Electronics - Energy

Using Raindrops to Power Wearable Electronics

Researchers from the University of Science and Technology Beijing report a wearable self-cleaning/charging power system (SPS) that can harvest electrical energy from falling raindrops.

Wearable and portable electronics require stable, sustainable sources of energy for continuous operation. Harnessing renewable energy to meet these requirements is appealing from an environmental perspective, and raindrops contain a large amount of mechanical energy that could potentially be used for this purpose.

The hydraulic triboelectric nanogenerator (H-TENG) is promising for wearable applications but generates AC current, which is not suitable for devices that require continuous power input. Integrating the H-TENG with a supercapacitor (SC), which can store energy in a safe and efficient way, offers a potential solution. Furthermore, designing a device that has built-in resistance to contaminants is essential in order to prevent performance degradation.

In their article in Advanced Functional Materials, Q. Zhang, Prof. Q. Liao, Prof. Y. Zhang, and co-workers from the University of Science and Technology Beijing report a wearable self-cleaning/charging power system (SPS) that can convert and store electrical energy from falling raindrops.

Structure of the SPS.

The SPS is composed of an H-TENG having four embedded fiber supercapacitors (FSCs) with a hematite (α-FeY2O3) on reduced graphene oxide (RGO) composite as the active material. The surface of the SPS contains many nanoscale-sized pores and particles, rendering it amphiphobic and repelling water, mineral oil, ethanol, gasoline, and other liquids.

When falling, positively charged water droplets interact with the H-TENG surface, charges of opposite polarity are induced on the two electrodes, driving free electrons to flow from electrode A to B until equilibrium is reached. As the droplets continue to slide down the surface, free electrons flow from electrode B to A until the charge is reversed. Stable electrical input can be generated if the water droplets continuously fall on and off the H-TENG.

For practical demonstration, the SPS was incorporated into a raincoat. After charging to 4 V by showering with water for 100 seconds, an LED worn on the chest of a raincoat could be powered for over 300 seconds.

 

To find out more, read the article here.

H-TENG operating principle.

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