Global Solar Energy has signed on five customers to buy all of the thin-film cells available from its first commercial plant this year, Tim Teich, the company’s vice president of sales and marketing, told Greentech Media this week.

Teich, who said he couldn’t disclose names because of confidentiality agreements, said that the customers includesolar-panel manufacturers and building-materials companies that plan to enter the solar market.

The company in March announced it was building a 40-megawatt thin-film plant in Tucson, Ariz., and in June said it would start selling its cells this month (see Competition for First Solar and Global Solar Strings Thin-Film Market Together).

Teich said Thursday that the Tucson plant is on track to fully ramp up by the end of the year. The plant is running at a rate of between 5 megawatts and 10 megawatts per year now, with two of five lines in operation, he said.

For comparison, First Solar (NSDQ: FSLR), the world's largest thin-film manufacturer, has a capacity of about 300 megawatts. But other thin-film companies are producing far less, and nobody has reached mass production of copper-indium-gallium-diselenide cells, the kind Global Solar makes.

The company is still operating its 4.2-megawatt demonstration plant, which began production three years ago, to supply its Sunlinq line of solar-powered chargers for camping, hiking and disaster relief, Teich said. The plant is slated for decommissioning by the end of the year.

In March, Global Solar said it would build a second plant, with the capacity to produce up to 35 megawatts of cells, in Berlin by 2009. Teich said this week that the plant will begin production this year and reach its full capacity next year.

The company also still plans to expand its Tucson plant to 140 megawatts of capacity in 2010.

Aside from its manufacturing facilities, Global Solar has been installing a solar field, connected to its Tucson plant, to defray the energy usage from the plant. The company in March said the 750-kilowatt field would power about 25 percent of the facility’s power usage.

Teich said that the installation has been going well – all the racking and panels are done – and that the company expects to flip the switch this fall.

He also spoke about the efficiency of the company’s cells. The new production lines are delivering an average cell efficiency of between 9 percent and 10 percent, which matches what Global Solar was getting at its demonstration plant.

“That’s really quite a feat considering all the equipment is brand new and when you first flip the switch [on a line], the efficiency is zero,” he said. “The tool might do what it’s supposed to, but when you take the whole line, everything has to be [tuned] together.”

The company plans to increase efficiency 1 percent each year for the next three years, reaching 12 percent to 13 percent by 2011, he said.

While copper-indium-gallium-diselenide cells, also called CIGS, have proven an ability to convert as much as 20 percent of the sunlight that hit them into electricity in the labs, some industry watchers have questioned whether efficiency would be a problem in real-life production.

The National Renewable Energy Laboratory earlier this week confirmed Miasolé, a startup also developing CIGS, had reached an efficiency of 10.2 percent (see NREL Confirms Miasolé's Solar Panel Efficiency).

But CIGS efficiencies, so far, are lower than the average efficiency of 10.6 percent that First Solar achieved at the end of last year with its cadmium-telluride cells.

Global Solar initially plans to sell strings of its cells to manufacturers that will assemble them into glass panels. Global Solar makes copper-indium-gallium-diselenide cells, which it initially plans to sell in strings, leaving its customers to assemble the strings into glass panels.

The company next plans to target the building-integrated solar market, Teich said.

Putting thin film on roof shingles could potentially drive down costs to $1.60 per watt, he said. One obstacle to building-integrated photovoltaics has been the lack of a barrier layer, or coating, to keep water out of the cells (see Miasolé Drops Out of DOE Program).

Teich said a handful of polymer companies already are working to develop the barrier coat, and added that Global Solar expects to enter the market in the next two years.