New nanogenerator harvests energy from raindrops, waves

BEIJING, April 1 (Xinhua) -- Hydropower is a significant source for generating electricity, but the mechanical Energy from the water system is far from those in giant dams. Scientists have developed a new type of triboelectric nanogenerator to harvest Energy from raindrops and waves.

In 2012, the triboelectric nanogenerator (TENG) was developed as a new power-generation technology to convert various mechanical Energy from the living environment into electricity, based on the coupling between triboelectric effect and electrostatic induction.

When a raindrop or wave impacts a surface, it produces a perfectly inelastic shock. The amount of Energy generated by the impact can be estimated with a mechanical-electric model.

For instance, when a raindrop impacts a polymer interface, the polymer starts to vibrate and electrodes embedded are used to recover the electrical charges generated by the vibrations.

In the new study published on the Beijing-based National Science Review, scientists from the City University of Hong Kong, University of Science and Technology of China, East China Normal University and other research institutions said the main bottlenecks to harvest such water Energy are the fast degradation of the interface material under harsh environments like high humidity, low temperature and submerged conditions.

When TENG is used for wave Energy harvesting, for instance, groups of microorganisms may form a biofilm on the interface under the submerged condition and lower the electricity generation efficiency.

The researchers said they developed a new type of nanogenerator with a slippery and configurable liquid layer called SLIPS-TENG.

SLIPS is a type of surface based on microstructured porous material infused with a lubricating fluid. From bacteria and water to oil and dust, the SLIPS surface is exceptionally repellent to any fouling challenge a surface may face, and it is self-cleaning.

Compared with conventional Teng designs, the researchers found that the slippery liquid layer significantly increases electricity generation capability of TENG.

For instance, SLIPS-TENG device with free-falling water droplets can light up bulb arrays at both 25 degrees Celsius and -3 degrees Celsius, whereas there is no obvious lighting at -3 degrees Celsius for devices with conventional designs.

The researchers said the marriage of SLIPS and TENG provides new perspectives on the design of blue Energy devices and can also be extended to various wearable and flexible devices.