Mid Sweden University

Energy harvesting enables the supply of low-power embedded sensor systems that perform important tasks, such as condition monitoring. In applications with rotating elements, like bearings, variable reluctance energy harvesters (VREHs) can provide a significant amount of power to the system; however, a power conditioning system is needed to extract the maximum power, manage an energy storage element, and regulate the output voltage. Previous works focus either on the optimum design of the harvester that maximizes the output power level with given space constraints or concentrate on the optimum design of the power conditioning system for a fixed harvester design. This work proposes co-designing both elements to optimize the power delivered to the energy storage element. The results show that the main variable connecting both systems is voltage. On the harvester side, it is demonstrated that different designs can provide different voltage levels while maintaining the maximum output power, while on the power conditioning side, a trade-off between rectification and conversion losses must be considered. This analysis is presented with simulations and validated with experimental results. Finally, the limitations of commercial power management units (PMUs) are exposed.