On the effects of inter-farm interactions at the offshore wind farm Alpha Ventus

Vasilis Pettas,Andrew Clifton,Matthias Kretschmer,Po Wen Cheng

doi:10.5194/wes-6-1455-2021

Abstract

Abstract. The energy transition means that more and more wind farms are being built in favorable offshore sites like the North Sea. The wind farms affect each other as they interact with the boundary layer flow. This phenomenon is a topic of current research by the industry and academia as it can have significant technical and financial impacts. In the present study, we use data from the Alpha Ventus wind farm site to investigate the effects of inter-farm interactions. Alpha Ventus is the first offshore German wind farm located in the North Sea with a fully equipped measurement platform, FINO1, in the near vicinity. We look at the effects on the wind conditions measured at FINO1 before and after the beginning of operation of the neighboring farms. We show how measured quantities like turbulence intensity, wind speed distributions, and wind shear are evolving from the period when the park was operating alone in the area to the period when farms were built and operate in close proximity (1.4–15 km). Moreover, we show how the wind turbine's response in terms of loads and generator and pitch activity is affected using data from a turbine that is in the vicinity of the mast. The results show the wake effects in the directions influenced by the wind farms according to their distance with increased turbulence intensity, reduced wind speeds, and increased structural loading.

Highlights

The reduction of produced emissions and the transition to renewable energy sources require a large increase in the installed capacity of wind
The results show that the mean wind speed decreased by 1 m s−1 over the periods, and the mean turbulence intensity increased from 5.5 % to 8.5 % due to the farm wakes from the neighboring farms
This figure can be used as a reference for the reader for the positioning of the farms and the azimuth sectors relative to FINO1, which is used as the origin

Summary

Introduction

The reduction of produced emissions and the transition to renewable energy sources require a large increase in the installed capacity of wind. Similar to single wind turbine wakes, the wind farms as a whole interact with the atmospheric boundary layer and create wakes that are propagated downstream (Porté-Agel et al, 2020) This phenomenon is more prominent in offshore farms where the machines used are larger, the ambient turbulence intensity (TI) is lower, and the surface roughness is lower than onshore sites. These effects need to be modeled and considered when planning the siting of wind farms as they can have a large impact on the operating conditions experienced by the neighboring wind farms. Neglecting such effects can lead to large deviations in the annual energy production (AEP) estimates, as well as the lifetime of the structural components (Lundquist et al, 2019)

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Discussion

Conclusion