Keith Bradsher, The New York Times 2 Jul 09; DUNHUANG, China — As the United States takes its first steps toward mandating that power companies generate more electricity from renewable sources, China already has a similar requirement and is investing billions to remake itself into a green energy superpower. Through a combination of carrots and sticks, Beijing is starting to change how this country generates energy. Although coal remains the biggest energy source and is almost certain to stay