Simulating the influences of bat curtailment on power production at wind energy facilities

There is a rapid, global push for wind energy installation. However, large numbers of bats are killed by turbines each year, raising concerns about the impacts of wind energy expansion on bat populations. Preventing turbine blades from spinning at low wind speeds, referred to as curtailment, is a method to reduce bat fatalities, but drawing consistent inference across studies has been challenging. We compiled publicly available studies that evaluated curtailment at six wind energy facilities in North America across 10 years. We used meta‐regression of 29 implemented treatments to determine fatality reduction efficacy as well as sources of variation influencing efficacy. We also estimated species‐specific fatality reduction for three species that comprise most fatalities in North America: hoary bat ( Lasiurus cinereus ), eastern red bat ( Lasiurus borealis ) and silver‐haired bat ( Lasionycteris noctivagans ). We found that curtailment reduced total bat fatalities by 33% with every 1.0 ms −1 increase in curtailment wind speed. Estimates of the efficacy for the three target species were similar (hoary bats: 28% per ms −1 , 95% CI: 0.4%–48%, eastern red bats: 32% per ms −1 , 95% CI: 13%–47% and silver‐haired bats: 32% per ms −1 , 95% CI: 3%–53%). Across multiple facilities and years, a 5.0 ms −1 cut‐in speed was estimated to reduce total bat fatalities by an average of 62% (95% CI: 54%–69%). Mortality reductions at individual facilities in any given year were estimated to fall between 33%–79% (95% prediction interval). Inter‐annual differences rather than inter‐site or turbine characteristics accounted for most of the variation in efficacy rates. Species‐specific average mortality reduction at 5.0 ms −1 curtailment wind speed was 48% (95% CI: 24%–64%) for hoary bats, 61% (95% CI: 42%–74%) for eastern red bats and 52% (95% CI: 30%–66%) for silver‐haired bats. Practical implication . curtailment reduced bat mortality at wind turbines in this North American study. Efficacy increased proportionally as curtailment speed is raised, and patterns and rates of efficacy were similar across species. This indicates that curtailment is an effective strategy to reduce bat fatalities at wind energy facilities, but exploration of further refinements could both minimize bat mortality and maximize energy production.

Studying migratory behavior of bats is challenging. Thus, most information regarding their migratory behavior is anecdotal. Recently, however, fatalities of migratory bats at some wind energy facilities across North America have provided the opportunity and impetus to study bat migration at fine spatial and temporal scales. Using acoustic monitoring and carcass searches, we examined temporal and spatial variation in activity levels and fatality rates of bats at a wind energy facility in southern Alberta, Canada. Our goals were to better understand the influence of weather variables and turbine location on the activity and fatality of hoary bats (Lasiurus cinereus) and silver‐haired bats (Lasionycteris noctivagans), and to use that understanding to predict variation in fatality rates at wind energy facilities and recommend measures to reduce fatalities. Overall activity of migratory bats and of silver‐haired bats increased in low wind speeds and warm ambient temperatures, and was reduced when the wind was from the North or Northeast, whereas hoary bat activity increased with falling barometric pressure. Fatalities of migratory bats in general increased with increased activity of migratory bats, increased moon illumination, and falling barometric pressure and were influenced by the interaction between barometric pressure change and activity. Fatalities of silver‐haired bats increased with increased activity, moon illumination, and winds from the south‐east. Hoary bat fatalities increased with falling barometric pressure. Our results indicate that both the activity and fatality of migratory bats are affected by weather variables, but that species differ in their responses to environmental conditions. Spatially, fatalities were not influenced by the position of turbines within a turbine row, but were influenced by the location of turbines within the facility. Our findings have implications for our understanding of bat migration and efforts to reduce fatalities at wind energy facilities. To maximize the reduction of bat fatalities, operators of wind energy facilities could incorporate migratory bats' response to environmental variables, such as barometric pressure and fraction of moon illuminated, into their existing mitigation strategies. © 2011 The Wildlife Society.

