As of: 01.06.2010

Study:
Acceptance and environmental compatibility of aircraft obstruction markings on wind turbines

Summary

Wind turbines (WT) with a total height above 100 m are increasing in number. Consequently, the proportion of WT with obligatory aircraft obstruction markings is rising. Recent residents' complaints suggest that obstruction markings may affect public support for wind farms. Up to now, whether obstruction markings cause stress or even substantial annoyance to residents living in the vicinity of wind farms has been an open question. To bridge this knowledge gap Gundula Hübner and Johannes Pohl, Martin-Luther-University Halle-Wittenberg, Institute of Psychology, analysed the social acceptance and stress impact of WT aircraft obstruction markings. This research was supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and the State Agency for Agriculture, Environment and Rural Areas of Schleswig-Holstein, Germany.

Applying methodologies from environmental and stress psychology, the following comparisons were analysed:

1. three types of day markings (xenon lights, LED, colour markings of the blades),
2. synchronised versus non-synchronised markings,
3. day and night markings,
4. markings in simple (plain, low building density) versus complex (forest, hills, high building density) landscapes,
5. markings with and without light intensity adjustment depending on visibility (i.e. low light intensity in case of clear, high in case of unclear sky),
6. highly versus non-annoyed subjects.

This quasi-experimental research design allows for causal conclusion concerning aircraft obstruction markings' stress impacts.

Residents living in the vicinity of a wind farm with a direct view of the WTs participated in a questionnaire survey. In total, 420 residents from 13 wind farms were included in the analyses. The questionnaire included 590 questions concerning stress and social acceptance of the local wind farm and renewable energies in general.

This research revealed no evidence of substantial annoyance caused by obstruction markings, but, generally speaking, small stress effects are evident. In comparison, residents were more annoyed by the wind farms’ noise and impact on the landscape. However, a differentiated analysis suggests specific strong stress responses, which infer a need for action. Under certain weather conditions, like cloudless nights, obstruction markings caused strong annoyance. Moreover, xenon markings clearly caused more intense and multifaceted stress responses than LED or blade colour markings. Additionally, xenon negatively affected the general acceptance of wind energy: residents in the vicinity of wind farms with xenon markings reported significantly lower acceptance. Synchronized navigation lights were less annoying than non-synchronized lights under certain weather conditions.

Overall, markings with light intensity adjustment proved to be advantageous. Residents without light intensity adjustment more frequently showed stress reduction activities to cope with the obstruction markings. Furthermore, the absence of light intensity adjustment had negative effects in simple landscapes. Over time, wind farms without light intensity adjustment caused a greater increase in annoyance in simple as compared to complex landscapes. Additionally, stress and annoyance during the wind farm planning and construction period augmented perceived annoyance by obstruction markings. Altogether, the interviewed residents wanted minor light intensity, synchronisation, and demand-oriented navigation lights. More specific, demand-oriented navigation lights switch on in case of approaching aeroplanes only.

Although no substantial annoyance was found, 16% of survey respondents were strongly annoyed. This group is characterised by more health problems compared to non-annoyed residents - independent from wind farm stress impacts. Following this result, their complaints have to be taken seriously.

To reduce stress caused by aircraft obstruction markings and to increase social acceptance of wind energy the following recommendations are suggested: abandon xenon markings, synchronise navigation lights, apply light intensity adjustment, and create less stressful planning and construction periods. In the future, demand-oriented navigation lights should be permitted in order to foster social acceptance of wind energy.

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Grant from: German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU);
State Agency for Agriculture,
Environment and Rural Areas of Schleswig-Holstein, Germany

BMU support code: 03MAP134

Project management: PD Dr. Gundula Hübner & Dr. Johannes Pohl
Institute of Psychology
Martin-Luther-University Halle-Wittenberg
06099 Halle (Saale)
Germany

Co-workers: Anja Mohs, Steffi Brecke, Stefan Schröpper

Grant period: 08/01/2008 - 02/28/2010

The study was supported by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety due to a decision of the Lower House of the German Parliament (Deutscher Bundestag) and by the State Agency for Agriculture, Environment and Rural Areas of Schleswig-Holstein, Germany.