500 suns? Not low tech. Precision tracking and rigidity in the mirror support regardless of wind or position is required. I gave up on concentrations over 50 as being too difficult to satisfy the commercial environment. :( Kirk
--- MH <[EMAIL PROTECTED]> wrote: > APS testing world's most efficient solar cells > By Ed Taylor, Tribune > Nov 1, 2004 > > http://www.eastvalleytribune.com/index.php?sty=30814 > > Arizona Public Service has started testing the > world's most efficient > solar cells at its Solar Technology and Research > Center in Tempe. > > The cells, which covert sunlight directly into > electricity, have the > potential to revolutionize the industry by making > solar energy more > cost-competitive with conventional energy sources, > said Peter > Johnston, manager of technology development for > APS. > > “This has been an evolutionary process, but this > technology has the > potential to bring revolutionary change,” he said. > > The new photovoltaic technology was developed by > the Spectrolab > division of The Boeing Co., and similar systems > have been used to > power spacecraft, including the Mars Rovers. The > APS test is the > first time it has been demonstrated as part of a > utility's electricity > grid. > > “It's small, a one kilowatt system, but it's the > world's first,” Johnston > said. > > The new device uses concentrating triple junction > solar cells, which > are composed of three layers of semiconducting > material, each of > which extracts energy from a different part of the > solar light > spectrum. The efficiency is further enhanced by a > system of mirrors > that concentrates the sunlight by 500 times onto > each cell. That is > about twice the concentration of existing > photovoltaic systems, > Johnston said. As a result, the new system is > expected to be about > 50 percent more efficient at converting sunlight > into electricity than > other technology APS has tested to date, he said. > > The silicon cells APS has been testing at the STAR > center have > about a 20 percent efficiency rating, meaning that > about 20 percent > of the sun's energy is converted to electricity. > The new cells, which > are made of layers of gallium indium phosphide, > indium gallium > arsenide and germanium, have a conversion > efficiency of about 32 > percent, Johnston said. > > Eventually Boeing hopes to increase that efficiency > to 50 percent, > he said. Increasing the efficiency of solar cells > is important to > bringing down the cost of solar energy. To date the > cost per > kilowatt of electricity produced from sunlight has > been about four > times greater than electricity produced from > conventional sources > such as coal. The new system may cut that cost in > half, making solar > still twice as expensive but closer to being > competitive, especially if > conventional sources of fuel continue to increase > in price, Johnston > said. The system is less costly because fewer cells > are needed, > which reduces the amount of expensive > semiconducting material that > is used, said Dr. Raed Sherif, manager of > terrestrial photovoltaic > activity at Boeing Spectrolab. > > APS plans to continue testing the system for about > a year and will > install improved cells as they are developed. The > purpose is to test > the reliability of the technology, which could > encourage more utilities > to give it a try, Sherif said. > > Because triple junction solar cells have functioned > successfully in the > extreme temperatures of space, Sherif believes they > will prove > reliable on Earth, even in the intense heat of > sunlight concentrated > 500 times. “We don't think the performance will > degrade, but that is > one of the things we need to demonstrate,” he said. > _______________________________________________ > Biofuel mailing list > [EMAIL PROTECTED] > http://wwia.org/mailman/listinfo.cgi/biofuel > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Biofuel archives at Infoarchive.net (searchable): > http://infoarchive.net/sgroup/biofuel/ > __________________________________ Do you Yahoo!? Check out the new Yahoo! Front Page. www.yahoo.com _______________________________________________ Biofuel mailing list [EMAIL PROTECTED] http://wwia.org/mailman/listinfo.cgi/biofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuel archives at Infoarchive.net (searchable): http://infoarchive.net/sgroup/biofuel/
