De overstap naar zonne-energie erg dichtbij?

Solar cells, the heart of the photovoltaic industry, must be tested for mechanical strength, oxidized, annealed, purified, diffused, etched, and layered.

Heat is an indispensable ingredient in each of those steps, and that's why large furnaces dot the assembly lines of all the solar cell manufacturers. The state of the art has been thermal or rapid-thermal-processing furnaces that use radiant or infrared heat to quickly boost the temperature of silicon wafers.

Now, there's something new.

A game-changing Optical Cavity Furnace developed by the U.S. Department of Energy's National Renewable Energy Laboratory uses optics to heat and purify solar cells at unmatched precision while sharply boosting the cells' efficiency.



The Optical Cavity Furnace (OCF) combines the assets that photonics can bring to the process with tightly controlled engineering to maximize efficiency while minimizing heating and cooling costs.

NREL's OCF encloses an array of lamps within a highly reflective chamber to achieve a level of temperature uniformity that is unprecedented. It virtually eliminates energy loss by lining the cavity walls with super-insulating and highly reflective ceramics, and by using a complex optimal geometric design. The cavity design uses about half the energy of a conventional thermal furnace because in the OCF the wafer itself absorbs what would otherwise be energy loss. Like a microwave oven, the OCF dissipates energy only on the target, not on the container.

Different configurations of the Optical Cavity Furnace use the benefits of optics to screen wafers that are mechanically strong to withstand handling and processing, remove impurities (called impurity gettering), form junctions, lower stress, improve electronic properties, and strengthen back-surface fields.

Making 1,200 Highly Efficient Solar Cells per Hour

NREL researchers continue to improve the furnace and expect it to be able soon to hike the efficiency by 4 percentage points, a large leap in an industry that measures its successes a half a percentage point at a time. "Our calculations show that some material that is at 16 percent efficiency now is capable of reaching 20 percent if we take advantage of these photonic effects," NREL Principal Engineer Bhushan Sopori said. "That's huge."

Meanwhile, NREL and its private-industry partner, AOS Inc., are building a manufacturing-size Optical Cavity Furnace capable of processing 1,200 wafers an hour.

At about a quarter to half the cost of a standard thermal furnace, the OCF is poised to boost the solar cell manufacturing industry in the United States by helping produce solar cells with higher quality and efficiency at a fraction of the cost.



The furnace's process times also are significantly shorter than conventional furnaces. The Optical Cavity Furnace takes only a few minutes to process a solar wafer.

NREL has cooperative research and development agreements with several of the world's largest solar-cell manufacturers, all intrigued by the OCF's potential to boost quality and lower costs.

R&D 100 Award Winner

NREL and AOS shared a 2011 R&D 100 Award for the furnace. The awards, from R&D Magazine, honor the most important technological breakthroughs of the year.

Billions of solar cells are manufactured each year. A conventional thermal furnace heats up a wafer by convection; a Rapid-Thermal-Processing furnace uses radiative heat to boost the temperature of a silicon wafer up to 1,000 degrees Celsius within several seconds.

In contrast to RTP furnaces, the Optical Cavity Furnace processing involves wafer heating at a relatively slower rate to take advantage of photonic effects. Slower heating has an added advantage of significantly lowering the power requirements and the energy loss, so it can boost efficiency while lowering costs.

"With all solar cells, optics has a big advantage because solar cells are designed to absorb light very efficiently," NREL Principal Engineer Bhushan Sopori said. "You can do a lot of things. You can heat it very fast and tailor its temperature profile so it's almost perfectly uniform."

In fact, the OCF is so uniform, with the help of the ceramic walls, that when the middle of the wafer reaches 1,000 degrees Celsius, every nook and cranny of it is between 999 and 1,001 degrees.

"The amazing thing about this is that we don't use any cooling, except some nitrogen to cool the ends of the 1-kilowatt and 2-kilowatt lamps," Sopori said. That, of course, dramatically lowers the energy requirements of the furnace.

