Printed PV: Nanosolar unveils 640MW utility-scale panel fab, high-efficiency CIGS cell production

Sept 9, 2009 - Tom Cheyney - PV-tech.org

After staying relatively quiet for much of the past year, thin-film PV manufacturer Nanosolar has come out with a full docket of announcements: the completion of its 640MW panel-assembly factory near Berlin celebrated during an event attended by the German Minister of the Environment and other dignitaries; the start of serial roll-to-roll production of its flexible copper-indium-gallium-(di)selenide cells in the company’s San Jose facility; $4.1 billion in panel purchases from customers--including some of the world’s largest utility companies; NREL-verified cell efficiencies up to 16.4%; and new technical details of both its printed CIGS cell technology and utility-scale panels.

The panel-making facility, located in Luckenwalde  (about 60 kilometers south of Berlin), can operate at a production rate of one panel every 10 seconds and is capable of reaching a peak capacity of 640MW when operated around the clock, according to Nanosolar. Called by TUV Rheinland inspectors “a factory unlike any we've ever seen,” the plant incorporates a fully automated, robotic line (pictured at left) integrated with a sophisticated in-line quality control measurement system to string and assemble the individually sorted and tested cells into panels. One innovative part of the production line is a high-throughput stack lamination technique developed with a "leading provider of lamination equipment."

The German panel factory is supplied with flexible aluminum-foil cells produced at the venture-backed company’s fab in San Jose. Nanosolar, which prints its cells using a proprietary CIGS ink in a mostly nonvacuum, low-cost process sequence, says it began serial production on its R2R processing line earlier this year.

"Getting to the point of serial production with the unusual extent of innovation and leapfrog cost reduction involved in our technology and delivering a product that out of the gate meets and exceeds the high bar set by the industry's existing volume manufacturers on performance and reliability is an accomplishment due to the incredibly hard work and perseverance of our team," says Nanosolar president/CEO Martin Roscheisen.

Although the facility is calibrated for rapid growth, current production is running at a subcapacity baseload rate of about 1MW per month, according to Nanosolar. Web widths run up to 1500mm on the cell line, while certain process steps can attain throughputs as high as 40m/min, he told PV Tech. A full roll of processed, unsingulated PV foil is equivalent to 100KW. 

The San Jose plant will be ramped in sync with the company's market-introduction plan, which it says focuses on achieving “product bankability” with commercial banks and delivering on the company's $4.1 billion in contractual customer commitments.

"With almost all large solar installations credit financed, broad-based product bankability is our key next commercial goal,” states the company CEO (pictured at left). “We have long prepared for this, including through the technology choices we have made, the strong balance sheet we have maintained, the quality of customers we have secured, and the local production we have built."

The product coming off those automated assembly lines is Nanosolar’s first offering, the Utility Panel—what it calls the industry’s first solar electricity module specifically designed as well as electrically and mechanically optimized for utility-scale solar power systems.

Featuring an innovative design scheme, the company says the IEC 61646-certified panel effectively eliminates the “balance-of-system penalty” that medium-efficient thin panels from First Solar and others have conventionally carried relative to higher-efficiency, more-expensive crystalline-silicon panels.

The Utility Panel is the industry’s highest-current thin module, by up to a factor of six, according to Nanosolar, and is also the first PV module certified by TUV for a system voltage of 1500V--about 50% higher than the next highest certified device. The combination of enhanced current and voltage enables utility-scale panel array lengths and results in a host of substantial balance-of-system cost savings, the company says.

On the mechanical side, the panel package employs a dual-tempered glass/glass design housing the flex cells, which is distinctly stronger than that of conventional thin-film-on-glass modules, achieving about 70% greater mounting span, thus facilitating substantially lower mounting costs, the company says.

The full panels as well as their components and materials have been put through a wide range of rigorous indoor and outdoor reliability and performance testing, done internally and with third-party firms, in a variety of geographic and climate conditions, and are certified under various IEC, UL, and other standards, according to Nanosolar.

“We have a huge effort on testing and are in fact expanding this even further,” Roscheisen told PV Tech. “We believe the standard tests are limited in some ways.  We are interested in looking at combinations of stresses as well as various forms of dynamic behavior.”

On the cell side, the National Renewable Energy Laboratory has independently verified that the company’s metal-wrap-through back-contact, printed-CIGS-on-metal-foil devices produced on its Gen 3 line have reached active-area conversion efficiencies as high as 16.4% during tests conducted earlier this year. “Our lab and production teams have managed to make more progress on efficiency than we had planned on in any of our business plans,” says Roscheisen.

Noting that “we print CIGS onto inexpensive metal foil, something that some have been skeptical can work while others have been wondering whether it can deliver cells better than 6% efficient,” he explains that the latest efficiency numbers for the foil cells actually  “represent two world records in one: It's the most efficient printed solar cell of any kind (all semiconductor and device technologies) as well as the most efficient cell on a truly low-cost metal foil (with a material cost of only a cent or two per square foot and mil thickness).”

Going beyond the champion cell results, Roscheisen reveals that “in terms of our current baseline production process, our best production rolls now achieve higher than 11% median efficiency measured as equivalent to panel efficiency, with very tight cross- and down-web uniformity.”

NREL’s Miguel Contreras, the senior scientist who supervises the CIGS group at the national lab, told PV Tech that his team has supported Nanosolar “with official measurements, characterization, transferring the know-how we have in making 20% solar cells in the labs. We showed them what the [film] structures look like, what they should shoot for, to improve their own processes and materials—that was our strongest contribution to them.”

But he gives full credit to Nanosolar, saying “truly, it’s to their merit on most or all of the work that’s been done. We just helped a little bit in their success, and I’m proud and honored to be part of that effort.”

(More info on Nanosolar's cell technology and the design and innovation behind its Utility Scale panel can be found in white papers and elsewhere on the company's relaunched website. Also check out the Chip Shots blog for an exclusive unfiltered interview with Nanosolar chairman/CEO, Martin Roscheisen.)

PHOTOS BY WILHELM BREUER, COURTESY OF NANOSOLAR