Posted on 12/09/2006 4:37:18 PM PST by neverdem
A tiny solar cell doubles the efficiency of common photovoltaics' conversion of sunlight to electricity by capturing the energy from a broader spectrum of light.
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.
Image: COURTESY OF SPECTROLAB
SOLAR EFFICIENCY: New solar cells capture more of the energy in sunlight by layering semiconducting material on top of germanium wafers, pictured here.
Thanks for the link.
Bye Bye Putie
Bye Bye Islamofascists
We hope you enjoy your slide back into the stone ages.
Solar cells are still a niche market. But once the costs drop to the point where they are viable for unsubsidized electric power augmentation for homes and business in places like the Southwest (where he have lots of sunlight and relatively little cloud cover), then the market will explode
Good questions, but I have no idea.
Renewable energy bump.
very little oil is used to make electricity
Unless solar energy is used to make something (perhaps hydrogen) that will displace the use of petroleum products in the transport fuels sector, this isn't going to reduce our dependence on foreign petroleum. Most electricity in this country comes from coal, followed by nuclear and hydro. Relatively little oil is burned to make electricity. Electric substitution in the transport sector would really help the imported oil dilemma.
Back feeding the grid is a pretty good start.
Generally the load peak is mid day, just when the sun provides peak power.
Pumping water back behind a dam while peak sun is available makes a pretty good battery.
When I installed a new roof, the tank and panels were removed. The tank was shipped off to the land fill. I stored the panels for the next 5 years. Eventually, I found a solar contractor who took them off my hands as replacement parts for a small number of customers who had the same setup.
"very little oil is used to make electricity"
If electric heat becomes cheaper than oil heat, oil will go down to $15/barrel.
"Most electricity in this country comes from coal, followed by nuclear and hydro."
Most new plants are cogens that use natural gas.
I've never heard that before. Old Dominion University has a good article about THE NATURE OF LIGHT RADIATED BY OUR SUN and discusses a lot of the irradiance variations. It sure doesn't mention spectral changes varying ever five minutes.
You might conserve some of the potential that the grid uses during the day, but you're still going to draw on those grid sources when the sun isn't shining, so we aren't going to displace them in any real sense, simply extend their potential.
Pumping water back behind a dam while peak sun is available makes a pretty good battery.
Pumped storage reservoirs generally have to be quite large to be economical, and siting those can be a challenge. Here is a case in point.
Not many people know it, but the genesis of the modern environmental movement is traced by many to the controversy surrounding the Storm King Mountain facility. This was a plant in the Hudson River Valley that was to be sited on property near land owned by quite wealthy individuals. These very wealthy landowners banded together to oppose Storm King Mountain, arguing that the presence of electricity transmission lines would obstruct their views of the Hudson River and its picturesque valley (this may sound an awful lot like the recent opposition to the Cape Cod wind farm project). Now, what was Storm King Mountain? Why, it was a pumped storage facility, meant to preserve generating capacity for excess energy generated on the grid, to be used during peak demand periods and perhaps when pollution levels elsewhere were high, forcing curtailment of the operation of heavily-polluting plants. Ask most people today what Storm King Mountain was and most people will say it was a nuclear plant, because that is what generates opposition. You'll generally get a slack-jawed deer-in-the-headlights look when you tell them it was really that darling of the solar energy crowd, a pumped storage reservoir. So when you see those Bohemian-looking scruffy environmentalist wackos demonstrating against some proposed generating facility, point out to them that they are more kin to wealthy New York landowners than any Friend Of The Earth.
Unfortunately, petroleum generates less than 3% of our electric power, so solar cells alone aren't going to free us from dependence on Middle Eastern oil. You will need huge improvements in battery technology for electric vehicles to be practical and fueled by solar energy. The triple junction solar cells in the article only address half of the problem.
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