Mitigation of Structural Demand to Wind Turbines: Experimental Investigation of Three Control Strategies

The adoption of wind turbines to produce electric energy nowadays represents one of the most promising alternatives to the use of the exhausting fossil fuel stocks. The actual tendency is toward the design of taller towers that can produce more power because excited by stronger winds. There is the need of designing these structures in a cost effective way, aiming to reduce the wind induced growing structural demand. Three different control systems are investigated and compared herein to this aim, on the basis of the experimental results gathered at the Structural Dynamics Laboratory of the Denmark Technical University. Two of these are passive (tuned rolling-ball damper, spherical tuned liquid damper), while the third one is semi-active and aims at realizing a time-variant base restraint. The experimental comparison of the three strategies, tested against two types of wind loads, allow to draw interesting conclusions and to provide useful hints to give rise to further developments of the technologies investigated.