Renewables’ share of the U.S. generation mix is expected to double by 2050, and as energy companies ready the grid for more solar and wind, they are looking for ways to reduce impacts to wildlife, too.
Duke Energy Sustainable Solutions, a nonregulated brand of Duke Energy, currently operates nearly 3000 MW of wind, with plans to add additional wind assets as it works to reach the company’s corporate goal of net-zero carbon emissions by 2050. The company owns and operates 23 wind sites in eight states with multiple in Texas, which has more wind generation and bat colonies than any other state.
While wind turbines produce an abundance of clean power, they do carry risks. For example, turbines have been shown to cause direct mortality to bat species, an issue the wind industry takes seriously. Bats have far-reaching ecological and economic impacts thanks to their role as critical pollinators responsible for the proliferation of a wide range of plants, while other species’ appetite for crop-destroying insects saves farmers billions of dollars every year in pest control costs.
To help mitigate the risk that wind turbines may cause to bat populations, Duke Energy Sustainable Solutions, NRG Systems, and Texas State University conducted field research and have been implementing bat deterrent solutions since 2017 at its Los Vientos wind facilities in the Rio Grande Valley area. The trials showed a 50% reduction in overall bat fatalities during the field-testing period. As a result, in July 2019, Duke Energy Sustainable Solutions embarked on a 5-year installation project that will eventually install NRG Systems’ Bat Deterrent System onto all 255 wind turbines at its Los Vientos III, IV and V wind sites.
“At Duke Energy, we’re focused on generating clean, renewable energy for customers while also protecting the native wildlife around our generation facilities,” said Greg Aldrich, lead environmental scientist with Duke Energy. “It is important to us to be a good steward of the environment, this means proactively identifying solutions to protect native wildlife, while producing clean, renewable energy.”
Dr. Sara Weaver, senior environmental manager at Bowman, who led the Los Vientos study during her doctoral candidacy at Texas State University, said, “Our results from this robust, two-year study indicate that NRG’s acoustic deterrents significantly reduce Brazilian free-tailed bat and hoary bat fatalities. Based on these results, the technology is a promising tool for reducing bat fatalities at wind turbines.”
How does NRG Systems’ Bat Deterrent System work?
NRG’s Bat Deterrent System “jams” bats’ echolocation capabilities, which they rely on to find prey and orient themselves. The Bat Deterrent System emits an ultrasonic acoustic field similar to bats’ natural calling frequencies. Researchers believe this interferes with their ability to receive and interpret their own echolocation calls and creates a disorienting airspace that is difficult to navigate. By doing this, bats are potentially discouraged from entering the treated airspace and safely pushed out of dangerous areas such as the rotor-swept zone of a wind turbine. The ultrasonic field emitted by the Bat Deterrent System does not harm the bats and quickly dissipates beyond the turbine rotor sweep. The sound cannot be heard by humans and has not been shown to affect other wildlife or livestock.
What you should consider before implementing the NRG Systems’ Bat Deterrent System
The mix of bat species at a wind farm, the facility’s location, time of year, and weather conditions need to be carefully considered when determining if NRG’s Bat Deterrent System is right for a project. The current version of NRG Systems’ Bat Deterrent System affects bat species whose call frequencies are between 20 kHz and 50 kHz. This covers all the bat species found in North America, including endangered myotis species, and a vast majority of bats found in Europe. Studies have recently been carried out in Africa and Asia, which will provide more insight into the solution’s efficacy in an even broader range of climates where an exceptionally diverse range of bat species exist. Many operators choose to conduct validation studies ahead of installing Bat Deterrent Systems on their turbines to ensure their project and its unique conditions are a good fit for the technology.
The evolution of the wind energy industry is trending toward wind turbines with longer blades and therefore a larger rotor swept area. According to the wind energy industry and wildlife researchers, the next challenge to overcome is physics. As wind turbines get taller and blades get longer to produce more power per turbine, sound levels will need to be amplified to cover the longer length of the blades. The physics of sound in air becomes a barrier to larger diameters for a sound-based system that is installed on the nacelle. Research is also being conducted to identify other configurations of the speakers and placements on the wind turbine to make the Bat Deterrent Systems even more powerful.
Research is already underway to identify ways to make the system effective for more species and to increase power and sound, or alternative speaker placement to achieve larger rotor-swept areas, which will result in more enhanced bat deterrent solutions.
How to install and maintain the Bat Deterrent System
Each NRG Bat Deterrent System features multiple Bat Deterrent Units (BDU) that generate the ultrasound. Each BDU is composed of five individual, solid state ‘speakers’ which are sealed from the elements so they can survive the harsh environment on top of the turbine. These BDUs are mounted on the nacelle (the covering that houses all the generating components) of the wind turbine, using metal brackets specifically designed for the shape of the nacelle. For speakers facing downward, holes are cut in the bottom of the nacelle for the speakers, which are then reinforced with another metal bracket.
NRG has in-house technicians to support in the installation of these BDUs as well as a network of installation partners that spans the globe. The Bat Deterrent System also includes a Deterrent Unit Controller (DUC) which is programmed with a schedule to tell the speakers when to turn on and off as well as provide information to the wind plant’s SCADA system. The DUC is also capable of monitoring the health of the BDUs and communicates when repair or replacement is needed. Given the solid-state nature of the speakers and the built-in monitoring, no annual maintenance is needed.
NRG Systems’ Bat Deterrent System is one of the most promising devices available for preventing bat fatalities. However, in order for bats and wind energy to successfully coexist, partnerships need to be established proactively between operators and researchers.
According to Tim Hayes, Environmental Director with Duke Energy Sustainable Solutions, installation of the Bat Deterrent System was purely voluntary. “At Duke Energy, safety of our communities and the wildlife that inhabit the areas where our facilities are located is our number one priority. We are pleased with the positive results we have achieved in Texas with our bat deterrent system and encourage other people to get ahead of introducing safety measures to preserve local bat populations.”
Jennifer Garber supports communications for Duke Energy’s nonregulated commercial renewables brand, Sustainable Solutions, which leads in sustainable energy and helps large enterprises reduce power costs, lower emissions, and increase resiliency. The team provides wind, solar, resilient backup power, and managed energy services to over 1,000 projects across the U.S. and has a total electric capacity of more than 5,100 megawatts of nonregulated renewable energy.
As NRG Systems’ Senior Marketing Specialist, Brittany Good crafts intriguing content that strengthens the company’s relationships with its customers while engaging new audiences. She is a graduate of Emerson College’s Writing, Literature, and Publishing program and has a background in journalism and digital marketing.
