulations are compared with the extreme turbulence load case prescribed by the IEC standard. The loads from the event simulations are generally lower for all considered load components, with one exception: ramp-like events where the wind speed rises to exceed rated wind speed can lead to extreme tower base fore-aft loads that exceed DLC 1.3 of the IEC standard.

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Ásta Hannesdóttir et al.
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Ásta Hannesdóttir et al.
Ásta Hannesdóttir et al.
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Short summary
We investigate large wind speed fluctuations from a 10 year period at the Danish coastal site Høvsøre. The most extreme fluctuations are not turbulent, but due to larger-scale weather phenomena. We find how these fluctuations impact wind turbines using simulations. The results are then compared to an extreme turbulence model described in the wind turbine safety standards and it is found that the loads on the different turbine components are not the same as what the standard describes.
We investigate large wind speed fluctuations from a 10 year period at the Danish coastal site...