Figure 1. Design and boosting strategies of the MO-TENG.
Although the ocean covers more than 70% of the Earth and is home to countless undiscovered species while playing a critical role in regulating global weather patterns, humans have explored only 5% of its vast expanse. The shift in energy paradigms and the ongoing deterioration of Earth’s environment underscore the urgency for deeper oceanic resource utilization. In this context, IoT technology is indispensable for monitoring ocean conditions, mining ocean data, and ensuring reliable offshore and underwater communications. It serves as a cornerstone in the development of the smart ocean.
However, the marine environment’s complexity and the limited battery capacity pose significant power supply challenges for the numerous and widely distributed marine monitoring devices. Advancing ocean energy harvesting technology is crucial for ensuring continuous power to these devices. While offshore solar, wind, and temperature differential energies are viable, wave energy stands out due to its high energy density and broad distribution. Many developers designed wave energy harvesters based on electromagnetic techniques aimed at large-scale power generation. Nevertheless, these devices often struggle to capture small amplitude and random wave motions, and they typically face issues such as high cost, large size, and difficulty in deployment and management.
Triboelectric nanogenerators (TENGs), leveraging the coupled effects of triboelectrification and electrostatic induction, present a new approach to transduce mechanical energy into electricity. With their inherited characteristics, TENGs yield great output performance in low-frequency excitation (< 5 Hz) and are distinguished by their simple structures, low costs, high power densities, etc. Consequently, in recent years, researchers have dedicated efforts to employing TENG technology to capture low-frequency, low-amplitude wave energy. This application facilitates the realization of self-powered marine IoT monitoring nodes, enhancing the sustainability and autonomy of marine observation systems.
A TENG can generate a high output voltage under low-frequency excitations, though it is characterized by low current and high internal resistance. The contact-separation mode of TENG exhibits relatively lower resistance but is challenging to excite with wave motion. While the sliding mode TENG can achieve higher current output, it is prone to wear issues. Despite also facing challenges of low current and high internal resistance, the rolling mode TENG offers significant advantages, including substantial charge transfer and minimal wear between friction interfaces. Consequently, there is an urgent need to develop energy output enhancement strategies for the rolling mode TENG to boost its feasibility for serving marine self-powered nodes.
To solve the above issues, we propose a rolling-mode triboelectric nanogenerator, equipped with multi-tunnel grating electrodes and opposite-charge-enhancement (MO-TENG), for efficient wave energy harvesting, as illustrated in Figure 1. This innovative device delivers significant instantaneous and root mean square power densities of 185.4 W/(m3·Hz) and 10.92 W/(m3·Hz), respectively. Leveraging stacked MO-TENGs and a customized power management module, this system can directly power 120 LEDs and a commercial navigation light. Furthermore, a comprehensive self-powered ocean sensing system design enables the MO-TENG-based buoy to perform self-powered wireless water quality sensing. Laboratory and in-situ ocean tests were conducted to assess and validate the system. All the demonstration diagrams can be found in Figure 2.
Figure 2. Self-powered application demonstration of the MO-TENG.
The significance of this work:
The methods developed in this work significantly improve the output performance of the rolling mode TENG. Furthermore, the power management module and self-powered ocean sensing system were well-designed and prompt MO-TENG to serve in the ocean. The feasibility of self-powered marine IoT nodes using MO-TENG has been demonstrated across various application requirements and wave excitation scenarios. Notably, this research represents a leading instance in the field where successful deployment and operation in a real marine environment have been achieved, marking a significant advancement towards the practical application of TENG technology.
If you are interested in our work, please refer to the paper published in Nature Communications following the link: https://www.nature.com/articles/s41467-024-51245-5. You can also find more related research works through our Lab websites:
Smart Materials & Structures Lab@HKUST(GZ)
Marine Self-powered System Lab@DLMU