Parametrically excited nonlinear piezoelectric compact wind turbine

A nonlinear piezoelectric rotary transducer is developed that makes compact low speed wind generators realizable. Compact wind generators provide power to sensor nodes in remote or hard to reach locations. Since the locations of the sensor nodes are not optimized in terms of wind speed, the compact wind generators should be able to produce power from low speed wind. At smaller scales piezoelectric transduction becomes more effective than electromagnetic transduction. Therefore one way of realizing the compact wind turbines is by replacing the electromagnetic generator with a piezoelectric transducer. This work presents a novel piezoelectric transducer where the rotation of the blades results in large oscillations of piezoelectric beams. The piezoelectric bimorphs are made bi-stable by incorporation of repelling magnetic force. The Magnetic force is due to interaction of permanent magnets at the tip of the beams with permanent magnets rotating with the blades. Since the magnetic force changes with blade rotation, the dynamics of the beams changes in time and the system is thus parametrically excited. Two configurations are presented one called tangential configuration and the other is radial configuration. An 80 mm x 80 mm x 175 mm nonlinear piezoelectric wind generator can generate milliwatts of power from wind as slow as 2 ms(-1). The proposed compact wind generators are experimentally investigated in two steps. First the piezoelectric transducer is examined through constant rotational speed tests. Second wind tunnel experiments are performed to characterize the entire wind generator. An analytical model is developed for the piezoelectric rotational transducer. The model is verified with the experimental results. The nonlinear phenomena captured by the experimental investigations are explained using the analytical model. The model is also used for more case studies identifying specifically the effect of parametric excitations. (C) 2012 Published by Elsevier Ltd.