Wind energy is important for achieving net-zero greenhouse gas emissions but also contributes to global bat mortality. Current strategies to minimize bat mortality due to collision with wind-turbine blades fall broadly into two categories: curtailment (limiting turbine operation during high-risk periods) and deterrence (discouraging bat activity near turbines). Recently, there has been interest in combining these strategies to achieve greater reductions in bat fatalities than either strategy might achieve in isolation. To investigate the effectiveness of combining curtailment with ultrasonic deterrent minimization strategies, we deployed six ultrasonic deterrents at nacelle height on 16 experimental turbines at Avangrid Renewables' Blue Creek Wind Energy Facility. We rotated between four conditions (normal operations, curtailment only, deterrent only, curtailment and deterrent) randomly assigned to four wind turbines each night between 15 June and 3 October 2017. We found that bat mortality at wind turbines was independent of wind speed. The effectiveness of ultrasonic acoustic deterrents varied between high-frequency-calling species (eastern red bats) and low-frequency-calling species (hoary bats, silver-haired bats, and big brown bats). When deterrents were active, mortality was twice as high for eastern red bats compared to the control. Conversely, deterrents had a weak dampening effect on bat mortality for low-frequency species. We found no additive effects on mortality reduction for turbines operating both curtailment and deterrents compared to either approach in isolation. Our findings suggest that ultrasonic acoustic deterrents may not be effective for both high and low frequency echolocating bats. The increase in fatalities of eastern red bats is alarming and underscores the importance of considering site- and species-specific effects of minimization solutions.

Curtailment of turbine operations during low wind conditions has become an operational minimization tactic to reduce bat mortality at terrestrial wind energy facilities. Site-specific studies have demonstrated that bat activity is higher during lower wind speeds and that operational curtailment can effectively reduce fatalities. However, the exact nature of the relationship between curtailment cut-in speed and bat fatality reduction remains unclear. To evaluate the efficacy of differing curtailment regimes in reducing bat fatalities, we examined data from turbine curtailment experiments in the United States and Canada in a meta-analysis framework. We used multiple statistical models to explore possible linear and non-linear relationships between turbine cut-in speed and bat fatality. Because the overall sample size for this meta-analysis was small (n = 36 control-treatment studies from 17 wind farms), we conducted a power analysis to assess the number of control-treatment curtailment studies needed to understand the relationship between fatality reduction and change in cut-in speed. We also identified the characteristics of individual curtailment field studies that may influence their power to detect fatality reductions, and in turn, contribute to future meta-analyses. We found strong evidence that implementing turbine curtailment reduces fatality rates of bats at wind farms; the estimated fatality ratio across all studies was 0.37 (p < 0.001), or a 63% decrease in fatalities. However, the nature of the relationship between the magnitude of treatment and reduction in fatalities was more difficult to assess. Models that represented the response ratio as a continuous variable (e.g., with a linear relationship between the change in cut-in speed and fatalities) and a categorical variable (to allow for possible non-linearity in this relationship) both had substantial support when compared using AICc. The linear model represented the best fit, likely due to model simplicity, but the non-linear model was the most likely without accounting for parsimony and suggested fatality rates decreased when the difference in curtailment cut-in speeds was 2m/s or larger. The power analyses showed that the power to detect effects in the meta-analysis was low if fatality reductions were less than 50%, which suggests that smaller increases in cut-in speed (i.e., between different treatment categories) may not be easily detectable with the current dataset. While curtailment is an effective operational mitigation measure overall, additional well-designed curtailment studies are needed to determine precisely whether higher cut-in speeds can further reduce bat fatalities.

