A water tube-based triboelectric nanogenerator (TENG) designed at City University of Hong Kong transforms irregular and low frequency mechanical energy, including ocean wave energy, into electricity.

The applicability of TENG technology is challenged by the need to maintain solid-to-solid contact of two tribo-materials; the resulting friction can degrade material surfaces and reduce system efficiency. Such Multiple TENG units can be integrated to increase electricity output. Source: City University of Hong KongMultiple TENG units can be integrated to increase electricity output. Source: City University of Hong Kongsolid-to-solid-based TENGs also require shell structures and mechanical components like rotors, holders and springs to harness random vibration energy, adding complexity to energy-harnessing designs.

The solution described in Advanced Energy Materials encapsulates water in a finger-sized tube. The triboelectrification process generates electric currents as water travels in the tubes between two electrodes. The device can be operated in rotation, swing, horizontal and other linear modes to tap energy from diverse mechanical movements in the environment, such as ocean waves, wind, body and vehicle movements.

The high contact intimacy of water and the tube surface improves the output volumetric charge density of the TENG, which was documented to reach 9 milliColoumbs/m3 at a frequency as low as 0.25 Hz. The researchers demonstrated a system with 34 TENG units designed to collect ocean wave energy, as well as a wristband housing 10 TENG units. The peak power generation of both systems was sufficient to power 150 LED light bulbs.

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