Solar Companies Merge Technologies in Bid for Utility-Scale Production

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Concentrating photovoltaic (CPV) solar power -- which marries traditional solar photovoltaic technology to large-scale concentrated solar power plants -- could ramp up utility-scale solar production, advocates say, especially in niche markets. But as with all developing technologies, the effort faces significant hurdles.

CPV technology involves magnifying the sun's energy hundreds of times via lenses or mirrors and focusing it onto small, extremely efficient photovoltaic cells. By magnifying the solar energy, the technology can reduce the amount of semiconductor material needed for the photovoltaic cell.

"In a lot of ways, it's merging the advantages of photovoltaic technology with the efficiency and ability to capture more sunlight that you get with concentrated," said Nancy Hartsoch, vice president of marketing for SolFocus, a California company. "You're basically focusing 650 suns onto that cell, so you're able to use a very, very small amount of photovoltaic material to capture a tremendous amount of sunlight and then convert it at very high efficiency."

SolFocus is among a handful of companies working on CPV technology. Its model involves a two-mirrored system that directs sunlight down an optical rod onto a small (1 square centimeter) photovoltaic cell. Several mirrored units are placed together on a panel, which is mounted on a tracking apparatus to follow the sun throughout the day.

Other companies are trying the same concept, albeit with slightly different technology.

New Mexico-based Emcore Corp., for one, uses optical lenses to focus the energy of 500 suns onto a tiny, super-efficient photovoltaic cell. And other companies are using various incarnations of mirrors or lenses on pedestals, dishes, troughs or carousels to magnify solar energy on tiny, highly efficient photovoltaic cells.

A dozen or so startup companies are wading into the field, tweaking designs that they claim will give the best performance, cost the least and be the most reliable. Even established companies like Sharp Corp., which has been in the solar business for nearly 50 years, are entering the field.

"I think there's a huge space [for CPV technology]," said Brad Collins, director of the American Solar Energy Society. "Solar deployment on a utility scale will explode in the next five years."

CPV's perks

CPV technology reduces the need for large amounts of photovoltaic material, which is often the most expensive part of a solar operation. But traditional photovoltaic companies installing panels on rooftops or in small arrays need not worry about the new kid in town. CPV is, by design, better suited for large utility-scale setups.

"It doesn't compete with traditional PV. The applications are different," Collins said. "One's going to be a power plant, and one is a distributed resource. It's not comparing apples to apples."

The technology, however, will compete with large concentrating solar power plants, Collins said.

Concentrating solar power, or solar thermal, involves using the sun's energy to create heat that can be turned into electricity.

Concentrating solar power and CPV are similar on many fronts. Both involve mirrors or lenses to magnify the sun's energy, both have the capability to produce utility-scale solar power, and both operate best in sunny areas like the southwestern United States.

The primary difference is the method used to convert the sun's energy into electricity.

"There are the big concentrating solar power plants -- the solar thermal stuff that's been around a long time -- and they use mirrors as we do in a different way," said Hartsoch, who is also director of the new trade group, CPV Consortium.

And as CPV requires less photovoltaic material than traditional photovoltaic technology, it likewise requires less water than concentrating solar power systems.

Hartsoch said SolFocus' design uses 4 gallons of water per megawatt-hour of electricity produced -- most of that to clean the panels -- compared with about 850 gallons per megawatt-hour at a solar thermal plant.

"I guess you could say it's a drop in the bucket," Hartsoch said.

The technology has some other perks, as well.

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