Feds Weigh in on Solar Power Tower Threat to Birds

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Golden eagle near the Palen Solar Electric Generating System site | Photo via California Energy Commission

The Fish and Wildlife Service has submitted a formal letter of concern to the California Energy Commission (CEC) on the threat to wildlife from power-tower-style concentrating solar facilities. While FWS's comments specifically concern the Hidden Hills Solar Electric Generating System proposed by BrightSource Energy, which that company put on the back burner this month, the concerns expressed in the letter may have serious ramifications for other BrightSource projects.

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Submitted to the CEC by the Migratory Birds Division of FWS Region 8 on April 3, the same day on which BrightSource asked the CEC to suspend the approval process, the letter criticizes BrightSource's studies of the effects of concentrated solar energy -- "solar flux" -- on birds, saying that the "dead chicken" experiments BrightSource's contractors CH2M Hill performed in Israel aren't particularly useful in gauging potential threats to wildlife from BrightSource's technology:

To correct this lack of information on the effect of solar flux on birds, FWS suggests further research.

That 4 kW/m2 is an interesting figure; it's four times the energy level found in average unobstructed sunlight in the California desert, but still less than the 5kW/m2 suggested by CEC staff as a likely safety threshold, and far less than the 50 kW/m2 BrightSource proposed as a threshold based on its own interpretation of the results of Santolo's dead chicken study in Israel.

Though Hidden Hills will remain a theoretical project for the time being, joining the ranks of BrightSource's Rio Mesa, and Siberia projects, the FWS letter does have implications for the company's Palen Solar Electric Generating System east of Desert Center, which BrightSource plans to build in partnership with the renewable energy firm Abengoa.

Palen's proposed design at present is substantially similar to that BrightSource had in mind for Hidden Hills and Rio Mesa: 170,000 mirrored heliostats would focus solar flux on boilers atop two 750-foot power towers, generating a nominal maximum of 250 megawatts of electrical power per tower. The intensity of solar flux around each tower can thus be presumed to be roughly equivalent at Palen and at the now-theoretical Hidden Hills, meaning equivalent risk to any flying wildlife in the area.

BrightSource bought the Palen project from bankrupt firm Solar Millennium, which planned to build a generating facility using parabolic solar trough technology. Palen has already been permitted by the CEC as a solar thermal facility, and BrightSource is now seeking an amendment to that permit to allow the plant's design to use power tower technology. That technology is substantially different from Solar Millennium's trough tech in many respects, and one of those respects is that solar troughs don't create anywhere near the amount of solar flux outside the boundaries of the troughs themselves that BrightSource's power towers would by design.

Palen would be sited on an alluvial plain just west of the Palen Mountains along Interstate 10. A biological consultant hired by BrightSource reported this month, after conducting an eagle survey within a 10-mile radius of the Palen site, that eagle populations in the area were "low," though camera trapping did reveal a young eagle regularly visiting a bait station in the Palens only about four miles from the project site -- a few minutes' flight. A photo of that eagle is at the top of this post. Here's another:

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Photo via California Energy Commission

In addition to that eagle, the contractor's camera traps also documented a range of wildlife from bobcats to gray foxes to turkey vultures, and this red-tailed hawk:

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Photo via California Energy Commission

It's worth noting that BrightSource also characterized the eagle population around Hidden Hills as "low," regarding which FWS observed in its April 3 letter:

The CEC, which is starting to take power tower solar flux very seriously, has announced that it will hold a separate informational hearing on the flux issue as it decides whether to let BrightSource go ahead with Palen's radical redesign. BrightSource is staking a great deal on Palen's success, and the FWS Hidden Hills letter is almost certainly a dash of cold water to the degree that it can be construed to apply to Palen as well.

FWS isn't just worried about eagles: the letter details the agency's concerns over migratory birds as well. Palen sits on a migration corridor between the Colorado River and the Coachella Valley, an important stopover for birds like the Nashville warbler heading toward more coastal climes for the summer. As the FWS letter points out open desert is pretty important for migrating birds, and that's likely as true for Palen as it was for the area surrounding Hidden Hills.

But it's the eagle issue where FWS speaks in the strongest terms, as it urges BrightSource to get more data and put together a management plan under the terms of the Bald and Golden Eagle Protection Act:

Given that the data in question doesn't exist and approval of a management plan takes time, FWS could delay things significantly if it decides its Hidden Hills concerns apply to Palen as well. BrightSource wants Palen online and generating power by 2016. Basing approval of the project on a year's worth of study of eagles and solar flux would push that schedule past the breaking point.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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