The aim of this paper is to identify facilitating and hindering factors for onshore wind energy development near natural conservation regions, in particular in Lower Saxony's Wattenmeer region. An applied research approach was deployed to connect individual aspects of wind energy technology and establish a cross-disciplinary perspective on the expansion of wind energy. To this end, relevant facilitating and hindering factors were identified and then validated by a group of academic experts. The main factors were grouped within the framework of Strengths, Weaknesses, Opportunities and Threats. In a subsequent step, a sample of experts in the wind power sector evaluated the relative importance of the key factors, using an Analytic Hierarchy Process. The results show that factors positively influencing wind energy expansion exceed the hindering factors. Wind electricity is likely to benefit from opportunities such as climate change and from industry-specific strengths, for instance the competitiveness of wind in the German electricity market. Barriers and uncertainties that influence the further development of the sector relate to strict ecological protection laws and limited spatial opportunities for new projects. Finally, basic policy strategies were formulated which aim at fostering strengths and opportunities of wind energy development and at reducing weaknesses and threats.

The objective of the study was to demonstrate attitudes towards wind energy facilities in the area of the Korsze Commune. The results of the study were processed using structure indices calculated from the respondents’ answers, which were analyzed in terms of social and economic factors. The study revealed that both the NIMBY syndrome and the lack of civic engagement influence attitudes towards renewable energy technologies in rural areas. The NIMBY (“not in my backyard”) term describes negative public attitudes towards proposed development projects. However, some trends towards more pronounced attitudes can be observed, depending on socioeconomic conditions. The research results imply that the measures taken to promote renewable energy technologies should be designed differently depending on the socioeconomic situation of the targeted audience. Young people might be reached via social media appropriate to their age, and through campaigns promoting local investments. For older people, traditional ways of communication can be used, but the information transmitted should include specific benefits for the whole society as well as for individual households. The conducted research revealed that, despite the fact that many authors deny the occurrence of NIMBY syndrome in relation to the wind energy, the NIMBY problem has occurred in the Korsze Commune. The biggest challenge in the survey was the unwillingness of the residents to participate in it, which only confirms the lack of social involvement.

Wind energy is one of the fastest-growing renewable energy technologies. One of the environmental concerns associated with wind energy development is noise emission from wind energy facilities, especially the low-frequency noise and infrasound that allegedly raises public health concerns. In order to analyze the noise emission from wind turbines and to aid future wind energy development, a numerical simulation tool for the prediction of low-frequency noise and infrasound emission from wind turbines is developed. The simulation tool is a low-order model developed by combining aerodynamic noise theories and basic working principles of wind turbines. 2-D airfoil aerodynamics calculation is coupled with a subroutine that solves Ffowcs Williams-Hawkings (FW-H) equation in time domain. By omitting unsteady aeroacoustics mechanisms, the low-order simulation model is capable of computing infrasound emissions from multiple wind turbines simultaneously. By utilizing the low-order simulation model, the effects of wind directions, wind turbine locations, and phases of wind turbine rotations on the consequent aerodynamic infrasound are studied. Results of aerodynamic infrasound computation imply that wind farm configuration or wind turbine phase adjustment can help reduce the noise level at certain locations, which makes the low-order simulation model a useful tool to aid wind farm siting and controlling.

Fatalities at wind turbines may threaten population viability of a migratory bat

There have been significant increases in wind energy generation in recent years with an 11-fold increase in installed capacity in the past decade. This increase has resulted in many regulatory bodies defining grid codes specifically for wind energy. This paper provides a guide to engineers wishing to perform grid code compliance studies in the South African context. Typical data that would be required, methodologies to perform the integration studies, assumptions made as well as selected results and analysis from various technical investigations of a proposed Wind Energy Facility (WEF) in South Africa are presented. The technical investigations use an Original Equipment Manufacturer (OEM) specific Wind Turbine Generator (WTG) model. The selected technical investigations presented include Low-Voltage Ridethrough (LVRT) as well as WEF switching analysis. Other aspects of the integration of WEFs including ramp-rates, Sub-Synchronous Resonance (SSR), start-up and stability are also briefly discussed.

