Building offshore wind turbines quickly and gently without disturbing marine life
How can you build foundations for offshore wind turbines creating as little disturbance as possible? That is the challenge facing all offshore wind turbine builders. In recent months, initial tests have taken place using a new construction technique that ‘turns’ the foundation piles into the ground rather than driving them. This new method, called Gentle Driving of Piles (GDP), is being tested at Maasvlakte under the supervision of TU Delft. For the Topsector Energy Top consortium for Knowledge and Innovation Offshore Wind, the GDP method is a prime example of an innovation that creates a win-win situation: it makes it easier to install monopiles while at the same time being a more friendly technology for underwater life.
Monopiles are the most commonly used foundations for offshore wind turbines (OWT). As the size of wind turbines is increasing, so is the size of the monopiles. For example, a six-megawatt OWT needs an approximately 80-metres-long monopile with a diameter of 8 metres, and this can weigh as much as 1300 metric tons (equal to 1300 average-sized cars). A considerable portion of these enormous steel posts needs to be driven into the ground, a challenging, time-consuming and expensive process. Dutch contractors are the world leaders in installing OWT foundations, and it is in their interests to make the installation process of the piles as efficient as possible.
To achieve this, researchers at TU Delft have developed a new method: the GDP Shaker. Up to now, most monopiles have been hammered into the ground, which causes a lot of vibration and underwater noise. This can be harmful to marine life in the vicinity, such as porpoises. For this reason, various methods are now being taken to reduce noise and vibration during the installation of the offshore monopiles, and these involve additional costs. The goal of the GDP project is to get the monopiles into the ground while causing as little disturbance as possible to the ground around the pile, just as quickly as using pile driving and without noise. One way is to drive the monopile into the ground by applying vibrations in the torsion direction.
Research on Maasvlakte
The initial results of tests on Maasvlakte 2 show that this method works and is highly promising. The research will continue next year. The initiators hope that this innovation will be ready for the first offshore pilot tests during the course of 2020, and that it will be ready for large-scale commercial use in around four years’ time.
GDP is a GROW project, a joint research programme on offshore wind aimed at accelerating research and innovation. The project partners are: TU Delft, Boskalis, Cape Holland, Deltares, DOT, Eneco, IHC IQIP, Innogy, Seaway7, Shell, SIF, TNO and Van Oord. During the test phase, the project partners were helped in their quest for funding and collaborative partners by the Topsector Energy Top consortium for Knowledge and Innovation Offshore Wind, and they received a grant from the Netherlands Enterprise Agency.