SolFocus Inc., a spinoff from H2Go in 2004, and Xerox's Palo Alto Research Center (PARC) on February 16 announced a research collaboration to develop solar Concentrator PV (CPV) systems. The broad agreement is to jointly develop CPV systems that can deliver low-cost, reliable solar energy. SolFocus CPV solutions can potentially:
- advance the market beyond current flat-plate silicon PV and it underlying cost limitations;
- deliver both short- and long-term cost advantages which is the critical metric of market success;
- position CPV to be competitive with conventional electricity; and
- open large new markets for clean solar energy
The venture builds on the original SolFocus design for concentrator photovoltaic technology (shown left). CPV technology creates electricity by using precision optical components such as lenses and mirrors to direct and “concentrate” sunlight onto high-efficiency solar cells. SolFocus’s prototype solar panels are smaller, cheaper, and easier to manufacture than the flat-plate photovoltaic panels that currently dominate the market.
CPV systems 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 cell material. Since the silicon in solar cells usually dominates the costs of the solar PV system, reducing the amount of silicon leads to substantially lower system cost and resulting cost per watt of output.
For higher concentrations that reduce silicon use by 100-1000 times more, it is cost-effective to use higher efficiency cells that increase the electricity generated from a given collection area—even though this PV material can cost up to ten times more than silicon.
SolFocus has developed two low-cost CPV module designs—Gen 1 and Gen 2 (Gen 1 shown above):
- Up to 2 MW (megawatts) of the Gen 1 design will be installed in 2006-2007 at pilot sites in California, Hawaii, and Shanghai, China.
- The Gen 2 design, which further improves performance and reduces costs at higher volume production, will be available for test installations a couple of years later.
- Both modules are targeted for rooftop- and field-installed solar systems.
Advantages Compared to Flat-plate PV
- Requires only 1/1000th 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
- Lowers the cost of solar electricity to less than half what is available today
- Operates at nearly double the efficiency of most flat-plate PV
Both CPV Modules
- Enabled by highest-efficiency cells available—Spectrolab (division of Boeing) triple-junction cells approaching 40% at over 500-sun concentration. 1 cm2 cells are used in Gen1 and 1 mm2 cells are used in Gen2.
- Employ non-imaging optics in Gen2
- Use glass—can easily meet 30-year lifetime requirements 1mm
- Use dry, passive cooling—no liquids or fans
- No moving parts in module—avoids mechanical failure in module
- Fully “enclosed”—no exposed mirrors or open fire hazards
- Use mirrors or reflective elements which allow purely reflective light entry—avoids the chromatic aberration of lens-based concentrators
- Use minimal components—have a number of “double-purposed” materials
- Have one-quarter the focal length of other systems—makes them extremely compact
- Assembled with high-throughput, automated technology
- Integrate the manufacturing capabilities of existing vendors—allows rapid product launches
Gary Conley, SolFocus chief executive officer, said, 'The first-generation panels will break price barriers in the market, but the second-generation panels with PARC technology will change the market for solar dramatically. The current installed cost of the flat-plate photovoltaic systems is about $7 per watt, but our approach should produce electricity for about half that amount – or less.”
During 2005, a total of six prototypes, of varying configurations between 500 and 2,000 Watts peak, were designed and are in the final stages of development and production. H2Go will install these first systems at various research sites to gain the best possible performance knowledge in the shortest period of time, and by calling upon extraordinary people with unique skills. The Gen1 products are in pilot production. First-generation SolFocus CPV prototypes were installed at PARC in January 2006. Up to 2 MW of the Gen1 design will be installed in 2006-2007 at pilot sites in California, Hawaii, and Shanghai, China.
Gen 2 CPV Module
The Gen2 design further improves performance, scalability and durability as well as reducing costs. The module design is based on a solid-state, or “one-piece,” concept featuring small reflective concentrator elements housed in a flat molded glass tile with mirrors on each side. The Gen2 module will be available for test installations in 3 or 4 years.
- Replaces discrete optical elements with a single, thin, flat, molded glass tile, schematic shown above, that incorporates small reflective concentrator elements and has mirrors on both sides
- Reduces size of optical design and uses smaller cells (1 mm2 )
- Flattest optics—similar to the geometry of Cassegrain optical telescopes
- Reduces processing steps—fabricates optical elements in a single glass pressing
- Can be assembled with high-throughput, automated technology
- Packs flat for low shipping costs and associated benefits of offshore manufacturing
- Avoids seals, filters, coverglass, and hard-to-clean surfaces
Each tile will contain 160 individual cells, generating a total of 30 watts of electricity, 285W/m2. Several tiles can be joined together to deliver the desired electrical output. Initially the tiles will be made with stamped glass, but as production volumes increase a rolled process will be used. The 11 x 17 inch (280 x 430 mm) tiles have an average thickness of 0.16 inches (4 mm). Early Gen2 modules are undergoing test.
The CPV systems will be produced for business, not residential applications. They are targeting large rooftop systems such as shopping malls, warehouses, factories and big box stores as well as field mounting for solar power plants.
The target installed cost for systems in high volume production is $1.00/W. The cost of goods sold (COGS) is projected to reach $0.55/W for Gen1 modules and $0.35/W for Gen2 modules at a 1GW per year production rate. They plan on selling about 2 MW of Gen1 modules to early adopters at approximately $5.00/W. SolFocus expects revenues in the next 18-24 months of $30 million to take them through to profitability. They have about $10 million in pending orders. SolFocus is in the process of hiring contract manufacturers in China.
CPV development at H2Go has depended upon collaborative efforts from the beginning. Early contributions in non-imaging optical design came from researchers at the University of California at Merced, who continue to contribute to optical design, system tests, automation, cost reduction and lifecycle/reliability.
Ben Gurion University in Israel developed the extremely compact compound non-imaging optical design which is employed in first generation systems and they continues to address projects in cell performance, endurance and optical nano-coatings.
Under the new agreement with PARC, it is contributing core patents and long-term technology development support for current and next-generation product lines in exchange for royalties and equity in SolFocus.
SolFocus is contributing H2Go's patents pending on the Gen1 design and optics, the Gen2 design and two more patents to be filed. SolFocus will hold all foreword intellectual property.
SolFocus competitors are Sunball which produces modules for relatively small installations, usually under 10kW; Sunflower, IAS, and Amonix produce larger modules which compete more directly with SolFocus. All use plastic Fresnel lenses in their designs which Solfocus claims have inferior optics and are less durable than their glass mirrors. The competitors have the advantage in that they are all in production with a track record being established.
Posts based on this announcement have appeared in Clean Break, which provided the link to the SolFocus presentation that was invaluable in preparing this post, Clean Edge, Joel Makower and sustainablog.
H2Go, Saratoga, CA
PARC, Palo Alto Research Center, Palo Alto, CA
Palo Alto Research Center Teams with SolFocus to Deliver Affordable Solar Energy, Press release, Feb. 16, 2006
SolFocus-Towards $1/W, presentation to NREL, November 8, 2005
Solar Concentrators, Scott Elrod, Palo Alto Research Center, February 2006
SolFocus, Inc., Palo Alto, CA