Federal support might turn green energy companies suddenly profitable, but after decades of losses, you should be skeptical of that. Renewable energy stocks surged higher Tuesday after Plug Power (PLUG 20.24%) announced receipt of a $1.66 billion loan guarantee from the U.S. Department of Energy. Plug currently has two hydrogen fuel facilities producing at full capacity, with a third approaching that mark. Plug says the government assistance will help it to "finance the development, construction, and owners ...