Images: Supersize solar power

Parabolic troughs, one of which is shown here, have been around for 25 years, and the technology will be around for at least another 25.

Parabolic troughs reflect sunlight to heat liquid carried through a tube above the troughs. That liquid is converted to steam, which drives a traditional electricity turbine.

One solar thermal power plant developer filed for bankruptcy in the early 1990s. But the technology is making a serious comeback. Building a solar plant in Arizona is cost-effective compared with a natural gas plant, said David Jallo, project head for the 280-megawatt Solana project at Arizona Public Service. At a recent Ceres conference, Jallo attributed this to solar costs going down, while costs of natural gas plants are going up.

These concentrating solar power plants are best suited for desert areas, like the southwestern U.S. and parts of Spain.