Current Research | Renewable Energy

Analysis of FOWT Performance under Extreme Load Conditions and Control Strategy

As a renewable and clean energy source, the usage of wind energy has shown an upward trend in recent years. The Floating Offshore Wind Turbines (FOWT) has won high importance due to the increased demand on the renewable energy. However, we are still facing challenges in the motion predictions of FOWT under extreme conditions, high wind speed or/and high wave amplitudes etc. Therefore, a fully coupled numerical tool that is able to accurately predict and analyse the motions and responses of the complicated FOWT system is increasingly needed.

In present study, we are developing such a numerical tool based on OpenFOAM, which is an open source CFD package and can be extended easily. This numerical tool has been developed and applied to various problems in the past few years and the results have been published as journal articles which can be downloaded on our group website. In present numerical methods, both the aerodynamics and the hydrodynamics are resolved by solving the incompressible Navier-Stokes equations including different turbulence models, and the Volume of Fluid (VOF) method is used to capture the free surface. Besides, a wave generation module is incorporated in present code which is able to model various types of waves. Considering the effect of mooring system on the performance of FOWT, a quasi-static mooring line analysis model is integrated in current numerical tool. As for the mesh motion, the arbitrary mesh interface (AMI) mesh technique in OpenFOAM is applied to deal with the rotating machinery problems. The surge, heave and pitch motions are applied to the whole computational domain.

My work focuses on further extending our existing code by introducing the control strategies. By setting up a specific state space model and using certain judge theorem and rules, we will testify the stability and controllability and investigate how the control system works under different working conditions, especially under extreme conditions.