The monopile is the most used type of foundation for offshore wind turbines and is expected to remain the preferred option for the foreseeable future. The dominant method for driving monopiles into the seabed is hydraulic impact piling, also known as hammering. However, this technique has the drawbacks of high noise emissions during pile driving and high loads on the monopiles. That is why there is a need for a more environmentally friendly pile-driving technique.
To this end, the GROW consortium is developing the Gentle Driving of Piles (GDP) driving technology. This method aims to make the pile installation process more efficient and environmentally friendly. The installation method is based on applying simultaneous low-frequency vertical and high-frequency torsional vibration on the monopile. This method is called “gentle” for its envisaged capability to reduce the driving loads and the noise, which is harmful to the environment.
The development of the GDP technology comprises five projects intending to have GDP installation technology commercially available offshore by 2027. The GDP technique was successfully demonstrated for application in sandy soil (GDP) and in clay (GDP1.2). In the SIMOX project further knowledge will be gathered to improve the offshore installation technology.
For the commercial application of a GDP shaker, it was necessary to make several adjustments to the original design. The principles on which the first prototype was built did not yet allow it to be scaled up to commercial size due to issues with fatigue and high energy consumption. There was also no proper control of the amplitude-frequency characteristic available yet. In this project we will therefore design, engineer, procure, construct and test an improved large-scale prototype of the GDP shaker that would be able to install monopiles of up to 4 m in diameter.
The new design of the large-scale GDP shaker will solve the problems by integrating new methods and principles. Instead of two eccentric motors, the shaker will be based on a series of smaller synchronised units. Each unit can independently deliver low-frequency vertical vibration or high-frequency torsion.
A new gripping system for the shaker will also be developed, which is essential for an efficient transfer of the torsional vibrations from the shaker to the monopile. The new GDP shaker will be tested in an onshore/nearshore test campaign by installing and removing a monopile with a diameter of 4 meters.
The project will deliver a newly designed, constructed and tested shaker that will prove the applicability of the GDP shaker to install large-scale monopiles with low noise. The project will also identify potential necessary adjustments and areas for improvement for the final commercial design of the shaker. The system is, therefore, fully integrated and tested before it goes offshore, which guarantees the efficient use of (financial) resources and also saves on natural resources (materials, energy) which might have a positive environmental impact.
We will use the results of this project, together with the insights from the GDP, GDP1.2 project and the SIMOX project, to carry out a demonstration campaign for the GDP technique. In GDP3.0, we will install offshore a full-scale monopile using the newly designed shaker. The results will prove to the industry that GDP is a safe, low-noise and cost-effective technique for installing large monopiles. After this, the technique can be applied commercially in the North Sea and elsewhere.
Below is the development schedule for GDP technology from initial idea to commercial application.
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This project is supported with a subsidy by the Dutch Ministry of Economic Affairs and Climate Policy and TKI Offshore Energy.