Oct. 7--Solyndra, the noisiest stealth start-up in Silicon Valley, emerges today as a solar heavyweight.

The company, based in Fremont in a series of large buildings visible from Interstate 880, says it has orders for $1.2 billion worth of its solar panels over the next five years. It has raised more than $600 million and already has 500 employees. And it plans to construct a second, larger plant in Fremont next year.

Solyndra comes to market with an innovative design, making cylindrical solar cells that resemble fluorescent bulbs. It uses a combination of elements -- and not silicon-- to create the semiconductor material used in its photovoltaic solar cells. And it targets a specific market -- the flat roofs atop thousands of commercial buildings around the world.

"There's a vast underutilized resource for generating solar power, and it's right over our heads," Chris Gronet, Solyndra's chief executive officer, said in an interview. "There's over 30 billion square feet of large, flat commercial rooftop space (in the United States). If we covered that with our solar panels, that would generate 150 gigawatts, enough electricity to generate power for 15 percent of U.S. homes."

The company, formed in 2005, started shipping solar panels in July. To date, the largest installation of its panels is the 50-kilowatt system on its own roof, but Kelly Truman, Solyndra's marketing vice president, expects larger systems to be in place before

the end of the year.

Solyndra differs from other solar companies in several ways. It makes solar panels from glass tubes, using 40 tubes per panel. Those panels are placed on racks about a foot above a roof's surface, thus taking advantage of the reflective light from the roof to generate more electricity. They aren't attached to the roof but held in place by gravity and the panel design, which allows the wind to blow through them, the company says. They snap in place, which cuts installation cost by 50 percent and installation time by two-thirds, Gronet said.

And because they don't need to be tilted, more of Solyndra's panels fit on a flat roof, he said.

The company uses a chemical mix of copper, indium, gallium and selenide, known as CIGS in the solar industry, as its reflective semiconductor material. The premise is that non-silicon thin-film photovoltaic solar offers a more affordable solution.

Gronet won't talk about the price of Solyndra's panel, saying it's part of the "negotiation dynamic" with the company's potential customers. But he said the promise of thin-film solar is based on its affordability.