Montana's bat populations face a wide array of conservation challenges, including loss of roosting sites, elimination of prey species, collision or drowning hazards at sites where they forage, drink, and mate, and a lack of baseline information on distribution and habitat use that is available to resource managers. In recent years, concerns have focused on fatalities at wind turbine facilities and those resulting from White-nose Syndrome (WNS). WNS has killed an estimated 5.7 to 6.7 million bats in eastern North America and 600,000 to 888,000 bats are estimated to have been killed at wind energy facilities across the United States in 2012 alone. These and other sources of mortality may be having significant impacts on bat populations because bats are long-lived and have only one or two young per year. Given these concerns, detectors were installed at nine sites in proximity to active, inactive, or remediated coal mines or proposed project areas across Southcentral Montana. These detectors are part of a regional network deployed over multiple years to document activity patterns of bats across Montana, and portions of northern Idaho, and the western Dakotas. agency and its staff. We extend considerable thanks to Chris Yde for facilitating this work, providing feedback on project implementation, and recognizing the importance of gathering year-round baseline information on bat activity in the region. We would also like to thank Mike Glenn for his assistance in detector placement, maintaining detector sites and collecting data, and Ashley Eichhorn for assistance with grants administration. Staff at Wildlife Acoustics assisted with questions regarding the SM2Bat+ ultrasonic detector/recorders and the SMX-US and SMX-U1 microphones and WAC to WAV and Kaleidoscope Pro software. Joe Szewczak provided Sonobat 4.1 software, feedback on its use, and the 2011 Humboldt State University Bat Lab's echolocation call characteristic summaries for western and eastern U.S. bats that we used to develop the call characteristic summary for Montana bats. John Horel with the MesoWest Research Group assisted with acquisition of weather station data through the MesoWest application programming interface. At the Montana Natural Heritage Program, Darlene Patzer assisted with grant administration, Shannon Hilty assisted with hand review of bat calls, and Dave Ratz assisted with

High bat mortality at wind energy facilities is a widely cited conservation issue, but the population-level impacts are not understood. In Illinois, the main species affected are migratory tree bats like the Hoary (Lasiurus cinereus) and Eastern Red (Lasiurus borealis).This research used deuterium isotope analysis of hair combined with ecological niche modeling (GARP: Genetic Algorithm for Rule-set Prediction) in a novel way to map the geographic extents of Hoary and Eastern Red bat specimens salvaged at a single central Illinois wind facility from 2008-2010. Hair was chosen after determining that the claw is currently a problematic tissue due to a lack of knowledge about bats' claw growth rates. Hair samples from different sample sites on the body were not significantly different from each other, and there was no significant variation among hair samples from the same body sample site. The proportions of isotopic extents of both bats' summer ranges revealed that the salvaged specimens came from areas that cover more than 50% of their summer ranges (hence, many populations). When males' and females' isotope extents were overlapped, Hoary bats had less than 50% overlapping of the sexes while Eastern Red bats had over 50%. Relationships among the salvage years and months were also examined. The percentage of overlap among specimen salvage years suggests that these bats utilize their complete range every summer. When each salvage month was examined, there was no evidence of a correlation between month of arrival at the wind facility and their summer geographic extent. This study shows the importance of specimens salvaged from wind facilities for studying both the population-level impacts of wind farm facilities and bat migratory biology.

Drivers of bat activity at wind turbines advocate for mitigating bat exposure using multicriteria algorithm-based curtailment

