Wednesday, May 07, 2008

Focusing on Solar's Cost

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By Tyler Hamilton

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Intense array: Sunrgi hopes that arrays of its concentrated photovoltaic module can produce electricity for as little as five cents per kilowatt-hour, while occupying one-sixteenth of the land required for a conventional solar park.
Credit: Sunrgi

For example, connected to the bottom of each cell is a small fluid-filled chamber that acts as a heat sink. Murthy says that the fluid contains high-temperature composites and nanomaterials that rapidly remove the heat from the cells. This "super cooling" allows the cells to stay cool enough to work, about 10 to 20 °C above ambient temperatures. Murthy won't say what materials are in the fluid. "It's our secret."

Electronics engineer Thomas Forrester, another founding partner at Sunrgi, says that the chamber isn't filled with much: "We're talking as little as drops of liquid." But it's enough, he says, to absorb the heat and move it to another part of the cell so that it can dissipate rapidly into the environment. Future versions will attempt to capture that waste heat as useful energy. "We have patents pending on other designs that do this," he says.

Simon Fafard, founder and chief technology officer at Ottawa-based Cyrium Technologies, a maker of high-end cells for the concentrated photovoltaic market, says that the heavy-duty heat sinks that Sunrgi relies on leave little room for error during manufacturing. "It also makes testing the cells a bit more of a challenge," he adds.

Forrester says that's why most of the founders of Sunrgi have an expertise in manufacturing. "The question people ask us is, why hasn't any other solar company done this?" he says. "Well, we're taking a different approach that directly applies principles from chip manufacturing. That's one of the keys to our technology."

But other challenges remain. Concentrated photovoltaic systems need direct sunlight to work, meaning that they must be designed to track the sun through the day. Fafard says that Sunrgi's system, at 2,000 times concentration, will need to use tracking with pinpoint accuracy to keep the light focused on the tiny solar cells. He compares it to looking at a star through a telescope: the higher the magnification, the more accuracy is required to keep the star within view of the lens. This makes Sunrgi's system potentially more vulnerable to the elements. "Wind would definitely be bad," says NREL's Friedman. "If the thing is shaking even a little bit, the light will go off the cell."

The need for direct sunlight also means that concentrated photovoltaic systems don't work on cloudy or hazy days when conventional solar systems can at least capture some of the sun's energy. "So it makes the most sense for places like Phoenix, Spain, Australia," says Fafard.

Sidlo says that Sunrgi will initially be targeting utility-scale developments and is in talks with strategic partners, including manufacturers. The company is currently self-funded but says that it is talking with top venture capitalists.

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