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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.

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:

Based on the evidence presented to date, elevated levels of solar flux generated by the focused energy from the heliostats may burn and damage exposed skin and feathers.... In addition, solar flux may injure birds directly via blinding. Degradation of eyesight could result in additional injury and mortality through collisions with objects in the environment (including the tower and heliostats), or preventing them from being able to perform normal life functions, including feeding, territorial maintenance, migration, or evading predators. In addition, mirrored heliostats and other infrastructure may cause injury and mortality by collisions. Based on Service's review of the applicant's docketed information and their expert testimony, we believe that none of the studies, including the applicant's contracted work on flux exposure of dead domestic fowl in Israel in the docketed report by [CH2M Hill's] G. Santalo, provide substantial insight as to what to expect at Hidden Hills or other proposed power tower facilities.

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

At this time, the Service notes that limited information is available and/or has been proffered by the applicant to fully evaluate direct, indirect, and cumulative impacts (blinding and burning) of flux to avian species. We recommend that third party scientific studies be conducted to correct the insufficient baseline information by testing hypotheses regarding the direct and indirect effects of avian exposure to elevated solar flux (above 4 Kw/m² [kilowatts per square meter]). In this way, the California Energy Commission, Bureau of Land Management, California Department of Fish and Wildlife, Nevada Department of Wildlife, and U.S. Fish and Wildlife Service may then make more fully informed decisions and better provide guidance on project siting, operation, and postconstruction monitoring.

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:

BrightSource has contracted surveys to assess use of the project site by Golden Eagles. BrightSource has characterized the use of the site by Golden Eagles as "low," despite documenting nesting territories in CA and NV and numerous incidental observations of Golden Eagles within and adjacent to the project footprint. The Service is cognizant of the large size of the project footprint (almost 5 miles²), the vast distances Golden Eagles travel in xeric habitat during daily forage and defense activities, and the potential for seasonal and annual variation in the number of breeders, floaters, subadults, and migrants which may use the project footprint and surrounding habitat during breeding and non-breeding movements. Upon review of the limited data provided by the applicant, the Service concludes the data the project proponent has presented are insufficient to document eagle use of the area through the annual cycle, and present a robust risk characterization of direct, indirect and cumulative effects to Golden Eagles.

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:

Based on an overview of the project proponents reported information, and our knowledge of the site, we conclude that the proposed project has the potential to affect Golden Eagles through a) the loss of foraging habitat, and b) the risk of direct take of eagles through injury or mortality caused by exposure to elevated levels of solar flux. For these reasons, we strongly encourage the project proponent to prepare an Eagle Conservation Plan to evaluate and address potential threats to eagles, describe the measures that BrightSource would undertake to avoid, minimize, rectify, reduce or eliminate, and mitigate those threats over the life of the proposed project. If, following robust analysis of available data, take is deemed to be likely, we recommend that the project proponent seek a programmatic take permit and use the Eagle Conservation Plan as of the basis for their permit application. Without an eagle take permit, take of eagles would be a violation 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.

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