As any surfer will tell you, waves pack a powerful punch. We are now making great strides towards capturing energy from the incessant movement of the ocean, thanks to advances in “blue energy” technology. In a published study ACS Energy LettersThe researchers found that by moving the electrode from the middle to the end of the liquid-filled tube, where the water is strongest, they greatly increased the efficiency of collecting wave energy.

The tube-shaped wave energy harvesting device developed by the researchers is called liquid-solid triboelectric nanogenerator (TENG). TENG converts mechanical energy into electricity by moving water back and forth inside the tube. One of the reasons why these devices are not yet suitable for large-scale applications is their low output energy. Guozhang Dai, Kai Yin, Junliang Yan and colleagues aimed to increase the energy harvesting ability of a liquid-solid TENG by optimizing the position of the energy harvesting electrode.

Experiment and results

The researchers used 16-inch clear plastic tubes to create two TENGs. Inside the first device, they placed a copper foil electrode in the middle of the tube; this is a common arrangement in conventional liquid-solid TENGs. For the new design, they placed a copper foil electrode at one end of the tube. The researchers then filled the tubes one-quarter full with water and capped the ends. The wire connected the electrodes to the external circuit.

When both devices were placed on a tabletop swing, water moved back and forth inside the tubes and produced electrical currents, thus converting mechanical energy (friction from impacts or the sliding of water toward the electrodes) into electricity. Compared to the traditional design, the researchers found that the optimized design increased the device’s conversion of mechanical energy into electrical current by 2.4 times.

In another experiment, the optimized TENG switched an array of 35 LEDs on and off as water entered an electrode-covered section of the tube and then discharged accordingly. The researchers say the demonstrations lay the groundwork for harvesting blue energy from ocean waves on a larger scale and demonstrate their device’s potential for other applications, such as wireless underwater signaling.