The use of photons also allows junctions to be formed quicker and at lower temperatures.

As America strives to reach the goal of 80 percent clean energy by 2035, the White House and the U.S. Department of Energy are challenging the solar industry to reach the goal of $1 per watt for installed solar systems. To reach that goal, manufacturers need better, less expensive ways to make solar cells. At $250,000, the Optical Cavity Furnace can do more, do it quicker, and do it at a lower capital cost than conventional furnaces.

Twenty Years of Great Ideas

For more than two decades, Sopori had great ideas for making a better furnace.

He knew that incorporating optics could produce a furnace that could heat solar cells, purify them, ease their stress, form junctions and diffuse just the right amount of dopants to make them more efficient.

"It's always easy on paper," Sopori said recently, recalling the innovations that worked well on paper and in the lab, but not so well in the real world. "There are moments … you realize that no one has ever done something like this. Hopefully it will work, but there are always doubts."

Trouble was, he'd come up with some elegant theoretical solutions involving optics, but wasn't able to combine them with the optimal geometry and materials of a furnace. "We've had a whole bunch of patents (12) to do these things, but what we were missing was an energy-efficient furnace to make it possible," Sopori said.

And then, combining his expertise in optics with some ingenious engineering with ceramics, he had his ah-ha moment:

NREL's Optical Cavity Furnace uses visible and infrared light to uniformly heat crystalline silicon wafers, especially at the edges, which are prone to cooling or heat loss, at unprecedented precision. The rays heat the sample, but the wafer never physically contacts the lamps.

The Optical Cavity Furnace is versatile. Each step in the solar cell manufacturing process typically requires a different furnace configuration and temperature profile. However, with the OCF, a solar cell manufacturer simply tells a computer (using NREL proprietary software) what temperature profile is necessary for processing a solar cell.

So, the OCF can perform five different process steps without the retooling and reconfiguration required by the furnaces used today, all the while incrementally improving the sunlight-to-electricity conversion efficiency of each solar cell.

http://www.zeitnews.org/e(...)cut-solar-costs.html

The Steady Rise of the Solar PV Manufacturing Industry Signals a Bright Future

Solar photovoltaic (PV) companies manufactured a record 24,000 megawatts of PV cells worldwide in 2010, more than doubling their 2009 output. Annual PV production has grown nearly 100-fold since 2000, when just 277 megawatts of cells were made. Newly installed PV also set a record in 2010, as 16,600 megawatts were installed in more than 100 countries. This brought the total worldwide capacity of solar PV to nearly 40,000 megawatts—enough to power 14 million European homes.



Made of semiconductor materials, PV cells convert solar radiation directly into electricity. Rectangular panels consisting of numerous PV cells can be linked into arrays of various sizes and power output capabilities—from rooftop systems measured in kilowatts to ground-mounted arrays of hundreds or even thousands of megawatts. (One megawatt equals 1,000 kilowatts.)

There are two main types of PV—traditional crystalline silicon and newer thin-film PV. In 2010, crystalline silicon production was more than double the output of 2009, accounting for over 80 percent of all PV produced. While thin-film production did not keep pace, it still grew by more than 60 percent. First Solar, a U.S. firm, maintained its leadership role in thin-film production, accounting for over 40 percent of world output, most of it produced in Malaysia.

Data provided to Earth Policy Institute by GTM Research show that Chinese manufacturers again dominated the global industry in 2010, with close to 11,000 megawatts of PV cell production. (See data at www.earth-policy.org.) This was the seventh consecutive year in which China at least doubled its PV output. Taiwan was a distant second with 3,600 megawatts produced, followed by Japan with 2,200 megawatts, Germany with 2,000 megawatts, and the United States with 1,100. The top five countries thus accounted for 82 percent of total world PV production.



