Images: Supersize solar power

The troughs have a mounting system that moves from east to west during the day to face the sun and maximize light intake.

Arizona Public Service is building a solar power plant using solar troughs from Spanish solar company Abengoa. The Solana project will use more steel than the Golden Gate Bridge and take up 3 square miles.

There are several other alternatives in concentrating solar power, where heat makes steam to turn a turbine. But if you look at the pipeline of planned projects, parabolic troughs dominate, said Reese Tisdale, an analyst at Emerging Energy Research. "Parabolic troughs are the technology du jour. It is not going away."