SolFocus has raised an additional $19.28 million, bringing the total Series C round to $66.78 million.

SolFocus, based in Mountain View, Calif., announced last month that it had raised $47.5 million as the first close for Series C. Back then, the company said the total round would be between $60 million and $70 million. Private Equity Hub reported the new, $19.28 million funding Monday based on SolFocus's regulatory filing with the U.S. Securities and Exchange Commission. UPDATE: A SolFocus spokeswoman said the company has raised only $47.5 million for Series C, so there isn't an additional $19.28 million.

Apex Venture Partners, New Enterprise Associates and NGEN Partners are among the investors. With $47.5 million in Series C, SolFocus has raised $143.1 million since inception, according to its Website. 

The startup has developed the concentrating optics technology that collects and focuses sunlight onto solar cells for electricity production. But it generates revenues by installing systems it assembles for solar project developers.

Each system is consisted of a solar panel containing the concentrating optics and solar cells made by others. The panels are mounted on trackers that tilt the panels at different angles throughout the day to face the sun.

SolFocus has said it wants to increase the installation of its systems from 0.5 megawatts in 2008 to 100 megawatts by the end of 2010.

SolFocus recent signed contracts with two new customers. The deal with EMPE Solar calls for developing 10 megawatts worth of systems in Spain. The contract with the Samaras Group involves installing 1.6 megawatts worth of systems in Greece.

Concentrating solar technologies became attractive a few years ago when silicon shortage began and its prices shot up. But silicon prices are falling quickly as more silicon makers bring new factories online.

Concentrating solar companies also must contend with the emergence of solar-thermal technologies, which use the sun's heat to generate electricity. Greentech Media analyst Eric Wesoff has described concentrating solar players as being "stuck in the middle between the rapidly commodifying silicon solar market and the well-financed, high-output concentrated solar thermal market" (see Wesoff's primer on concentrating solar: CPV, Part 1, CPV, Part 2, CPV, Part 3 and CPV, Part 4.).

SolFocus already has to compete against a slew of startups within the concentrating solar field, such as GreenVolts, Covalent Solar and Skyline Solar. 

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