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Science/Tech See other Science/Tech Articles Title: New Way to Generate Electricity From Rain Can Power 100 LED Bulbs Per Drop Tapping into the water cycle and generating electricity from rainy days could be one way to grow our renewable energy use. Until now, scientists have been unable to get water droplets to produce a significant amount of power - but we may finally have a breakthrough. While we're still a long way from umbrellas that double up as generators, the latest approach shows there might be a way to get power from rain showers at a level of efficiency that makes these systems practical. New research has found a method that could generate enough power from a single droplet of rain to light up 100 LED bulbs. That's a big jump forward in efficiency, in the region of several thousand times. "Our research shows that a drop of 100 microlitres of water released from a height of 15 centimetres [5.9 inches] can generate a voltage of over 140V, and the power generated can light up 100 small LED lights," says biomedical engineer Wang Zuankai from the City University of Hong Kong (CityU). That sounds like a surprising amount of voltage, but the engineers used some ingenious tricks to make it happen. Scientists have been looking into this type of power production for years, but the physics of converting the energy of raindrops into electricity are much harder to do than harvesting the energy from a rising tide or a flowing stream. One of the improvements the team built into their droplet-based electricity generator (DEG) was the use of a polytetrafluoroethylene or PTFE film, which is able to accumulate a surface charge as it's continuously hit by water droplets, until it gradually reaches saturation. The team found that as water droplets hit the surface and spread out, the drops act as a 'bridge' that connects two electrodes: an aluminium electrode and an indium tin oxide (ITO) electrode (with the PTFE on top). rain 2(Wanghuai et al., Nature, 2020) The droplet bridge in turn creates a closed-loop surface so that all of the collected energy can be released – droplets act as resistors, and the surface coating acts as a capacitor. This approach could eventually be applied anywhere that water hits a solid surface, the researchers say – the hull of a boat, the inside of a water bottle, or the top of an umbrella. "The significance of this technology is the much enhanced electric power per falling rain droplet, which makes the device much more efficient to convert energy from a falling droplet to electricity," chemist Xiao Cheng Zeng, from the University of Nebraska-Lincoln, told Sarah Wells at Vice. There's plenty of work still to do to get this ready for practical use however, with the researchers hoping to have a prototype ready in the next five years. The research has been published in Nature. Post Comment Private Reply Ignore Thread Top • Page Up • Full Thread • Page Down • Bottom/Latest Begin Trace Mode for Comment # 2.
#1. To: Horse (#0)
But not for very long. That water droplet's velocity after falling 15 cm is going to be about 1.7 m/s, and its kinetic energy is going to be about 144 microjoules. So even if Dr. Zeng could harvest all of the droplet's energy (impossible), and each of his 100 LED lights is a small single diode requiring say 10 mA at a forward voltage of 2 V, then his water droplet would power those lights for only about 72 microseconds. But if for his 100 LED lights he's talking about a typical screw base LED light bulb like you'd use in your kitchen -- say 10 Watts each -- then the on-time drops by a factor of 500 to only 0.14 microseconds. Don't blink.
Good advice. ;)
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