Piezoelectric energy harvesting from rotating applications can be realized by the use of harvesters, the basic part of which is a piezoelectric material. Such harvesters have various structures but most of them contain a cantilever composite beam, which consists of the carrying material and the piezoelectric material. A diversification of the harvester structures is, above all, the result of the application of additional mechanical structures, the task of which is to deform the cantilever composite beam. In contrast to these approaches, this article presents the simulation and laboratory investigation of the piezoelectric energy harvesting from a rotating shaft without the use of any additional mechanical structure. Energy harvesting was realized by the use of macro fiber composite (MFC), which was directly glued onto the rotating shaft surface, instead of on a cantilever beam being a part of the additional mechanical structure. In the theoretical part of the article, a mathematical model of piezoelectric energy harvesting from the rotating shaft with the use of MFC was elaborated. This model was verified on the basis of the laboratory experiments. On the basis of the simulation and laboratory experiments it was found that both an increase in the rotation frequency of the shaft and an increase in the stress in a rotating shaft caused a linear increase in the voltage generated by the MFC and caused an exponential increase in power generated by the MFC. These characteristics are significantly different to the characteristics obtained for harvesters consisting of a cantilever beam, in which the maximal value of a voltage and a power is generated only for a resonant frequency of a cantilever beam. In spite of these differences the optimal load resistance for the specific rotation frequency of the shaft can be calculated from the formula used to calculate the optimal load resistance for a harvester based on a cantilever beam.

The article presents an experimental study of a system consisting of a piezoelectric energy harvesting device, Graetz bridge rectifier, capacitor, voltage comparator and radio transmitter. In the presented experimental study, the recovered electrical energy is accumulated in the capacitor and is used to send signals by a radio transmitter. In the first part, the application of piezoelectric energy harvesting devices based on the cantilever beam in wireless monitoring systems is discussed. In the second part, the mathematical model of energy conversion in the piezoelectric energy harvesting devices is presented. In the third part, the characteristics obtained during laboratory research are presented.

Energy harvesting from mechanical vibration of buildings is usually realized by the use of devices, in which the main element is a prismatic beam with a rectangular cross-section. The beam has been the subject of scientific research; it is usually constructed with a carrying substrate that does not have piezoelectric characteristics and from piezoelectric material. In contrast, this investigation sought to create a beam structure with a piezoelectric composite only. The entire beam structure was made of a prototype piezoelectric particulate composite. Based on courses of voltage obtained in laboratory experiments and known geometry of the specimens, a series of finite element method (FEM) simulations was performed, aiming to estimate the piezoelectric coefficient d₃₁ value at which the mentioned voltage could be achieved. In each specimen, sedimentation caused the formation of two distinct layers: top and bottom. The experiments revealed that the presented prototype piezoelectric particulate composite converts mechanical stress to electric energy in bending mode, which is used in energy harvesting from mechanical vibration. It is self-supporting and thus a carrying substrate is not required in the harvester structure.

This article presents a comparison of the course of a creep phenomenon in the control system of a bimorph actuator, in which control voltages were applied to both piezoelectric layers, with the course of the creep phenomenon in the control system of a unimorph actuator, in which a control voltage was applied to only one piezoelectric layer. The bimorph actuator was built from two layers of piezoelectric composite, macro fiber composite was applied, and a carrier layer made of epoxy laminate was used for production of printed circuit boards. A comparative analysis was carried out on the basis of 22 laboratory experiments in which the vision system was used to measure a displacement change of six points of the bimorph actuator structure. Based on the results of laboratory experiments, it was noted that the duration of a transient part is approximately the same in a system with a control voltage applied to one MFC patch as in a system with control voltages applied to two MFC patches. In the system with control voltages applied to two MFC patches, the position change due to the creep process is more than two times bigger in comparison to the system with the control voltage applied to one MFC patch.