As with all human activities, wind energy has impacts. At wind facilities, birds and bats can be at risk. In aggregate, hundreds of thousands of birds and bats are killed by wind turbines every year.
While this amount is less than bird mortality from other anthropogenic sources of bird mortality, there’s more uncertainty about bat mortality, and the numbers for both birds and bats give reason for concern.
Proper siting of wind farms is the primary strategy, and toward that end, the U.S. Fish and Wildlife Service (USFWS) and several state wildlife agency recommendations for surveying birds and bats on proposed wind power sites have become increasingly stringent.
But even with the best surveys and most careful siting, wind turbines still kill birds and bats. The consequences for the wind power industry—and for anyone who supports the growth of clean, renewable power—are significant. Beyond the intrinsic value of the wildlife that are harmed, financial and reputational consequences can ensue.
Stiff penalties, operational changes
In 2013 and 2014, two wind farm operators in Wyoming signed criminal plea agreements for killing eagles and other birds protected by the Migratory Bird Treaty Act (MBTA). PacifiCorp Energy agreed to pay $2.5 million and Duke Energy Renewables $1.9 million (to USFWS and state agencies), and both agreed to conservation practices and operational changes (the costs of which are capped at $600,000 annually), according to an article by Svend Brandt-Erichsen published by NAWindpower.
The wind power industry has been taking bird and bat mortality seriously long before these high-profile plea agreements, developing solutions through the American Wind Wildlife Institute and other forums.
One result: In 2015, a large consortium of wind power operators agreed to change their operations during the July-October bat migration season. They will program their turbines to pivot parallel to the wind during periods of low wind and other conditions when bats are most active. Research has shown that this practice can cut fatalities by 30 percent, according to National Geographic.
“The financial impacts of this strategy will vary by wind farm,” said E & E’s Mike Morgante, operations manager. “Projects with very robust wind resources will experience the least impact, while others will sacrifice more revenues.” All the operators will incur costs to reprogram turbines, as well as from additional wear and tear.
Eagles are top concern
The bird species of greatest concern is golden eagles. Protected by the Bald and Golden Eagle Protection Act, as well as the MBTA, golden eagle populations are under pressure. Golden eagle strikes were a compelling factor in the Wyoming plea agreements—with PacifiCorp paying a higher fine due to a larger number of fatalities.
Wind power is not the main culprit in golden eagle mortality. The main causes are starvation, poisoning, and shooting, according to Brian Millsap of the USFWS, who spoke at a December 2015 National Renewable Energy Laboratory (NREL) workshop on eagle detection and deterrents.
The status quo approach to detecting eagles is to use human biomonitors who search for approaching eagles. Biomonitors are part of the compliance plans agreed to by Duke and PacifiCorp and are being used voluntarily by others.
While staff hired as biomonitors may appreciate the work and income, for wind power operators, the cost of deploying teams of biomonitors in multiple shifts for many years has a negative impact on rate of return—and may raise the cost of electricity produced. As such, the industry is looking toward new technologies that—though more costly up front—will result in savings over time.
The 2015 NREL workshop also included discussions on using drones and trained crows to harass eagles, and deploying horizontal planes of light to make it harder for eagles to detect prey on the ground, thereby making the wind farm less attractive.
Radars and cameras the top contenders in detection
The NREL conference showcased both developers of detection technologies presenting their work in radar systems (including SRC and DeTect), and developers of camera-based systems (including DTBird and RES Americas). Additionally, Normandeau Associates presented work on thermographic cameras and acoustic identification systems.
Radar has benefited from research funding unrelated to eagles or wind turbines (such as detecting birds and drones at airports). It can identify flocks of birds at longer distances than camera-based systems, but has less ability to identify species, according to the NREL report. While that capability may develop, in its current status, radar needs to be combined with cameras or other technology to identify eagles.
“A camera-based system doesn’t reach out as far as radar but is better at identifying species,” said RES Americas’ Tom Hiester in an interview with The Current. RES developed its IdentiFlight camera system to identify bald and golden eagles and California condors, although the firm has other species in its sights, including smaller raptors of concern in Europe and whooping cranes in the United States.
“We’re focused on detecting large birds the size of an eagle at the distance of 1,000 meters, then making a real-time decision if the bird is a species of concern; if so, is it in jeopardy of being hit by a wind turbine. Then the system signals the wind turbine to shut down,” said Hiester.
Scientists from the Peregrine Fund recently completed a test at a Wyoming Duke Energy wind farm that compared IdentiFlight system performance (four IdentiFlight units consisting of eight stationary cameras mounted on a tower, plus back-end hardware and software) against that of human biomonitors. RES expects the results to be published on the American Wind Wildlife Institute website in early 2017. A single unit is also being tested on a Minnesota wind farm.
A key economic driver for the success of any detection technology is its accuracy. “It is very important to avoid false positives,” states the NREL report.
“Lost revenue as a result of downtime during curtailment periods is only one consideration and may be the smallest loss to a wind company,” states the report. “Excessive, rapid, emergency shutdown situations presumably cause blades to wear out prematurely. Lost generation when multi-megawatt turbines come out of service for repair or replacement is 100 to 1,000 times greater than the cost of lost generation during curtailment events.”
It seems clear that advanced sensing and deterrent technologies will play a growing role in balancing the growth of wind power with the imperative to protect birds and bats.
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