Restrictions on environmental impact and the requirement for noise mitigation measures during offshore wind farm construction activities, such as pile driving for foundation installation, requires innovative technologies to be developed. The industry has tackled the challenge by working in collaboration with knowledge and research institutes, such as TNO, to find new tools and methods for construction.
For example, devices with specialised underwater acoustics to safely and temporarily drive marine mammals and fish away from active construction zones during piling work have been developed by Dutch companies and are now being used. Such devices can prevent potential hearing loss to porpoises. In one design that acts like a window blind, special acoustic resonators can target specific frequencies that produce the most noise. Robust design means waves and currents have little or no effect.
Such innovative devices can be used in conjunction with what is known as a Big Bubble Curtain that has compressors that blow air into submerged tubes, whilst vessels can have hydro sound dampers. Each foundation is encircled by the tubes. When the air is blown in, the tubes rise and form a circular wall of bubbles around the foundation. This circular bubble curtain effectively encloses any pile driving noise, limiting its dissipation further afield.
Hydropowered BLUE Piling
Meantime, Dutch companies and knowledge institutes are working on an exciting development called BLUE Piling technology. This innovative technology can be used to drive piles for offshore wind farms using hydropower rather than the traditional steel ram. The BLUE Piling Technology significantly reduces noise by tackling the noise at the source. This means noise mitigation measures such as those used in other conventional pile-driving technologies are no longer necessary.
The BLUE Hammer uses a large water tank to provide a more energetic, but quieter, blow for offshore installation. It is designed to reduce underwater noise levels by up to 20 dB (SEL), and is predicted to reduce the fatigue damage during installation on the pile by up to 90 per cent.
There are more innovative developments and products underway, and Dutch companies and organisations along the whole offshore wind supply chain are part of an industry-wide collaborative effort to make noise mitigation a priority, along with other initiatives to reduce environmental impact.
The Dutch Approach
Environmental Impact Assessments are just one element to minimising the impact of offshore wind farms on the environment. A new wave of innovative technologies is also being developed and deployed, especially for the construction phase of an offshore wind farm. These revolve around noise mitigation and limiting damage to the seabed and marine ecology generally.
The Netherlands has some of the most stringent environmental regulations for offshore wind farm construction in the world. Therefore, Dutch companies and knowledge institutes have been at the forefront of developing, testing, and implementing noise mitigation technologies and new methods of construction with noise mitigation built in. There are some new and exciting developments on the horizon too.
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