See: http://www.renewableenergyworld.com/rea/news/article/2014/04/concentrating-solar-power-under-fire-glaring-planning-oversight-or-easily-remedied-issue
QUOTES [Clifford Ho of Sandia National Laboratories' Concentrating Solar Technologies Department says] "I believe some of the glare that's being viewed is taking place when the heliostats are in a standby mode." During peak daylight hours, it is common for a number of heliostat mirrors to be taken offline to prevent heliostats from directing more thermal energy to the turbine than it is capable of receiving. Ho said that during standby, these heliostats are focused on aim points next to the receiver, forming a ring of glare above the tower. According to Ho, the sunlight reflected from heliostats that are in standby mode could be having an exacerbating effect on the amount of reflection being emitted. In examining photos of the glare taken by passengers flying over the Ivanpah plant, Ho said it's apparent to him the intense light is emanating from the heliostats not in use. "You can clearly see the difference between what's just the diffuse reflection from the towers versus one or more heliostats that are in standby mode and reflecting light toward the observer." Ho has performed helicopter surveys of heliostats in standby mode at Sandia National Laboratories' National Solar Thermal Test Facility. "It's bright," he said, emphasizing that the Sandia CSP array is much smaller than that of Ivanpah. "When you're close, it can be like looking into the sun." . . . One possible solution, as suggested by Ho, is to reposition heliostats that are in standby mode so that they stand vertically -- thus reflecting the glare toward the ground instead of upward. - Jed
