A Marie Curie action allows to address a common problem from various angles. We found the necessary expertise in a relatively small consortium, consisting of the Technical University of Denmark (DTU), the Geophysical Institute at the University of Bergen (UiB), the Ecole Polytechnique Federal de Lausanne (EPFL), the Eberhard-Karls-University in Tübingen (EKUT) and the University of Copenhagen (UCPH). Additionally, we invited three of the largest offshore wind developers to the consortium (Vattenfall, Equinor and RWE), a company for vertical axis turbines (SeaTwirl) and Charles Meneveau from the University of Johns Hopkins University (JHU). In the end, we trained 13 PhD students and 6 short-term fellows. One of the fellows had the others as research topic, investigating the collaboration aspects between the students and groups from a humanities perspective (UCPH).
In the consortium, we chose expertise within wind and wind farm modelling with Large Eddy Simulations (LES)(DTU and EPFL), the mesoscale WRF model including wind farm parameterisations inside the model (DTU), built a small wind farm in a wind tunnel (EPFL), had an expert in wind speed observations from satellite (DTU), two groups performing lidar observations (UiB and DTU), and two groups with Uncrewed Aerial Systems (UAS) expertise (EKUT and UiB). One of the developers (RWE) also contributed with access to an offshore wind farm, the Rødsand 2 wind farm near the Danish island of Lolland. Their support for sailing the lidars on the crew transfer vehicles for nearly a year is highly appreciated, as well as their facilitation of access to the substation for installation of the scanning lidar. RWE, as well as Vattenfall and Equinor, hosted students. SeaTwirl collaborated on the adjustment of a load calculation tool for vertical axis floating turbines, and JHU received students.
While the main planned offshore campaign did not work out as planned, Train2Wind created significant progress for being able to investigate the research questions further, both from a conceptual and an experimental side. We were able to (for the first time) measure the wind with two lidars on a ship at many places inside and outside an offshore wind farm, aided by a scanning lidar from the substation for a shorter time period. We also improved satellite based SAR image conversion to wind speeds, and developed a turbulence model as well as improved the wind farm parameterisation in weather models. The turbulence influence in a flow model was investigated, and the measurements of turbulence by UAS was shown to be able in a virtual environment. An improved analytical wake modelling framework was developed, and another one was used for wind farm control. We also improved modelling for vertical axis turbines. For the experimental side, we developed a particle measurement and a much faster hygrometer, a flying sonic anemometer and a motion controlled ship-borne lidar. The time for 5-hole probe calibration was cut from a day to 20 minutes using robotics. Using this, for the first time, Kelvin-Helmholtz billows were detected over a working wind farm. All those individual results and the trained fellows will bring the modelling and measurements of wind farm flows forward.