President Barack Obama's trip to California is aimed at boosting clean energy, but might have a backlash from labor unions.  

Obama spoke today at a Walmart in Mountain View to highlight the fact that the retail giant has a goal of using energy sources that are 100 percent renewable.  

However, Walmart has also been sharply criticized for low wages and focusing on hiring part-time workers rather than creating full-time positions.  

One Walmart employee wrote in "Salon" that she hoped Obama would tell the company to pay its employees enough to pay the bills and take care of their families.