Design principles for coupled piezoelectric and electromagnetic hybrid energy harvesters for autonomous sensor systems.

Despite the many studies reporting mW-level power output from various hybridized energy harvesters, few succeeded in demonstrating real-life applications such as the commercial Internet of Things (IoT) sensor modules. This owes in large part to the limited time-averaged power output, especially under the requirement for the power-consuming circuitry such as rectifiers and AC to DC converters. At the heart of the limited power lies the lack of detailed analyses and optimization strategies to hybridizing two or more distinct energy harvesters. Here, we first develop design guidelines and optimization strategies based on a parametric model for hybridized energy harvesters coupling two or more distinct mechanisms. The model treats electric current-generating energy harvesters as electric dampers in the spring-mass-damper system and seeks to minimize the total damping consisting of electrical and mechanical damping. We then demonstrate the design guidelines to an oval-shaped hybrid energy harvester consisting of piezoelectric and electromagnetic generators, achieving the time-averaged power output of 25.45 mW at 60 Hz and 0.5 G input vibration. Also, the detailed analyses reveal that the two coupled generators operate in a complementary manner, maintaining a reasonable power output even when one generator suddenly degrades or fails. We finally demonstrate powering a commercial IoT sensor module with the hybrid energy harvester, receiving the sensed information to a smartphone via Bluetooth connectivity. Design principles for effective hybridization of two distinct energy harvesters are developed and demonstrated, powering an IoT sensor module. Image 1 • We establish the design principles for hybridizing two distinct energy harvesters. • Reducing mechanical damping while increasing electrical damping is critical. • We demonstrate piezo- and electromagnetic hybrid generator with 25 mW average power. • We demonstrate powering commercial IoT sensors with the hybrid energy harvester. [ABSTRACT FROM AUTHOR]