Hybrid Triboelectric–Electromagnetic Nanogenerator Based on a Tower Spring for Harvesting Omnidirectional Vibration Energy

Vibration is one of the widespread phenomena in our surroundings, and a lot of research has been conducted to harvest it; however, due to its low frequency and random directions, there are few solutions to achieve omnidirectional energy harvesting. Based on a tower spring, this paper proposes an omnidirectional hybrid triboelectric–electromagnetic nanogenerator (OD-HNG) to harvest the omnidirectional vibration energy. The triboelectric nanogenerators (TENGs) are designed into a multilayered structure to enhance space utilization, and the electromagnetic generator (EMG) unit is hybridized to increase the output of OD-HNGs further. Benefiting from the design of the tower spring, the OD-HNG can respond to the external excitation in both vertical and horizontal directions, and its operational bandwidth is extended, allowing it to perform omnidirectional and broadband vibration energy harvesting very effectively. When OD-HNG is installed on a bicycle at a regular riding speed, a 1000 μF capacitor can be charged to 1.75 V in 20 s and has been successfully used as the power supply of portable electronic devices, ambient temperature monitors, and self-powered systems. More significantly, by harvesting the vibration energy from the vehicle-mounted environment, the OD-HNG can power portable electronic devices and environmental sensors continuously. These characteristics show that the tower spring-based OD-HNG is capable of very effective omnidirectional and broadband vibration energy harvesting and provides a good candidate for harvesting low-frequency vibration energy on a large scale.