PHOTON International The Photovoltaic Magazine

Evergreen Solar doubles furnace growth to two string ribbons

String ribbon PV manufacturer Evergreen Solar Inc. announced an improvement to its crystal growth furnaces on Dec. 4, which allows the simultaneous growth of two silicon ribbons rather than one. Dubbed Gemini, the new process would double furnace output.

	© Evergreen Solar Inc.
Seeing double: Evergreen's pilot furnace can grow two 81 mm wide polycrystalline ribbons, about 2.5 cm apart and each 2 m long, before being diamond-scribed for laser cutting into wafers.

Mark Farber, Evergreen's president and CEO, says Gemini is still in its R&D phase but expects commercial production with the new technology to begin in late 2003. The 60 single-ribbon furnaces are »retrofittable,« says marketing and sales manager William Kanzer, although the timeline for the changeover is unclear. The number of furnaces equipped with the new process that would be required to reach Evergreen's stated goal of increasing production capacity from 3 to 8 MW by the end of 2003 is also uncertain, adds Kanzer. Farber does not expect the 12.8 percent efficiency of the vertically pulled 81 mm wide ribbons to decrease under the double-ribbon process. He declined to estimate how much it might reduce costs, saying only that this would be »enough to make it exciting.«

The company is also in a »very early R&D« phase on doubling the process to four ribbons, adds Farber. In addition, research is being carried out on reducing ribbon thickness from about 300 µm to 100 µm. While Evergreen has already grown the double ribbon at 100 µm, Farber says the yield was low: »We won't rush into production unless the yield is comparable to the current process.«

On the day of the announcement, made half an hour before the NASDAQ closed, the share price ended down 17 percent at $0.98. By Dec. 31, 2002, it was up to $1.29.