[BusinessWeek] John O’Donnell started thinking about saving the world 30 years ago. In his first job, in the late 1970s, he worked to harness fusion–the nuclear reaction that powers the sun–at Princeton University’s famed Plasma Physics Lab. “The sense was, if it was successful it would change the world,” O’Donnell recalls. It wasn’t successful. O’Donnell moved on. Over the years, he started companies that made supercomputers and semiconductors. He lived out of suitcases, raised scores of millions for his companies, and had three kids. But when his Campbell (Calif.) chipmaker was sold and its operations moved to Shanghai last year, the recently divorced O’Donnell jumped off the roller coaster. “I told myself: ‘I have a year to figure out if there is something I could do that would be of use,” he says. He’s convinced he has found that something. The idea is to slow global warming and cure the planet’s energy woes, not with plasma or windmills or “clean” coal smoke, but with mirrors.