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Solar Expansion

Technologies are scaling up quickly to meet industry needs.

Fortnightly Magazine - December 2009

to lower prices and improve efficiency across the value chain. That means PV cells, panels and tracking systems are becoming cheaper and more efficient and cost less to install, operate and maintain.

While improving cell efficiency basically entails altering chemical recipes, panel costs are further reduced by streamlining manufacturing processes. Still, deciphering which PV technology is best for an installation basically comes down to site location and the amount of available space.

The two primary cell technologies are crystalline poly-silicon and thin film. Crystalline technology is the most expensive to produce but generally offers the best cell efficiency, typically ranging from 16 to 20 percent. Thin film technology is cheaper to produce but also less efficient, at or slightly above 10 percent, depending on the supplier. Therefore, thin film requires at least twice the physical space to produce the same energy as crystalline.

But there are other PV flavors too, including cadmium-telluride (CdTe), a type of thin-film technology that offers higher efficiency, typically around 12 to 16 percent, and copper-indium-gallium diselenide (CIGs), which offers cell efficiency levels comparable to crystalline but involves comparatively unproven manufacturing processes.

With its high efficiency rating, crystalline generally is considered most advantageous where space is limited. But some argue its output can degrade in hot desert climates. Thin film performs well in hot climates and is a good fit where space isn’t an issue.

Regardless of the technology, all cell producers are working to boost cell efficiency and reduce manufacturing costs. For example, earlier this year First Solar, the Tempe, Ariz.-based CdTe-thin film panel supplier, said it has reduced its cost for solar panels to $1 a watt, and claimed the lowest manufacturing cost in the industry. The company reduced its per-panel manufacturing cycle time to roughly 2.5 hours, which it says is one-tenth the time it takes to manufacture a crystalline panel.

San Jose-based crystalline panel supplier SunPower, on the other hand, announced in October it soon would begin producing panels with a 20.4 efficiency rating, which it says is the highest ever efficiency rating for a full-sized solar panel— a claim confirmed by the National Renewable Energy Lab (NREL). It also introduced the T20 tracker, a single axis ground mounted system the company says has fewer moving parts, a simpler mechanical structure, better wind resistance and is pre-assembled to speed installation.

“You’ve got a 1.5 HP motor at the end of a whole string of trackers. It works like a Venetian blind,” says Julie Blunden, vice president with SunPower. “We’ve lowered the manufacturing cost, the O&M costs, and generated more watts per tracker.”

Ironically, the announcements coincided with the commissioning of FPL’s 25-MW DeSoto Next Generation Solar Energy Center in Arcadia, Fla. The plant, now the country’s largest utility-owned PV plant, employs SunPower’s previous solar panel design, rated at 18.7 percent efficiency, and solar tracker equipment.

“In the traditional utility cycle, the time between commissioning a new power plant technology often is measured in years or decades,” says Blunden. “With the solar industry, it’s entirely different because there are multiple opportunities for technological improvements across