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Iberdrola Renewables, BWEC second year of ground-breaking bat study again shows large reduction in bat mortality

Iberdrola Renewables, BWEC second year of ground-breaking bat study again shows large reduction in bat mortality

Click Here  for a PDF version of this press release.

November 11, 2010

GARRETT, Pa. - The second year of ground-breaking research to study the interaction between bats and wind turbines at the Casselman Wind Power Project shows that increasing cut-in speed of the turbines, the minimum wind speed necessary for turbines to begin spinning and producing electricity, during low wind periods in the late summer and early fall reduced bat mortality up to 93%. The study was published online November 1, 2010 in Frontiers in Ecology and the Environment, a journal of the Ecological Society of America.

Iberdrola Renewables, the owner of the Casselman wind farm, partnered with independent conservation group, Bat Conservation International (BCI), to implement the ground-breaking study at the southwestern Pennsylvania wind power project.

BCI's work is being conducted through the Bats and Wind Energy Cooperative (BWEC -, which is a coalition of the American Wind Energy Association (AWEA), the U.S. Fish and Wildlife Service, the National Renewable Energy Laboratory and BCI. The cooperative's work focuses on identifying and addressing potential wind energy impacts on bats.

From late July to mid-October in 2008 and again in 2009, Iberdrola Renewables, working with BCI researchers, conducted a controlled experiment in which selected wind turbines at the Casselman project were stopped during relatively low wind-speed nights as recommended by BCI in the late summer and early fall. This represents the first U.S. - based effort reporting the effects of shutting down turbines on reducing bat deaths.

"We were pleased to confirm in the second year of the study what we discovered in the first year - that increasing the cut-in speed on turbines during summer-fall migration periods greatly reduces fatality risk for bats which are a valuable part of the ecosystem, while proving the measure to be a cost-effective means of adapting management of the facility," said Stu Webster, wind permitting director for Iberdrola Renewables.

Although it was crucial for this study, curtailing turbine operations is not likely to be the complete solution to reducing the impact on bats in all circumstances or locations, but it may be a practical solution at some northeastern U.S. sites where elevated bat mortality has been a concern, company officials said. This study is one of a series of collaborations with BWEC at five Iberdrola Renewables wind plants. The results of the 2008 and 2009 Casselman study were reviewed and approved by BWEC's Scientific Advisory and Oversight Committees, the latter of which includes representatives of the U.S. Fish and Wildlife Service and the National Renewable Energy Laboratory, before being made public.

Dr. Ed Arnett, conservation scientist at Bat Conservation International and program coordinator for the Bats and Wind Energy Cooperative, led a team of scientists that tested the reduction in bat deaths by increasing the minimum wind speed necessary for turbines to begin spinning and producing electricity into the power grid.

"We hypothesized that bat fatalities could be lowered substantially by reducing the amount of turbine operating hours during low wind periods when bats are most active. During the study period, bat fatalities were reduced from 44 to 93 percent at turbines that were partially curtailed during low wind nights compared to those turbines that were fully operational the whole time," said Arnett.

The Casselman study has wider implications for the wind energy industry as a whole.

"AWEA is a founding member of the Bat Wind Energy Cooperative, and we are glad to see this next step in identifying ways to address impacts of wind energy on bats," said Denise Bode, AWEA CEO. "We see this partnership as being a valuable resource not only for Iberdrola Renewables, but also for the entire wind energy industry."

The Casselman Wind Power Project, located in Somerset County, also marks an important environmental first for the state of Pennsylvania by putting an abandoned coal mine to productive use. Eight of the project's turbines are located atop infill from a surface mine. In total, the 23 turbines at this wind power project generate 34.5 megawatts (MW) of clean, renewable energy and contribute jobs and tax revenue to the local community.

The company has made multiple commitments to wildlife, becoming the first US wind power company to adopt an Avian and Bat Protection Plan at all its wind farms and the first wind power company in the world to test the use of a Merlin Avian Radar Systems to curtail power generation during certain conditions at a Texas project. The complete study can be seen at

Iberdrola Renewables, Inc. is headquartered in Portland, Ore., with more than 850 employees. It is part of the Iberdrola Renovables global group, the world's leading provider of wind power with more than 11,000 MW of renewable energy in operation around the world, and more than 4,300 MW of that wind power located in the U.S.

Art Sasse, Director, Communications & Brand, Iberdrola Renewables, 503-796-7740
Paul Copleman, Media Relations, Iberdrola Renewables, 207-641-2805
Ed Arnett, Bat Conservation International, 512.327.9721; 541.520.5252 (cell)

Additional Resources:

  • To view a video story on the Casselman Wind Power Project, visit
  • B-roll of the Casselman Wind Power Project, coal mining activities and bat data collection
  • Print-quality still images of wind technicians at work, coal mining activities and bat data collection


About Avangrid

About Avangrid: Avangrid, Inc. (NYSE: AGR) aspires to be the leading sustainable energy company in the United States. Headquartered in Orange, CT with approximately $44 billion in assets and operations in 24 U.S. states, Avangrid has two primary lines of business: networks and renewables. Through its networks business, Avangrid owns and operates eight electric and natural gas utilities, serving more than 3.3 million customers in New York and New England. Through its renewables business, Avangrid owns and operates a portfolio of renewable energy generation facilities across the United States. Avangrid employs approximately 8,000 people and has been recognized by JUST Capital in 2021, 2022, 2023 and 2024 as one of the JUST 100 companies – a ranking of America’s best corporate citizens. In 2024, Avangrid ranked first among utilities and 12 overall. The company supports the U.N.’s Sustainable Development Goals and was named among the World’s Most Ethical Companies in 2024 for the sixth consecutive year by the Ethisphere Institute. Avangrid is a member of the group of companies controlled by Iberdrola, S.A. For more information, visit


About Iberdrola: Iberdrola is one of the world's biggest energy companies and a leader in renewables, spearheading the energy transition to a low carbon economy. The group supplies energy to almost 100 million people in dozens of countries. With a focus on renewable energy, smart networks and smart solutions for customers, Iberdrola’s main markets include Europe (Spain, the United Kingdom, Portugal, France, Germany, Italy and Greece), the United States, Brazil, Mexico and Australia. The company is also present in growth markets such as Japan, Taiwan, Ireland, Sweden and Poland, among others.

With a workforce of nearly 40,000 and assets in excess of €141.7 billion, across the world, Iberdrola helps to support 400,000 jobs across its supply chain, with annual procurement of €12.2 billion. A benchmark in the fight against climate change, Iberdrola has invested more than €130 billion over the past two decades to help build a sustainable energy model, based on sound environmental, social and governance (ESG) principles.

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