President-elect Barack Obama will have a difficult time significantly increasing U.S. alternative energy production, outgoing U.S. Energy Secretary Samuel Bodman said Wednesday. As part of his economic stimulus plan, Obama wants to double output of alternative energy over the next three years, but “I think it's going to be extremely difficult to get there in three years,” Bodman said in a final briefing with reporters before he leaves office next week. Renewable energy sources, which include solar, wind, hydroelectric, geothermal, biofuels, and other biomass, accounted for 7 percent of U.S. energy supplies in 2007, according to the Energy Department. Bodman said increasing solar energy “would be easier” because there are more companies that make solar panels, while increasing wind power will be more difficult because of tight manufacturing capacity to build wind turbines. “I'm not saying you can't do it,” Bodman said of Obama's goal. “It depends on how much money you spend. We have spent a lot of money, but could you spend even more, and can you throw more [government] money at it? You could. I don't think it's wise, myself, because I think we're spending about at the rate which makes sense.” Steven Chu, Obama's nominee to be the next energy secretary, told a Senate committee on Tuesday he was committed to developing more renewable energy sources.