THE FUTURE OF CONCENTRATING PV, INDUSTRY OVERVIEW, MAJOR PLAYERS, WILL CPV MAKE IT?

Semprius has a core semiconductor technology the firm believes can make concentrating photovoltaics (CPV) a competitive solar technology.

Semprius and the CPV industry has its work cut out for it.   The flat panel photovoltiacs (PV) industry has grown at a compound annual rate of about 41 percent per year for the last decade to reach its current 2010 shipment pace of 15 gigawatts. 

CPV, despite its promise, has not really gotten out of the gate, and 2010 CPV installations are still well under 10 megawatts.

While silicon and thin-film PV ramp up shipments amidst plunging prices, CPV is mired in a chicken-and-egg problem of needing volume to drive down costs but not getting to volume because of high prices.

There has been some cause for hope.  Amonix, armed with a 25-megawatt power purchase agreement (PPA) from Southern California Edison, seems to be one of the few CPV firms with the technology and financial runway to make CPV work.  SolFocus has gotten some CPV traction in Saudi Arabia.  Concentrix, now owned by Soitec, has shown some signs of life and has partnered with Johnson Controls.  Some folks believe early-stage Morgan Solar has a chance.  Optical networking giant JDSU has entered the CPV semiconductor contest.  There's also rooftop CPV from Soliant.

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 $0.77 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 more recently, won an additional $7.9 million from Applied Ventures, ARCH Venture Partners, GVC Investment Fund, Intersouth Partners, In-Q-Tel, Illinois Ventures and X-FAB Semiconductor Foundries.

The 30-employee firm aspires to be a vertically integrated manufacturer of high-concentration PV (HCPV) 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 -- that's close to the world's best performance.  The firm expects their triple-junction cells to have efficiencies in the high thirties.  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 this 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.

Nancy Hartsoch, VP at SolFocus, estimates that the amount of CPV shipped in 2010 will be 12 megawatts to 15 megawatts with an "installed base of about 8 megawatts."  She suggests that 2011 will see 100 megawatts shipped, a substantial growth curve. 

According to the CPV Industry Report 2010 from CPV Today, CPV installations in the U.S. will grow from 1.5 megawatts to 75 megawatts in the next five years.  Those numbers imply a market doubling every year for the next five years, growing much faster than the PV market as a whole.  

Even if accurate, CPV at 75 megawatts would account for about 0.2 percent of the total solar PV market, a niche market at best -- suited for locations with poor water resources, high DNI and subsidies directed specifically at CPV.

COMMENTARY:  Concentrating photovoltaic systems use lenses or mirrors to concentrate sunlight onto high-efficiency solar cells.  These solar cells are typically more expensive than conventional cells used for flat-plate photovoltaic systems. However, the concentration decreases the required cell area while also increasing the cell efficiency.

Concentrating photovoltaic technology offers the following advantages:

• Potential for solar cell efficiencies greater than 40%
• No moving parts
• No intervening heat transfer surface
• Near-ambient temperature operation
• No thermal mass; fast response
• Reduction in costs of cells relative to optics
• Scalable to a range of sizes.

The high cost of advanced, high-efficiency solar cells requires the use of concentrated sunlight for systems to achieve a cost-effective comparison with both the cost of concentrator optics and other solar power options. NREL has focused on the development of multi-cell packages (dense arrays) to improve overall performance, improve cooling, and install reliable prototype systems.

Efficiency and output— not a slam dunk

"When we decided to move beyond our semiconductor roots at OPEL, we decided to manufacture a CPV system including both the concentrator optics and the solar cell," says Middleton. "Even though the principle behind CPV is straightforward, implementation is tricky."

Indeed, CPV systems require a well-engineered "package" that incorporates optics, semiconductor material, and—common to all CPV systems—solar tracker hardware to maximize output. This requirement for trackers is the reason CPV manufacturers target utility-scale installations: Trackers preclude cost-effective installation for residential applications. OPEL Solar offers both small single-axis trackers (42 modules for a 3800 W output) and utility-scale dual-axis trackers (100 modules for a 9000 W output) that can also be used to increase the output of a PV system by 40%. Each roughly 11 × 62 in. OPEL module consists of six optical elements focused on six solar cells, with a rated output of 90 W ± 3% at 900 W/m² solar irradiance. Even though the definition of a "module" differs for each supplier, a quantitative comparison of various optical designs can be formulated, assuming a linear relationship between solar irradiance values (see table).

"All watts are not created equal," Middleton explains. Even though an analysis of power output (W) versus physical area (m²) for CPV modules can give a ballpark indication of which technologies provide the best "concentration" factor in terms of optical design and chosen PV material for the solar cell, nearly every company I spoke with rightly explained that the numbers are not straightforward. "A CPV system is more than the optics and solar cell: The contributions of tracking precision, module lifetime, solar irradiance/site temperature, and inverter/electronics, all need to be considered," says Middleton. "This is also true when comparing CPV to, say, thin-film or silicon systems: Even though silicon may be running at $2 per watt, and thin film $1 per watt, thin-film systems are more costly to install on a per-watt basis and require a much larger installation area to achieve the same output due to their reduced conversion efficiencies."

Concentrix Solar also emphasizes the reliability mantra. "Because our lenses and solar cells are smaller than in typical Fresnel-based CPV systems, the heat load is very small, and system reliability is improved," says Gombert. The Concentrix Solar module has an active area of approximately 80 × 40 cm composed of 200 single lenses (40 × 40 mm) focused on 200 solar cells, each with a 2.3 mm active area (see Fig. 3). This point-focusing module offers a 500× concentration factor, with an output of 75 W measured at an irradiance of 850 W/m².

