A novel design for an adaptive aeroelastic energy harvesting system: flutter and power analysis

Extracting energy from waste sources could be a new prospect toward energy crisis, specially from wind energy. A simple mechanical system, including mass and spring, if combined with a wing, could extract more energy. A novel design for a cantilever beam with an airfoil is presented in this paper for harvesting more energy. This design allows the harvester to operate in a wider range of airspeeds. Electrical energy will be extracted from a piezoelectric patch on the beam. This novel design moves a point mass along the beam regarding the airspeed because this movement might compromise between flutter occurrence and more energy extraction. In order to understand this compromise, the effect of the position of the point mass on the onset of flutter instability and output power of the system is investigated. Mathematical models include both linear and nonlinear aeroelastic models. For flutter analysis, a linear model called finite state model is used. The nonlinear part of the problem is modeled by ONERA dynamic stall model. A parametric study is conducted in order to have a better understanding of design criteria. Both flutter onset airspeed and output power are achieved for ten different places of the point mass on the beam. According to the results, a passive mass-positioning system could be able to set the position of the point mass for any given airspeed. Based on these results, a proper passive mechanism is designed including a set of springs, strings, guiding rails, pulleys, and a parachute. The aeroelastic model used in this paper is validated by experiments of the state of the art. The novel mechanism in this design-oriented paper continues the concepts and experiments, presented in the literature.