Do you know the power generating facility that is popular among children in Africa? It's a simple funny see-saw "the Energy-Saw."It generates electricity as a by-product of play. Approximately 10 minutes of average see-saw use can power two 11W appliances for 20-25 minutes.

PlayMadeEnergy

PlayMade Energy's mission is to bring renewable electricity to schools in the developing world through the fun of play.
The Energee-Saw is a simple and fun see-saw which generates renewable electricity as a by-product of play. Units containing wind-up technology also contain batteries which store the energy as it is produced whilst playing. These units can then be moved into the classroom or school office for low drain electrical appliances to be connected.