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The development of wind farms is one of the priorities of Latvenergo AS in the coming years. A comprehensive assessment of the impact on the environment and the local population is a key factor for successful development and commissioning of wind projects. To develop wind projects responsibly and respect the local population, we have introduced operating principles that we adhere to in the work process. These principles help us better understand people's concerns and find solutions to address them.

When developing the operating principles for the development of our wind projects, we emphasise that the projects must be developed responsibly towards the environment, the local population and ourselves. Our four key operating principles are:

• Working and giving back to Latvia;
• Being socially responsible;
• Respecting the environment;
• Choosing climate-neutral solutions.

In order to observe these basic principles during the planning of wind projects, close attention is also paid to the factors affecting the public, such as safety, flickering caused by wind turbines, noise pollution and infrasound, as well as the general public attitude towards wind energy. Strict construction regulations are in place to ensure that wind turbines have a minimal impact on the daily lives of the local residents. As long as they are followed, the impact on people is limited to a minimum. What are then the main factors of wind turbines that affect people? Keep reading to learn more.

In our latitudes, one of the factors that can affect the safety of nearby people during the operation of wind farms is icing during the cold months. It forms in wet and cold climate when a layer of water forms on the blades of a wind turbine and then freezes. Icing poses both generation performance and safety risks, for example icing of wind turbine blades reduces the blades’ aerodynamic characteristics and increases vibration levels, thereby reducing the efficiency of the WPP and causing increased turbine wear. There are also safety risks associated with the detachment of ice from the blades[1]. In order to reduce icing and limit the aforementioned risks, anti-icing and de-icing technologies are used with the main goal of preventing the formation of ice layer on the blade. Systems are also equipped with sensors, cameras and measuring instruments to identify the risk of icing in a timely manner. These technologies allow wind farms to be built in virtually all conditions, even in arctic regions, harnessing the advantages of the colder areas – sparse population meaning a lesser impact on residents and higher air density[2], allowing for higher turbine performance.

Another factor affecting human well-being created by wind turbines is the flickering. It is caused by the movement of the rotor blades, as they periodically shade the sun and create moving shadows on the ground and the surface of various objects[3]. Flickering can become a nuisance to people when the shadow of the blades hits the courtyard or a residential building. Today's modern high-power wind rotors produce flickering with a frequency of 0.3 to 1 Hz, but for this effect to be dangerous to human health, the flickering has to be more intense (at least 3-60 Hz). So far, flickering has not been directly linked to adverse effects on human health, but it can certainly be considered a nuisance[4] and this is taken into account when developing wind farms. To limit the effects of flickering, technologies that reduce the disturbance have been developed. Systems where light sensors, GPS receivers and specially designed algorithms work together help adjust the operation of the wind farm so that individual turbines are stopped at the moment when their shadow can cause a disruptive flickering effect[5]. These systems are widely used and reduce the discomfort caused by flickering. Studies show that people's complaints about the flicker effect are more often related to the general attitude towards wind turbines rather than to the inconvenience caused by the flickering effect itself[6].

A factor affecting people that is difficult to assess is the noise pollution. Research conducted in the European Union and worldwide shows that noise pollution from wind power plants can be a nuisance to people living near them; however, its harmful effects on human health have not been scientifically proven[7]. The noise pollution from wind turbines during their operation mainly occurs in two ways – the mechanical noise from mechanical components, i.e., the generator and the transmission, and the aerodynamic or turbulent flows noise that occurs as the rotor blades split the air. This aerodynamic noise – a pulse-like whirring sound – is specifically what is considered the biggest source of noise nuisance[8]. It is best heard in the immediate vicinity of the wind turbine and the impact of the sound decreases with distance.

The impact of infrasound is also mentioned in the context of operation of wind turbines. Infrasound has been studied in depth in the study by the Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg (Baden-Württemberg Environment, Measurement and Nature Protection State Institution) Low-frequency noise incl. infrasound from wind turbines and other sources published in 2016[9]. The study has shown that infrasound measurements at a distance of 700 metres from an operating wind turbine does not significantly differ from the measurements at the same location when the turbine is turned off. It was concluded that infrasound is mainly produced by the wind itself, rather than the turbines.

