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For Immediate Release: August 10, 2004
Contact: Percy Della (916) 654-4989

Repowering with Larger Turbines at Safer Locations
May Be Key to Reducing Bird Deaths at Altamont, Says Report

Sacramento - Research findings are "sufficiently robust" for the wind industry to begin repowering with larger turbines in safer locations, or implementing measures to avoid or reduce bird deaths at Altamont Pass, according to a consultant's report for the California Energy Commission.

The report released today by the Energy Commission documents the results of a four-year study to address causal relationships between wind turbines and bird mortality in the Altamont Pass Wind Resource Area and to determine measures that could be implemented to reduce the incidence of bird collisions. Funded by the Commission's Public Interest Energy Research (PIER) program, the study was conducted by BioResource Consultants from Ojai, California.

There's heightened urgency to resolve the environmental concerns, says the report, since it can be a hindrance to California's goal of producing 20 percent of its electricity from renewable sources, including wind, by 2010. That's because Alameda County will not allow permits to increase electrical production at Altamont beyond the existing 584-megawatt capacity "until there is demonstrated progress toward" reducing bird kills. Overall wind turbines in California have an installed generating capacity of 2,000 megawatts, including 800 megawatts at the Altamont Pass.

The study estimates that 1,766 to 4,721 birds, of which 881 to 1300 are protected raptors, are killed annually at the Altamont Pass, the world's largest wind farm region. Researchers studied bird behaviors, raptor prey species availability, wind turbine and tower design and location, landscape attributes, and range management practices to better explain the variation in bird mortality. The goal was to develop models that could be used to predict high collision-risk situations and site new turbines in lowest risk locations.

Researchers found that bird species more prone to collision spent more time flying within close proximity of wind turbines and at heights at or below the rotor planes of the wind turbines. The turbines at the Altamont Pass are of very old designs and much smaller in size than what are currently being installed at newer wind farm developments. Researchers also found that turbines at the end of turbine rows, on either end of a gap in the row, in deep canyons, and in isolation caused disproportionately more collisions than other turbines. In addition, they concluded that perching on turbines and horizontal towers are less important factors than previously suspected.

These and other findings led the researchers to conclude that the most effective solution to reducing bird collisions in the Altamont Pass area is to replace the numerous small existing turbines with fewer, larger turbines on taller towers. The newer turbines are much more efficient, with one turbine generating the same capacity as seven to 10 older ones, thus allowing for more generation and fewer opportunities for collision. However, researchers caution that siting new turbines must follow prescriptions derived from the research. The paper suggests placing new turbines at locations and in arrangements that will result in lower risk for birds to collide with turbine blades. Siting turbines in lower risk locations is key to reducing bird mortality, according to the researchers.

Wind operators in the Altamont Pass applied for repowering permits in 1998 but never completed this effort due in part to the bird issue and uncertainty caused by the deregulation of the electricity market. Some operators are now gearing up for repowering, but others do not have immediate plans to initiate this effort.

The report provides mitigation measures to implement with the existing turbines. If successfully put in place throughout the Altamont Pass area, these measures may reduce bird mortality by up to 50 percent for some species. These steps include: relocating selected, highly dangerous turbines; removing broken and non-operating turbines; installing structures at the ends of turbine strings to divert birds to fly around the turbines; and, management practices - other than poisoning - to control rodents that may congregate around the base of turbines and are food sources for birds.

To compensate for continuing, unavoidable losses, the researchers recommend securing habitat to protect affected species in perpetuity. In addition, the new turbines and any mitigation measures implemented to existing turbines will need to be monitored for a period of three years to determine if they result in a reduction in bird mortality.

Wind turbines provide up to 3.5 billion kilowatt-hours of emissions-free electricity in California annually. The report says identifying and implementing new methods and technologies to reduce or resolve bird mortality in the Altamont Pass will help producers increase wind electricity yield at the site and apply the mortality-reduction methods at other sites around the state and country.

The Commission's PIER Program is considered the nation's most comprehensive ratepayer-funded environmental and energy technology research. The program awards up to $62 million a year in partnership with individuals, organizations, businesses, utilities and public and private research firms to bring environmentally safe, affordable and reliable goods and services to the marketplace.

The 520-page report, "Developing Methods to Reduce Bird Mortality in the Altamont Pass Wind Resource Area," is available on the Energy Commission's website at:



Attention Editors:

Pictures of wind turbines can be downloaded from the photo information exchange page of the National Renewable Energy Laboratory's web site at:


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