Gas supply challenges for PV

by Debra Vogler, Senior Technical Editor, Solid State Technology

Dec. 11, 2008 – Many presenters at last week’s Thin-Film Solar Summit (San Francisco, CA, Dec. 2-3). extolled the advantages of achieving economies-of-scale by building larger PV factories. However, such endeavors also bring challenges in terms of delivery of critical supplies such as process gases. To this end, Anish Tolia, market development/solar for Linde Electronics, informed attendees that as the industry scales production, gas technology can significantly impact the cost/Watt (see Fig. 1).

Strong solar and LCD panel growth is straining global supplies for silane, the most critical raw material, but most of the supply chain captive by polysilicon manufacturers, observed Tolia. Future solar applications will use more silane than any other application that demands silane today — he estimates that the future requirements for silence will be ~67,000tons/year of silane, about double the amount used for semiconductors and LCD manufacturing (excluding polysilicon production).

Gases can impact all critical cost levers. (Source: Linde)

To address the supply issue, Linde has made some strategic investments in silane production in Europe with a couple of long-term contracts to lock in a supply. “Due to economic issues, the ramps that were planned for 2009-2010 are slower than anticipated, so for now we’ve covered the (silane) gap,” Tolia said, but the long-term issue is whether production capacity can keep up with demand — “How much confidence do we have in demand forecast[s] to invest $100M up-front in a silane manufacturing plant?” It will come down to a business decision, but Tolia added that there’s no fundamental reason why silane production cannot keep up with demand.

Reducing cost/Watt requires a transition from “supplier” to “industry partner.” (Source: Linde)

Linde has been particularly focused for the last year on finding ways to help the industry reduce cost of production through gases. Tolia observed that the traditional gas supplier business model has seen companies act more like suppliers rather than partners (see Fig. 2). “In solar production, gases have an impact on the end product — we have to think like a module maker,” which cares about keeping costs down, he said.

Gas suppliers need to help the industry achieve its goal of <$1/Watt, and to that end Linde has initiated a number of programs. One focuses on reducing material costs via a recycling program for gases, especially those with low utilization such as silane. Another step that can be taken is replacing NF3 with fluorine (for cleans) to reduce cleaning time and reduce material costs (see Fig. 3). An added benefit when using fluorine for cleans is that it has a global warming potential (GWP) of 0 vs. 17,000 for NF3. — D.V.

Replacing NF3 with fluorine can reduce clean time by 3×; total line throughput can be improved by up to 10% by faster cleaning. (Source: Linde)


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