Abstract
The paper presents an experimental study of applying variable loads on a vertical-axis wind turbine (VAWT). The experiment is conducted in an open-jet wind tunnel on a two-bladed Darrieus VAWT equipped with active individual blade pitch control. Variable loads are achieved by dynamically changing the pitch angle of the individual blades and by keeping the wind speed of the tunnel constant. The blade loads are measured using strain gages and the flow velocity is measured upwind and downwind of the rotor using a hotwire. Dynamic inflow phenomena are clearly visible both in the turbine loads and in the velocity field. A time delay based upon the flow convection in the wake is identified. It results that the induction of the turbine can be controlled by changing the pitch of the blades. The experimental database allows to validate a new dynamic inflow model for VAWT and will be made publicly available for research purposes.
Highlights
Compared to the conventional horizontal-axis wind turbines (HAWTs), vertical-axis wind turbines (VAWTs) show advantages: among others the location of the centre of gravity closer to the ground makes verticalaxis wind turbine (VAWT) a potentially better solution for offshore floating applications [1]; they are less noisy and suitable for the installation into urban environments [2]
Since the loads of the VAWT vary considerably during one rotation, it is necessary to present the data in the azimuthal domain to assess the aerodynamic performance of the turbine
This study presents an experimental campaign of applying variable loads on a VAWT by means of individual blade pitching
Summary
Compared to the conventional horizontal-axis wind turbines (HAWTs), vertical-axis wind turbines (VAWTs) show advantages: among others the location of the centre of gravity closer to the ground makes VAWT a potentially better solution for offshore floating applications [1]; they are less noisy and suitable for the installation into urban environments [2]. The VAWT’s performance is complex due to the 3D unsteady aerodynamics, such as dynamic stall, and the occurrence of structural effects. Additional complexities may be introduced by the motion of the floater or by a sudden change in the wind speed (i.e. gust). The consequent variation of the inflow wind velocity or the turbine loading cause dynamic inflow conditions at the rotor. This unsteady effect can be better investigated with scaled wind tunnel testing under controlled conditions
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