Semprius, a developer of concentrating photovoltaic (CPV) systems, raised $20 million of a $30 million venture round led by Siemens Venture Capital along with existing investors Arch Venture Partners, Applied Ventures, Illinois Ventures, Intersouth Partners, In-Q-Tel, and GVC Investment as per SEC documents.

The funding will go to establish a 5-megawatt pilot plant expandable to 35 megawatts, according to the company in an email statement to Bloomberg.  Siemens owns a 16.1 percent stake in Semprius.

Semprius has a core semiconductor technology the firm believes can make CPV more competitive.

Semprius and the CPV industry has its work cut out for it.  The flat plate photovoltiacs (PV) industry has grown at a compound annual rate of about 41 percent per year for the last decade to reach its current 2011 shipment pace of 20 gigawatts. And the price of c-Si solar continues to fall every calendar quarter. GTM Research has recently published a detailed analysis and forecast on the CPV market.

Still, CPV has shown some life of late -- led by Amonix, Soitec, and SolFocus winning utility-scale contracts in high-DNI regions.

Ben Kortlang, a partner at Kleiner Perkins and investor in Amonix, claimed that CPV from Amonix "is cheaper than First Solar."  First Solar is currently at about $0.75 per watt with their thin-film solar panels, so those are bold words from KP.

Spun out of the University of Illinois and founded in 2005, Semprius raised a $4.7 million round A in 2007 and won an additional $7.9 million round in 2009.

The 30-employee firm aspires to be a vertically integrated manufacturer of high-concentration PV panels using their own gallium arsenide (GaAs) micro-transfer printing-based chips while selling the panels to system integrators for mounting on 2-axis trackers.

Semprius does its own cell design and outsources the epi. Their micro-transfer printing technology allows the firm to reuse the GaAs substrate rather than shipping the expensive substrate out the door with every cell. Semprius claims that by reusing the substrate, they can reduce the cost by fifty percent.  The cell structure is grown on top of a release layer so that the cells can be epitaxially lifted off as part of the micro-transfer printing process.

The Semprius GaAs double-junction cells measure 600 microns by 600 microns -- 300 times smaller than the standard industry cells, which in turn results in fewer defects, better quality, and the use of less current and therefore less heat through the cell, according to Bob Conner, the VP of Photovoltaics at Semprius. Smaller chips also mean smaller optical elements and simpler optics, as well as a smaller module size.  Less heat means that Semprius can dispense with the heat sinks and heat spreaders used by the majority of CPV players.  Conner hails CPV as having the highest conversion efficiency, lowest temperature degradation and the highest capacity factor of all solar power technologies.

Semprius claims a 32 percent efficiency at 1,000 suns for their double-junction cells. A silicone-on-glass lens array concentrates the sunlight onto a small glass ball lens, which illuminates the microcell and provides a +/-0.8 degree angle of acceptance at 1000x concentration. 

Semprius deployed one of their systems at Tucson Electric Power (TEP) in August of last year using their modules and an automated solar tracking system developed by Siemens. The tracker, which uses a Siemens automation system and NREL’s Solar Positioning Algorithm, provides a tracking accuracy of better than 0.2 degrees.
In order to be successful, Semprius needs to be better than all other HCPV companies and comparable to the very best wafer silicon and thin-film module companies.  At the rate costs are dropping for silicon solar panels, that is a very high hurdle. Semprius also competes against triple-junction chip firms Emcore, Spectrolab, JDSU, Solar Junction, Cyrium, and Azure Space.

Semprius joins fellow CPV firms GreenVolts and Morgan Solar in winning funding in the last month.