The Korea Advanced Institute of Science and Technology (KAIST) announced on January 18 that its research team led by professor Choi Yang-kyu developed a triboelectric energy harvester which allows electricity to be generated when a simple electrode is attached to a plastic container and the container is filled with water and shaken. The triboelectric nanogenerator is a generator that produces electricity by means of the friction between the water and the surface of the container.
These days, researchers around the world are working on energy harvesters using kinetic energy, which are roughly divided into piezoelectric ones that convert pressure to electricity and triboelectric ones that use the frictional static electricity between a polymer film and a metal surface. The former require special dielectrics and processes, which result in higher costs, while the latter are limited in durability and efficiency due to friction and wear and power generation allowed only in certain directions.
However, the research team succeeded in addressing both of the problems at the same time by covering the top and bottom surfaces of a cylinder formed of PTFE with aluminum plate electrodes and causing electricity to be generated when the water in the cylinder is shaken. “This device uses the friction between the water and the container surface, and thus is much more durable than existing devices based on the friction between solid surfaces,” professor Choi explained, continuing, “In addition, it has a higher level of power generation efficiency because it generates electricity by means of motions in all the directions in which the water is shaken.”
He added, “We tested this device by using a water bottle which is 5.5 cm in diameter and 12 cm in length and shaking the bottle five times a second and found that it generated electricity with a voltage of 22 V and a maximum current of 1.45 mA, which is enough to run a light-emitting diode and charge an electric condenser.” The professor mentioned that the device is very easy to make at a cost of less than a dollar per unit, and thus can contribute to power supply problems in less-developed countries and regions. Details of the research are available on the October 2015 edition of the Nano Energy journal.