Structural Performance and Power Production of Wind Turbine Systems with Bend-Twist Coupled Blades in Underrated Wind Conditions

The implementation of bend-twist coupling effect on wind turbine blades on the structural performance and power production of wind turbine system exposed to underrated wind conditions are studied. The structural performance of wind turbine systems are evaluated by the decrease in damage equivalent loads in the whole wind turbine system and reduction in maximum fiber direction stresses in the blades with the exploitation of off-axis plies in the main spar caps of the wind turbine blades. Wind turbine models with designed GFRP bend-twist coupled blades are generated in a multi-body code which uses a superelement blade definition. 325-second transient aeroelastic analyses of wind turbine systems are performed for different constant wind definitions for power production evaluation, and structural performance is assessed based on the damage equivalent load reductions in the whole wind turbine system that is exposed to turbulent wind profiles for six-hundred seconds as stated in IEC standards, and lessening in fiber direction stresses in the blades. Results show that for underrated, rated, and overrated average hub height wind speeds, bend-twist coupled blades ensure considerable reductions in the loads at the cost of slight reduction in generated power in underrated wind speeds