Overview of coastal effects on offshore wind farms Measurement flights: TU Braunschweig collects data for optimising wind farms

The use of wind energy from offshore wind farms off the North Sea coast is indispensable for the energy transition in Germany. The proximity to the coast influences the yield of the wind farms here. Especially the wind from land towards the sea and temperature differences between land and water play a role in the atmospheric transition area between land and sea. Over several years, Technische Universität Braunschweig has carried out measurement flights with two research aircraft in the area of the entire German Bight as well as ground-based wind measurements on the islands of Helgoland and Norderney.

The analysis of the data obtained shows that the wind speeds in individual offshore wind farms depend heavily on the wind direction and the shape of the coastline in this area. The increase in wind speed depends greatly on the mixing of the atmosphere, and in the typical situation where warmer air masses are transported over the cooler sea surface, the increase in wind speed takes significantly longer.

This study provides the basis to better understand interactions with the state of the sea, the thermal properties of the tidal flats and the surface roughness as well as atmospheric turbulence in the future.

• Further information on the study: Press release of the Helmholtz Centre Hereon
• Original publication in “Meteorologische Zeitschrift”: Coastal impacts on offshore wind farms – a review focussing on the German Bight area

Background

The area that can be used for wind energy in the German Bight is limited. Therefore, wind farms are usually built in groups, so-called wind farm clusters. Such clusters can consist of several hundred wind turbines. While wake currents are generated behind the turbines, upstream the wind is reduced by blockage effects. As a result, the turbines encountered by the wake convert less energy and are subjected to greater loads. Under certain atmospheric conditions, wakes can extend over distances of more than 50 kilometres.

Project data

The “X-Wakes” project is being carried out in a large consortium coordinated by the Fraunhofer Institute for Wind Energy Systems. Project partners are the Institute of Flight Guidance at TU Braunschweig, the Eberhard Karls University in Tübingen, the Helmholtz Centre Geesthacht, the Karlsruhe Institute of Technology, the University of Oldenburg, and UL International GmbH. Various wind farm operators and the Federal Maritime and Hydrological Agency are involved in the project as associated partners. The research project is funded by the Federal Ministry for Economic Affairs and Energy for the period 2019-2023.