A novel optimised nacelle to alleviate wind turbine unsteady loads

Abstract

A comparative study of the effectiveness of an innovative optimised nacelle on fatigue loads alleviation and performance improvement in both upwind and downwind configurations has been conducted. The idea is to optimise wind turbine nacelles using flaps to push the flow towards outer spans, which leads to improved turbine performance, as well as mitigates unsteady loads, therefore, extending the fatigue life of wind turbine's components. Theoretical explanations indicate that in the case of upwind configuration, increasing downstream velocity leads to a reduction in turbine power. However, lower wind speeds seen by inner spans lead to mitigate thrust load generated by inner spans. In the case of downwind configuration, increasing upstream velocity leads to improve turbine power based on the turbine Euler equation, and pushing flow towards outer spans with higher lift/drag ratios leads to mitigate unsteady loads generated by inner spans. Experimental results show that using flaps to optimise the nacelle shape not only mitigates unsteady loads and therefore extends the fatigue lifetime of blades but also improves turbine power and yaw stability. Furthermore, using flaps in downwind configuration can compensate for the adverse effect of wind turbine yaw misalignment on the wind turbine performance and unsteady loads.