Here's a far-out idea: Stick an energy harvester inside a soccer ball so it stores power as the ball gets kicked.
This concept may sound a little wacky at first, but it has a practical application. A small start-up company called Uncharted Play in Wappingers Falls, N.Y. came up with what it calls the Soccket as a way to bring electrical power to remote locales that lack electricity. Kick the Soccket around for a half hour and you'll have enough juice to power an LED lamp for three hours. The LED plugs into the ball. Uncharted Play also says the Soccket can charge cell phones, a benefit in such places as far-removed African villages where cell phones are considered to be critical appliances.
Uncharted Play has two main pieces of intellectual property in the Soccket. One is the ball material itself which is constructed from a custom water-resistant EVA foam that is both durable and soft to the touch. The ball is rigid enough to function as a conventional soccer ball but it is not inflated. The second is a patented pendulum-like mechanism inside the ball that captures the kinetic energy generated during normal play.
The patent on the ball's pendulum mechanism recently issued. A look at it reveals some of the mechanics involved. The pendulum, weighing about 20 or 30 gm, basically spins a 6-V dc motor that functions as a generator. The motor is geared at 11:1 so it can spin fast enough to produce useful electrical current. Juice from the motor charges a 3.7-V 800 mAh lithium-ion battery. Total output is 6 W.
Even with all this gear inside the ball, Uncharted Play says the whole thing weighs only about one ounce more than a standard soccer ball. Moreover, the resulting ball behaves as though it's CG is at its center, judging by video on the Uncharted Play site.
The company is still in the money-raising mode and has a Kickstarter campaign underway.