Innovative Hydrodynamic Research Facilities for Offshore Renewable Energy: a Case Study on the Effects of Biofouling

Abstract Experimental testing of offshore renewable energy (ORE) systems (ocean wave energy, floating offshore wind, etc.) in all stages along the TRL-TLP development trajectory is paramount to gain insights into the dynamic behaviour, survivability, and other aspects of the design. In concert with numerical modelling techniques, physical wave tank and flume tests provide the necessary information for proof of concepts, design optimisation, or design of energy maximising control strategies. In particular, experimental test facilities provide the opportunity to test ORE systems in realistic and, most importantly, controlled environments. Available test facilities mostly differ in terms of their operational parameter space, e.g., maximum wave heights, maximum water depths, maximum model scales, the ability to model wave-current interaction or climate conditions. At TU Braunschweig and the Coastal Research Centre, Hannover, a number of novel experimental research facilities recently became available for testing of ORE systems. These facilities, namely a Salt-water Wave-Current Flume (SWCF) and the Large Wave Current Flume (GWK+), show specific features which distinguish them from already existing facilities. The SWCF allows testing of devices in a seawater environment with full control over the aquatic and hydraulic boundary conditions. The GWK+ is unique in its ability to test devices at large scale in harsh offshore environments. This paper presents in detail the capabilities and features of the novel research facilities, thereby highlighting their potential to enhance the modelling and analysis of ORE system, filling current knowledge gaps, and push systems forward on the TRL-TLP development trajectory. A case study on the analysis of live marine growth on the monopile showcases the specific features, providing unique data and unprecedented results.