Piezoelectric energy harvesting from vortex-induced vibrations on a GFRP beam with embedded piezoelectric patch

In the present era, the demand for energy continues to increase and nevertheless, energy resources are gradually decreasing. Therefore, extracting energy from the operating ambient is of great importance especially for industrial applications. Among the numerous available ambient energy sources, wind energy is one of the most promising and prevalent energy sources existing in the environment. In this study, a piezoelectric energy harvester (PEH) consisting of an electromechanical coupling of GFRP cantilever beam with an embedded piezoelectric patch is developed for wind energy harvesting. The cantilever beam under the wind flow vibrates due to the pressure field that occurs on the leeward side of the beam. The generation of the pressure field is based on the vortex shedding phenomenon. Theoretical model of the regarding electromechanical coupling subjected to vortex induced vibration is presented and the effect of the pressure field having various vortex shedding frequencies on harvested power is investigated by means of numerical simulations validated with an experimental study. In order to determine the effect of the direction in which the wind excites the PEH, two wind flow conditions are considered; cross wind and head wind. According to the results, it was found that the PEH generates considerably more voltage outputs under cross wind loading than that obtained from the head wind excitation. In cross wind case, maximum open circuit voltage of 82.4 V is obtained at the wind speed of 6 m/s with the vortex shedding frequency of 18 Hz, which is very close to the second resonance frequency of the PEH. With a calculated load resistance of 100 kΩ, the resulting maximum direct voltage and electric power is 58.7 V and 11.5 mW, respectively. As far as the energy efficiency of PEH is concerned, it is determined that the efficiency is about 0.75 for the frequency of 18 Hz, which is quite acceptable for energy harvesting. It is concluded that a composite PEH with an embedded piezoelectric patch can be used as an effective energy harvester for the vortex induced vibration when the vortex shedding frequency is close to its resonance frequency.