Optimized yield in offshore wind farms: Measurement campaign in C²-Wakes project gets underway

Together with its project partners RWE, ForWind (University of Oldenburg – Institute of Physics), and Helmholtz-Zentrum Hereon, the Fraunhofer Institute for Wind Energy Systems IWES is investigating in the “C²-Wakes – Controlled Cluster Wakes” research project how the total energy yield of offshore wind farms can be optimized. The aim of the project is to utilize an extensive offshore wind measurement campaign and modeling methods to determine if and how large-scale wake effects and the global blockage effect can be reduced in the future. The project is set to make significant contributions to climate change mitigation and ensure reliable and cost-efficient energy supply. To date, little research on this topic has been conducted anywhere in the world. The project is being funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) with a total of around €2.86 million.

Space-efficient wind energy expansion required

By 2030, at least 80% of electricity is to be produced from renewable energies. Offshore wind energy has an important role to play in this endeavor, and the expansion plans and associated tendering volumes have accordingly been significantly increased. The German government plans to increase the offshore wind energy capacity to at least 30 gigawatts (GW) by 2030 and at least 70 GW by 2045. This growth is regulated and promoted in the German Offshore Wind Energy Act (WindSeeG). The strategic planning is laid down in the area development plan and is relevant for the design, installation, and operation of wind farms. As the areas available for offshore wind farm development in the German Bight are limited, efficient utilization of this space is required to maximize the benefit of offshore wind. Therefore, offshore wind farms are often installed in groups known as clusters. Precise determination of the wind potential helps to optimize the energy yield from the areas. In the Controlled Cluster Wakes research project, “C²-Wakes” for short, scientists are investigating how the planning and operation of large offshore wind farms and wind farm clusters can be improved and rendered more efficient.

Improved methods for optimized wind farm yields

The turbines in large wind farm clusters can influence each other, with wakes with lower wind speeds and higher turbulence developing behind the turbines. Improved modeling and measurement of the wakes thus allows optimized site selection and resource planning for future offshore wind farms. The scientists plan to investigate how wakes from different wind farms overlap and how wake-optimized operational management may impact these effects in large offshore wind farms on both internal and also large-scale wakes. This requires extensive measurements and validated models. To this end, the project team is collecting data via a comprehensive scanning lidar measurement campaign in RWE’s Amrumbank West offshore wind farm close to the German island of Heligoland. The devices installed on the wind turbine nacelles measure the flow fields downstream of the wind turbines. Using the acquired data, the scientists can analyze how the wind speeds evolve within the wind farm as well as how internal and large-scale wake effects behind the wind farm change if the control strategy is adapted, for example by testing wake steering.

“In the C²-Wakes project, we can draw on our findings from the earlier research project X-Wakes, where we gained a fundamental understanding of the interaction between long-range wake effects, the global blockage effect, and the coasts in the German Bight. These findings help us to investigate whether and how large-scale wind farm effects can be influenced. Among other things, we are combining assumptions about future wind turbine technologies, wind farm designs, and active wake steering,” explained Dr. Martin Dörenkämper, project coordinator, Fraunhofer IWES.

As part of the project, the scientists at the University of Oldenburg, ForWind, are developing and evaluating high-resolution simulation methods and lidar measurement scenarios. The team from Helmholtz-Zentrum Hereon is analyzing satellite data and further developing methods for wind field reconstruction, which, in turn, should provide an answer to the question of how different wind turbine technologies, wind farm structures, and wind farm layouts impact wake effects. Offshore wind farms off the British coast will be analyzed as well.

Thomas Michel, COO RWE Offshore Wind, said: “We are pressing ahead with the expansion of offshore wind energy worldwide. At the same time, we also intend to further accelerate the development and demonstration of innovative solutions. With the research results of the C²-Wakes project, we have the opportunity to make offshore wind energy even more cost-effective and efficient.”

The offshore scanning lidar measurement campaign started in early April with the installation of three devices and is intended to run for a period of at least six months. The data acquired will be used in the scope of the project for the validation of improved models. The research project was launched in May 2023 and will run for three years. In addition to scientific publications, the results will also be made available to industry and planning authorities in the form of recommendations for action and further developed open-source software tools such as the FOXES wind farm planning software.

Contact at the Fraunhofer Institute for Wind Energy Systems IWES
Project coordination, Dr. Martin Dörenkämper, Group Manager
Phone: +49 (0)471 14290-579
E-mail: martin.doerenkaemper@iwes.fraunhofer.de
Project coordination, Dr. Julia Gottschall, Chief Scientist
Phone: +49 (0)471 14290-354
E-mail: julia.gottschall@iwes.fraunhofer.de