Boosting power output of flutter-driven triboelectric nanogenerator by flexible flagpole

One important component of Industry 4.0 is the Internet of Things (IoT) which links every “things” by distributed wireless sensor nodes (WSNs). Most sensor nodes are small in size, consume little energy and are adaptive to the environment. Small and local power generation is desirable for such WSNs, and harvesting energy from ambient wind is one of the potential methods. To harvest small-scale wind energy effectively, a promising device called flutter-driven triboelectric nanogenerator (FTENG) was lately developed, which converts kinetic energy in the self-fluttering motion of a flag to electricity. Many studies focused on material development to increase the surface charge density of the surfaces to enhance the energy output of FTENG, but few tried to enlarge the fluttering motion by considering the structural design. This study shows that by simply replacing the rigid flagpole in the FTENG with a flexible flagpole, the energy output is enhanced. The fluttering dynamics of the flags with rigid and flexible flagpoles was recorded by high-speed camera. It was found that when the flag was held by a flexible flagpole, the fluttering amplitude and the contact area between the flag and electrode plates were increased. The channel width, flag thickness, and flag length in relation to the voltage, current and power outputs were also investigated in this study. The greatest enhancement can reach 113 times when the wind velocity is 10 m/s. In a demonstration experiment, the device can light 254 LEDs and a temperature and humidity wireless sensor. In addition, the device has a stable output in a one-hour durability test. Comparing with other FTENGs from the literatures, our device has a lower critical velocity and a higher energy output. Besides, our design was integrated into other FTENG structures and got an enhancement of more than two folds in power density. This work demonstrates the use of a flexible flagpole to enhance the output performance of an FTENG by increasing the fluttering mechanical energy and increasing the contact area. Based on the performance obtained in this study, the improved FTENG has the potential to be applied in smart cities as a power source for IoT WSNs.