The growth of wind power as an aspect of Minnesota’s portfolio of electricity has been propelled to its current level by policy initiatives at both the federal and state levels. Existing statutes establish requirements for further expansion of wind energy in this state in the years to come. Locally, production economics exert their influence as wind speed and duration are translated to capacity factor, which reveals the amount of power that can be generated at a particular site. After the flow resource is thus quantified, comes the calculus of economic viability. This consists of determining the capital and operating costs and eligibility for loans and grants as well as the negotiations of wind rights, easements, and power purchase agreements. To date, policy initiatives have been directed toward the production, or generation side of this variable flow resource. Entrepreneurs and lawyers have become more skillful at organizing business forms that can effectively bring together partners capable of utilizing the substantial tax benefits available through the federal Production Tax Credit (PTC) as well as attractive state-sponsored incentives and tariffs offered by utilities. The variable nature of electrical power capacity from wind has been problematic for utilities, which try to meet the variable loads required by the summed demand of their customers. In Minnesota, peak power demands occur in summer months when wind power is the lowest. In addition to seasonal demands, daily and weekly patterns must be accommodated by utilities serving the markets for electricity. By developing and using an investment model, it is possible to understand investor motivations driving the growth of wind energy in this state and the country. Net present values (NPV) and internal rates of return (IRR) are calculated over the life of power production projects conforming to various conditions such as wind capacity factor, the federal Production Tax Credit (PTC), state incentive plans for community-based energy providers, federal grant and loan programs, as well as emerging opportunities to sell “green tags” for renewable power generation. The numerous incentives provided for windpower development on the generation side highlight the difficulties of providing sufficient transmission capacity for to carry this power from the often remote areas where generated to load centers. Equivalent incentives deployed with similar imagination are needed to enhance investment in a transmission system capable of carrying increasing volumes of wind and other renewable sources of electricity.

Large numbers of migratory bats are killed every autumn at wind energy facilities in North America. While this may be troubling from a population perspective, these fatalities provide an opportunity to learn more about bat migration and the origins and summer distributions of migratory bats by using endogenous markers. Such markers include stable isotope values, which have been used to answer questions about ecological systems, such as trophic levels and food webs, and the origins and migratory routes of animals. To estimate the origins of migratory bats, we determined nitrogen (δ15N), carbon (δ13C), and hydrogen (δ2H) stable isotope values of fur (δ15Nf, δ13Cf, δ2Hf,respectively) from hoary bats (Lasiurus cinereus) and silver‐haired bats (Lasionycteris noctivagans) killed at a wind energy facility in southern Alberta, Canada. We determined that mean isotope values varied among species, year, sex, and age class. δ13Cfand δ2Hfvalues indicated that silver‐haired bats likely originated in the boreal forest, farther north and/or at higher elevations than the aspen parkland‐like habitat suggested by the isotope values of hoary bats. IsoMAP analysis indicated that bat fatalities may have originated from a large catchment area potentially hundreds of kilometers away. Our data provide further evidence for a migration route along the eastern slopes of the Rocky Mountains that is used by bats from across Alberta and beyond, and suggest that fatalities at a single wind energy site have the potential to have far‐reaching ecological and population consequences.

BackgroundTo achieve climate targets, a transition to low-carbon energy production is necessary. However, conflicts between different interests, values and priorities, particularly at the community level, can constrain this transition. This paper aims to analyze lines of conflict and opportunities to build bridges between conflicting interests in the expansion of wind energy in Germany at the local level, to achieve successful implementation of wind energy projects.ResultsOur analysis of four cases of local-level wind energy projects in Germany shows that limited local options for action reinforce the need for local actors to maximize the benefits of energy transition projects. In addition to the conflict over scarce space, the lines of conflict at the local level run primarily along the dimensions of costs and benefits, winners and losers. Real or perceived procedural and distributive injustices had the potential to fuel resistance to wind energy projects in the analyzed cases. However, wind energy projects were successfully implemented despite the presence of local opposition.ConclusionsThe results show that, by integrating procedural and distributive justice into the project planning and implementation and offering tailored solutions, community support for expansion of renewable energy projects can be enhanced. The paper advances the concept of societal ownership (“gesellschaftliche Trägerschaft”), which suggests the willingness of members of a community to tolerate decisions even when some conflicts related to the decision remain unresolved. Societal ownership is presented as an alternative to the concept of simple acceptance; it implies a more positive, more supportive community attitude, where members aim to address conflict as a normal aspect of decision making. Rather than sweeping alternative opinions aside, the community addresses alternative viewpoints, seeking to achieve greater procedural and distributive justice. In this way, a sense of societal ownership of a project can develop, enhancing its likelihood of success.