Brightness in the Desert: Reflective Overshot in Ivanpah Power Towers

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by Emil Morhardt

Flying back to LA from New York the other day, just when I thought we should begin descending, a bright light flooded the cabin from the north. It was emanating from the ground, I’d estimate 50 miles or so away, and was too bright to look at directly—it seemed about as bright as the sun. I couldn’t take a picture until we were way past it, and then through a dirty window, from 35,000 feet, on my iPhone, but you can get the idea from the picture above. I don’t know what my fellow passengers who were actually looking out the window thought…UFO maybe…but I knew just what it was: light reflected past the collectors from the three power towers BrightSource Energy (http://bit.ly/1pkD6D80) has erected in Ivanpah Valley, along Interstate 15 just west of the Nevada state line. Fully on, which the must have been, they produce 377 MW of electricity by using a semicircular array of mirrors to reflect sunlight onto boilers at the top of three towers. From the ground, the tops of the towers are lit up, but nothing else. From 35,000 ft at the right location they produce a powerful beacon reflecting a good deal of light back into space. Why?

It must be a design feature. Better to make sure the collector is completely saturated with solar rays rather than going to a lot of effort not to reflect light past the target, but I’m guessing that this overreach wasn’t covered in the BLM environmental impact statement—at least I don’t see any sign of it there ( http://on.doi.gov/11WnV86 ) but it’s 350 pages long so I might have missed it. Are birds attracted to a light source as powerful as this? Does it bother aviation? Whatever it might do, I don’t think there are any other such powerful light sources on the ground anywhere, so it might warrant some study. Most concerns about light pollution are related to keeping a dark night sky. No problem of that sort here, since when the sun is down there is nothing to reflect. I’m wondering if there are any studies at all of daytime light pollution. I’m hoping that Jennifer Rigney, BrightSource’s press person (email below) will enlighten us with a comment.

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