Reliability analysis for hydrokinetic turbine blades

Reliability is an important element in the performance of hydrokinetic turbines. It is also a driving factor of the system lifetime cost. In this paper, we perform time-dependent reliability analysis for the blades of a river-based horizontal-axis hydrokinetic turbine. Based on the stochastic representation of the monthly river velocity and material strength, a limit-state function is established with the classical blade element momentum method. In the limit-state function, a failure is defined as the event when the flapwise bending moment exceeds the allowable moment that corresponds to the ultimate strength of the material. The upcrossing rate method is employed to calculate the time-dependent reliability of the hydrokinetic turbine blade over its design life period. The results indicate that setting a proper cut-out river velocity is important for the reliability of the hydrokinetic turbine blade.

► River flow climate has longer memory than wind climate.
► Time-dependent reliability analysis method should be employed for hydrokinetic turbine blades.
► Reliability of hydrokinetic turbine blades decreases with time.
► Probability of failure of hydrokinetic turbine blades is sensitive to the cut-out river flow velocity.