Colloquia

Samenvatting

Amidst the energy transition and the expansion of the wind energy sector, Vertical Axis Wind Turbines (VAWT), a type of cross-flow turbine whose blades rotate around an axis perpendicular to the incoming wind, pose many advantages for both urban and deep-sea offshore regions. Unlike Horizontal Axis Wind Turbines (HAWT), the generator may be placed at sea level, reducing turbine scale coupling to height, enabling the use of light-weight floating setups. Furthermore, the wake structure of VAWT allows placing wind turbines closer together, achieving higher wind farm energy extraction density.

However, VAWT's pose their own challenges:  the very topology that provides all these practical advantages over HAWT's also causes a large fluctuation in local flow conditions within each rotational cycle, creating a highly complex dynamic flow regime and large cyclic loading. Furthermore, standard VAWT’s also lack self-starting capability and have a large frontal blade area.

In this research, a modular research platform scaled wind turbine was developed, to allow investigating experimentally the influence of any geometrical parameter on wind turbine performance in the wind tunnel.

To find the best solution for abovementioned problems caused by varying flow conditions, the system was equipped with a fully electronic, programmable individual pitch mechanism, giving complete control of the blade pitch at any point in the cycle.

An analytical model was developed to generate the most efficient pitching trajectory, and this strategy was tested in the wind tunnel for various turbine configurations (different number of blades, chord lengths, spans), demonstrating significant performance improvements over conventional setups.

In future research, the experimental setup may be used to map the complete VAWT parameter space, optimize the pitch trajectory to minimize cyclic loads, cross-validate numerical and analytical models, enable self-learning pitch optimization, and study the wake of a pitch actuated VAWT for the first time.