He was a junior in high school when the routine shower generated his first thoughts about harnessing the power of magnets to propel cars and trucks in a more fuel-efficient way. Before going to bed, he sketched out a few rough ideas. Gonzalez, now 21, has since turned that idea into a proposal that last week netted him the $100,000 first-place award in the ConocoPhillips Energy Prize competition, which offered cash to aspiring young entrepreneurs with ideas about energy-conserving technology. In the typical motor vehicle, Gonzales said, just 20 percent of the energy generated by the engine actually makes it...