Instead of generating complaints, rainy weather could one day be generating electricity, according to researchers at the National University of Singapore, who have demonstrated that droplets falling through a tube can light up 12 LEDs.
Their study, funded by the Singaporean Ministry of Education, the Agency for Science, Technology and Research, and the Institute for Health Innovation & Technology was published in ACS Central Science journal, explains how they harnessed a principle known as “plug flow” by allowing water to flow from a tower through a metal needle into a narrow tube in short bursts. This caused the droplets to form short columns of water separated by air pockets.
Materials coming into contact with each other can gain or lose their surface charges – witness the way rubbing a balloon on one’s hair creates “static electricity.” So, as the spurts of water and air then passed through the 32-cm tall, 2mm-wide vertical polymer tube and against its conductive inner skin into a cup positioned below, the unbalanced electrical surface charges separated and were harvested by wires.
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The experiment managed to convert more than 10% of the energy of the water falling through the tubes into electricity – a far more efficient result than previously thought possible. What’s more, that positive result was produced in conditions where the droplets were flowing far more slowly than rainfall, leading the researchers to hypothesise that a rainfall system could generate even more energy, even more efficiently.
Taking things a step further, the chemical and biomolecular engineers then tried sending the water through two tubes, both simultaneously and sequentially, and were able to double the energy output. This led them to try chanelling the water through four tubes, via which they successfully powered 12 LEDs (light-emitting-diodes) for 20 seconds.
While the idea of hydroelectricity usually conjures images of gigantic, costly, and sometimes damaging infrastructure such as damns, water turbines, and power plants, along large bodies of water like rivers, the Singapore team has proven a process that indicates clean and renewable electricity could be generated from much smaller amounts of water – even raindrops. It’s a more human-sized technology that could be installed in urban locations, such as in the roofs of dwellings and other buildings, they point out.
“The setup is simple; no equipment is needed,” the researchers explain. “Hence, it is inexpensive and environmentally friendly to install, operate, and maintain,” and they add: “scaling up can be achieved readily in three dimensions for large-scale harvesting of energy from nature. It can be used anywhere, including in urbanized areas.”
