Hybrid Piezoelectric Power Cell Converts and Stores Energy

A new self-charging power cell technology developed by scientists at the Georgia Institute of Technology (Georgia Tech; Atlanta) directly converts mechanical energy to chemical energy. Then, the power is stored until it is needed to generate electricity. Although the technology is supported by such military institutions as the Defense Advanced Research Projects Agency (DARPA) and the U.S. Air Force, it is not difficult to imagine that it could eventually be used in such medtech applications as miniature implantable devices and handhelds.

The new hybrid generator-storage cell utilizes mechanical energy more efficiently than systems using separate generators and batteries because it eliminates the need to convert mechanical energy to electrical energy for charging a battery. The cell is based on a piezoelectric membrane that drives lithium ions from one side of the cell to the other when the membrane is deformed by mechanical stress. By means of an electrochemical process, the lithium ions driven through the polarized membrane by the piezoelectric potential are directly stored as chemical energy. The source of mechanical energy can be as simple as shoes striking pavement, which can generate enough electricity to power a small device such as a calculator.

"People are accustomed to considering electrical generation and storage as two separate operations done in two separate units," remarks Zhong Lin Wang, a Regents professor in the School of Materials Science and Engineering at Georgia Tech. "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."

Thus far, Wang and his team have built and tested more than 500 power cells. The generator-storage cell, he says, will be as much as five times more efficient at converting mechanical energy to chemical energy as a two-cell generator-storage system. "One day we could have a power package ready to use that takes advantage of this hybrid approach," he adds. "Almost anything that involves mechanical action could provide the strain needed for charging. People walking could be generating electricity as they move."

For more information on this technology, visit the Georgia Tech Newsroom.