Reducing offshore pile driving noise: Shape optimization of the impact hammer

摘要

Offshore wind energy is an emerging source of electricity generation and new offshore wind parks are under construction around the world. The foundation of offshore wind turbines is most often realized driving steel monopiles into the sea bed using impact hammers, a technique that causes high underwater sound pressure levels threatening to harm marine mammals and other sea life. In order to protect the marine fauna, limiting values have been introduced by several countries. Their fulfillment until now has been possible applying state-of-the-art sound mitigation systems. However, rapidly increasing dimensions of wind turbines with accordingly increasing pile diameters require an ongoing development of sound mitigation systems. Nowadays applied sound mitigations systems, e.g. bubble curtains, reduce the propagation of the emitted sound, but do not affect its generation. Therefore, modifying the sound source, i.e. the hammer and pile, to reduce the generation of the sound, has recently gained attention. This contribution focuses on the development of a hammer that causes less noise but is still capable of driving the pile. First results of optimizing the shape of the impact hammer regarding its acoustic characteristics are presented.