Its Hawaiian name means half-leaf, in reference to its wings uncanny resemblance to a cooked taro leaf. The federally endangered peapea, or Hawaiian hoary bat, holds a special distinction as the Aloha States only living native land mammal, first migrating to the Hawaiian Islands an estimated 10,000 years ago. While researchers are not entirely sure how these tiny navigators found themselves on the remote island chainperhaps blown in from a storm or riding on ocean debristhey know that when humans arrived on the Hawaiian Islands around 400 C.E, half-leaf had already been living in paradise for roughly 8,000 years. In 2015, the peapea was designated as Hawaiis official state land mammal, solidifying its place in the states culture. However, as Hawaii looks towards a future in renewable energy, the peapea faces a new challenge.
The Kawailoa Wind Farm sits on the North Shore of Oahu just 30 miles north of Honolulu. First operational in 2012, the 69-megawatt, 30-turbine facility is the largest wind farm in Hawaii. Operating at full capacity, the wind farm generates enough renewable electricity to power 23,000 homes annuallya huge leap for Hawaii, whose state legislation set an ambitious goal of reaching 100 percent renewable energy by 2045.
Renewable energy has a number of advantages over other energy sources, particularly when it comes to the issue of climate change, says Michael Schirmacher, Director of BCIs Bats and Wind Energy Program. But with new technologies there are sometimes unanticipated challenges, such as the impact of wind turbines on bats.
A 2013 study estimated that between 2000 and 2011, 650,000 to 1.3 million bats died from collisions with wind turbines in the United States and Canada. However, wind farms, like Kawailoa Wind, attempt to lessen the impact by curtailmentreducing operating time of turbine blades during high risk periodsat night when wind speeds are relatively low.
A study conducted on the mainland United States and Canada have shown this strategy can reduce fatalities by 44 to 93 percent, while still allowing 99 percent of the electricity to be produced. Unfortunately, even with these methods, certain species, like the peapea, appear particularly susceptible to wind turbines.
BCI has been working with companies, like NRG systems, to test ultrasonic acoustic deterrents (UADs). These devices emit a high frequency soundoutside the range of human hearingthat bats will avoid. It is hypothesized that UAD devices can be a safe and effective method of reducing bat-turbine collisions.
We want to try to understand as much as we can about the bats so that we can employ the best strategy to minimize the impact of wind energy on this species, says Brita Woeck, Environmental Compliance Manager for Kawailoa Wind.
A cooperative approach, like the work at Kawailoa Wind Energy Project, is an efficient way to resolve these issues because it brings everyone to the table to collectively share ideas, expertise, etc., which are vital in addressing these complex issues, says Schirmacher.
Kawailoa Wind has partnered with BCI to gather information on the behavior of peapea at their facility. Using infrared cameras, BCI has been studying the effectiveness of acoustic deterrents at Kawailoa. By utilizing specialty cameras and software, BCI can analyze the interactions between the bats and the turbines, while testing the effectiveness of the UADs under a variety of circumstances. The information generated by these studies will support researchers in broadening the understanding of bat behavior and the efficacy of deterrents to reduce bat fatalities.
Bats are extremely difficult to study, because in most cases we need specialized equipment, such as ultrasonic detectors and infrared cameras, to hear them or see them. Then you add the challenges present on Hawaii: its hot, humid marine environment, and the fact that it was hurricane season…I will just say it has kept us on our toes, admits Schirmacher. But this will be the first time we can examine detailed flight paths of these bats, using methods and a 3D software we developed with partners, which can help answer behavioral questions that are essential in reducing the impact to this endangered species. It is great to work with partners that are willing to work cooperatively to understand the problem and develop cost-effective solutions.
Woeck hopes that effective UADs can be deployed on all 30 of Kawailoas turbines in the next year, reducing the risk turbines pose to the peapea. With the potential were seeing right now on the mainland, were hopeful that we can use this technology to minimize impact on the bat; and so far, the signs are pointing in that direction.