By Ed Sperling
Mountain View, Calif –Dec. 17, 2008—Solar cells may be one of the ultimate system-level design challenges.
While it’s well understood how to make solar cells far more efficient—gallium arsenide, for example would make solar cells 35% to 40% efficient compared with CMOS, which is about 20% to 22% efficient—the problem has to be overlaid on a cost vs. efficiency equation. Gallium arsenide would increase the cost of solar cell chips by about 10 times, rendering it completely useless to commercial adoption of the technology, according to T.J. Rodgers, CEO of Cypress Semiconductor and chairman of the board at SunPower.
The dark horse material is cadmium telluride, which is currently being researched as a possible replacement for CMOS. Unlike CMOS, which has an indirect bandgap, cadmium telluride has the same kind of direct bandgap as gallium arsenide, which makes it more efficient.
But the even bigger problem lies outside the packages of solar cell arrays. Rodgers says it costs $750 per unit for the solar cells, and about the same amount of money to install it on a roof. He said the technology wrapped around the solar cell needs to be dramatically simplified to bring down the cost.
“The installation is too high and electronics are too expensive,” he said. “All of those things will be improved. By 2012, the goal is to match PG&E’s cost for producing electricity. In a couple of years, the price of solar will be cheaper and you will start seeing exponential growth.”
National Semiconductor claims to have solved one piece of the puzzle. Brian Halla, chairman and CEO of National, showed off a battery management device this week that he claims will greatly improve the efficiency of existing solar installations.
“A string of solar panels today works like the batteries in a Maglite flashlight,” he said. “If one goes out, they’re all bad.”
He said the same applies to solar panels, where one may be partially shaded for part of the day and throws off the electricity generated by the others. By routing the power through the device, he said far more power is generated.
Both companies, as well as Actel, are experimenting with a number of new system-level designs that can either generate or conserve electricity. Among the technologies being tested:
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Heat-generated electricity. A device being researched will wrap around the smokestack on diesel trucks is expected to produce 2Kw/hr. that currently is wasted. The same device can be applied to a hot exhaust pipe on a car to charge a battery. While it won’t fully run a hybrid car, it may increase the mileage by 10 percent.
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Commercial fuel cells. These are expected to show up in commercial generating stations over the next several years.
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Non-fixed solar farms. These are expected to begin operation over the next several years so they track the sun’s arc instead of fixed cells that can only produce electricity during part of the daylight.
John East, president and CEO of Actel, noted that the total savings from eliminating imported oil and avoiding wars fought to preserve oil could amount to about $1.5 billion a year, making it likely that such projects will become increasingly attractive sources of research and development over the next four years.