In its annual results for 2023, RWE reported on its last year’s financial performance and many of its offshore wind developments, but also on research projects related to the wake effect at offshore wind farms.

Last year, RWE, together with project partners, completed two such studies and embarked on a new project on wake effects. Two of the initiatives have been funded by the German Ministry for Economic Affairs and Climate Action (BMWK).

In planning new wind farms, developers calculate various factors affecting their performance. One important factor is the wake effect, where the wind slows down and swirls once it encounters a turbine, reducing the yield of the wind turbines positioned behind. To make sure offshore wind farms produce as much power as possible, this effect needs to be taken into account during the planning of a project.

Currently, standard computer models are used for these calculations, but as offshore wind farms become more tightly packed, especially in places like the North Sea, highly precise calculations are needed, meaning that the existing models will need to be refined, according to RWE.

In 2023, the offshore wind developer joined a project called C2-Wakes (Controlled Cluster Wakes), which will involve studies at three adjacent RWE offshore wind sites in the North Sea. Supported by the BMWK, the project aims to help gain a better understanding of the effects of offshore wind generation on wind patterns.

According to information on BMWK’s EnArgus portal, C2-Wakes was granted nearly EUR 2.9 million, with most of this amount allocated to the German Fraunhofer Institute for Wind Energy Systems (IWES) which is the coordinator for the joint research project and is working on the further development of measurement and modelling methods for large-scale wind farm effects. The focus of Fraunhofer IWES’s work is also on deriving recommendations for action to reduce large-scale wind farm effects for the planning of future very large offshore wind farm clusters.

RWE’s part of the project, which was granted nearly EUR 295,000, involves a LiDAR measurement campaign within an offshore wind farm that the company operates in the German North Sea. The research and development work performed together with the measurement campaign will focus on improving existing in-house models by comparing and adapting them both with measurement data obtained from the campaign, as well as with modelling results from the project partners using more complex models.

Last year, the German company completed two research projects revolving around the wake effect at offshore wind farms.

The company contributed to the X-Wakes project, which was also supported by the German Ministry for Economic Affairs and Climate Action and led by Fraunhofer IWES, by providing the researchers with extensive data from RWE’s wind farms and enabling them to carry out wind measurements using sensors mounted to buoys in the vicinity of the wind turbines.

The X-Wakes project will allow for more accurate predictions of changes in wind conditions resulting from the planned large-scale expansion of offshore wind farms in the North Sea.

A second project RWE completed last year, named Global Blockage Effect in Offshore Wind (OWA GloBE), was related to the ‘blockage effect’, the phenomenon of wind dropping in speed just before it hits the turbine.

“Only if the global blockage effect is calculated accurately can the wake effect be simulated precisely. Data obtained through OWA-GloBE is now being used to optimise computer models deployed throughout the industry,” RWE explains.

The measurement campaign for the OWA GloBE project, an RWE-led joint industry project organised under the Carbon Trust’s Offshore Wind Accelerator (OWA), was launched in 2021 and then extended by four months in 2022.

The project, whose aim was to reduce the commercial uncertainty around the modelling of the blockage effect, also attracted other organisations involved in developing offshore wind farms, including Ocean Winds, Ørsted, The Crown Estate, and TotalEnergies.

At the beginning of 2023, RWE also teamed up with DNV to validate the implications of long-distance wake effects from large offshore wind clusters.

RWE said its models predicted that large clusters of offshore wind farms could have far-reaching wind-shadowing effects, impacting the yield of future offshore wind farms. The company’s preliminary model outlined that these effects can have an impact up to 200 kilometres or more and cause the energy yield in the wake areas to be reduced – in certain cases by over ten per cent.

DNV’s scope of work in the joint study last year was to validate the effects of the initial modelling results by independently carrying out an analysis of RWE’s data and performing CFD modelling to review the company’s findings.

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