A federal analysis of avian mortality at utility-scale solar facilities released earlier this week with little fanfare was unable to determine the cumulative impact on birds posed by the 1-megawatt-or-greater installations.
The report was produced by the environmental science division of Argonne National Laboratory and the National Renewable Energy Laboratory with funding from the Department of Energy’s SunShot Initiative — a project that seeks to make solar energy cost-competitive with other forms of electricity by the end of the decade.
Utility-scale installations that connect directly to the electric transmission grid are currently the cheapest way to produce power from solar energy, the analysis said.
There are about 800 such solar projects either in the pipeline, in construction or in operation in the United States, according to data from the Solar Energy Industries Association, a trade group. Together, the projects could produce more than 43 gigawatts of electricity — enough to power more than 30 million homes.
But the 82-page study, which included more than seven pages of bibliographic references, concluded that "the paucity of information for solar energy facilities and its lack of standardization make it impossible to develop an industrywide avian mortality estimate or comparison with any scientific certainty."
There are two types of utility-scale solar plants: large photovoltaic panel installations that use cells to convert sunlight to electric current, or newer — and more controversial — concentrated solar power facilities.
CSP systems use mirrors to heat an elevated, liquid-filled receiver known as a "power tower." The molten-hot liquid can then be converted to steam and generate electricity by spinning a turbine or be stored to generate electricity later when the sun isn’t shining — a major advantage over traditional, intermittent renewable energy projects.
New CSP facilities like the Mojave Desert’s gleaming Ivanpah solar plant, however, have been tarnished by reports of birds and bats getting scorched in midair after flying between the mirrors and tower. These "streamers" have been a public relations nightmare for Ivanpah developer BrightSource Energy Inc., operator NRG Energy Inc. and other companies that covet the power tower technology (Greenwire, Jan. 19).
A study released last week, for instance, estimated that 3,500 birds died at Ivanpah in just its first year of operation (Greenwire, April 24).
But to arrive at a scientifically valid figure for bird deaths for different types of utility-scale solar facilities or the sector as a whole, the national labs report said regulators and industry need control for factors that can cause avian mortality figures to vary widely between projects or even between audits of the same facility. These issues include the efficiency of searchers and the effort they put into finding dead birds, the levels of predation and scavenging done by other animals in the area, and an area’s background bird mortality rate.
Currently, there is also a major lack of data about utility-scale projects. The researchers could only find avian monitoring plans or fatality data for 15 solar facilities. And of the seven solar plants that had bird death information, "systemic avian fatality data were available for only four," the report said.
Once the utility-scale solar industry’s avian fatality data have been standardized and more widely collected, the impact of the sector can be compared with other power sources like U.S. fossil-fuel-fired power plants, which kill about 14 million birds per year.
To aid in the data standardizing and collecting efforts, researchers recommended that regulators and utility-scale solar developers learn from the wind energy industry’s experiences. After many years of ad hoc efforts to protect birds from wind turbines, a committee of federal, state and tribal agencies; the wind industry; and conservation officials created voluntary guidelines for wind energy developers aimed at limiting bird kills and minimizing other damage to natural resources (Greenwire, March 23, 2012).
Similar standards for utility-scale solar facilities could help to standardize bird death reporting, evaluate the exact causes of avian mortality and identify appropriate mitigation measures, the researchers said.
But rushing to require project developers to implement untested or unfounded mitigation strategies before they’ve figured out how to improve their data collection and analysis could distract from the opportunity to conduct scientifically rigorous research and "provide meaningful solutions," the report said.
"For the solar industry, participating in research to address wildlife impact challenges in the early stages of the growth of this energy sector may help avoid situations that the wind industry experienced, in which informative research was delayed or conducted under study designs that did not adequately address the issues," the researchers said.
The researchers have shown an "the overarching need for systematic monitoring and reporting, as well as further research into avian impacts from solar development," said Julie Falkner, senior director of renewable energy at Defenders of Wildlife, a conservation group. "We must address these issues to understand the risk posed by solar development to important avian populations, and the opportunities to effectively reduce that risk."
Falkner was one of nine reviewers who provided the national labs with pre-publications feedback on the report. Other commenters included officials from BrightSource Energy, the state Bureau of Land Management offices, the California Public Utilities Commission and the academic community.
The BrightSource official, Senior Vice President Joe Desmond, said the company was "encouraged by the results of the report."
Referring to its Ivanpah CSP plant, Desmond added, "We are committed to continuing our efforts to make our path-breaking facility into an industry-leading example of responsible power generation in every way."
The Department of Energy suggested that the report would aid in its effort to promote renewable, low-cost, utility-scale solar projects while protecting birds, bats and other natural resources.
"The key to developing any energy resource is making sure that we develop it safely and responsibly," DOE spokeswoman Dawn Selak said in a statement. "The Department is committed to helping to minimize the impact of solar energy development on the environment, including local wildlife."