Offshore wind turbine foundation monitoring, extrapolating fatigue measurements from fleet leaders to the entire wind farm

Wout Weijtens,Christof Devriendt,Tim Verbelen,Alexandros Iliopoulos,Nymfa Noppe

doi:10.1088/1742-6596/753/9/092018

Wout Weijtens, Christof Devriendt + Show 3 more

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https://doi.org/10.1088/1742-6596/753/9/092018

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Abstract

The present contribution is part of the ongoing development of a fatigue assessment strategy driven purely on in-situ measurements on operational wind turbines. The primary objective is to estimate the remaining life time of existing wind farms and individual turbines by instrumenting part of the farm with a load monitoring setup. This load monitoring setup allows to measure interface loads and local stress histories. This contribution will briefly discuss how these load measurements can be translated into fatigue assessment of the instrumented turbine. However, due to different conditions at the wind farm, such as turbulence, differences in water depth and foundation design this turbine will not be fully representable for all turbines in the farm.In this paper we will use the load measurements on two offshore wind turbines in the Northwind offshore wind farm to discuss fatigue progression in an operational wind farm. By calculating the damage equivalent loads on the two turbines the fatigue progression is quantified for every 10 minute interval and can be analyzed against turbulence and site conditions. In future work these results will be used to predict the fatigue life progression in the entire farm.

Highlights

Offshore wind is developing in Europe at a rapid pace, with ever growing turbine sizes and greater distances to shore the demand for structural monitoring of the substructures has become more relevant than ever
The proposed approach is the fleet leader concept, in which a limited number of representative turbines are instrumented with accelerometers and strain gauges
The results from these turbines are extrapolated to the entire farm using an empirical formula

Summary

Introduction

Offshore wind is developing in Europe at a rapid pace, with ever growing turbine sizes and greater distances to shore the demand for structural monitoring of the substructures has become more relevant than ever. Jackets are lattice structures which can be favorable in large water depths and at sites with strong wave action Other foundation types such as gravity based, tri-pod and tri-pile foundations have been installed in the past but represent a far smaller population. For offshore wind turbines on monopile foundations fatigue life is a design driver [2, 3, 4].

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