While Germany ranks fourth in solar cell manufacturing, it towers above all other countries in terms of actual electricity generation from solar panels. Germany has widened its lead in this category each year since overtaking Japan in 2004 and, after adding 7,400 megawatts in 2010, now boasts 17,200 megawatts of installed PV. This is more than 40 percent of global capacity and over four times the 3,800 megawatts in Spain, the number two country. PV in Germany now generates enough electricity to meet the power demand of some 3.4 million German homes.

Japan installed close to 1,000 megawatts of new PV capacity in 2010. It is the third-ranked country in installed PV, with a total of 3,600 megawatts. As solar adoption accelerates in Japan, its national target of 28,000 megawatts by 2020 may be easily surpassed, especially as the country weighs energy alternatives following the March 2011 Fukushima nuclear disaster.

By nearly doubling its total PV power capacity in 2010, Italy vaulted past the United States to claim the fourth position in the world solar rankings, with 3,500 megawatts. With an expected 8,000 megawatts of new PV in 2011, likely overtaking Germany in new installations, Italy will have already exceeded its official 2020 goal of 8,000 megawatts. Enel, Italy's leading utility, sees the country reaching 30,000 megawatts by 2020—enough to satisfy half of its current residential electricity needs.

PV capacity in the United States also saw strong growth in 2010, increasing by more than 50 percent to reach 2,500 total megawatts. California, which now has more than 1,000 megawatts connected to the grid, again led all states in new PV installations. But a number of other states, including New Jersey, Nevada, and Arizona, are ramping up their solar capacity as well, driven by programs and incentives at the state and federal levels.

Until very recently, China's status as PV manufacturing powerhouse had not translated into much solar generation at home, as panels were seen as too expensive in the domestic market. While the vast majority of Chinese-made PV is sent abroad, a growing government commitment to increasing solar power as part of the energy mix is now catalyzing substantial PV capacity gains. Total installed PV in China grew 140 percent to nearly 900 megawatts in 2010. This was the first full year for the national Golden Sun program, which covers half the investment and grid connection costs of a solar project. It is expected to result in at least 1,000 megawatts of new installations each year after 2012.

http://www.zeitnews.org/e(...)den-intern-sant.html

En Nederland blijft achter. Heel goed gezien van onze politici om hier niet in te investeren

Morocco to host first solar farm in ¤400bn renewables network

Morocco has been chosen as the first location for a German-led, ¤400bn project to build a vast network of solar and windfarms across North Africa and the Middle East to provide 15% of Europe's electricity supply by 2050.

The Desertec Industrial Initiative (DII), a coalition of companies including E.ON, Siemens, Munich Re and Deutsche Bank, announced at its annual conference being held in Cairo on Wednesday that "all systems are go in Morocco", with construction of the first phase of a 500MW solar farm scheduled to start next year. The precise location of the ¤2bn plant is yet to be finalised, but it is expected to be built near the desert city of Ouarzazate. It will use parabolic mirrors to generate heat for conventional steam turbines, as opposed to the photovoltaic cells used in the UK.

The 12 square kilometre Moroccan solar farm will, said Paul van Son, Dii's chief executive, be a "reference project" to prove to investors and policy makers in both Europe and the Middle East/North Africa (MENA) region that the Desertec vision is not a dream-like mirage, but one that can be a major source of renewable electricity in the decades ahead.

Van Son described Desertec as a "win-win" for both Europe and MENA, adding that the Arab spring had created both opportunities and "questions" for the ambitious project. Discussions are already underway with the Tunisian government about building a solar farm, he said, and Algeria is the next "obvious" country, due to its close proximity to western Europe's grid. Countries such as Libya, Egypt, Turkey, Syria and Saudi Arabia are predicted to start joining the network from 2020, as a network of high voltage direct current cables are built and extended across the wider region.

German companies and policymakers have dominated the Dii conference, reflecting the nation's recent decision to totally phase out nuclear power by 2022 in reaction, in part, to the Fukushima nuclear disaster in Japan in March. By comparison, not a single representative from the UK was at the conference.