Wind turbine technology is constantly evolving to make the turbines quieter and continuous advances are also being made in the design of turbine blades[10], in the choice of noise-reducing materials[11] and in the technical solutions of turbines, for example, using transmissionless wind turbines. Nevertheless, it is impossible to exclude the noise pollution caused by the operation of turbines completely; therefore, the laws and the regulations by the Cabinet of Ministers contain strict provisions for assessment, mapping and application of noise to a specific project. In Latvia, these requirements are even stricter than in other European countries, prescribing the minimum distance of 800 m between a turbine and any residential buildings. This ensures a safe distance from the turbine so that the operation of turbines does not affect people's well-being.

Despite the fact that wind turbine technology and current building regulations dictate and ensure that the development of wind farms is carried out in a responsible manner towards the environment and the people, residents living near wind farms are often concerned that the turbines will negatively affect their well-being. It should be noted that often it is general information about the very existence of these influencing factors, rather than their actual impact, that forms the negative image of wind turbines in the public perception. This phenomenon is attributed to the so-called wind turbine syndrome, which alleges that wind turbines cause various symptoms, such as headaches from low-frequency noise or trouble sleeping. In reality, however, the wind turbine syndrome is more of a psychological phenomenon, with people attributing symptoms directly unrelated to wind turbines to the influence of a nearby wind farm[12].

The cautious and often critical attitude of local residents towards such large-scale projects as wind farms is understandable. These concerns of local residents should be taken into account and people should be informed and reassured through educating. The developer of the wind farm should remember that they are the guest here and are planning to stay for quite a long time, so, as a polite guest should, they should also treat the hosts with respect and understanding. Wind energy is the pathway to a cleaner, safer, independent future, and the implementation of wind projects is important not only for our enterprise, but for the entire nation. That is why these projects demand united, purposeful and respectful work both at the enterprise and national level.

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[1] Olivier Parent, Adrian Ilinca, Anti-icing and de-icing techniques for wind turbines: Critical review, Cold Regions Science and Technology, Volume 65, Issue 1, 2011, Pages 88-96, ISSN 0165-232X, https://doi.org/10.1016/j.coldregions.2010.01.005

[2] Ibid.

[3] Environment State Bureau, Guidelines for Environmental Impact Assessment of Wind Power Plants and Recommended Requirements for Construction of Wind Power Plants. https://www.vpvb.gov.lv/lv/media/827/download

[4] Ibid.

[5] DNV, Shadow flicker protection system for wind turbines. https://www.dnv.com/services/shadow-flicker-protection-system-for-wind-turbines-72275

[6] Ryan Haac, Ryan Darlow, Ken Kaliski, Joseph Rand, Ben Hoen,In the shadow of wind energy: Predicting community exposure and annoyance to wind turbine shadow flicker in the United States, Energy Research & Social Science, Volume 87, 2022, 102471, ISSN 2214-6296, https://doi.org/10.1016/j.erss.2021.102471

[7] Environment State Bureau, Guidelines for Environmental Impact Assessment of Wind Power Plants and Recommended Requirements for Construction of Wind Power Plants. https://www.vpvb.gov.lv/lv/media/827/download

[8] Ibid.

[9] Herrmann, Lorenz, et al. "Low-frequency noise incl. infrasound from wind turbines and other sources." INTER-NOISE and NOISE-CON Congress and Conference Proceedings. Vol. 253. No. 3. Institute of Noise Control Engineering, 2016.

[10] Shubham Deshmukh, Sourodeep Bhattacharya, Anuj Jain, Akshoy Ranjan Paul, Wind turbine noise and its mitigation techniques: A review, Energy Procedia, Volume 160, 2019, Pages 633-640, ISSN 1876-6102, https://doi.org/10.1016/j.egypro.2019.02.215

[11] Stefan Oerlemans, et. al. Reduction of Wind Turbine Noise Using Optimized Airfoils and Trailing-Edge Serrations, 2009, AIAA Journal, 1470-1481, 47, 6.

[12] Baloh, Robert W., and Robert E. Bartholomew. "Modern-Day Acoustical Scares: From ‘The Hum’to ‘Wind Turbine Syndrome’." Havana Syndrome. Copernicus, Cham, 2020. 107-127.

Andis Antāns,
Wind and Solar Park Development Project Manager of Latvenergo AS