Numerical modelling for wind farm operational assessment in complex terrain

Wind farm operation in very complex terrains generally involves complicated and severe environment for wind turbines. Strong speedups, extreme wind veer and high turbulence create a harsh environment for turbine safety and durability. A detailed analysis of the wind field can be very useful in order to isolate the most dangerous conditions and prevent exceptional loads. In this study it is investigated to what extent numerical free flow model can give reliable information on the operational behaviour of wind farms. For this reason, two wind farms, having very different features, are selected: the former is sited on a very gentle terrain and its dynamics is mainly driven by wake interactions, while the latter is instead sited on a very complex terrain. The wind field induced by the orography is calculated with two different numerical approaches, CFD (Computational Fluid Dynamics) and mass consistent modelling. Numerical results are compared and validated against experimental measurements from anemometer met-masts and from turbines SCADA (Supervisory Control And Data Acquisition) data sets. The analysis demonstrates that wind field models can give very useful information on rotor alignment patterns and on their influence on the overall park performance.