tagged w/ solar cells
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A new process that simultaneously combines the light and heat of solar radiation to generate electricity could offer more than double the efficiency of existing solar cell technology, say the Stanford engineers who discovered it and proved that it works. The process, called "photon enhanced thermionic emission," or PETE, could reduce the costs of solar energy production enough for it to compete with oil as an energy source.
Stanford engineers have figured out how to simultaneously use the light and heat of the sun to generate electricity in a way that could make solar power production more than twice as efficient as existing methods and potentially cheap enough to compete with oil.
Unlike photovoltaic technology currently used in solar panels – which becomes less efficient as the temperature rises – the new process excels at higher temperatures.
Called "photon enhanced thermionic emission," or PETE, the process promises to surpass the efficiency of existing photovoltaic and thermal conversion technologies.
"This is really a conceptual breakthrough, a new energy conversion process, not just a new material or a slightly different tweak," said Nick Melosh, an assistant professor of materials science and engineering, who led the research group. "It is actually something fundamentally different about how you can harvest energy."
And the materials needed to build a device to make the process work are cheap and easily available, meaning the power that comes from it will be affordable.
Melosh is senior author of a paper describing the tests the researchers conducted. It was published online Aug. 1 in Nature Materials.
"Just demonstrating that the process worked was a big deal," Melosh said. "And we showed this physical mechanism does exist; it works as advertised."
Most photovoltaic cells, such as those used in rooftop solar panels, use the semiconducting material silicon to convert the energy from photons of light to electricity. But the cells can only use a portion of the light spectrum, with the rest just generating heat.
This heat from unused sunlight and inefficiencies in the cells themselves account for a loss of more than 50 percent of the initial solar energy reaching the cell.
If this wasted heat energy could somehow be harvested, solar cells could be much more efficient. The problem has been that high temperatures are necessary to power heat-based conversion systems, yet solar cell efficiency rapidly decreases at higher temperatures.
Until now, no one had come up with a way to wed thermal and solar cell conversion technologies.
Melosh's group figured out that by coating a piece of semiconducting material with a thin layer of the metal cesium, it made the material able to use both light and heat to generate electricity.
"What we've demonstrated is a new physical process that is not based on standard photovoltaic mechanisms, but can give you a photovoltaic-like response at very high temperatures," Melosh said. "In fact, it works better at higher temperatures. The higher the better."
While most silicon solar cells have been rendered inert by the time the temperature reaches 100 degrees Celsius, the PETE device doesn't hit peak efficiency until it is well over 200 C.
Because PETE performs best at temperatures well in excess of what a rooftop solar panel would reach, the devices will work best in solar concentrators such as parabolic dishes, which can get as hot as 800 C. Dishes are used in large solar farms similar to those proposed for the Mojave Desert in Southern California and usually include a thermal conversion mechanism as part of their design, which offers another opportunity for PETE to help generate electricity as well as minimize costs by meshing with existing technology.
"The light would come in and hit our PETE device first, where we would take advantage of both the incident light and the heat that it produces, and then we would dump the waste heat to their existing thermal conversion systems," Melosh said. "So the PETE process has two really big benefits in energy production over normal technology."
Photovoltaic systems never get hot enough for their waste heat to be useful in thermal energy conversion, but the high temperatures at which PETE performs are perfect for generating usable high-temperature waste heat. Melosh calculates the PETE process can get to 50 percent efficiency or more under solar concentration, but if combined with a thermal conversion cycle, could reach 55 or even 60 percent – almost triple the efficiency of existing systems.
The team would like to design the devices so they could be easily bolted on to existing systems, thereby making conversion relatively inexpensive.A new process that simultaneously combines the light and heat of solar radiation to... more
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SYDNEY scientists have scored gold, helping create the world's most efficient technology for turning sunlight into electricity.
Just as swimmers and runners struggle to shave 10ths of a second off their times, solar cell scientists battle for years to add fractions of a per cent to the efficiency of their creations.
US researchers developed experimental technology that could turn 42.7 per cent of the sunlight received into power - a world record.
By comparison, commercial cells often used in solar modules on Australian roofs convert only about 15 per cent.
The US technology was made of five separate cells, each tuned to draw energy from different parts of the light spectrum. One, for example, was designed to collect energy from the ultraviolet light band, while another, at the other end of the spectrum, was tuned to the far infrared.
By replacing one of the US cells with a new design developed by the Photovoltaic Centre for Excellence at the University of NSW, the technology's efficiency has now been nudged to a record 43 per cent.
The Sydney cell converts 46 per cent of red and near infrared light received into electricity, ''dragging up'' the overall efficiency of the American technology just 0.3 percentage points.
While progress may seem agonisingly slow, ''years of effort went into developing the cell'', the university's photovoltaic centre research director, Martin Green, said.
Although highly experimental, and far too expensive for commercial solar panels, the cell will inevitably inspire other researchers to race to develop even better technology.
