With an aperture size of 7.3 meters, the concentration factor of the new 275 kilowatt Sunray system is over 100 times that of normal sunlight. The 3M panels are half the weight of glass panels and provide 94.5 percent reflectivity, with testing of the performance confirmed by NREL, the U.S. National Renewable Energy Lab.
The system utilizes 3M’s Solar Film 1100 and Gossamer frame design; the combination of the two technologies is said to reduce the cost of a parabolic solar field by 25 percent, according to 3M, based in St. Paul, Minnesota.
"The 3M Solar Mirror Film 1100 offers a number of significant advantages over traditional glass mirrors, including higher reflectance, less weight and improved mechanical properties," says Dan Chen, manager of the renewable energy division at 3M, in Minneapolis. The film is a mere 117 microns thick, and has a total solar reflectance of 94 percent, the company says. Composed of a silver metalized weatherable acrylic film and is designed for use in concentrating solar collectors.
The 3M/Gossamer system cost savings is derived from reduced equipment and installation costs, the companies suggest. "By combining 3M innovations in materials and Gossamer Space Frames innovations in structure and alignment, we are leading the industry on a new cost-reduction trend," comments Glenn Reynolds, president and co-founder of Gossamer Space Frames, based in Huntington Beach, California.
The Sunray facility, near Barstow, California, is owned and operated by Cogentrix Energy LLC. The facility was formerly known as Solar Energy Generation Systems I and II, or SEGS I and SEGS II, which came online in 1984 and 1985.
These were the first two utility-scale solar trough plants built in the world, designed to provide up to 43 megawatts of electric capacity under contract to Southern California Edison. The plants operate as Qualifying Facility Independent Power Producers under the Public Utility Regulatory Policies Act, with a special Standard Offer 2 type of power purchase agreement to Southern California Edison, according to an NREL profile.
Another parabolic solar system utilizing the 3M/Gossamer technology is scheduled to start up in June, although more details are not yet available, according to a 3M spokesperson.