Renewable energy technologies generally consist of two distinct processes: energy generation (using sources such as coal, solar, wind, etc.) and energy storage (such as batteries). These two processes are always accomplished through two separate units, with the first process converting the original form of energy to electricity, and the second process converting electricity to chemical energy. Now for the first time, engineers have demonstrated that energy can be generated and stored in a single device that converts mechanical energy directly to chemical energy, bypassing the intermediate step of electricity generation. The device basically acts as a hybrid generator-battery unit, or in other words, a self-charging power cell.
Read more at: http://phys.org/news/2012-08-self-charging-battery-energy.html#jCp