Solar concentrators seem perpetually to be the zero-billion-dollar market in green technology, but times are changing.

Soliant, which spun out of Caltech, has come out with a new version of its concentrator/PV module system that it says can deliver power for "the lowest price per kilowatt hour for commercial rooftop installations," or 8 cents per kilowatt hour.

The new product, the SE-1000x, contains eight solar modules per tracking panel and can deliver up to 504 watts of power. The earlier version, the SE-500, contained six modules. Soliant's system actually combines two concentrators and relies on a somewhat exotic III-V materials solar cell, not a crystalline silicon cell. The SE-1000 concentrates sunlight 1,000 times. The old one concentrated it 500 times. A tracker to more accurately aim the system at the sun is also part of the package.

Like Solyndra and some of the PV/solar thermal products, Soliant does not make a one-size-fits-all module. Instead, the company's system is designed for flat, commercial roofs, and in particular, the flat commercial roofs in sunbelt regions like Arizona, New Mexico, Israel, Italy and Spain. Soliant estimates that there are five million rooftops in the U.S. alone that could generate 500 megawatts of power. Total power output is important in this market because of the limited real estate. A standard solar panel will produce 300 watts or less of peak power.

If I were Tom Friedman, I'd sum up this trend toward solar panel diversity, which started back in early 2009, in a quaint catchphrase. A solar panel for every rooftop and a rooftop for every panel. Too wordy. Sol-tastic. Well, you get the idea. Keep your eye on it. Diversity is the future.

The big problem for concentrators, however, has been the continual, relentless decline in price of both crystalline silicon and cadmium telluride solar modules. The rapid price cuts in 2008 and 2009 put the concentrator mark into the deep freeze. While prices are still declining, they aren't declining as fast, giving breathing room to concentrators. Another positive factor: solar module makers will increasingly have trouble squeezing efficiency gains out of their products. Concentrators give them a path, potentially, to boost power output more rapidly with less cost.

The company is run by Terry Bailey, who took on the CEO job almost exactly a year ago. Before that, Bailey worked at Evergreen and Apple. Rockport Capital, Nth Power GE Financial Services and others have invested in the company.

Expect to hear more about concentrators at Solar Power International, kicking off today. Both SolFocus and Solaria will be making presentations, among others.