Piezoelectric connectors for energy harvesting purposes on wind-excited buildings

Recently, the concept of smart buildings has become more frequent, and technologies such as Building Automation (BA) and Structural Health Monitoring (SHM) are becoming common concepts in modern construction. Those systems require the installation of devices that are powered supplied by cables or batteries. Usually, the sensors may be placed in remote places, making difficult the maintenance or the replacement of such appliances. Two main issues may arise in this situation, which are the availability of power to be provided and sustainability when talking about the disposal of cables, for example. As a proposal for such problematics, this Ph. D. thesis presents the concept of a new equipment capable of providing an infinity power supply to those referred sensors. The equipment is named PID. PID stand for piezoelectric dampers, and they work embedded in structural members of the building. The PID device concept involves energy harvesting, which is the process of extracting energy from the environment or a system and converting it into electrical energy. The present work goes from the conception of the device to the analysis of its operation using numerical simulation. The first general idea adopted is that besides the production of electrical energy to supply the smart devices, it also must present structural features due to the place where it is installed. Later, it is also considered a fact that the devices when installed in the building may produce additional damping to the structure. The PID design is a built device with a piezoelectric core material. These materials’ nature can convert mechanical energy into electrical energy or vice versa. Plus, the piezoelectric core may be able to buckle and impact the lateral walls of the device, and this impact, when occurred, can enhance the amount of harvested energy. The amount of produced energy from piezoelectric material is directly related to the frequency of vibration, which in this case can increase due to the impact phenomena. The analysis of this work was performed in ANSYS® software due to its features to interact with the electrical and structural area. Due to similarities in the robustness of such equipment, it was first adopted the concept of a rubber bearing to investigate its behavior. The use of those known civil engineering devices arose due to their ability to support structural loads. A specific type of rubber bearing, the lead rubber bearing (LRB), presents a composition likewise what this work seeks, which is a robust structure with a lead core inside it. From that, the lead core was first replaced by a piezoelectric material to reproduce an initial prototype analysis of the PID. After building a 3D model of the PID, some analyses were performed so that the behavior of the device could be understood, as well as the manner it should be input into the building model. A multilevel methodology was then proposed so the steps could be divided into phases to better organize the device’s functioning, where the output of one level is used as the input of the next, having cascade comportment. It starts from the global model, which is a steel frame building based on the input of a Power Spectra Density (PSD) of the Wind, collecting the data from where the PID device is located on the building. By collecting the Power Spectra Density of the Displacement of the PID ends, it is generated a time-history of that data and it is next applied to the 3D model of the PIDs. From that, it can be obtained the dynamic data from the piezoelectric core to be finally applied to the last level of work of this project, which is the energy harvester model. Then, the power is evaluated. Finally, it was concluded that the device’s performance met what was expected. This project was focused on the conceptual design of the PID device as well as its initial operation. A case study was conducted where it was possible to investigate the device and all the multilevel procedures proposed by this research. Among the PIDs distribution on the building and the evaluation of the results, it was necessary to go through some concepts and the peak acceleration and the stress strength of the piezoelectric material core, demonstrating that the PID distribution may face some limits yet to be investigated. In the end, the harvested energy value showed a great amount even with the limitation imposed.