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Professor Green estimated that by combining hundreds of advanced experimental cells, each tuned to different parts of the spectrum, an efficiency rating of up to 86 per cent was theoretically possible. But, he warned, ''it's not as easy as it sounds''.SYDNEY scientists have scored gold, helping create the world's most efficient... more
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"WASHINGTON — Imagine a carbon sheet that's only one atom thick but is stronger than diamond and conducts electricity 100 times faster than the silicon in computer chips.
That's graphene, the latest wonder material coming out of science laboratories around the world. It's creating tremendous buzz among physicists, chemists and electronic engineers.
"It is the thinnest known material in the universe, and the strongest ever measured," Andre Geim , a physicist at the University of Manchester, England , wrote in the June 19 issue of the journal Science.
"A few grams could cover a football field," said Rod Ruoff , a graphene researcher at the University of Texas, Austin , in an e-mail. A gram is about 1/30th of an ounce."
It can transmit electricity 100 times faster than silicon, is very mailable and one gram can cover a football field? Think of the applications: robotics, aviation, solar cells, lighter weight. . . everything!"WASHINGTON — Imagine a carbon sheet that's only one atom thick but is... more
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New Energy Technologies has announced that new tests of the Company's ultra-small solar cells for use in its transparent SolarWindow have demonstrated substantially superior performance over current thin-film and solar photovoltaic technologies at generating electricity from artificial light - an important advantage over conventional solar technologies which are limited by their capacity to function well where exposure to direct sunlight is available.
"One of the biggest issues with today's solar products is their dependency on direct sunlight, which our cells have demonstrated the potential capacity to overcome," explained Mr. Meetesh V. Patel, Esq., President and CEO of New Energy Technologies, Inc.
"We're now actively working to coat these cells onto transparent glass in order to fabricate our SolarWindows, which generate electricity and have the potential to be installed virtually anywhere that either direct sunlight or artificial lighting such as fluorescent systems emit visible light.
In contrast, today's building-integrated solar and photovoltaic products are limited to installation on south-facing surfaces, as is the case with currently-available solar materials tested in these newest experiments."
In a series of new experiments, researchers repeatedly tested New Energy's ultra-small solar cells on a 1"x1" substrate against today's popular solar materials for their capacity to produce electricity under varying artificial light conditions, mimicking the levels of light exposure in homes and commercial offices.
In every case, New Energy's solar cells, the smallest reported organic solar cells of their kind in the world, exponentially outperformed all of the conventional materials tested.
Under normal office lighting conditions, without the benefit of outside natural light from windows, New Energy's ultra-small solar cells produced:
Almost 2-fold greater output power density than monocrystalline silicon, an established commercial solar cell material; More than 8-fold greater output power density than copper-indium-selenide, known for its high optical absorption coefficients and versatile optical and electrical characteristics; and
More than 10-fold greater output power density than flexible thin-film amorphous-silicon, a popular 'second-generation' solar thin-film material.
New Energy's solar cells generate electricity not only from the visible radiation found in sunlight but also by using the visible light found in artificial illumination, such as the fluorescent lighting typically installed in offices and commercial buildings.New Energy Technologies has announced that new tests of the Company's ultra-small... more
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Why so many green jobs are sprouting in Colorado.
Talk from Washington suggests that investments in renewable energy, infrastructure, and public transit may be a partial solution to our economic woes. For the last several years, the Denver region has been staging a trial run of this strategy, one that shows both its promise—and perhaps its limits.
The Mile High City occupies the high ground when it comes to clean energy—and clean living. Denver's sheer outdoorsiness can be by turns charming and infuriating. (The question "What do you do?" is likely to be answered with an outdoor activity, not a profession.) When I showed up at Gov. Bill Ritter's office, an aide was carting a bicycle rack out of the inner sanctum. And while the state's jewel of a capital may be testimony to its heritage of extraction—walls of Colorado-mined rose onyx, a dome covered in gold, and Works Progress Administration-era frescoes paying tribute to coal mining—a new Colorado is dawning. In November 2004, Denver-area citizens voted to boost sales taxes to expand the region's light-rail system, and the state's voters approved a ballot initiative mandating that utilities draw a chunk of electricity from renewable sources. The quasi-independent republic of Boulder is a capital of composting, recycling, hybrid-driving, and general eco-fabulousness.
Ritter, a Democrat elected in 2006, speaks of the dawning of a "new energy economy," fueled by the shifting zeitgeist but also by the state's research universities, local institutions such as NREL, and anticipated stimulus funds. A quick case study: Abound Solar, which started producing thin-film solar material in April in Loveland, was hatched in a laboratory at Colorado State University in the 1980s, received $15 million in Department of Energy funds in the 1990s, and in recent years has raised $150 million in private capital.Why so many green jobs are sprouting in Colorado.
