Offshore Wind: New Installation Technique Tested

New methods of constructing wind farms at sea are playing a major role in reducing costs and shortening building times. One of the latest, a new vibratory technique, has been tested on land and shown to be up to 10 times faster and to generate lower peak noise emissions.

RWE Innogy, Bilfinger Offshore, DONG Energy, EnBW, E.ON and Vattenfall joined forces last year and launched a pilot project to test the alternative installation method for offshore foundations. The project was part of the Carbon Trust Offshore Wind Accelerator, a research and development program for reducing the costs of offshore wind energy.

The tests involved a comparison of the conventional method of impact hammering with the vibration of steel piles in a test environment on land. It aimed to prove whether vibratory piling can offer a faster and more environmentally friendly method of installing steel foundations for offshore wind farms and to evaluate the method with regard to stability.

In Summer 2014, three steel piles were vibrated and another three piles were hammered conventionally into saturated, sandy soil on a test area near Cuxhaven, Germany. The piles were then left in the ground for a period of four month before they underwent static load testing, which examined how the piles behave when subjected to the kind of lateral load that is typical in offshore conditions.

RWE Innogy was the project lead and contracted Bilfinger Offshore, who also sponsored parts of the project, to execute the major test works. The 4.3m diameter monopiles were the very first produced from the new Steelwind Nordenham fabrication facility, the hammer was supplied by IHC Hydrohammer and the vibrator was supplied by PVE Dieseko.

Technical University Braunschweig ran the data capture, such as installation times and noise emissions in collaboration with various other institutions and technical experts alongside certification and regulatory authorities.

RWE Innogy now plans to build on these tests and launch an additional subproject intended to investigate ways of optimizing the installation methodology itself.