Obama plays football with energy-generating ball
2 July 2013 Last updated at 19:29 BST
During the final day of his three-country tour of Africa, US President Obama made time to fit in a kickabout with an energy-generating football.
The "socketball", the idea of two Harvard students, converts the kinetic energy of the ball's movement into stored electrical energy, and just half an hour's play is apparently enough to provide hours of light.
Tom Esslemont reports.