Piezoaeroelastic Energy Harvesters Research Articles

Uncertainty Quantification of Piezoelectric Energy Harvesters from Aeroelastic Vibrations

A stochastic approach is presented to evaluate the uncertainties associated with variations in design parameters of a piezoaeroelastic energy harvester. The sensitivities of the harvested power to variations in the load resistance, the eccentricity (distance between the center of mass and the elastic axis), and the nonlinear coe cients are also determined. Moreover, the non-intrusive formulation of the polynomial chaos expansion in terms of the multivariate Hermite polynomials was employed to quantify the sensitivities in the harvested power and the plunge and pitch motions. The results show that the relationship between the input parameters and the harvested power is highly nonlinear. The results show also that the generated power is most sensitive to variations in the eccentricity and that the nonlinear coe cient of the plunge spring is less influential than the nonlinear coe cient of the torsional spring on the harvester's performance.

Camber Effects on the Power Harvesting from Piezoaeroelastic Systems

We investigate the effects of the aerodynamic loads on the performance of piezoaeroelastic energy harvesters. The harvester consists of a rigid airfoil having a pitch and plunge degrees of freedom with a piezoelectric coupling attached to the plunge degree of freedom. The Unsteady Vortex Lattice Method is used to model the unsteady flow and predict the loads. An iterative scheme based on Humming’s fourth order predictor-corrector method is employed to solve simultaneously and interactively the governing equations. The effects of varying the airfoil camber coeffcient are determined. We demonstrate that increasing the camber does not necessarily increase the level of the harvested power.

Enhancement of power harvesting from piezoaeroelastic systems

We investigate the effects of varying the eccentricity between the gravity axis and the elastic axis on the level of energy harvested from a piezoaeroelastic energy harvester consisting of a pitching and plunging rigid airfoil supported by nonlinear springs. The normal form of the dynamics of the harvester near the Hopf bifurcation is used to determine the critical nonlinear coefficients of the springs and maximize the harvested power for different eccentricities. Two configurations are evaluated in terms of the power generated from limit cycle oscillations and a range of operating wind speeds. The impact of the load resistance on the harvested power is also assessed.

Design of piezoaeroelastic energy harvesters

We design a piezoaeroelastic energy harvester consisting of a rigid airfoil that is constrained to pitch and plunge and supported by linear and nonlinear torsional and flexural springs with a piezoelectric coupling attached to the plunge degree of freedom. We choose the linear springs to produce the minimum flutter speed and then implement a linear velocity feedback to reduce the flutter speed to any desired value and hence produce limit-cycle oscillations at low wind speeds. Then, we use the center-manifold theorem to derive the normal form of the Hopf bifurcation near the flutter onset, which, in turn, is used to choose the nonlinear spring coefficients that produce supercritical Hopf bifurcations and increase the amplitudes of the ensuing limit cycles and hence the harvested power. For given gains and hence reduced flutter speeds, the harvested power is observed to increase, achieve a maximum, and then decrease as the wind speed increases. Furthermore, the response undergoes a secondary supercritical Hopf bifurcation, resulting in either a quasiperiodic motion or a periodic motion with a large period. As the wind speed is increased further, the response becomes eventually chaotic. These complex responses may result in a reduction in the generated power. To overcome this adverse effect, we propose to adjust the gains to increase the flutter speed and hence push the secondary Hopf bifurcation to higher wind speeds.

Modeling and analysis of piezoaeroelastic energy harvesters

This work investigates the influence of structural and aerodynamic nonlinearities on the dynamic behavior of a piezoaeroelastic system. The system is composed of a rigid airfoil supported by nonlinear torsional and flexural springs in the pitch and plunge motions, respectively, with a piezoelectric coupling attached to the plunge degree of freedom. The analysis shows that the effect of the electrical load resistance on the flutter speed is negligible in comparison to the effects of the linear spring coefficients. The effects of aerodynamic nonlinearities and nonlinear plunge and pitch spring coefficients on the system’s stability near the bifurcation are determined from the nonlinear normal form. This is useful to characterize the effects of different parameters on the system’s output and ensure that subcritical or “catastrophic” bifurcation does not take place. Numerical solutions of the coupled equations for two different configurations are then performed to determine the effects of varying the load resistance and the nonlinear spring coefficients on the limit-cycle oscillations (LCO) in the pitch and plunge motions, the voltage output and the harvested power.