3M's Renewable Energy Division and Gossamer Space Frames have unveiled what they claim is the world's largest aperture parabolic trough solar collector. Called the Large Aperture Trough (LAT) 73, it has an aperture size of 7.3m, and a concentration factor of more than 100x, which the companies say are world benchmarks.
3M and Gossamer designed the LAT 73 to cut the equipment and installation costs of concentrated solar power (CSP) systems. The demonstration system is fully operational, and has been installed at the Sunray Energy facility in Daggett, Calif., which is owned by Cogentrix Energy. This facility is the longest operating CSP facility in the US. The demonstration CSP solar collector system reduces the installed cost of a parabolic trough solar field by more than 25 percent.
The new CSP collector system has been operating since October of last year. At peak output, it provides about 275kw of electricity to the total output of the Sunray Energy facility, which is contracted to Southern California Edison. The collector system utilizes the durability, design flexibility, and high reflectivity of 3M Solar Mirror Film 1100 reflector panels.
Solar Mirror Film 1100 is a silver, adhesive-backed, metalized reflective film designed specifically for CSP, concentrating photovoltaic and solar thermal installations. Compared to glass mirrors, it has higher reflectivity, improved mechanical properties, and 50 percent lower weight. Total hemispherical reflectivity is 94.5 percent, which declines to 93 percent after 14 years of weathering, according to 3M's extensive testing. Specular reflectivity is 95.5 percent, and the material weighs 332g per square meter.
The highly accurate, large aperture collector design of the LAT 73 is enabled by a combination of the film's superior optical performance and light weight. The National Renewable Energy Laboratory (NREL) has verified the system's performance, measuring it at an optical accuracy of greater than 99 percent, according to 3M.