Simple vibration model for the design of a vertical axis wind turbine

Wind turbines are widely used these days as one of renewable energy sources. In this paper, a dynamic model of a vertical axis wind turbine is developed by considering coupling effects among shaft bending, shaft torsion, shaft tension, rotor tension and rotor bending. The modal characteristics of the vertical axis wind turbine were obtained by using the dynamic model. The accuracy of the proposed model was first validated by comparing its numerical results to those obtained with a commercial program. Then, the effects of key design parameters such as shaft length, shaft diameter and rotor cross section area on the modal characteristics of the wind turbine were investigated. The natural frequency loci veering phenomena occurred when those parameters varied. The loci veering phenomena were associated with the mode shape switch between shaft bending and rotor bending, which should be carefully examined to improve the vibration quality of the wind turbine. The main contribution of this study is to propose a simple vibration model by which the effects of various design parameters on the modal characteristics of the vertical axis wind turbine can be investigated. Some design guidelines related to the vibration performance are also suggested.