Jochen Homann, the state secretary at Germany's Federal Ministry for Economics and Technology, told the conference: "We undertook major reforms in German energy policy this summer and Desertec opens up an opportunity for us. We want to enter the age of renewables with sustainable sources of electricity supplying 80% of our power generation by 2050. As we accelerate our phase-out of nuclear power, we need to safeguard an affordable supply of electricity and we will be interested in importing renewables supplies in the future. Germany's government will continue to support Desertec. It is an inspiring vision which is good for foreign, climate and economic policies."

But Homann stressed there would be "pre-conditions" for guaranteeing long-term support from the Germany government. He said there must be "liberalisation" of the energy markets across the MENA region: "North Africa still provides huge subsidies for fossil fuels. There will need to be regulatory improvements. Only then will renewables be able to compete and a common market created. And other European states must participate, too."

Hassan Younes, Egypt's minister of electricity and energy, told the conference that Egypt was keen to participate and that it hoped to have a 1,000MW windfarm built by 2016 in the Gulf of Suez, adding to the 150MW "hybrid" gas-solar power plant that opened 100km south of Cairo earlier this year.

The conference was told via a Dii promotional video that the network of solar and windfarms across the MENA region would help to "halt migration" into Europe, by fast-tracking the rise of the region's youthful population out of poverty and unemployment.

The Desertec plan was welcomed by many in Germany, including chancellor Angela Merkel. However, some German critics argued that the concept of transmitting solar power from Africa to Europe was not proven and that a billion dollar project does not fit in to the country's green energy plan.

German development NGO Germanwatch raised concerns that local people should benefit from the scheme, though Desertec representatives said the energy generated will first be used by the people of north Africa before being exported. Andree Böhling, energy expert at Greenpeace Germany, said: "We have to avoid European companies getting their hands on local resources, therefore we will follow the project carefully."

http://www.zeitnews.org/e(...)ewables-network.html

quote:

Op zaterdag 5 november 2011 10:32 schreef tntkiller het volgende:
Sharp ontwikkelt zonnecel met record-efficiëntie van 36 procent

Door Yoeri Nijs, zaterdag 5 november 2011 10:17, views: 888

Sharp heeft de efficiëntie van een prototype-zonnecel verhoogd naar 36,9 procent. De fabrikant bereikte het percentage door de weerstand tussen de drie lagen waar de cellen uit zijn opgebouwd te verlagen. Hoe dat precies werkt, is onduidelijk.

De zonnecellen zijn opgebouwd uit verschillende fotovoltaïsche lagen die twee of meer elementen als indium en gallium bevatten. Vanwege hun efficiëntie worden dit soort samengestelde zonnecellen met name in satellieten toegepast.

Sharp claimt dat het de weerstand tussen de drie verschillende lagen heeft weten te verminderen, zonder in detail te treden hoe dit bereikt is. Het percentage van 36,9 procent zou een record zijn. Het verbeteren van de efficiëntie gaat met kleine stapjes. In 2009 wist Sharp ook al een verbeterde conversie te bewerkstelligen. Toen behaalde het bedrijf met dezelfde fotovoltaïsche lagen een rendement van bijna 35,8 procent.

http://tweakers.net/nieuw(...)-van-36-procent.html

Nice!

Nanoantennas could make for more efficient solar panels

Radio waves are a type of electromagnetic energy, and when they're picked up by traditional metallic antennas, the electrons that are generated can be converted into an electrical current. Given that optical waves are also a type of electromagnetic energy, a team of scientists from Tel Aviv University wondered if these could also be converted into electricity, via an antenna. It turns out that they can - if the antenna is very, very short. These "nanoantennas" could replace the silicon semiconductors in special solar panels, which could harvest more energy from a wider spectrum of sunlight than is currently possible.

The nanoantennas are constructed out of small amounts of aluminum and gold, and are each less than a micron in length - because light has such a short wavelength (as compared to radio waves), short antennas provide the optimal absorption. After being created, the nanoantennas were then exposed to light, to determine how well they could receive and transmit light energy. According to the initial tests, 95 percent of the wattage being absorbed by the antennas was passed along, with only 5 percent being wasted.



