Systems that convert kinetic energy into electric energy have made great strides in recent times, from mobile phone charging bicycle dynamos to tiles that turn footsteps into electrical energy.

Recently researchers at Georgia Institute of Technology have come up with what they believe is a more efficient approach. They have developed a self-charging power cell that directly converts mechanical energy to chemical energy. The cell stores the power until it is released as an electrical current. By creating a generator-storage cell, they have eliminated the need for systems using a separate battery or generator, reducing the amount of weight and space normally required to accommodate devices for generating, storing and delivering energy for people on the move.

Zhong Lin Wang, a Regents professor in the School of Materials Science and Engineering at the Georgia Institute of Technology, claims that the generator-storage cell will be as much as five times more efficient at converting mechanical energy to chemical energy as a traditional two-cell generator-storage system.

“People are accustomed to considering electrical generation and storage as two separate operations done in two separate units,” he says. “We have put them together in a single hybrid unit to create a self-charging power cell, demonstrating a new technique for charge conversion and storage in one integrated unit."

The power cell consists of a lithium-cobalt oxide (LiCoO2) cathode and a titanium dioxide anode (TiO2 nanotubes) separated by a PVDF film. When pressure is applied to the cell, the PVDF generates piezoelectric voltage, driving the lithium ions in the electrolyte from the cathode to the anode thereby charging the cell.

The system could be used to convert mechanical energy from walking, from the tires of a vehicle, from ocean waves or from mechanical vibrations.

One obvious application is in the military, where soldiers could use the system for recharging battery-powered equipment as they walk. This is why the project has the backing from the Defense Advanced Research Projects Agency (DARPA), the US Air Force as well as the US Department of Energy, the National Science Foundation, and the Knowledge Innovation Program of the Chinese Academy of Sciences.

Source: Georgia Tech

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