Concentrator Photovoltaics

PARC & SolFocus second-generation CPV design significantly improves the efficiency, reliability, and footprint of concentrator photovoltaics – while drastically reducing costs

Flat-plate PV (photovoltaics) – which produces electricity by having sunlight directly strike panels made of expensive silicon wafers – has dominated the market. Grid-connected PV is the fastest-growing energy technology in the world.

However, silicon feedstock shortages and rising wafer prices have highlighted the need for technologies that reduce the use of silicon or other semiconductor materials, which usually dominate the costs of the total installed PV system.

CPV (concentrator PV) approaches offer an effective, practical way to keep solar cell conversion efficiencies high while keeping semiconductor material costs down.

PARC Approach

PARC & new venture SolFocus, Inc. have developed CPV systems that will deliver lower cost solar electric power and eventually compete with conventional electricity sources. The systems are currently targeted for commercial rooftop and utility-scale field installations, and prototype systems are now operating at a number of pilot sites.

How It Works

Close up of a single molded concentrator element [larger image]

CPV technologies use relatively inexpensive optics such as mirrors or lenses to “concentrate” or focus light from a relatively broad collection area onto a much smaller area of active semiconductor PV material. CPV systems must be pointed directly at the sun because they work by focusing sunlight onto a targeted area, and therefore require trackers which follow the sun’s trajectory throughout the day. Since CPV systems require less semiconductor material to capture a given amount of sunlight, it's still cost-effective to use more expensive and higher efficiency cells to increase the electricity generated from a given collection area.

Technology Roadmap & Details

With strong early contributions in non-imaging optical design from researchers at the University of California at Merced, SolFocus' CPV solutions build on PARC expertise in optical system design, optoelectronics, and advanced materials and processes for electronic packaging.

Compared to flat-plate devices, PARC's CPV:
-	requires only 1/500th of the expensive, active semiconductor material as other PV systems to generate the same amount of electricity from the sunlight falling on a given area; and
-	lowers the cost of solar electricity to less than half what is available today.

PARC & SolFocus CPV second-generation modules:

Cross-section of Gen 2 CPV module tile How it works: Sunlight enters from the top, striking the primary mirror. The light is reflected to the secondary mirror, and then concentrated onto a 1 mm2 triple-junction cell which is optically coupled to the glass. The design results in a smaller, thin, flat, molded glass CPV tile. [larger image]