In California, three of the state's largest utilities have announced a handful of solar thermal projects that combined will almost meet state requirements for 3,000 megawatts (3 gigawatts) of renewable energy by 2016, Wachs says.

"You can get a big chunk of (power) from solar thermal, so it's a quick, easy way to meet your regulatory requirements," said the trade group's Judd.

Nevada Power, a unit of Sierra Pacific Resources SRP , is the biggest reason for solar thermal growth this year, thanks to its 63 megawatt plant that opened in June. It makes up 60% of Nevada's solar capacity, says Tom Fair, Sierra Pacific's executive for renewable energy.

"In order to make a dent (toward meeting alternative energy requirements), we have to bring in large-scale facilities," Fair said.

There are no publicly traded U.S. companies solely in the solar thermal plant business. There are a handful of privately held companies in this field. Also into solar thermal is one of the largest makers of renewable energy systems in the world: Spain's Acciona, a $9 billion firm publicly traded in Europe.

The company sells both PV and solar thermal technology, but it's made a bet on solar thermal plants for the U.S., says Peter Deprey, chief executive of Acciona Energy in North America.

"We see a lot of promise right now in solar thermal," he said. "I talk to a lot of utilities. They all want larger-scale plants."

Ausra, a Palo Alto, Calif., company that recently moved from Australia and landed $40 million in venture funding from Silicon Valley heavyweights Khosla Ventures and Kleiner, Perkins, Caufield & Byers.