The device contains two parts including a set of flat, spiral shaped coils which consists of three groups of coils with identical winding direction, connected in series keeping 1cm space between them. Each coil group consists of five layers of flat coils with a diameter of 25mm and 50 windings placed one onto another with an insulating layer in between. Planar coils are made of copper wire with a diameter of 0.22mm. The second generator part is a lightweight, small and strong neodymium (Nd) magnet with double magnetic field structure. The volume of the generator (coils + magnet) is around 4.8cm cubed and its mass 45g.
Due to the flat, spiral-shaped inductive elements, the natural motion of the jacket's sleeves are used to move a magnet along the coils (which are fitted near the jacket's side pockets) instead of the traditional "magnet inside a coil" motion. The team say that the energy harvester can be used as a mobile and ecologically clean source of energy which is easy to use and does not substantially change the visual properties of textile structures with its size or weight. The generator with the flat coil does not need extra room for magnet motion as it is located in a different part of the garment and therefore can be implemented in almost any garment.
The prototype was tested with the wearer walking at different speeds of 3, 4, 5 and 6 km/hr which, according to the researchers, corresponds to the slow, normal and quick walking of a middle-aged man. The researchers concluded that flat inductors for energy harvesting should be investigated and their prototype showed that the insertion of the coils was achieved without any deformation of the garment.
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