The Echo

Putting Technology to the Test

Published on September 20, 2017
Written by Michelle Donahue

It’s been a busy summer for BCI’s wind energy team.

In June, performance testing of a new ultrasonic bat deterrent device began at the first of three North American wind energy facilities. Funding for this first test was provided by the U.S. Department of Energy. Subsequent tests also began at two other facilities in July and August.

BCI technicians search for dead bats at the base of a turbine.
Courtesy of Michael Schirmacher, BCI

Working with Brogan Morton, of NRG Systems, which has been spearheading the design and construction of the units, BCI Wind Program Director Cris Hein, and Michael Schirmacher, Wind Program Manager, coordinated the tests with three separate wind energy partners to gather data on how the new ultrasonic units performed atop a range of wind turbine models.

The tests involved a total of 48 turbines, each of which was fitted with six deterrent units. To test how effectively the devices could keep bats from approaching or interacting with the wind turbines, units were mounted on the nacelle. The idea was to create a constant “cloud” of ultrasound around the airspace where bats typically approach wind turbines.

A primary goal of the tests was to determine how well they worked to reduce bat fatalities. Preliminary studies, conducted nearly a decade ago, showed promising results, particularly for hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans). Yet, additional studies are required to prove the effectiveness of this technology.

A secondary goal of the tests was to assess their functionality on different turbine designs and their ability to withstand environmental conditions. Though they appear similar from a distance, wind turbines vary in height, nacelle shape, cut-in speed, and rotor blade length. The tests were designed in part to determine whether the units could be used at any wind facility in the U.S. or Canada, regardless of the turbines in use at a given site. In addition, the deterrents must survive the punishing environmental conditions atop a 300-foot-tall tower. Earlier designs suffered from overheating and water intrusion. Therefore, a lot of effort focused on making the devices more robust.

“We want to know if the units would break down, if they were robust enough to withstand being on top of a turbine, year after year, and still perform as we expect they should,” Hein said. Wind energy producers need to know that the devices they may be investing in won’t need to be replaced after just a few years.

The team used thermal cameras to monitor bat activity during preliminary deterrent
background tests.
Courtesy of Cris Hein, BCI

The tests will each run for about three months, with the final investigations wrapping up in October. Devices are being looked at in a variety of latitudes, in different weather conditions and humidity levels—humidity being one of the primary factors that affect the distance ultrasound can travel.

Timing of the tests was chosen to coincide with the autumn bat migration season. This also is the period of greatest risk for bats as nearly 80% of fatalities occur at this time.

Previous work by Hein and Schirmacher has shown that limiting the spinning of wind turbines at low wind speeds can reduce bat fatalities. But as turbines become ever more efficient at generating power from even low wind speeds, reducing their operations to limit impacts on wildlife also means limiting the power they produce. Thus, there is a need for alternative impact reduction strategies that are cost-effective and viable in low wind areas.

“We all know that with the climate challenges we face, renewable energy is a good path, but we can’t ignore the local effects on wildlife,” Morton added. “But we don’t have to choose between the two. Technology can break the tension between those things.”

At the conclusion of the tests, the hope is that the deterrents will prove to reduce bat deaths by at least as much as limiting rotor operations would, Morton said. Test partners are hoping to see a reduction of 50 percent or more in bat fatalities—a similar level as can be demonstrated by reducing rotor operations under low wind speeds at night.

The wind industry itself has been a critical partner in the whole process—providing sites for testing, feedback on what constitutes “cost effectiveness” from an industry standpoint, and additional bat mortality studies.

Hein and Schirmacher have provided invaluable guidance for NRG Systems as it worked to build the devices themselves, Brogan said, giving the company insights into bat biology as it worked to build devices capable of transmitting ultrasound in a range that would work on bats most impacted by turbines, such as hoary bats.

“Without BCI’s inputs into these things, none of this would have been possible,” Brogan said. “We would have been shooting in the dark.”

Sharing Wind Expertise

Hein and Schirmacher also recently attended the 2017 Wind Energy and Wildlife Impacts (CWW) conference in Portugal, bringing some of the wisdom they’ve gained over the last several years of research and development to share with international partners. More than 350 participants from 20 countries attended.

Highlights:

Revamped fatality estimators. With funding from the National Renewable Energy Laboratory, and in partnership with the US Geological Survey (USGS), BCI participated in a workshop sharing results of its work with the wind industry and statisticians from the United States and Europe in developing new, easier-to-use fatality estimator software. The goal was to better account for variability among wind energy sites that previous fatality estimator programs could not.

Technology for reducing fatalities: Hein participated at an invitation-only meeting with experts from seven different countries to discuss the use of technology, and spoke about his work with ultrasonic acoustic deterrents.

International foundations for the future: In addition to looking at next steps with NRG Systems for testing their ultrasonic deterrents in Europe, the BCI team also met with several other international partners to discuss how to adapt work being done in the U.S. and Europe for their own country’s needs and limitations. For example, because many countries cannot afford to clear large plots of land beneath wind turbines to effectively search for bat carcasses beneath, BCI and the USGS are working to develop a sampling methodology that only uses roads and gravel pads.

In November, BCI will host a Bats and Wind Energy Workshop at the 2nd Congress on Latin American Bats, El Salvador. This is an opportunity to interact with representatives from all Latin American and Caribbean countries and discuss the challenges and opportunities for monitoring and reducing impacts from wind turbines on bats.