Wave impact energy harvesting through water-dielectric triboelectrification with single-electrode triboelectric nanogenerators for battery-less systems

This paper evaluates the effect of water-dielectric interfaces for wave impact energy harvesting at low frequencies (0.7 Hz-3 Hz) on the output performance of Water-Dielectric Single Electrode Mode Triboelectric Nanogenerators (WDSE-TENG). The triboelectric effect is generated between water (with a net positive charge) and a hydrophobic dielectric layer (with a net negative charge). Different WDSE-TENG configurations were tested using distinct hydrophobic materials. The water-fluorinated ethylene propylene (FEP) combination resulted in the best output performance. On the contrary, an output performance reduction by a factor of 3.53 was measured with seawater-dielectric interfaces. This can be compensated by increasing the contact area, with the best performance obtained using silicone rubber compound (Acetoxy, Elastomer) utilizing a WDSE-TENG with two-dielectric layer configuration. Employing seawater as a triboelectric material, the highest electrical output power and power density of 79.18 mW and 0.344 mW/cm(2) was generated with a grid of WDSE-TENG, comprising five devices connected in parallel. The output voltage, current, transferred charge, stored energy and energy conversion efficiency (ECE) values of the grid of connected WDSE-TENG devices were compared against a single device. Such energy harvesters were able to power an ultrasonic range sensor and a one-way wireless transmitter for motion detection, distance measurement, and monitoring weather conditions. The stored energy and generated power were similar to 5.96 mJ and similar to 5.18 mW, respectively. Furthermore, the integration of the grid of WDSE-TENG with a power management control circuit (PMCC) is able to increase the output power and hence offer the potential to power up electronic devices with power consumption requirements between 1 mW and 100 mW. The results demonstrate that the grid of WDSE-TENG offers an innovative energy harvesting approach using water as a triboelectric material. The device can be used as an energy source for smart batteryless wireless sensing systems at water-structure interfaces in aquaculture (e.g. for fish detection or water level measurement) and weather condition monitoring.