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Emerging from stealth, Part III: Solyndra launches impressively, but questions remain

10 October 2008 | By Tom Cheyney | Chip Shots
solyndra_signAfter hearing the Solyndra story from CEO Chris Gronet and VP Kelly Truman, touring the front-end factory floor, and seeing the 50-KW demonstration system on the roof, I must admit that I am impressed by the cylindrical CIGS company. The pairing of its unique and compelling form factor and significantly lower installation costs could be a winning combination in the lucrative low-slope commercial rooftop PV market.

But there are several areas of concern in need of clarification, so one can more comprehensively evaluate whether Solyndra's prospects for success are indeed, er, tubular.

For starters, I will make no attempt to analyze the possible impact of the current meltdown of the financial system on Solyndra, other than to state the obvious: it will be more difficult to raise capital and open lines of credit in the coming months.

But there is one place where dollars are involved that Solyndra needs to be more open about. Although there's been ample lip service paid to the company's ability to drive toward a variety of definitions of unsubsidized grid parity, Gronet and this team have yet to reveal any hard numbers as to the retail (or wholesale) price tags of the panels and systems. It would be helpful to know what the darn things cost!

They won't talk about their current cost-per-watt manufacturing metric, let alone the roadmap to getting to that buck-a-watt sweetspot and beyond. They may have a fully automated, highly controlled, even high yielding factory and a proprietary process that uses less absorber materials than other CIGS schemes, but what I saw on the fab floor did not strike me as a disruptively inexpensive approach. Three out of the four main process steps use vacuum deposition, the other (for the junction partner/buffer layer) employs a wet-spray technique--none of which screams "low-cost manufacturing solution."

The claimed 12-14% conversion efficiencies for Solyndra's tube modules are certainly competitive with other CIGS, CdTe, and amorphous-silicon TFPV players and even match up well with the low end of the crystalline silicon module spectrum. But what's lacking is a third-party, NREL or NREL-like evaluation of the tubes' efficiencies, let alone any efficiency numbers for the panels. And just because one's champion cells or modules achieve a certain conversion efficiency doesn't necessarily reflect the tightness of one's overall efficiency distribution curve.

Yes, the actual geographics and climatic placement of the PV systems have a big impact on their ultimate efficiencies and at the end of the day, it's about the electricity produced by the panels, not just how well they convert those photons to electrons. But there's a bit of gamesmanship in Solyndra's refusal to play by the established rules of stated conversion efficiencies. And speaking of the photovoltaically created voltage streaming from those panels, just how much juice might be flowing?

The ingenious glass-to-metal sealed end-cap on each tube seems to be an elegant, robust approach to keeping CIGS-killing moisture out. But can the hermetically sealed caps survive the necessary 20-25 years and demonstrate the level of reliability needed to compete with silicon and other thin-film PV? The Solyndra systems have all been run through their testing paces, and they apparently passed with flying colors. But testing's one thing, actual field life is another. And silicon's got a decades-long head start.

Then there's the question of scaleability. The initial 40-MW line in Fab 1 is running at a pretty high capacity, I'm told. The second line--the to-be-standard 70 MW--is still a work in progress, with a limited amount of product coming off of it and heading for the back-end facility. Some tools are still in what Truman called "various stages of startup." The plan is to build out capacity in the second fab (and future ones) in increments of 70 MW, cookie cutter-style.

But first the Solyndra crew has to crank up the initial 70-MW line in a timely, high-yielding manner. Some CIGS aficionados question the ultimate ability of a coevaporation-style process like that in use at the Fremont fab to scale economically to high volume. At the end of the day, nameplate ain't run rate. PV factories of many flavors are notorious for their low capacity utilization numbers, and CIGS companies still have yet to prove their high-volume, 100 MW-plus production mettle.

I ran some idealized numbers based on the limited production-metric data that have been provided by Solyndra, to see how the math worked on a unit versus megawatt basis. If the panels are 180 W peak and each panel contains 40 tube modules, then each tube is 4.5 W or so. A quick punch of the calculator reveals that it takes 5555 panels (with 222,000 tubes) to fill out a megawatt's worth of PV.

Solyndra has stated that it can run one tray of 48 tubes through the main process every 100 seconds or so. If we extrapolate that for a year, with the line running full bore 24/7, that comes out to 41,472 tubes per day, or 1036.8 panels, leading to an annual rate of 378,432 panels. Divide that 5555 into the larger number, and the answer comes to 68.1 MW, pretty darn close to that stated 70-MW nameplate capacity.

I know these are strictly back o' envelope calculations, with little relation to real world manufacturing conditions. I don't think Solyndra will hit 100% yields and achieve 100% uptimes with its toolsets. But it does offer a rough estimate.

Another figure cited by Solyndra is its supposed ability to process 50 panels per hour on its back-end line. So let's do the math: that's 1200 panels per day, 8400 per week, and 436,800 annually. Divide that hypothetical (very very hypothetical) yearly output figure by 5555 ppMW and you end up with 78.6 MW's worth of those cylindrically equipped panels--still a figure within the range of relatively benign deviation from that 70-MW mark.

Despite my outburst of number crunching, the theme underlying all these concerns remains this: Solyndrans, show us (more of) your data!

With $1.2 billion in orders already booked, the likes of customers Phoenix Solar and Solar Power Inc. must obviously believe in the company and its product, or they wouldn't have agreed to put up hundreds of millions of dollars to buy the stuff. But Solyndra must now demonstrate a First Solar-like laser focus on executing the ramp of its first fab and then building, equipping, and scaling its planned six-line, 420-MW factory in order to take its place in the photovoltaic pantheon.

To read the first two parts of the blog series on Solyndra, click here and here.

Reader comments

It's called total internal refraction. The sunlight bounces around the outside tube hitting the backside of the internal CIGS coated one. Same as a schott tube in a CSP plant.
By Mark Newman on 17 November 2008
In addition to learning something about the cost...I'm a bit confused by the tubular cells that I've seen in news items. Half of the CIGS material will always be in shadow...leading to 50% less power than if the material were flat-plate-ed, not to mention power loss from shadowed cells...or does CIGS work completely different from silicon in this respect???
By disdaniel on 11 October 2008

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