Can concentrated PV (CPV) compete against the still-plunging prices of standard photovoltaics? Semprius and its investors think so.

Semprius just added another $7.5 million in venture capital to its war chest for its high-concentration PV systems. The funding came from existing investors Siemens Venture Capital, ARCH Venture Partners and Intersouth Partners. That follows a $3M financing earlier this year. The company has received more than $30 million in VC funding since its inception, plus some DOE funding as well.

Other investors in Semprius include Morgan Creek Capital Management, Illinois Emerging Technologies Fund, Applied Ventures, and In-Q-Tel.

Semprius has been working on building a 5-megawatt pilot plant that is expandable to 35 megawatts. Semprius claims to have set the world-record CPV solar module efficiency using epi from Solar Junction. The firm recorded a module efficiency of 33.9 percent.

Semprius has a core semiconductor technology the firm believes can make CPV more competitive. In December of last year, NREL validated a 41 percent efficiency at 1,000 suns for a Semprius cell, close to the world record.

Semprius -- like the larger CPV industry -- has its work cut out for it. The flat-plate photovoltaics (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 published a detailed analysis and forecast on the CPV market.

The leaders in the CPV systems markets are Amonix, Soitec, and SolFocus, but things have been relatively quiet in CPV of late. The largest operating CPV power plant in the U.S. is the Hatch site in New Mexico, at least until the 30-megawatt Alamosa project comes online.

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 firm aspires to be a vertically integrated manufacturer of high-concentration PV panels using its 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. The firm's micro-transfer printing technology makes it possible to reuse the GaAs substrate rather than shipping the expensive substrate out the door with every cell. Semprius claims that by reusing the substrate, it can reduce costs by 50 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. 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. 

Semprius claims a 32 percent efficiency at 1,000 suns for its 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 its systems at Tucson Electric Power (TEP) in August of 2010 using its modules and an automated solar tracking system developed by Siemens. The tracker, which also uses 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 the 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.