SOLAR EFFICIENCY: New solar cells capture more of the energy in sunlight by layering semiconducting material on top of germanium wafers, pictured here.
Image: COURTESY OF SPECTROLAB
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A tiny chip similar to the solar cells carried by many satellites and other spacecraft today--including the surprisingly long-lived Mars Rovers--has shattered previous records for maximum efficiency in producing electricity from sunlight. "This is the photovoltaic equivalent of the four-minute mile," affirms Larry Kazmerski, director of the Department of Energy's National Center for Photovoltaics in Colorado. "This is a disruptive technology that eventually could provide us, at least in the Southwest, with cost-competitive electricity fairly quickly."
The specifics: a germanium wafer is spun at high speeds and subjected to various gases that encourage the growth of layers of semiconducting material such as gallium arsenide. "We have somewhere between 20 and 30 layers of semiconductor material," explains David Lillington, president of Spectrolab, Inc., which developed the new cell. The resulting layers in one single solar device respond to different spectra of light. The top layer, for example, captures the energy of blue light while the middle layer absorbs green and the bottom uses red. Such triple-junction solar cells are specially tuned to work with concentrated light, in this case the wattage of 240 suns.
The resulting efficiency nearly doubles that of standard silicon solar cells, which hover at 22 percent. That gain requires, however, the use of light-concentrating devices, such as miniature plastic lenses and mirrors. The new solar cell achieved 40.7 percent efficiency under such concentrated light at the testing center at the National Renewable Energy Laboratory in Colorado. One cell of just 0.26685 square centimeter (or roughly 0.04 square inch) pumped out 2.6 watts of electricity when bathed at the maximum light concentration. "Every five minutes the spectrum of the sun changes," Kazmerski explains. So tests are conducted "under a simulator where everything stays constant."
Even though installed cells would require concentrators, the fact that fewer cells can produce the same amount of power--and that similar cells are already widely produced--means this system could potentially generate electricity in the range of 8 to 10 cents per kilowatt-hour--roughly equal to consumer electricity prices today. "Eventually it's hoped that it will come down enough to rival the price of traditional energy although that is future tense," notes Dave Garlick, a spokesman for Spectrolab's parent company Boeing.
"This could mean a significant increase in the penetration of solar power," says Clark Gellings, vice president of innovation at the Electric Power Research Institute, a think tank. "The real barrier was the cost of the device." Many utilities have already invested in solar, including giant solar farms in Portugal and China. In the U.S., Xcel Energy plans to build a relatively modest eight-megawatt solar power plant in Colorado next year using similar concentrated solar cells as well as other technology. "This is not a technology that is 10 years away," Kazmerski adds. "This is a technology that we are going to see out working next year."
Nevertheless, the record-breaking solar cells are at least 12 months away from full-scale manufacturing, Lillington says. "Before we put this new cell into production it needs to go through a qualification process to make sure it can withstand the rigors of the environment." Of course, its Martian peers have lasted 28 months in that harsh, alien environment.
And the triple-junction solar cell may not hold the efficiency record for long. "We are also looking at four-, five-, even six-junction solar cells," Lillington notes. "There are at least three or four different approaches to take the efficiency into the 45 percent range." And that means the price of energy harvested directly from the sun will continue to drop.
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8 Comments
Add Commenti thought it would be effective if every house was covered with solar panels . we could all feed into the grid and maybe we all get a paycheck ,too. at least pay nothing.
Reply | Report Abuse | Link to thisWhy are these new solar panels not being mass produced and placed on electric cars to recharge batteries?
Reply | Report Abuse | Link to thisThis article was written two years ago, I have yet to see this knowledge massively applied, as it should be. JamesDavis to the words out of my mouth, the space is the problem with the car application, and there cut that to a 1/4th. Humans need to get their crap together if the don't want to cause themselves near extinction in the next 30 years. Solar panels last nearly forever and there is gobs of money to make after the first 3-7 years pay off cost. If money is all you primates care about, there is your incentive.
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all the world waiting for the 5,6,7 junctioned solar cell , which can bring revolution in efficiency, environment friendly and cost of living matter.....and so on . Why we could n't make it fast and spread wide. Taking time on this matter may be harm full for our environmental balance........
Reply | Report Abuse | Link to thisJames, The earth recieves about 1000 Watts of energy per square meter. Even if the solar cells were able to recuperate 50% of that a car would receive between 2500 and 5000 Watts (the top surface of a car would vary between 5 and 10 square meters). This is the same as 6.7 to 13.4 horsepower. This power is similar to a small (sub 200 cc) motorcycle or a riding lawnmower. Most cars require 40 hp or more just to maintain 50 mph (80 km/h). Recharging batteries would also help but at $8/Watt, would definitely be cost prohibitive. That could add another $20,000 to the price of your already expensive electric or hybrid vehicle. That's why :-D
Reply | Report Abuse | Link to thisFirstly, I find your name funny because I'm the same person it would seem, above the level of realization of the "primates" or plebs as I perfer. 2ndly, I believe it to be much nearer then 30 years. I study just about every field of scientific study in depth and feel strongly we're just a couple years from what I've deemed "The boiling point", the fraction of a degree that transforms earth. If you're trying to survive it, let me know cause if all I have planned for the next year succeeds I will be. Ps: Look up the "Year without summer" on wikipedia, you might find it interesting, and I believe this will be repeating if not this summer then next. I've pretty much designed a self-sustaining durable structure and am preparing to become a "Geonaut". Hopefully you get a notification on the reply.
Reply | Report Abuse | Link to thisJames, the main reason batteries in cars are not charged by solar panels is radio interference. This was the reasoning for the 2010-201- prius models only having the panels connected to a cooling/ventilation system and not the battery. The amount of current tranferring to the battery basically made the radio futile(which I would be fine with anyways cause I play my own, not a media fed part of a herd) as the masses enjoy radio this power was redirected.
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