Talk from Washington suggests... more
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Solar electricity has a future: It is renewable and available in unlimited quantities, and it does not produce any gases detrimental to the climate. Its only drawback right now is the price: the electric power currently being produced by solar cells in northern Europe must be subsidized if it is to compete against the household electricity generated by traditional power plants.
At "Laser 2009" in Munich, June 15 to 18, Fraunhofer researchers will be demonstrating how laser technology can contribute to optimizing the manufacturing costs and efficiency of solar cells.
Cell phones, computers, MP3 players, kitchen stoves, and irons all have one thing in common: They need electricity. And in the future, more and more cars will also be fuelled by electric power. If the latest forecast from the World Energy Council WEC can be believed, global electricity requirements will double in the next 40 years. At the same time, prices for the dwindling resources of petroleum and natural gas are climbing.
"Rising energy prices are making alternative energy sources increasingly cost-effective. Sometime in the coming years, renewable energy sources, such as solar energy, will be competitive, even without subsidization," explains Dr. Arnold Gillner, head of the microtechnology department at the Fraunhofer Institute for Laser Technology in Aachen, Germany.
"Experts predict that grid parity will be achieved in a few years. This means that the costs and opportunities in the grid will be equal for solar electricity and conventionally generated household electricity." Together with his team at the Fraunhofer Institute for Laser Technology ILT in Aachen, this researcher is developing technologies now that will allow faster, better, and cheaper production of solar cells in the future.
"Lasers work quickly, precisely, and without contact. In other words, they are an ideal tool for manufacturing fragile solar cells. In fact, lasers are already being used in production today, but there is still considerable room for process optimization."
end of excerptSolar electricity has a future: It is renewable and available in unlimited quantities,... more
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Chris Eberspacher, PhD, V.P. of engineering at Nanosolar, Inc. gives an informational video of where technology is going with the production of solar cells. Nanosolar has developed an efficient and low cost way to produce solar cells.Chris Eberspacher, PhD, V.P. of engineering at Nanosolar, Inc. gives an informational... more
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photo: California Governor’s Office
California Governor Arnold Schwarzenegger on Monday terminated talk that the recession will crimp California’s fight against global warming when he ordered every utility in the state to obtain a third of its electricity from renewable sources by 2020. And in a move that will shake up the land rush to build solar power plants in the desert, Schwarzenegger signed an executive order to streamline and prioritize the licensing of such projects.
“One of the great things about California, of course, is that we always push the envelope,” said Schwarzenegger at startup OptiSolar’s solar cell factory in Sacramento, surrounded by a triptych of solar panels, utility executives and environmentalists. “That is why today I’m proposing that we set our sights even higher. This will be the most aggressive target in the nation.”photo: California Governor’s Office
California Governor Arnold Schwarzenegger... more
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By Julie Steenhuysen
CHICAGO (Reuters) - U.S. researchers have found a way to make efficient silicon-based solar cells that are flexible enough to be rolled around a pencil and transparent enough to be used to tint windows on buildings or cars.
The finding, reported on Sunday in the journal Nature Materials, offers a new way to process conventional silicon by slicing the brittle wafers into ultrathin bits and carefully transferring them onto a flexible surface.
"We can make it thin enough that we can put it on plastic to make a rollable system. You can make it gray in the form of a film that could be added to architectural glass," said John Rogers of the University of Illinois at Urbana-Champaign, who led the research.
"It opens up spaces on the fronts of buildings as opportunities for solar energy," Rogers said in a telephone interview.
Solar cells, which convert solar energy into electricity, are in high demand because of higher oil prices and concerns over climate change.
Many companies, including Japanese consumer electronics maker Sharp Corp and Germany's Q-Cells are making thin-film solar cells, but they typically are less efficient at converting solar energy into electricity than conventional cells.
Rogers said his technology uses conventional single crystal silicon. "It's robust. It's highly efficient. But in its current form, it's rigid and fragile," he said.
Rogers' team uses a special etching method that slices chips off the surface of a bulk silicon wafer. The sliced chips are 10 to 100 times thinner than the wafer, and the size can be adapted to the application.
By Julie Steenhuysen
CHICAGO (Reuters) - U.S. researchers have found a way to make... more
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William Yuan, a seventh-grader from Portland, OR, developed a three-dimensional solar cell that absorbs UV as well as visible light. The combination of the two might greatly improve cell efficiency. William's project earned him a $25,000 scholarship and a trip to the Library of Congress to accept the award, which is usually given out for research at the graduate level.
“Current solar cells are flat and can only absorb visible light,” he said. “I came up with an innovative solar cell that absorbs both visible and UV light. My project focused on finding the optimum solar cell to further increase the light absorption and efficiency and design a nanotube for light-electricity conversion efficiency.”
You know, that's just what I was thinking when I was 12, but my idea didn't quite work. Well, it was just a paper towel roll with "Solar Rays" written on the side in Sharpie, and I tried to use it to melt G.I. Joe figures. But still. Well done, William!William Yuan, a seventh-grader from Portland, OR, developed a three-dimensional solar... more
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