One of the most extraordinary sources of electricity using astonishing features of carbon nanotubes has been developed by an international team of scientists from the University of Texas in Dallas and Hanyang University in South Korea.
Nanotubes and how they are used
Nanotubes are one of multimolecular structures in which carbon atoms may be arranged. They resemble hollow cylinders with a diameter 10,000 times smaller than a human hair. Nanotubes’ walls are made of graphene – one of allotrope forms of carbon. The most popular form is graphite, others include diamond, spherical fullerenes of various sizes and, finally, graphene, in which carbon atoms are arranged in a flat structure consisting of regular hexagons. The nanotube wall is rolled up graphene.
Scientists developed nanotube yarn, which, when put into an electrolyte and mechanically stretched or twisted, with each motion generates energy that may be harvested (hence the name “harvester”) as electric current. Such yarn, twisted 30 times a second, may provide power of about 250 W per kilogram. During experiments, a piece of yarn weighing less than a fly could generate, with every stretching movement, power sufficient to light up a single LED.
„We generate more power than any other harvesters ever before”, said the Dallas research team manager, Ray Baughman. He added that no other alternative source, developed over the past decades, has provided so much power and energy. „Just 31mg of carbon nanotube yarn harvester could provide the electrical energy needed to transmit a two-kilobyte packet of data over a 100m radius every 10 seconds”, stressed Baughman. For now, the nanotube harvester is, obviously, awfully expensive but its features pave the way for generating electricity from mechanical energy like sea wave motion. Such an experiment has already been conducted using a 10cm piece of yarn.
How it works
Nanotubes generate energy thanks to their unique features. Nanotube yarns are supercapacitors which, when put into an electrolyte, do not need any external electric field for charging. The electrolyte charges accumulate on the nanotube themselves. When the tube is twisted or stretched, its volume decreases bringing the charges on the yarn closer to one other. This increases their power which, as electric current, may be collected from the fibres or harvested like grain on a field. Afterwards, the cycle is repeated multiple times.