The location of the wind farm was selected based on the results of different studies and the geological factors of the coastal area of Hiiumaa. The wind farm map shows seabed depths and shoals. The wind farm is designed to extend as far offshore as possible, taking into consideration the bird-sensitive Apollo shoal. The development area has a sea depth ranging from 10 to 40 m, with limestone bedrock situated 0 to 20 m beneath the seabed. If the wind turbines were moved just a few kilometres further offshore, the sea depth would range from 80 to 150 m. Fixed foundation wind turbines have not been installed at such depths before and the technology for floating foundations is not yet mature. The occurrence of ice in Estonian marine areas further complicates the design of foundations. To date, the only offshore wind farm constructed in ice conditions is located 1.2 km off the coast of Finland at a water depth of 9 m and on a fixed foundation.
Other countries have not observed or experienced any negative impacts with regard to a reduction in the number of tourists following the establishment of offshore wind farms. On the contrary, coastal areas near wind farms have experienced the emergence of a new form of tourism centred around the provision of services linked to wind turbines, such as boat rides and diving near turbines, the sale of souvenirs etc. The Rampion offshore wind farm in England is a prime example of such boat trips, fishing excursions and diving opportunities being offered near wind farms. Impact assessments indicate that tourists’ desire to see wind turbines in person is greater than their desire to avoid beaches with turbines.
In the European Union, permits for wind farm construction are granted for a limited period of time – for 50 years under Estonian law – after which the permit must be extended or the wind farm must be demolished. Wind turbines are dismantled and removed from their foundations. Today, around 85% of a wind turbine is recyclable and this figure is steadily increasing. The steel components of the wind turbine, such as the tower and foundation reinforcements, are easily recyclable. Approximately 40% of the steel currently in circulation is recycled and, at the end of useful life, around 80% of steel is recycled.
Gravity-based foundations consist primarily of concrete. The foundations can be removed from the sea and then reprocessed, however, this would require another environmental impact assessment to be carried out due the formation of new natural habitats on the foundations over the decades.
The greatest challenge is to transform wind turbine blades into raw materials to facilitate a true circular economy. At present, wind turbine blades that are disposed of are typically crushed and then used as high-quality aggregate, cut and then used as construction material or preserved for future reuse. Nevertheless, it can be expected that these possibilities will continue to expand over the course of half a century.
Modelling indicates that the legal limit of 40 dB for night-time noise of wind turbines occurs offshore and at a distance of around 8 km from the coast. The noise of wind turbines cannot be heard on shore. Noise modelling results take into consideration the downwind sound propagation and the technical specifications of the wind turbine based on a wind speed of 10 m/s. Offshore wind turbines reach their peak power output at a wind speed of 10 m/s and the rotor speed remains the same even as the wind speed increases, that is until the turbine is shut down at a wind speed of 30 m/s. The noise analysis conducted at a wind speed of 10 m/s is thus suitable for determining the loudest possible noise. In the case of wind speeds lower than 10 m/s and different wind directions, the noise levels from wind turbines are even lower.
The 255 MW Tootsi-Sopi wind farm in Pärnu County will be completed in 2024. A total of 38 wind turbines with a hub height of 240 m and a rotor diameter of 163 m will be erected there.
Since no offshore wind farms have currently been built in Estonia, there have been no complaints. In terms of onshore wind turbines, it can be said that the people living in the vicinity of wind turbines mostly have a neutral or positive attitude towards them. Generally, the questions that arise concern noise, shadows, flashing lights and impact on birds. We have been able to reduce many of these concerns as wind turbines create virtually no shadows and the blinking of lights can be prevented in the design phase.
Given the specific seabed geology, the use of gravity-based foundations is considered in the construction of the Hiiu offshore wind farm. Such foundations are essentially concrete cones for which a uniform gravel base structure is installed. This type of foundation holds the turbine up thanks to its mass. The northern coast of the island features limestone at a depth of 0 to 20 m from the seabed, which makes the use of monopile foundations commonly used in the North Sea impractical. Around the world, 80% of offshore wind farms use monopile foundations driven into the seabed, but this solution is not suitable for the waters of the Hiiu offshore wind farm.
The foundations of turbines used in offshore wind farms are essentially artificial reefs. These structures provide habitats for different species of marine flora and fauna, including food and shelter for many species of fish.
Low-frequency noise and infrasound, which are inaudible to humans, raise a lot of questions. Specialists from Ramboll Finland conducted a separate expert assessment of the infrasound and low-frequency noise in the North-West Estonia Offshore Wind Farm. Sounds with frequencies below 20 hertz (Hz) are called infrasound. Infrasound can be generated by natural processes (such as low-frequency atmospheric oscillations and wind) as well as by industries and equipment operating at a slow speed. In the case of wind turbines, infrasound is produced mainly downwind when the rotor blade of the turbine passes the mast, but also upwind when wind turbines with a horizontal axis generate uneven low-frequency noise as the rotor blades rotate. The levels of infrasound emitted by wind turbines are of a similar magnitude to those produced by natural phenomena. Therefore, the infrasound generated by the proposed offshore wind farm poses no negative impacts on human health and well-being. Low-frequency noise refers to sound waves with frequencies ranging from 10 to 200 hertz (Hz). The expert assessment modelled low-frequency noise levels at a total of 12 points, nine of which were located along the coast of Hiiumaa and three at a distance of about 5 km from the coast. Low-frequency noise levels were calculated both indoors and outdoors. The results of the assessment indicated that the noise levels generated by the proposed wind farm at the specified points of receipt were below the recommended thresholds established by the government.
Between 2007 and 2016, the shallow areas of the proposed wind farm accounted for 0.2% of the total coastal fishing volume. Trawling is legally permitted only in marine areas with a depth greater than 20 m. This depth corresponds to the limit depth of wind turbine installation. According to the online application PlanWise4Blue, the wind farm area does not significantly impact the areas of industrial fishing. When the construction of wind turbines is completed, the areas of offshore wind farms can be used for aquaculture, including fish farming. Turbine masts help minimise the impact of waves and ice in the area and they can also serve as an additional anchorage point for cages. Turbines also help prevent ships from colliding with fish farming cages. The electricity generated by the wind turbines can be used to power feed barges.
Wind energy is one of the energy technologies with the lowest carbon footprint. It takes a wind turbine roughly half a year to produce the amount of energy needed to manufacture it. If the carbon emissions from the energy used to manufacture the wind turbine are spread over the lifetime of the wind turbine, the average CO2 emissions of the wind farm are around 12 grams per kWh produced. This figure, however, is steadily decreasing as the energy system continues to become cleaner. For comparison, electricity production from oil shale has a carbon intensity of about 1,000 grams per kWh and natural gas about 450 grams per kWh.
|Material||Percentage of total mass|
|Steel and iron materials||82.4%|
|Aluminium and alloys||1.3%|
|Copper and alloys||0.9%|
|Glass / carbon composites||9.5%|
|Lubricants and fluids||0.4%|
Source: Vestas V236-15MW materials, 2022_09_Material-Use-Brochure_Vestas.pdf.coredownload.inline.pdf