Chances are you've heard of hybrids and biofuels, but what about oil-producing yeast and turbinelike buoys that transform ocean waves into electricity? Those are just a few of the alternative-energy sources that may power the future, according to Fred Krupp, president of the Environmental Defense Fund and coauthor, with Miriam Horn, of "Earth: The Sequel" (Norton). "Everyone knows the current story of melting glaciers, rising sea levels, worsening hurricanes, dying coral reefs," says Krupp. " 'The Sequel' is the story of what happens next. We are just on the threshold of a great race." Solar-power technology is our best bet for now, says Krupp, but quirkier projects are essential elements of a smart, diversified energy strategy. New technologies might turn wood and fiber