Maybe concentrators are no longer the Rodney Dangerfield of solar.

Congentrix Energy announced today that it would build a 30-megawatt solar park for a division of Xcel Energy in Colorado. While solar parks of this size are becoming somewhat common, this deal is unusual in that the field will be composed of multi-junction solar panels combined with concentrators and trackers from Amonix.

That makes it the largest concentrator deal on the market. And more may follow. In April, Amonix raised $130 million.

Concentrators essentially employ lenses (like the Fresnel lens in Amonix's system), mirrors, trackers (which move a solar panel with the sun) and other technology to artificially increase the amount of light that strikes a set of panels or cells. The more light that strikes a solar panel, the more energy it will produce. Concentrated PV systems in a way are light-concentrated solar thermal power plants, but instead of concentrating heat, they concentrate light.

The cells inside the panels used for concentrator systems are often composed of layers of various materials (the multi-junction part). These panels can convert 30 percent or more of the light that strikes them into electricity. Amonix says its panels are 32 percent efficient and contain cells that are 39 percent efficient. The absolute record for efficiency belongs to a cell constructed of multiple layers of silicon, gallium and indium at the University of New South Wales, sporting 43 percent efficiency. Conventional crystalline silicon cells can convert up to 23 percent of the light that strikes them into power and may top out at 25 percent.

More power and higher efficiency -- what could go wrong? Cost. Many concentrator companies were formed in the early part of the decade in the middle of a silicon shortage. The shortage ended, Chinese module makers came on the scene to drastically cut the cost of solar, and concentrator deals dried up. Those multi-junction cells aren't cheap either -- cost explains why most of them get consumed in aerospace.

Like fuel cells, concentrators remain a zero-billion dollar industry.

But things have been picking up. Worldwide, Amonix, for instance, has installed 14 megawatts' worth of capacity. "Amonix is the only company that has more than a few years of on-the-ground performance data. Their product reflects the learned reality that CPV as a utility-scale product shouldn’t try to look, smell or feel like PV (SolFocus) or attempt to minimize installation resources or cost (GreenVolts). They don’t try to hide the cranes and large equipment needed to construct their systems. They also spin/track ten times the kilowatts per unit compared to any of the other CPV competitors," a consultant told us recently.

SolFocus, a company known for dramatic ups and downs, said recently that it would have 10 megawatts in the ground by the end of the year.

Concentrix Solar, German-based CPV vendor, funded by Good Energies and recently purchased by Soitec, just announced the opening of a U.S. office, added more people, and celebrated a CEC listing.

Meanwhile, Solaria -- which specializes in low concentrating technologies -- raised $45 million and hired Dan Shugar as CEO.

And you may see SunPower champion concentrators. CEO Tom Werner told us that the company is looking at concentrators as a way to get around the looming 25 percent wall in crystalline efficiency. Skyline Solar has also made headway with a concentrator made from comparatively inexpensive sheet metal stamped at a Mexican auto plant.

The future is by no means guaranteed. Cost remains the ruling fact of life in solar and concentrators add cost. The technology also only makes sense in particular geographies and circumstances. Banks also remain reluctant to fork over cash for projects that rely on untested technologies, with "untested" meaning anything that hasn't been field tested for 15 years.

But compared to a year ago, this looks like a world of opportunity.

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Eric Wesoff contributed to this story.