In early 2009, a Spanish solar power company will break ground outside the little town of Gila Bend, southwest of Phoenix, to build what will be the world's largest solar power plant. At maximum capacity, the Solana Power Plant will supply at least 70,000 households. The deal has been forged, but there's one possible glitch: The plant hinges on an extension of the federal solar investment tax credit, due to expire at the end of this year....