CPV vs. traditional PV

A major advantage of CPV systems over crystalline-silicon solutions is superior performance in geographical regions with high solar irradiance (high temperature). "When temperatures reach 40°C, a crystalline silicon solar panel rated at 100 W will put out just 75 W due to the temperature coefficient of silicon," says Middleton, "However, our solar panel will produce 94 to 96 W." For high-solar-irradiance regions, CPV systems perform better than traditional silicon, taking up less physical area per watt than either crystalline silicon or thin-film solutions. In fact, Gombert says that in sunny locations, electricity production costs are 10% to 20% lower for FLATCON CPV systems compared to conventional flat-plate modules. However, unlike traditional flat-plate PV, CPV systems will not function on cloudy days as the optics cannot focus diffuse illumination.

Semprius

Semprius is developing concentrator photovoltaic (CPV) modules for large-scale solar power generation. Semprius' proprietary micro-transfer printing technology enables CPV modules constructed from a large array of very small gallium arsenide-based, multi-junction solar cells. Module cost is minimized by using high concentration ratio. Inexpensive optics concentrate 1,000 suns onto the high-efficiency solar cells, which only cover 0.1% of the module area.

Semprius Competitive Advantages:

• Unique design and assembly - Low cost
• Many cells - Highly redundant, improved reliability
• Very small cells - Thermal management at no added cost
• Short optical path - Very high efficiency optics, thin and light
• Wide optical acceptance angle - Reduced tracker cost

CPV Advantage

 CPV offers the lowest solar Levelized Cost of Energy (cents per kWh) in sunny, dry climates. High energy (kWh) production is achieved through use of two-axis trackers and gallium arsenide-based, multi-junction solar cells, which provide the highest conversion efficiency and lowest temperature degradation. Energy production is well-matched to high demand periods, such as summer afternoons, which have the highest time-of-delivery multipliers. CPV systems high efficiency minimizes the number of trackers and amount of land required for a project. CPV's ground-mounted deployments reduce installation and operations & maintenance costs. Lastly, CPV systems are very modular and can address multiple markets; they can be readily installed close to the load, avoiding congested transmission lines or in central solar farms. Click here for more resources.

Far-reaching Platform

Semprius' patented micro-transfer printing technology brings for the first time, high performance semiconductors to virtually any surface, including glass, plastic or metal substrates or even other semiconductor wafers. By liberating the semiconductor devices from their traditional substrates, Semprius technology enables the construction of a wide variety of new products with large-area, thin, and lightweight form factors, high reliability and low cost. The resulting circuit devices have levels of performance comparable to the original semiconductor.

We are offering licenses to our micro-transfer printing technology for non-solar applications, including: OLED displays, LCD displays, large area sensors, medical devices and more.

In January 2010, Semprius, Inc. announced that it has been selected by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to negotiate a $3 million subcontract funded by the DOE to commercialize its promising solar energy technology.

In January, 2010, Semprius, Inc. and Siemens Industry, Inc. announced that they had entered into a joint development agreement to co-develop and deploy plug-and-play demonstration systems based on Semprius Solar Module Arrays and Siemens automation and control components. The systems are slated to be installed at numerous test sites around the world, including major utilities, commercial sites, international test locations and government facilities.

Semprius investors includes:  

• April 2007, Semprius raised $4.7 million in Series A funding from Arch Venture Partners, Intersouth Partners and Illinois Ventures to continue its process development.
• June 2007, Semprius was awarded a Small Business Innovation Research Phase I grant of an unspecified amount by the National Science Foundation to help demonstrate transfer printing of highperformance semiconductors on flexible materials.
• July 2007, Semprius received a strategic investment of $7.9 million from Applied Ventures to enable development of new generation of flexible electronics and integrated heterogeneous semiconductors. Applied Ventures is the venture capital arm of Applied Materials, Inc. (*Nasdaq: AMAT).
• June 2009, Semprius closed a $6.4 million Series B round of venture funding. Existing investors ARCH Venture Partners, Applied Ventures, Illinois VENTURES and Intersouth Partners were joined by In-Q-Tel and GVC Investment Fund. 
• January 2010, Semprius received a stategic investment of $1.5 million from X-FAB,  and effective immediately, will be the designated foundry for Semprius technology.

The total CPV market is expected to reach $266 million by 2014, with Europe commanding the maximum market share at 59.3%, followed by 32% for the Americas.  Even though CPV will represent less than 1% of the total $38.1 billion worldwide PV market by 2014, its proponents say that its growth rate will be higher (33% to 39% compared to 12.5% for the overall PV market) and that it has the potential to achieve grid parity faster than competing technologies.

Semprius is not the only company competing for leadership in the CPV market segment. Currently, CPV systems are commercially available from:

• Concentrix Solar (Freiburg, Germany) 
• OPEL Solar (Shelton, CT) 
• Emcore (Albuquerque, NM) 
• SolFocus (Mountain View, CA)
• Amonix (Seal Beach, CA) 
• Prism Solar Technologies (Highland, NY) 

Plus a host of other small and large solar-cell companies.   

Solar industry leader Amonix may have a legup on the rest of the competitive field having secured $129.4 million
 in private equity financing from Kleiner Perkins Caufield & Byers. 

Indeed, the number of different concentrating optical designs is even larger than the number of commercial companies in this arena, as more and more new technologies are being developed in research labs everyday. 

Courtesy of an article dated December 20, 2010 appearing in GreenTechSolar and an article dated February 1, 2010 appearing in OptoIQ