With the high-speed development of the Internet of Things (IoT), powering such a massive number of wireless IoT sensors with chemical batteries become more and more unpractical. To make the IoT sensors self-sustained, Piezoelectric Energy Harvesting (PEH) technology provides an excellent solution to power the devices with a relatively long service time. By harvesting the ambient mechanical vibrations, PEH could generate a stable power source without wind or light.

Currently, the famous bearing manufacturer, SKF, collaborates with TU Delft to design a self-sustained smart IoT roller with PEH technology, which will be implanted in huge bearings, such as the bearing in the wind turbines. This thesis project is a feasibility study investigating the possibility of replacing the chemical battery with the Piezoelectric Energy Harvester in SKF's smart IoT roller, called Sensor Roller.

The objective of this project includes the system design of two generations of the prototype harvester. The first prototype concentrates on the properties of the piezoelectric material, while the second prototype focuses on the structure of the harvester. The design work consists of the raw data analysis of the target roller from SKF and the prototype construction and simulation in COMSOL Multiphysics. Besides, to make the results more reliable, two stages of the test with the practical components are made to study the harvester's performance under the actual working condition of the roller in the bearing. As a result, a tube shape Piezoelectric Energy Harvester with suitable materials and parameters is built. According to the simulation results, under a safe pressure level of the piezoelectric material, the proposed harvester achieves 8.1mW output power, which is enough for the loading sensors. The designed Piezoelectric Energy Harvester is being manufactured at present, and it is planned to be installed in the target roller to get the system-level test in the future.

In addition to the harvester, some rectifiers are designed and taped out to improve the performance of the proposed Piezoelectric Energy Harvesting system. Three rectifiers are made with the Silicon Carbide (SiC) process to obtain a high voltage and temperature tolerance: a Full Bridge Rectifier (FBR), a Passive Rectifier, and a Synchronized Switch Harvesting on Inductor (SSHI) rectifier. Meanwhile, another SSHI rectifier is made with the 0.18um Silicon BCD process that focuses on solving the cold-startup problem. Consequently, simulated with the real transducer of the proposed harvester, both the FBR circuit and the Passive Rectifier circuit with the SiC process achieve over 10mW output power, and the SiC SSHI circuit achieves 37.1mW output power. As for the cold-startup SSHI rectifier circuit, it successfully reduces the required open circuit voltage by 4x to start up the SSHI system from the cold state.

The results of this project show the great potential for applying the Piezoelectric Energy Harvesting technology to power the IoT sensors in the roller of bearing. Although some future works should be finished to build the commercial version of the energy harvesting roller, we are convinced that the fully self-sustained Sensor Roller with Piezoelectric Energy Harvesting technology will possibly show up in the near future.