October 17, 2006 4:31 PM PDT
Sharp expanding beyond silicon in solar
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At the Solar Power 2006 Conference and Expo here, the company is showing off several prototype solar panels and a new system it hopes will increase efficiency and make it easier to install new solar systems. One prototype solar panel combines a tiny solar cell measuring about a quarter of an inch per side that sits beneath a Fresnel lens (a ridged lens originally used in lighthouses), which radically concentrates sunlight. Further improving its performance, the solar panel rotates with the sun.
Overall, Sharp says the panel can convert 36 percent of the sunlight that strikes it into electricity, far higher than the 13 to 22 percent conversion rates of commercial silicon solar cells.
Sharp has also developed prototype solar cells that combine a layer of amorphous silicon and a layer of conventional, crystalline silicon, said Ron Kenedi, vice president of Sharp's solar-energy solutions group. These solar cells are nearly transparent, so they could potentially be used in windows. Sharp has installed some of these cells at its latest LCD (liquid crystal display) plant in Kameyama, Japan, which obtains much of its power through various "clean" energy sources.
In another experiment, the company has inserted a layer of LED (light-emitting diode) lights between the two layers of the experimental combo cells. The solar cells power the LED lights, which can then light a room at night. Sharp is also experimenting with solar cells made from organic materials and different types of silicon.
The experimentation arises from a belief that different types of panels will be required for different applications, said Kenedi.
"You can't use the same product on the ground as on the roof. You have to have different weapons for each one of the wars," he said.
Cheap and easy
The solar panel with the concentrating lens is one example of a use-specific panel. This system, which may come to market in the next year or two, would be used for solar power plants--large installations in a field that would pass power onto the grid. These systems, for example, most likely would not be seen on suburban rooftops.
The underlying solar cell, which converts sunlight to electricity, in these panels is made out of III-V compounds (molecules made from elements in the III and V columns of the Periodic Table of Elements). Producing chips from these materials, such as gallium arsenide, is expensive. Thus, the solar cell needs to be small. The lens, by contrast, is much less expensive and measures a few inches across. The panel itself measures about 12.5 feet by 16 feet and contains 270 lenses. Overall, a complete panel with 270 lenses can churn out 2.9 kilowatts and rotates with the sun for maximum efficiency.
Unlike traditional solar panels, these panels require direct sunlight and can't, for example, harvest energy from light reflected off snow. So they work best in dry areas with lots of sunlight, such as the southwestern United States.
"The cell is expensive if you use it as it is," without the lens, acknowledged Kenedi, "but it will outperform traditional solar cells in the right conditions." The lens concentrates the energy to make it seem as if 700 suns are pointing at the solar cell, he added.
Sharp is also producing equipment for conventional silicon solar panels. At the show, the company announced that it hopes to bring what it calls a solar racking system to the U.S. The system, which is already in use in Japan, essentially cuts down the time it takes to put a solar system on a roof by about 20 percent.
On the consumer front, Sharp announced a partnership with Citibank that will let customers finance new solar systems through a home equity line of credit.
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