Normally when making an electrical system that relies on batteries, engineers create two parts, one to generate or bring in electricity from another source, and one to store the energy for doling out when needed. Because of the inherent inefficiencies in such a system, a group of engineers have invented a new kind of electronic device that both creates electricity and stores it. The team from Georgia Tech describes their device in their paper published in the journal Nano Letters. In it, the team as Zeit News describes, used several different divergent technologies to create a device that may soon serve as the basis for most hand held electronics, such as phones and tablet computers.
The idea, Zeit News says, was to figure out a way to capture what they describe as naturally occurring energy, such as that used by people when walking and then to hold it in the same device. To do that, the team implemented a piezoelectric device that creates electricity from simple movements, in this case, the motion of a foot moving up and down when a person walks. That motion causes a coil to be moved back and forth through a small magnet field which is how electricity is generated. To make it happen in practice, they took one of the coin sized batteries typically used in watches and reworked the electronics that allow it to move electrons in and out, adding the piezoelectric device in between the electrodes. In so doing, electricity that is generated moves directly to the storage part of the battery where it is held until needed. When that times comes, it then moves out from the opposite electrode just as it would were it a normal battery.
To test the device, the team says in their paper, they simply attached the device to the bottom of a shoe, put the shoe on a foot and started walking. They found that the up and down movement provided more than enough energy to keep the battery fully charged as they walked.
Zeit News says that rather than having to move from mechanical to electric to battery the new device allows for direct mechanical to battery translation of energy, making the system nearly twice as efficient as traditional systems, and what’s more, does so at less cost. The only down side to the system is that no energy is created and stored when the person is not walking, but the team says they are working on a solution for that by perhaps using the energy created when a person breathes causing their chest to expand and compress.