Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design

Abstract

The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provided, with a focus on their ability to accommodate the coupled dynamic behaviour of floating offshore wind systems. The exemplary design and testing methodology for a monolithic concrete spar platform as performed within the European KIC AFOSP project is presented. Results from the experimental tests compared to numerical simulations are presented and analysed and show very good agreement for relevant basic dynamic platform properties. Extreme and fatigue loads and cost analysis of the AFOSP system confirm the viability of the presented design process. In summary, the exemplary application of the reduced design and testing methodology for AFOSP confirms that it represents a viable procedure during pre-design of floating offshore wind turbine platforms.

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

“…According to Berger et al , the total installed offshore wind power capacity is expected to exceed 40 GW by 2020, while the levelized cost of energy is epxected to decrease by 30% on a global average. To maintain this trend, research has been focusing, among others, on wind turbine reliability, support structures, energy yield optimization and installation cost as well as on new wind turbine concepts like floating and vertical axis wind turbines . However, the overall cost of offshore wind energy is still, to a large extent, driven by operational and installation cost, because offshore access is limited by the meteorological conditions and the availability of transportation.…”

A CFD study of coupled aerodynamic‐hydrodynamic loads on a semisubmersible floating offshore wind turbine

“…Moreover, previous experimental works did not adequately consider the same material, construction methods, or deployment method as the full‐scale system . In particular, a scaled‐down model experiment in a wave basin inherently has limitations on the simultaneous satisfaction of both Froude and Reynolds scaling laws . The scaled‐down model is typically scaled by the dimensionless Froude number to ensure the similarity of platform hydrodynamic whereas the tip‐speed ratio and wind speed to wave celerity ratio between scales is maintained to entirely consistent with Froude scaling .…”

“…7 In particular, a scaled-down model experiment in a wave basin inherently has limitations on the simultaneous satisfaction of both Froude and Reynolds scaling laws. [8][9][10][11] The scaled-down model is typically scaled by the dimensionless Froude number to ensure the similarity of platform hydrodynamic whereas the tip-speed ratio and wind speed to wave celerity ratio between scales is maintained to entirely consistent with Froude scaling. 8 However, an experiment on a FOWT is usually more expensive than a sophisticated design tool, which is preferred for cost-effective solutions during the design process.…”

New perspectives in offshore wind energy

“…However, accuracy and reliability of joint aerodynamic-hydrodynamic laboratory tests on scaled wind turbines are major challenges, owing essentially to the difficulties of a simultaneous scaling of wind and wave loadings. The theme issue includes two papers, by Matha et al [50] and Jaksic et al [51], presenting experimental results in wave basins.…”

“…Matha et al [50] outline an integrated approach to the design of wind turbines on floating supports, combining in a multi-step optimization procedure simple formulae for a preliminary selection of relevant design parameters, numerical simulations accounting for coupled dynamic behaviour with a different accuracy level, and scaled testing methodologies in wave basins to validate numerical simulation results, adjust the hydrodynamic coefficients used in the simulations, check potentially critical cases and quantify model uncertainties. Challenges involved in a fully coupled aero-hydro-servo-elastic numerical modelling, and in a simultaneous aerodynamic and hydrodynamic scaling, are discussed thoroughly.…”