Generating power for developing nations could be child’s play — literally — according to an engineering professor at the University of Michigan. Raj Pandian has proposed harnessing the energy from playground equipment (such as teeter-totters, merry-go-rounds, and swing sets) in Third World villages, then using it to power light bulbs, radios, sewing machines, telephones, and other useful electronics. The energy generated by the repetitive motion of the playground equipment would be stored in batteries, a technique that has proved successful in Pandian’s laboratory models. The professor’s idea is one of a series of projects seeking to tap into “people power” to provide electricity to the 40 percent of the global population that lacks reliable energy sources.