Self charging power cell converts and stores energy in a single unit

By eliminating the need to convert mechanical energy to electrical energy for charging a battery, the team at the Georgia Institute of Technology says the new hybrid generator storage cell utilises mechanical energy more efficiently than systems using separate generators and batteries. The cell uses a piezoelectric membrane that drives lithium ions from one side of the cell to the other when the membrane is deformed by mechanical stress. The lithium ions driven through the polarised membrane by the piezoelectric potential are directly stored as chemical energy using an electrochemical process. By harnessing a compressive force, such as a shoe heel hitting the pavement from a person walking, the power cell generates enough current to power a small calculator. The researchers say that a hybrid power cell the size of a conventional coin battery can power small electronic devices and could have military applications for soldiers who might one day recharge battery powered equipment as they walk. "People are accustomed to considering electrical generation and storage as two separate operations done in two separate units," said Zhong Lin Wang, a Regents professor in the school of materials science and engineering. "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 team estimates that the cell will be up to five times more efficient than a two cell generator storage system and could also reduce the weight and space required by separate generators and batteries. "One day we could have a power package ready to use that takes advantage of this hybrid approach," Wang said. "Almost anything that involves mechanical action could provide the strain needed for charging. People walking could be generating electricity as they move."