Stion Solar: Two Modules In One
The company will likely release its first product-a copper indiumgallium selenide (CIGS) solar module-in June, said CEO Chet Farris in an interview. Stion currently is in the final stages of certification forits CIGS module. It will then follow up in 2011 with a module made up of two separate modules mechanically sandwiched together: one of Stion’sCIGS panels and another from the company made of solar cells containingchalcopyrite.
The idea behind the tandem module is that the CIGS layer and the more unusual layer can harvest energy from different ranges of the spectrumof light. Ideally, this will let the combined panel produce more energyconsistently during a single day.
Prototypes of the tandem cell have an efficiency of around 15 percent while the CIGS cells have a circuit efficiency of around 13 percent.
Stion, he added, will also produce its panels largely on industrystandard equipment. One tool for making the CIGS panel and one tool formaking the other cells has been customized, but everything elsebasically comes from the basic lines of equipment makers, which lowersmanufacturing costs.
"We’ve always had this pursuit of a tandem," he said. The modules are on glass substrates.
At volume manufacturing levels, Stion will produce CIGS and tandemjunction modules for less than $1 a watt, he added. The low price inpart comes from the manufacturing equipment strategy and part comes from the design of its CIGS modules. The cells in the module do not have tobe strung together independently.
"From a cap ex point of view it will be less than a dollar a watt,"Farris said.
Will 2010 be the long awaited year of CIGS? Maybe. Global Solar,Solyndra and Miasole are already producing panels for commercialproduction. Global has a total manufacturing capacity at two sites of around 75 megawattsand tests conducted at NREL on Global’s CIGS modules on a flexiblestainless steel substrate exceed 13 percent efficiency. Ascent Solar Technologies, meanwhile, said it has begun to manufacture CIGS moduleson flexible substrates with a 10.5 efficiency.
Stion has a small manufacturing facility that can produce 5 megawatts of cells a year. The first production is already committed tocustomers. It will expand to 10 megawatts and later, of course, try tomove well beyond that if all goes well. Stion will initally focus oncommercial customers and later target utilities for large scale solarfarms when factory capacity increases.
Globally, the solar industry produced 8.95 gigawatts worth of solarmodules in 2009, according to Shyam Mehta of GTM Research, so the totalCIGS production remains a drop in the bucket. CIGS proponents, however,claim they will expand production and will be able to undercut the costof crystalline silicon modules-which now sell for around $1.75 to $1.50 a watt-while beating the efficiency of other thin films like cadmiumtelluride or amorphous silicon. Cad Tel solar modules hover around 11percent efficiency while amorphous silicon solar cells hit around 7percent efficiency. Some tandem amorphous cells can achieve around a ten percent efficiency with a cost that will approach 70 cents a watt inthe relatively near future. NREL has produced some CIGS cells exhibiting an efficiency of over 19 percent.
CIGS has been held back by the difficulty of moving toward massmanufacturing: getting those four elements to work together is likeorganizing a Van Halen reunion. Nearly every manufacturer uses adifferent process and many have had to customize their equipment as aresult. Nanosolar has a printing process while Miasole uses a sputtering process that has its roots in the hard drive business. Solopowerapplies the materials with electroplating.
Stion employs a two-stage sputtering process.
Although many CIGS companies now seem to have a handle onmanufacturing issues, they also face a very different market than whenmany started in the mid-90s when silicon remained in short supply. Now,solar manufacturing capacity exceeds demand, a global economic crash has made investors skittish and Chinese manufacturers have relentlesslydriven down the cost of crystalline silicon panels. Whether they canovercome these real world hurdles remains an open question. Back in2008, Stion said it aimed to produce modules in 2011 for around $3 a watt-it clearly has had toadapt to a different world.
Farris, however, points out that Stion has got this far with only $44 million–$34 million from investors and $10 million in debt. Other CIGS vendors have raised hundreds of millions of dollars.
Rumors have floated for years about Stion’s exact formula. Many havespeculated that the company was working on quantum dot solar cells(which sources close to the company have denied in the past) or solarmodules that combined CIGS and amorphous silicon. In the past, it haseven denied that its panels would be CIGS too. Technically, if you think of the tandem product as its signature offering, that’s true.
"We have a number of materials in our toolbox, some of which we areusing for the current products and others of which we will deploy in the future," Farris said. "We are a materials-agnostic company in that ourplan has always been to manufacture high-efficiency, low-cost thin-filmproducts using commercially scalable materials and processes, and wefocus on solutions which fit those criteria."
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