In order to tap the world wide offshore wind resources above deep waters, cost efficient floating platforms are inevitable. Tension-Leg Platforms (TLPs) could enable that crucial cost reduction in floating wind due to their smaller size and lighter weight compared to spars and semi-submersibles. The continuous development of the GICON®-TLP is driven by computer-aided engineering. So-called aero-hydro-servo-elastic coupled simulations are state-of-the-art for predicting loads and simulating the global system behavior for floating offshore wind turbines. Considering the complexity of such simulations, it is good scientific praxis to validate these numerical calculations by use of scaled model testing. This paper addresses the setup of the scaled model testing as carried out at the offshore basin of the École Centrale de Nantes, as well as the numerical model for the GICON®-TLP. The results of dedicated decay tests of the scaled model are used to validate the computational model at the first stage and to determine the natural frequencies of the system. Besides different challenges to the scaled model during the survey, it was possible to take these difficulties into account when updating the numerical model. The results show good agreements for the tank tests and the numerical model.

Floating substructures for wind turbines are commonly credited for enabling the offshore wind industry, so far focused on fixed substructures, to expand into deeper waters. As per Arent et al. (Improved offshore wind resource assessment in global climate stabilization scenarios, [4]), 77% of global offshore wind potential is located in water depths deeper than 60 m. However, floating substructures do not yet meet the market expectations with regard to LCOE. By integrating new materials as well as modularity into the design, the costs of the tension leg platform (TLP) development presented in this pater have been significantly reduced. Pre-stressed Ultra-High-Performance-Concrete (UHPC) pipes will be used for this sub-structure. The buoyancy bodies will be fabricated using concrete shell elements known from tunnel engineering. The use of casted iron for the nodes and the Transition Piece (TP) leads to further advantages regarding design and costs. All components are designed for transportability (e.g. via railway) in order to ensure a high level of flexibility within the supply chain. The structural design has been calculated to support turbines of up to 6 MW rated power and more. In October 2017, a scaled model (1:50) of the new substructure design for use with a 6 MW turbine was successfully exposed to wind and wave loads at the Ocean Engineering Tank of the École Centrale de Nantes (ECN). In June 2018, a second measurement campaign was started, and in September 2018 a third campaign will be run to verify the transport & installation process. Th presentation and paper will focus on the TLP design as well as on the model fabrication and scaling. Furthermore, measurement results from the ECN test will be presented. Therefore, the presentation will introduce the measurement setup as well as the measurement types to verify the simulation model. Finally, the verification of the simulation model with the measurements will be highlighted.

A crucial problem regarding the offshore electricity generation is the levelized costs of energy (LCOE). This is an even larger problem for floating substructures for offshore wind turbines. This paper highlights a substructure for floating offshore wind turbines (FOWT) for a one step installation process. It deals with the parametric study of the TLP's structure to gain hydrostatic and hydrodynamic stability during the transport and installation process of the TLP equipped with a 6 MW wind turbine. At first a hydrostatic analysis with the software tool MOSES (V7.06.062) has been performed. Hydrodynamic simulations with ANSYS AQWA (V17.2), based on 2D potential flow theory, have been conducted afterwards to get information about the motion behavior of the TLP in wind, current and waves.