Impact of a Connection Structure of Macro Fiber Composite Patches on Energy Storage in Piezoelectric Energy Harvesting from a Rotating Shaft

Energy collection in a capacitor, which was charged by four connection structures of Macro Fiber Composite (MFC) patches, was the subject of laboratory research. The first structure was the delta circuit created by three MFC patches and connected with a three-phase rectifier; the second structure was the delta circuit created by three MFC patches and connected with a three-phase rectifier; the third structure was the parallel connection of three circuits, each of which consisted of an MFC patch and a full bridge rectifier; and the fourth structure the series connection of three circuits, each of which consisted of an MFC patch and a full bridge rectifier. Laboratory experiments were carried out on a laboratory stand which consisted of a rotating shaft, three MFC patches powering an energy storage system, and a data acquisition system. The star connection generated the highest values of voltage across a capacitor in the long time period. The delta connection produced the highest capacitor-charging power. The shortest time to reach a target voltage on the capacitor equal to a few volts was achieved by use of the delta or parallel connection. The delta connection generated target voltage equal to a few volts across a capacitor in the shortest time at a lower level of stress in the shaft, but the difference between the charging times by the delta circuit and by the parallel connection decreased as the stress in the shaft increased.