A solar energy project in the California desert seems to have injured and killed a surprising number of birds in the first two and a half weeks of September, according to data furnished to a state agency that went public Monday. And more than half of those injuries have been linked by project biologists to the facility's concentrated solar energy.
Between September 3 and September 19, workers at BrightSource Energy's Ivanpah Solar Electric Generating System in the Mojave Desert's Ivanpah Valley recorded 20 dead birds found on the project site near Primm, Nevada, 13 of which showed signs of scorching and singeing consistent with injuries from concentrated "solar flux."
As ReWire reported last month, Ivanpah workers found an injured peregrine falcon on site September 6. According to the new data from BrightSource, the falcon's injuries were consistent with overexposure to solar flux. A common yellowthroat was found alive with burn injuries on the site on September 5 and shipped to a rehab facility. The BrightSource data doesn't mention the eventual fate of either bird, but U.S. Fish and Wildlife Service spokesperson Jane Hendron confirmed to ReWire last month that the falcon succumbed to its injuries two days later.
The document, a spreadsheet posted by the California Energy Commission on its website Monday, was provided by BrightSource on September 20. It thus does not include any mortalities recorded in the last 10 days of the month. Ivanpah staff recorded 71 injured or killed birds on site from January 3 through September 19, meaning that approximately 29 percent of the project's recorded bird mortalities for the year so far took place in the first two and a half weeks of September.
Among the birds recorded as killed on the site in early September were a western tanager; a blue-gray gnatcatcher; a white-throated swift; chipping and Brewer's sparrows, a Cassin's vireo; a house finch; two mourning doves; a brown-headed cowbird; an American coot; MacGillivray's, Wilson's, and black-throated gray warblers; and six birds that were too badly damaged to identify positively but which probably included two sparrows, a warbler, a sandpiper, and a hummingbird.
The cowbird and one of the doves were judged to have died after colliding with some of the thousands of mirrored heliostats on the site. Biologists could not reliably determine the cause of death of seven of the birds. Which means that pending news on the fate of the yellowthroat, at least 12 of the birds killed at Ivanpah in early September showed clear signs of injury from solar flux.
By contrast, there were seven recorded bird mortalities at the site in August, and eight in July. BrightSource and its partners NRG Energy and Google have been ramping the 377-megawatt plant up in anticipation of beginning to deliver power to the grid by the end of the year, and that means more time spent with at least one of the towers "in flux."
Solar flux is a technical term meaning the rate of flow of solar energy through a given area. Bright unamplified sunlight has a solar flux of about a kilowatt per square meter of the earth's surface. In the sense in which solar power engineers use it, solar flux generally means solar energy that has been concentrated to the point where it can create steam that's used to generate electricity.
Though it's long been known that concentrated solar flux has the potential to harm living tissue, with delicate structures like feathers suffering damage at 160°C or below, actual safe levels of solar flux exposure for wildlife have been a chronic source of disagreement between BrightSource and state and federal regulators.
Solar flux's potential threat to wildlife has been of increasing concern over the last year as BrightSource has proposed several larger projects that would conceivably generate more intense flux fields. In its Preliminary Staff Assessment of the one such BrightSource project still on the drawing board, the proposed Palen Solar Electric Generating System, the CEC's staff suggested that the impact of Palen's solar flux on Riverside County's desert birds could be considerable. CEC staff went on to caution that without more hard data on the flux and wildlife issue, Palen's potential wildlife impacts would be difficult to assess.
It looks as though Ivanpah may be providing some of that hard data.