Wind energy is one of the most promising sources of renewable energy, as it is clean, abundant, and cost-effective.
However, the installation of wind turbines in offshore environments poses several challenges and impacts, especially for marine life.
One of the main impacts is the noise and vibration generated by pile driving, a method that involves hammering steel piles into the seabed to anchor the wind turbine foundations.
This noise can disturb or harm marine animals, such as whales, dolphins, and porpoises, that rely on sound for communication, navigation, and foraging.
Gravity-based foundations: A novel solution
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Gravity-based foundations are large concrete structures that sit on the seabed and rely on their weight to provide stability for the wind turbine, as per Phys.org.
They consist of a concrete base into which the shaft of the wind turbine is installed. They offer several advantages over pile driving, such as:
Less noise and vibration: Gravity-based foundations do not require pile driving, which reduces the underwater noise and vibration that can affect marine animals. Instead, they are constructed on land or floating platforms, and then towed and lowered to the seabed using cranes or barges.
Less disturbance and damage: Gravity-based foundations do not penetrate or disturb the seabed as much as pile driving, which reduces the physical and ecological impacts on the benthic (bottom-dwelling) communities and habitats. Instead, they rest on the seabed surface or a thin layer of gravel or sand.
More flexibility and adaptability: Gravity-based foundations can be installed in deeper waters and different types of seabed conditions than pile driving, which increases the potential locations and configurations for offshore wind farms. They can also be removed or relocated more easily if needed.
Gravity-based foundations are not a new concept, as they have been used for other offshore structures, such as oil and gas platforms, bridges, and lighthouses.
However, they have been recently applied to offshore wind turbines, with several pilot projects and demonstrations around the world.
One of the first examples of offshore wind turbines using gravity-based foundations is the Blyth Offshore Demonstrator, a project developed by EDF Renewables in Northumberland, UK, as per Innovation Toronto.
The project consists of five wind turbines with a total capacity of 41.5 megawatts (MW), enough to power 34,000 homes.
The project was completed in 2017 and was the first offshore wind farm in UK waters to use gravity-based foundations.
The gravity-based foundations used in the Blyth Offshore Demonstrator were designed by Royal BAM Group, a Dutch construction company.
They were built at a dry dock in Newcastle upon Tyne, using 1,800 tonnes of concrete and 600 tonnes of steel reinforcement each.
They were then floated to the installation site using a semi-submersible barge and lowered to the seabed using ballast tanks.
The installation of the gravity-based foundations was monitored by scientists from Newcastle University, who assessed the impacts on marine animals, such as dolphins and porpoises.
The scientists used cetacean echolocation recorders to measure the presence and activity of these animals before, during, and after the installation.
The results showed that gravity-based foundations had no long-term negative effects on a dolphin or porpoise occurrence, while porpoise occurrence increased during and after the installation.
They also showed that other factors, such as the month, hour of the day, tidal currents, and vessel sonar activity influenced the presence of dolphins and porpoises.
The Blyth Offshore Demonstrator is an example of how gravity-based foundations can provide a more marine-friendly solution for offshore wind turbines.
It also shows how scientific research can help to evaluate and improve the environmental performance of offshore wind projects.
