Piezoelectric Energy Harvesting from a Rotating Shaft to Power a LoRa-Based Wireless Sensor

Surface monitoring of a machine rotating shaft requires wireless sensors due to technical difficulties of leading cables along the rotating surface. Wireless sensors on the shaft surface can be supplied by batteries or by electricity generated at the location where the wireless sensor is used. The conversion of energy into piezoelectric materials enables the generation of electrical energy from the mechanical energy of shaft. One of the piezoelectric materials that can be used for this purpose is Macro Fiber Composite (MFC), which consists of piezoceramic fibers embedded in a polymer matrix. The article presents the results of laboratory experiments on rectifier systems for six MFC patches glued onto the shaft surface to generate electrical energy to continuously power a wireless sensor. The wireless sensor was based on LoRa technology and consisted of three main parts: a transmitter module, a temperature sensor, and a microcontroller. Eight rectifier circuits used to convert AC to DC, generated by six MFC patches, were tested. Based on the experiment’s results, it was found that the rectifier system consisting of three pairs of MFC patches connected in a delta allowed for obtaining the largest amount of electrical energy compared to the other tested connections. In each of these three pairs, the MFC patches were connected in parallel. Electric energy generated by six MFC patches allowed for a continuous and correct power supply Lora-based sensor.