Not only are the nanoantennas efficient, but when their length is varied, the wavelength that they can absorb changes. Therefore, the researchers believe that one panel containing a variety of lengths of otherwise-identical nanoantennas could harvest energy from a much broader solar spectrum than is presently allowed by semiconductor technology.

To that end, the Tel Aviv team is now in the process of creating experimental plastic solar panels, nano-imprinted with varying lengths and shapes of nanoantennas. They are also looking into the electromagnetic-energy-to-electrical-current conversion process, with hopes of improving it.

Although silicon is not a particularly expensive material, the scientists believe that the superior efficiency of their panels could allow them to be smaller than present photovoltaic panels, and thus more cost-effective.

Similar research is also under way at the Idaho National Laboratory, where researchers have been developing plastic sheet solar panels stamped with nanoantennas.

http://www.zeitnews.org/n(...)nt-solar-panels.html

'Fool's gold' aids discovery of new options for cheap, benign solar energy

Pyrite, better known as "fool's gold," was familiar to the ancient Romans and has fooled prospectors for centuries – but has now helped researchers at Oregon State University discover related compounds that offer new, cheap and promising options for solar energy.

These new compounds, unlike some solar cell materials made from rare, expensive or toxic elements, would be benign and could be processed from some of the most abundant elements on Earth. Findings on them have been published in Advanced Energy Materials, a professional journal.

Iron pyrite itself has little value as a future solar energy compound, the scientists say, just as the brassy, yellow-toned mineral holds no value compared to the precious metal it resembles. But for more than 25 years it was known to have some desirable qualities that made it of interest for solar energy, and that spurred the recent research.

The results have been anything but foolish.

"We've known for a long time that pyrite was interesting for its solar properties, but that it didn't actually work," said Douglas Keszler, a distinguished professor of chemistry at OSU. "We didn't really know why, so we decided to take another look at it. In this process we've discovered some different materials that are similar to pyrite, with most of the advantages but none of the problems.

"There's still work to do in integrating these materials into actual solar cells," Keszler said. "But fundamentally, it's very promising. This is a completely new insight we got from studying fool's gold."

Pyrite was of interest early in the solar energy era because it had an enormous capacity to absorb solar energy, was abundant, and could be used in layers 2,000 times thinner than some of its competitors, such as silicon. However, it didn't effectively convert the solar energy into electricity.

In the new study, the researchers found out why. In the process of creating solar cells, which takes a substantial amount of heat, pyrite starts to decompose and forms products that prevent the creation of electricity.



Based on their new understanding of exactly what the problem was, the research team then sought and found compounds that had the same capabilities of pyrite but didn't decompose. One of them was iron silicon sulfide.

"Iron is about the cheapest element in the world to extract from nature, silicon is second, and sulfur is virtually free," Keszler said. "These compounds would be stable, safe, and would not decompose. There's nothing here that looks like a show-stopper in the creation of a new class of solar energy materials."

Work to continue the development of the materials and find even better ones in the same class will continue at the National Renewable Energy Laboratory in Colorado, which collaborated on this research.

The work was done at the Center for Inverse Design, a collaborative initiative of the College of Science and College of Engineering at OSU, formed two years ago with a $3 million grant from the U.S. Department of Energy. It was one of the new Energy Frontier Research Centers set up through a national, $777 million federal program to identify energy solutions for the future.

The OSU program is different from traditional science, in which the process often is to discover something and then look for a possible application. In this center, researchers start with an idea of what they want and then try to find the kind of materials, atomic structure or even construction methods it would take to achieve it.

Finding cheap, environmentally benign and more efficient materials for solar energy is necessary for the future growth of the industry, researchers said.

"The beauty of a material such as this is that it is abundant, would not cost much and might be able to produce high-efficiency solar cells," Keszler said. "That's just what we need for more broad use of solar energy."

http://www.zeitnews.org/c(...)gn-solar-energy.html